SOUTHERN REGIONAL POWER COMMITTEE BENGALURU · Line tripped on operation of Backup impedance...

Minutes of the Special Meeting held on 03.06.2016 with M/s KPCL Page 1

SOUTHERN REGIONAL POWER COMMITTEE BENGALURU

Minutes of the Special Meeting on Pending Protection Issues of M/s KPCL held on 03.06.2016

Introduction

A Special Meeting was held on 03rd June 2016 at SRPC Secretariat, Bengaluru to deliberate on the pending

protection issues of M/s KPCL. The list of participants is enclosed at Annexure - I. Sh. S.R. Bhat, Member Secretary (MS), SRPC welcomed Sh. P. Bhaskar, Technical Director, KPCL, and Sh. M.

Shivamallu, Chief Engineer (Elec. Design), KPCL, and other Members and Participants to the Meeting. He

informed that the present meeting had been convened to deliberate on all outstanding pending protection

issues of M/s KPCL. At the outset, he appreciated the active participation of KPCL in all the meetings of

Protection Coordination Sub-Committee (PCSC) of SRPC, and also placed on record the co-operation extended

by KPCL management in resolving/ addressing various protection issues, whether related to protection audit

recommendations or specific recommendations of PSAG & PCSC meetings. However, since certain issues were

observed to be occurring recurrently at their major generating stations such as 400/ 220 kV Raichur TPS and

220 kV Nagjheri PH, it was considered prudent to bring the same to the notice of higher management of KPCL

so that the appropriate action could be initiated in right time. He further stated that certain issues such as

providing auto-reclosure on all 220 kV lines emanating from Kali complex, status of works at Sharavathy

Generating Station, providing double-bus operation at KPCL’s 220 kV generating stations, etc. would also be

discussed in the Meeting.

The following issues were deliberated in the meeting:

1. Recurring Grid Disturbances (GD’s) at Nagjheri Power Station

Sl. No. Date & Time of Event /

Gen loss & Load Loss

Reason

(i) 22.02.2016 at 12:36 hrs

Gen Loss: 500 MW;

Load Loss: 99 MW

220kV lines from Nagjheri PH started tripping from 11:00

hrs due to transient faults in lines. 220kV Narendra-

Ambewadi lines-1&2 got tripped which resulted in loss of

evacuation path to Nagjheri station resulting in tripping of

running Units and complete outage at Nagjhheri power

station. 220kV Ambewadi station also got de-energized

due to tripping of source feeders, i.e., 220 kV Narendra-

Ambewadi-1&2 and 220kV Nagjheri-Ambewadi-1&2.

(ii) 18.03.2016 at 14:40 hrs

Gen loss : 300 MW;

Load loss : 333 MW

Ambewadi Narendra line-2 tripped on fault and 220kV

Ambewadi Narendra line-1 tripped due to over-loading.

Running Units at Nagjheri also tripped during the event

due to tripping of evacuating lines

(iii) 14.04.2016 at 12:29 hrs

Gen Loss: 640 MW

220 kV Nagjheri - Bidnal line tripped on Y-B fault at 12:28

Hrs. At the same time, five running generating units (1,3,4,

5 & 6) at Nagjheri tripped on operation of Generator

Transformer’s back-up Over Current & Earth Fault

protection.


SLD:

The single line diagram of 220 kV Nagjheri PH as provided by KPCL is given at Annexure-II.

The GD-1 events at Sl. Nos. (i), (ii) and (iii) were discussed in PCSC-51 meeting held on 25.02.2016,

PCSC-53 meeting held on 28.04.2016, and PCSC-54 meeting held on 26.05.2016 respectively. While the

first event was on account of poor maintenance of the 220 kV lines surrounding Nagjhri PH, the second

event was due to non-factoring in of the over-loading of Ambewadi-Narendra lines in the SPS at Nagjheri

PH. The third event was due to tripping of the running Units for a through fault on account of improper

settings of GT’s O/C and E/F protections.

Deliberations:

1.1 Line maintenance issues:

SRLDC stated that since most of the lines tripped on transient single phase to earth fault, regular line

patrolling & clearing the trees/ branches in the ROW of the lines warrants urgent attention by KPCL &

KPTCL.

To this, KPTCL informed that the matter had been taken up with concerned Line Operation and

Maintenance wing to carry out corridor clearance and maintenance as per schedule to avoid frequent

line faults in this corridor. A letter had also been addressed to Chief Engineer, Bhagalkot zone, to ensure

lines in & around Kali complex are maintained in healthy condition.

To avoid tripping of transmission lines on transient faults, KPCL/ KPTCL was recommended to carry out

periodic patrolling of lines, and ensure their proper maintenance by carrying out jungle/ bushing

clearance and trimming of tree branches within the RoW of transmission lines as per the SRPC

transmission line patrolling guidelines (available under the menu item "All Uploads Operation

Miscellaneous Transmission Line Patrolling Protocol / Guidelines for Southern Region" on SRPC

website).

1.2 SPS Modification at Nagjheri PH (NPH)

In both 1 (i) & 1 (ii), it was observed that prior to Nagjheri PH outage, NPH – Hubli lines and NPH – Bidnal

line were under OPEN condition due to bus shutdown at Hubli SS and/or transients faults on the

respective lines. Under these conditions, one of the Ambewadi – Narendra D/C lines got tripped on a


transient fault, and led to the over-loading of the other line. As a result, the other line also got tripped

on O/C protection. Since the Nagjheri – Kodasalli lines had already been kept OPEN as per SLDC, KPTCL

instructions, NPH was effectively left with no evacuating lines, which ultimately led to the tripping of

NPH running Units on over-frequency.

In this regard, KPTCL explained that the existing SPS (given at Annexure-III) had been designed to

operate with the loci of faults lying on the Nagjheri bound 220 kV lines. Accordingly, it was configured to

operate with a delay of 1 sec in the event of over-loading (current exceeding 590 A) of any of its

evacuating lines, and was not co-ordinated with the operation of over current protection of Ambewadi-

Narendra D/C lines. Now in the instant cases, the loci of faults were on the lines emanating from the

substations surrounding Nagjheri, but away from it. As a result, even though the SPS at Nagjheri PH was

in healthy condition, it had not operated due to non-fulfilment of the conditions required w.r.t loading

and current flow on the lines.

It was further observed from the existing SPS that only that running Unit out of Unit-3 and Unit-6 with

maximum generation would be tripped as a result of SPS operation. As such, further reduction/ backing-

down of generation at NPH was not possible if Unit-3 and Unit-6 were already under outage condition.

This implied that a loss to the extent of 600 MW (by virtue of Ngajheri PH outage) was very much a

reality if tripping of Ambewadi – Narendra D/C lines were to take place under such conditions.

On this, SRPC/ SRLDC opined that while modifying the existing SPS so as to factor in over-loading of

Ambewadi-Narendra lines could offer immediate relief, it would do well for KPTCL as a long-term

solution to undertake re-conductoring (with HTLS type of conductors) of 220 kV Nagjheri – Ambewadi

D/C line, 220 kV Ambewadi – Narendra D/C line, 220 kV Nagjheri – Kodasally D/C line, and 220 kV Kaiga

– Kodasalli S/C line.

To this, KPTCL agreed to take into account all factors affecting NPH generation including over-loading of

Ambewadi – Narendra D/C lines, and assured that the thus suitably modified SPS would be put into

service after taking necessary approval from their management. KPTCL also agreed to take up

re-conductoring of the above mentioned 220 kV lines with their management.

The modified SPS at NPH as proposed by KPTCL is given at Annexure-III.

SRLDC and SLDC, KPTCL were requested to kindly go through the details of the above proposed SPS

with focus on the limiting values of various time-delays & current flows, and furnish their comments to

KPTCL for incorporation of the same.

KPTCL was recommended to implement the final version of the modified SPS at Nagjheri PH at the

earliest.

KPTCL was further recommended to actively undertake re-conductoring (with HTLS type of conductors)

of 220 kV Nagjheri – Ambewadi D/C line, 220 kV Ambewadi – Narendra D/C line, 220 kV Nagjheri –

Kodasally D/C line, and 220 kV Kaiga – Kodasalli S/C line, and furnish an action plan for implementing

the same.

1.3 Revising GT back-up protection settings appropriately at Nagjheri PH

SRPC/ SRLDC stated that the operation of Generator Transformer’s back-up Over Current & Earth Fault

(high-set) protection for a through fault was not in order (the fault current was stated to be 3.2 kA).

Accordingly, there was a need to revise the settings of GT’s back-up O/C and E/F protections considering

their individual contribution to solid bus fault at 220 kV bus of Nagjheri PH.

To this, KPCL informed that they had revised GT’s back-up protection settings in the recent past only

from 5 A to 7.5 A. However, in view of the current GD, Discrete Relay High set values had been

re-calculated and assured that the same would be loaded in stages in consultation with OEM of Relays

(M/s Andritz).


1.4 Putting 220 kV Nagjheri-Kodasalli lines into service

It was noted that the 220 kV Nagjheri- Kodasalli D/C lines had been kept opened based on SLDC, KPTCL

instructions. In this regard, it was pointed out that closing of these lines could have averted this grid

disturbance since there was sufficient generation at all Generating Stations (esp. Nagjheri) in Kali

Complex, and brought to KPCL & KPTCL’s attention the study carried out in respect of similar grid

disturbance that occurred there on 22.02.2016 at 12:36 hrs. (Minutes of PCSC-51 issued vide SRPC letter

no: SRPC/SE-III/PCSC-51/2016/ 1702-35 dated 16.03.2016, where it was recommended to put 220 kV

Kodasalli - Nagjheri D/C lines into service if more than 200 MW generation from Kali Complex (with

Nagheri Contribution not less than 50 MW) is ensured on sustained basis.

To this, KPCL informed that Nagjhari- Kodasalli Lines 1 & 2 had been kept in service since 23.05.2016 @

08.06hrs.

2. Trippings involving 400/ 220 kV Raichur TPS

Sl. No. Details of Event Date & Time

Reason

(i) Tripping of 400 kV Raichur TPS -

Mahboobnagar line

05-04-2016

at 10:23 hrs

Line tripped on operation of Backup

impedance protection of line reactor.

Direct trip was received at Mahboobnagar

end.

(ii) Tripping of 400kV Raichur TPS Bus-2

13-04-2016 at 21:12 hrs

Y-ph Pole of Tie-breaker of Unit-4 at RTPS failed. Unit-4 got tripped on operation of Generator Differential, Reverse power & LBB protection. Operation of LBB protection led to tripping of BUS-2 at RTPS

(iii) Tripping of Units at Raichur TPS Gen loss: 760 MW

15-04-2016 at 15:36 hrs

During testing of retrofitted distance protection in 400kV Raichur-2 feeder, LBB protection trip DC got extended to Bus trip. This resulted in tripping of 220kV bus at RTPS and subsequently tripping of all connected 220kV elements. Unit-4 which is connected to 400kV Bus got tripped due to tripping of Station Utility Transformer that is connected 220 kV bus

The above Grid Incidents (GI’s) were discussed in PCSC-54 meeting held on 26.05.2016. While the first GI

seemed to be on account of mal-operation of Line Reactor back-upprotection, w.r.t. the second GI it was

informed that during the synchronization process of Unit-4, when the excitation voltage was at 15 kV,

the Y-Pole of Tie-breaker (of Unit-4) got blasted. As a result, Unit-4 got tripped on Generator Differential,

Reverse power & LBB protection. Operation of LBB protection led to tripping of 400 kV Bus-2 at RTPS.

Similarly, the third GI was also not in order as the 220 kV side seemed to be on single-bus operation.

Further, there was also a need to provide alternative source to Unit-4 auxiliaries, esp. when the SUT,

from which the Unit-4 auxiliaries are presently being fed, goes out.

SLD:

The single line diagram of 400/ 220 kV Raichur TPS as provided by KPCL is given at Annexure-II.


Deliberations:

2.1 Tripping of 400 kV Raichur TPS -Mahboobnagar line on 05.04.2016 at 10:23 hrs

SRPC/ SRLDC stated that operation of back-up impedance protection of Line Reactor (LR) at RTPS end on

400 kV Raichur TPS - Mehboobnagar line was not in order as there was no signature of any fault in the

PMU plot around the time of occurrence of this tripping.

To this, KPCL stated that it was a typical case of mal-operation of the corresponding electro-mechanical

relay, and informed that they were ready to take LR out of service, if permitted, in view of the short

length of the line. On this SRLDC stated that even though it was a short line, due to prevailing of high

voltages at RTPS, best option would be to convert this LR into a Bus Reactor.

The issue was further discussed, and it was noted that there was neither the availability of additional

circuit breaker nor the space required for reconfiguring the bays. As such, it was recommended to KPCL

to keep the referred electro-mechanical back-up impedance protection relay under observation, and

replace it with a spare at the earliest.

2.2 Tripping of Raichur TPS 400 kV Bus-2 on 13.04.2016 at 21:12 hrs

KPCL informed that Y-ph Pole of Tie-breaker of Unit-4 at RTPS failed while synchronising it. Unit-4 got

tripped on operation of Generator Differential, Reverse power & LBB protection protections. It was

explained that due to surface conduction over the Unit-4 Tie-breaker, LBB relay of 400 kV Bus-2 got

operated leading to tripping of all breakers connected to it. The reason for surface current was attributed

to the deposition of ash, heavy mist & humidity on account of Unit-4’s proximity to cooling towers.

In this regard, SRPC/ SRLDC brought to KPCL’s attention the occurrence of similar event due to LBB

operation of Main & Tie breakers of Unit-7 on 12.11.2015 at 00:30 hrs, when it was recommended

among other things to provide dedicated breaker flashover protection, and to take necessary preventive

measures such as measurement of dynamic contact resistance, and over-hauling (hot-line washing) of

breakers at regular intervals to ensure healthiness of breakers.

To this, KPCL informed that hot-line washing of breakers is already in place. Further, they have also

initiated steps (tendering is in progress) for applying RTV Silicone high voltage insulator coatings to all

ceramic insulators of equipment like CT, PT, CB, Isolators etc.

When enquired about providing breaker flashover protection, KPCL assured that they would look into it.

To this, it was explained that breaker flashover is an abnormal condition and may result in severe

damage to capital equipment like Generator and Generator Transformer. Additionally it may also result

in explosion of Circuit Breakers which can damage the nearby equipment in Switchyard and put

Substation personnel at risk. As such, detection of flashover reliably and operating the protection system


to isolate the affected breaker and generator in minimum possible time is all the more important, and

informed that such a protection can be implemented using a logic based on immediate sensing of arc

current supported by breaker status to reliably declare a flash. In this regard, papers contributed by

Adani personnel on (i) “Adaptive Logic for Breaker Flashover Protection”, (ii) “External Flashover of

Generator Circuit Breaker in Coastal Power Plants having Air Insulated Switchyard”, and (iii) “Practical

Interlock Logics to prevent undesired Circuit breaker closing, Isolator opening & charging of Bay in

Substations using IEDs” are enclosed at Annexure-IV for kind perusal and necessary action.

Thus, KPCL was recommended to undertake the following remedial measures to avoid breaker

flashovers:

replacing all porcelain insulators with composite insulators

carrying out hot-line water washing of all insulators on regular basis.

applying Room Temperature Vulcanizing (RTV) Silicone high voltage insulator coatings to all bus-

connected ceramic insulators of equipment like CT, PT, CB, Isolators etc.

KPCL was also recommended to take steps to provide dedicated breaker flashover protection to all

breakers at Raichur TPS at the earliest.

2.3 Tripping of Units at Raichur TPS on 15-04-2016 at 15:36 hrs

KPCL informed the following:

KPCL informed that at the time of the incident, Unit Auxiliary Transformer of Unit-4 was under

maintenance; hence Unit-4’s auxiliaries were being fed from the Station Transformer-4 (ST-4). As ST-4


was deriving its power from 220 kV bus, and since 220 kV side was being operated on single-bus, LBB

operation of 220 kV Bus led to tripping of ST-4. This failure of supply to Unit-4 auxiliaries resulted in

tripping of Unit-4.

In this regard, SRLDC enquired about the reasons for not providing double-bus operation at 220 kV level

at RTPS, and the general practice being adopted w.r.t. double-bus operation at the other generating

stations of KPCL. To this, KPCL informed that excepting at 220 kV RTPS, its all other 220 kV generating

stations were being operated on double-bus operation only.

It was noted with concern that in spite of the availability of two buses along with healthy bus-coupler,

all generating units (1, 2 & 3) and the loads/ feeders at 220 kV were put on single bus operation at 220

kV RTPS. As such, KPCL was recommended to put in service the double-bus operation at 220 kV RTPS

by suitably distributing loads within 15 days.

3. Revival schedule & status of works in progress at Sharavathy Generating Station.

KPCL informed the following:

Units- 6,7 & 8 and 2 lines (Shimoga 3 & 4) are in service.

Order placed on M/s ABB on 22.03.2016 for balance 7 Units & 7 lines with DCS adapting state of art technology.

Implementation schedule:

KPCL also informed that Units – 9 & 10 would be synchronized by 06.06.2016; and all other remaining Units would be synchronized by 30.06.2016.

4. Auto-Reclosure scheme implementation on all 220 kV lines emanating from Kali Complex

The issue has been deliberated in various PCSC meetings. Since most of the faults that occur on 220 kV

lines emanating from Generating Stations in Kali Complex are transient single phase to ground faults, the

outages such as those mentioned at Sl. No. 1 could be avoided by providing A/R on the 220 kV lines of

Kali Complex.

When enquired about the action initiated by KPCL in this regard, KPCL informed the following:

Implementation of Auto-reclosure scheme would be taken up after retrofit of new version Numerical

Distance relays for Main-2 protection.


PO had been placed on M/s Schneider Electric Infrastructure Ltd. for supply of Numerical protection

relay to be used as Main-2 protection. Materials received at site. Erection work would be taken up

shortly.

However, when KPCL expressed the apprehension of their GT’ breakers switching on to high fault

currents, it was clarified that the time-differentiated A/R scheme as detailed in the minutes of PCSC-51,

(also reproduced below) can be implemented:

“In this, after a line is opened from both ends (generator end & remote end) on

A/R operation, the remote end will be auto-reclosed as usual after the elapse of

its dead-time (say, 1 sec). However, the generator end relay will check for the

line voltage after elapse of an elongated dead time (say 1.3 or 1.5 sec; here the

additional 0.3 or 0.5 sec has been included as a safety time margin). If the line

voltage so sensed is healthy & normal (which implies that the fault has already

been cleared), then generator end will be auto-reclosed; else 3-ph trip will be

given at generator end to open the other two phase poles.”

On this, KPTCL stated that by above scheme even though the generator end is effectively prevented

from closing on to fault, there is also a need to prevent auto-reclosing altogether when the fault current

is prohibitively high, as it could lead to high-voltage phenomena, and result in cascade tripping of the

connected lines.

The merit in the KPTCL’s argument was thoroughly discussed, and it was agreed to implement blocking

auto-reclosure on heavy fault currents (say 70 % of the corresponding bus-fault level) on experimental

basis on any one line connected from Sharavathy Generating Station as explained below:

“In this, additionally an Over Current (O/C) element is kept enabled to operate at

70 % of the corresponding bus-fault level at both ends of the line, and is

configured to block A/R at the originating end alongside sending Direct Trip (DT)

command to the other end. By this, as long as the fault current is less than the set

value of O/C element, auto-reclosure will be attempted for the tripped line in

accordance with the above detailed time-differentiated A/R scheme. However,

when the fault current exceeds the set value of the O/C element, A/R function will

be blocked at the originating end, and DT will be sent to the other end”.

Thus, KPCL was recommended to implement auto-reclosure on all 220 kV lines emanating from Kali

complex in accordance with the above detailed time-differentiated A/R scheme.

Further, KPTCL, in coordination with KPCL, was requested to implement and validate on experimental

basis the above detailed logic for blocking Auto-Reclosure on heavy fault currents on any one line

connected from Sharavathy Generating Station, and furnish a report on the efficacy/viability of the

scheme for implementation on all transmission lines.

5. Tap-Change of KPCL Stations

Station Unit Present tap &

Corresponding

voltage (in kV)

Recommended Tap &

Corresponding

Voltage (in kV)

Kadra All units 7 & 225.5 8 & 222.75

Kodasalli All units 7 & 225.5 8 & 222.75

Sharavathy 9 2 & 231 4 & 220


KPCL informed that the Taps at Kadra and Kodasalli Power Houses had been kept at 7/225.5 to suit

system condition against the recommended value of 8/225.75 for matching generator voltage with

system voltage. Similarly, at Sharavathy Generating Stations (SGS), the 9th Unit GT-tap could not be

changed due to technical problems. KPCL informed that tendering is in progress for procurement of

115 MVA Generator transformers, after which the required tap would be provided at SGS.

On this, SRLDC explained that since the system voltage for synchronization is 220 kV at Kadra & Kodasalli,

and the recommended value is nearer to this, KPCL’s reservations on changing to recommended tap are

mi splaced.To this, KPCL agreed to look into the issue, and adjust tap positions accordingly.

KPCL was recommended to adopt the SRLDC recommended tap-positions at their Kadra (all Units),

Kodasalli (all Units) and SGS (Unit-9) stations at the earliest.

6. Compliance of pending Recommendations of the following Power System Analysis Group (PSAG) Meetings

The status of recommendations of PSAG-3 held on 04.09.2013 to analyze the multiple trippings that at

Sharavathy HPS on 18-08-2013 is given at Annexure-V.

The status of recommendations of PSAG- 6 held on 05.02.2014 to analyze the multiple trippings at

Raichur TPS on 26-01-2014 and 30-01-2014 is given at Annexure-VI.

The status of recommendations of PSAG-10 held on 12.11.2014 to analyze the Grid Disturbances at

Kadra, Kodasalli and Kaiga Power Stations that occurred on 26-09-2014 and 05-10-2014 is given at

Annexure-VII.

The status of recommendations of PSAG-13 held on 22-23 April, 2015 to analyze the cause of multiple

trippings that took place at RTPS and Raichur-PG on 09.03.2015 & 11.04.2015 is given at

Annexure-VIII.

It was noted that generally recommendations involving procurement activities are pending. As can be

seen from the furnished status, the erection & commissioning activities for the recommended works are

under progress.

7. Pending Implementation of PCSC Recommendations

The latest status of compliance of recommendations of various PCSC meetings relating to KPCL Stations is

given at Annexure-IX.

It was noted that steps had been taken to implement various PCSC recommendations relating to revision

of specific relay settings, enabling of A/R scheme, replacement of old electromechanical relays with

numerical relays at KPCL Stations, etc.

8. Protection Audit Recommendations (Phase- I & II)

The latest status of compliance of Protection Audit recommendations (Phase-I and Phase-II works) pertaining

to KPCL Stations is given at Annexure-X.

It can be seen from the furnished status that all works of Phase-I & Phase-II have been targeted to be

completed before 30.12.2016, the dead-line for which KPCL has committed before Hon’ble CERC in their

application seeking time-extension for implementing protection audit recommendations relating to their

stations.


9. High resistance faults are frequently observed in 220kV lines in Kali complex due to the dense vegetation. Faults are often observed to be cleared by back up protections. The resistive reach of distance protection relays to be reviewed along with proper vegetation management. KPCL informed that they were seized of the matter, and assured that the Resistive reach of lines would be

revised in co-ordination with KPTCL.

10. Fault level at Raichur TPS

During failure of R-phase CT of 400/220kV ICT-1at Raichur TPSat 21:44 Hrs on 01-05-2016 the fault current

recorded in DR was 36 kA. Suitable actions need to be planned as fault level may exceed 40kA in near future.

To take care of the situation arising out of 400 kV RTPS bus fault level exceeding 40 kA, KPCL informed

that in RTPS area switchgear which can withstand such fault level only are being put into service in recent

days. Further, materials with design specifications considering 50 kA only are being procured. The same

will be CONSIDERED and adopted in all future replacements.

11. Differential protection for 400kV lines

400kV Raichur-Raichur TPS line-1&2 and 400kV Raichur-YTPS and in future lines from Bellary pooling station

to nearby generating TPS are to be provided with differential protection as frequent over-reach is observed

with distance protection relays.

KPCL informed that DIFFERENTIAL PROTECTION for 400 kV lines would be provided in consultation with

KPTCL and considering site feasibility.

12. Faulty distance relay in 400kV RaichurTPS-YeramarusTPS line

400 kV RTPS-YTPS line is tripping from Raichur TPS end for any through fault due to problem in distance relay

at RTPS end.

KPCL informed that the SOTF logic implemented in Micom P444 distance relay at RTPS end on 400 kV RTPS –YTPS line had been wrongly configured with continuous enabling, due to which whenever any fault takes place on down-stream network, it is invariably acting to trip the line.

Now the ALSTOM make P444 relay settings were revised on 01.05.2016 in consultation with M/s

ALSTOM, and the line is found to be stable.

13. D.R and station event logger to be triggered with operation of Main and Back-up protections of transmission

line/ generator /bus-bar protection with proper time synchronization for proper analysis.

KPCL informed that protection relays with built-in Disturbance Recorder (DR) and Event Logger (EL) with

facility to synchronize with GPS were being procured and commissioned.

To this SRPC/ SRLDC while appreciating KPCL’s initiative in procuring new protection (numerical) relays

with DR and EL and time-synchronization facilities, informed that the new relays must be suitably

configuring for recording even those events that occur on operation of back-up protections of

transmission line/ generator /bus-bar. To this, KPCL agreed to take necessary action for capturing events

on back-up protection operation.


14. Integrity test for Station earth mats in KPCL stations

As per CPRI report, improper earthing was one of the reasons attributed for fire incident at Sharavathy

power house. Station Earth mat integrity test need to be carried out at all KPCL power station as a

precautionary measure.

KPCL informed that New Earthing System as per design of M/S CPRI would be put into service, which

would be in addition to the existed earth mat. KPCL also assured that Station Earth-mat integrity test

would be carried-out at all KPCL power stations as a precautionary measure.

Vote of Thanks

MS, SRPC thanked Technical Director, KPCL and other Officials from KPCL & KPTCL for participating in the

Meeting. He hoped that with active cooperation, visible improvement would be witnessed in the near future

on these pending protection issues.

*****

Annexure-I

Annexure-II

SHAHPUR-1

SHAHPUR-2

Annexure-II

SPS Logic at Nagjhari (15-08-12)

Revised to 600MW after 26-06-14.

EXISTING SPECIAL PROTECTION SCHEME FOR NAGHJARI GENERATING STATION : FLOW LOGIC

Tripping of Hubli-Sirsi 1 &2 lines

Or Tripping of Bidnal-Harthi 1 &

2 lines will lead to tripping of

Generating units U3 0r U6 @

Nagjhari, based on the condition,

if Total Gen (including Kodasalli

lines inflow @ Nagjhari) is > 900

MW

KODASALLI 2

KODASALLI 1

INPUT FROM GEN AND KODASALLI LINES

TRIP MAX OF G3 AND

G5

G3

G6H

UB

LI 1

CURRENT <30 A OR BREAKER TRIP

LINE CURRENT

BREAKET TRIP

G1 TO G6 GEN IN MW

ANY ONE HIGH






LINE CURRENT

BREAKET TRIP

LINE CURRENT

BREAKET TRIP

LINE CURRENT

LINE CURRENT

LINE CURRENT

BREAKET TRIP

HU

BLI

2

BID

NA

L 1

BID

NA

L 2

AM

BEW

AD

I 1

AM

BEW

AD

I 2

HU

BLI

1H

UB

LI 2

BID

NA

L 1

BID

NA

L 2

AM

BEW

AD

I 1A

MB

EWA

DI 2

KO

DA

SALL

I1

KO

DA

SALL

I 2

LINE CURRENTS

ANY LINE CURRENT >590 A (DELAY 1 SEC)

ANY LINE CURRENT <30 A OR BREAKER TRIP ORANY DI COMMAND FROM HUBLI OR BIDNAL AND TOTAL GEN >900 OR ANY LINE CURRENT >590 A

TOTAL GEN

ANY LINE CURRENT<30 A OR BREAKER TRIP AND TOTALGEN >900

LIINE LOAD

LIINE LOAD

MAX OF G3 AND G6

TOTAL GEN

HU

BLI

BID

NA

L

SPS DI INPUTS FROM RTU

ANY DI COMMAND FROM HUBLI OR BIDNAL AND TOTAL GEN >900

Annexure-III

SPS Logic at Nagjhari (15-08-12)

Case 1e) Any line Current is > 590 A OR In Bidnal-Harthi 1 & 2 & Bidnal-Soundatti if any line current is < 30A or Breaker tripped, DI command shall be sent from Hubli to Nagjhari & Gen> 600MW then one unit which is generating Max will be tripped.

MODIFIED SPECIAL PROTECTION SCHEME FOR NAGHJARI GENERATING STATION : FLOW LOGIC(Revised as on June 2016)

Case 1a) Any line Current is > 590 A for 1.5 sec & Gen> 600MW then one unit which is Max of 6 units will be tripped.

Case 1b) Any line Current is > 590 A for 2 sec OR in Ambewadi-Narendra 1 & 2 lines if any current is > 700A, DI command shall be sent from Ambewadi to Nagjhari & Gen> 300MW then one unit which is generating Max will be tripped.

Case 1c) Any line Current is > 590 A for 2.5 sec OR in Ambewadi-Narendra 1 & 2 lines if any current is < 30A & the other line current is > 800A, DI command shall be sent from Ambewadi to Nagjhari & Gen> 200MW then one unit which is generating Max will be tripped.

Case 1d) Any line Current is > 590 A OR in Hubli-Bidnal 1 & 2 if any line current is < 30A or Breaker tripped, DI command shall be sent from Hubli to Nagjhari & Gen> 600MW then one unit which is generating Max will be tripped.

INPUT FROM GEN AND KODASALLI LINES

TRIP MAX OF G1 TO

G6G

G1 TO G6 GEN IN MW

AMBEWADI 1

HUBLI 1

ANY LINE CURRENT >590 A

TOTAL GEN

ANY LINE CURRENT >590 A , Gen> 300MW (DELAY 2SEC)

AMBEWADI 2

In Ambewadi-Narendra 1 & 2 if any line current >700A, DI command shall be sent from Ambewadi to Nagjhari

In Ambewadi-Narendra 1 & 2 if any line current is < 30A & the other line current>800A, DI command shall be sent from Ambewadi to Nagjhari

HUBLI 2

HUBLI 3

In Hubli-Bidnal 1 & 2 if any line current is < 30A or Breaker tripped, DI command shall be sent from Hubli to Nagjhari

Bidnal

In Bidnal-Harthi 1 & 2 & Bidnal-Soundatti if any line current is < 30A or Breaker tripped , DI command shall be sent from Hubli to Nagjhari

ANY LINE CURRENT >590 A , & Gen >600 MW (DELAY 1 .5 SEC)DELAY 1.5 SEC

ANY LINE CURRENT >590 A DELAY 2 SEC

ANY LINE CURRENT >590 A DELAY 2.5 SEC

ANY LINE CURRENT >590 A , Gen> 200MW (DELAY 2.5 SEC)

ANY LINE CURRENT >590 A

DELAY 1 SECANY LINE CURRENT >590 A , Gen> 300MW (DELAY 1 SEC)

ANY LINE CURRENT >590 A DELAY 1 SEC ANY LINE CURRENT >590 A , Gen> 300MW (DELAY 1 SEC)

Annexure-III

Adaptive Logic for Breaker Flashover Protection of Generator. Sanjay Bhatt

Protection Automation and Metering Group Adani Power Training and Research Institute

Adani Power Limited, Ahmedabad [email protected]

1. ABSTRACT:

Flashover can occur on any breaker in the network where an overvoltage condition is present, but the probability is higher for breakers being used to synchronize two isolated power systems; e.g. on generator breakers, line breaker connecting two separate sources or grids. For Generator/line breaker, the Period is considered as critical in view of withstanding rise in voltage vector appearing across poles of Circuit Breaker and the arc quenching process before generator/line synchronization, or just following generator/line tripping respectively. The circuit breaker for above said applications for must be designed capable of maintaining the sufficient insulation level to withstand the same. The detection of flashover reliably and operating protection to isolate the affected breaker and generator in possible minimum time calls for a logic based on immediate sensing of arc current supported by breaker status to reliably declare a flash. This paper describes the logic adapting the numerical relaying logic blocks with current status different from conventionally used and also described in IEEE guideline for Generator Protection C37.102.

2. KEYWORDS: Breaker Flashover, Generator Protection for GT Breaker flashover, unintended arc across Generator breaker

3. INTRODUCTION:

(I) It is because the vectors of the protected generator and grid vector across circuit breaker poles are slipping with respect to a power system. This will lead to a condition to establish at least twice rated phase-neutral voltage across the generator circuit breaker. Due to the system and machine operation condition it is quite often possible that even higher voltage may be established. This will lead to establishment of arc between two poles of circuit breaker, which may be internal or external, leading to failure of breaker damaging self and also nearby equipments and persons. Further the establishment of arc will also lead to the asynchronous energisation of Generator with grid and create oscillation damaging Generator Transformer / Generator. Detecting the flashover The abnormal rise in voltage just after generator tripping is most likely due to following reasons,

Prime mover failure: which is associated by the excitation level not matching instantly with the lowering of active power, where the pre-failure level of excitation might be maintained until AVR action takes place.

AVR malfunction: this is associated with failure of AVR to discharge energy through discharging resistor at the time of tripping boosted by residual flux.

Annexure-IV

Page 1 of 23

2 Adaptive Logic for Breaker Flash over protection of Generator.

The peak to peak voltage appearing across circuit breaker is indicated at Fig.1 below.

During the synchronization process, the out-of-phase angle between breaker contacts changes from 0 to 360 degrees continuously. Voltage between breaker contacts reaches its maximum instantaneous value when the angle difference between the voltages is 180 degrees, with a magnitude equal to double the nominal phase-to-ground peak voltage; posing severe stress to the insulation. May also result in out of step and swing.

The flash over thus occurred in most of the cases are of single phase in nature as because of probability of maximum peak to peak voltage at a time is for one phase and very rare may be of two phases depending up on deterioration of insulation and repeated peak across each phase.

(II) Detection of Flash over The detection of arc as a fault is very tricky due to lower magnitude and also resembling the breaker status with selectivity among various normal and abnormal grid behavior and remote fault. The arc current will always reflect as a Zero sequence or Negative sequence current which can be detected typically as under.

Fig 1- Typical One and Half CB arrangement possible breaker flash over due to peak to peak voltage across CB open contacts Breaker

Fig 2a- Typical CT connection to detect breaker arc current as residual current for Generator directly connected to Grid

Fig 2b- Typical CT connection to detect breaker arc current as residual current for Generator connected to Grid through Transformer.

Annexure-IV

Page 2 of 23


Typically the detection of Neutral over current from Generator or Generator transformer as referred in fig (2a & 2b) with Breaker OPEN status is interpreted as breaker flash over condition, and after certain small time delay tripping is declared out. Alternatively detection of Negative sequence current at Generator Neutral and phase side with Breaker status is also used for detection of breaker flash over condition.

(III) Action: Tripping of associated bus is essential here, because, merely tripping of Generator or excitation will also initiate tripping of Generator breaker and still the breaker is shunted by flash arc current, with the breaker is already in OPEN status, will subsequently cause initiation of LBB and after certain time delay of LBB timer will trip Bus breakers, which is delayed tripping as per LBB setting and initializing scheme.

(IV) Reliability & Selectivity.

(a) Limitation of above logic remains always within the reliability of the breaker status, because defective status of breaker obtained through breaker auxiliary switch many times falsify due to switch and related gearing alignment and contact issues. During the defective status of breaker associated with remote fault or short duration unbalance due to auto reclosing will cause to operate the

logic undesirably causing tripping of Generator and bus also. However use of GT neutral current with interlocking of GTCB may lead to mal-operation when the Breaker contact is defective, which enables the function during normal operation of unit. Further the setting of IN for Flash over detection is kept low enough for effective detection of flash current therefore any earth fault or unbalance in the grid / line may lead to operation of the function. Use of Generator Neutral CT will avoid the possibilities of above mal-operation during grid disturbances. However pure single phase flash may not be reflected at Generator Neutral side because of the zero sequence isolation at generator side for faults on GT side.

(b) In case of Generator connected with one and a half breaker bus arrangement detection of breaker flash over if actual, will not identify the breaker (Main or Tie) which has undergone flash over. Pl. refer fig 1, where it has been indicated that the Generator / Line can be connected either from Main or Tie breaker and therefore the flash over condition may be for either of two breaker. Thus the automatic and reliable detection of the breaker which has undergone the mishap must be identified and output action should be relevant to the identification. It is now obvious that action to isolate the Generator from Grid should be separate for each condition with unique identification. Merely detecting breaker flash over condition from the breaker status (composite may be of Main and Tie) and neutral current from Generator Transformer or Generator, with action for Tripping of Bus bar and Class A tripping for Generator is not sufficient as well not truly as per requirement defeating the aim for Breaker flash over protection intended so.

Above limitation for reliability and selectivity will place a threat to undesired tripping, delayed tripping or stability aspects too.

& Breaker OPEN Status

IN>

I2p>

I2n>

TRIP Excitation& BUS

& Breaker OPEN Status

TRIP Excitation& BUS

Fig 3- conventional logic to detect breaker flash over

Time

Time

Annexure-IV

Page 3 of 23


(V) Solution: Addressing above limitations with feasible solution is possible with following considerations. As earlier discussed Broadly two criteria are required to detect breaker flash over (i) Breaker OPEN status (ii) sensing of Neutral current at GT or Negative sequence current at Generator terminal and (iii) third one essential for One and Half breaker Bus arrangement is, identifying the affected breaker. The output actions are then decided and forwarded with suitable circuit schemes. (a) Detection of Breaker Status.

Indirect assessment of breaker pole status can only be done by detecting flow of current through all three phases simultaneously registering a status in logic block and removing also the register status as low, i.e. using flipflop block triggered by current threshold. Also as per IEEE GUIDE FOR AC GENERATOR PROTECTION: Std C37.102-1006, 4.7.1 Open generator breaker flashover protection: ‘Generator breaker flashover may also be detected by breaker pole disagreement relaying. This relay monitors the three-phase currents flowing through the breaker and senses whether any phase is below a certain low threshold level (indicating an open breaker pole) at the same time that any other phase is above a substantially higher threshold level (indicating a closed or flashed-over pole).’ Logic using FlipFlop :

Above logic criteria are indicated at Fig 4. The flow of current through circuit breaker at HV side of Generator Transformer is considered as Phase current (Iph) and IN as GT neutral current. The OPEN status is detected when all three phases detect current below 2% (or practically as low possible setting available in relay which can be detected reliably. The OPEN status implies isolated

condition of Generator from grid and SET the FlipFlop. The output of FlipFlop makes input of AND gate high arming for Breaker flashover protection active. On detection of neutral current in GT or Negative sequence current at Generator will operate breaker flash over protection trip output. The normal operation of Generator can be considered as (i) Before & During synchronizing (ii) After Synchronizing and (iii) Grid fault when Generator is normal in service (iv) After isolating from grid. (i) Before & during synchronizing there

is no current flow and hence FlipFlop O/P is High. There will not be Iph and IN hence keeping the logic O/P as low.

(ii) Immediate after synchronizing there will be Iph >5% (or to be set as possible initial loading normally) resetting the FlipFlop after 200 mS.

(iii) Machine running normally will also prevail condition (ii) above.

(iv) After tripping of machine there will be Iph<2% as set above will immediately put function in service.

Fig 4- Breaker open status Detection logic based on current threshold using SR FlipFlop

SR Flip Flop

S

R

O

IPh <2% 3 Phase

IPh > 5% 3 Phase

T = 200 mS

& IN> 10 to 20%

T = 100 mS

TRIP ALL / BUS TRIP

Iph= Phase current, IN = GT Neutral current

For 1-1/2 Breaker bus, separate logic for Main and Tie breaker path current.

Annexure-IV

Page 4 of 23


Logic using AND –OR blocks : Some of the basic versions of IEDs do not have the Flip Flop logical blocks, for which following logic using basic AND – OR and Timer blocks can be used as indicated at Fig-5 here under.

The lower current threshold for any one phase is monitored for OPEN status, this implies for resetting only when all three phases have current more than 2% i.e. all poles closed. The drop out timer is intended for keeping function armed for 200 mS. after synchronizing during which practically picking up of load by Generator more than 5%.

All four conditions mentioned in earlier paragraph for Generator are addressed here

also detecting reliably the breaker flash over condition.

The IN setting for 10 to 20% is intended for detecting lower arc current as low as 10% keeping in consideration normal maximum unbalance current.

The delay in output is chosen as 100 mS for stability and reliability purpose considering normal breaker closing time and inherent difference in closing of individual pole and also initial unbalance current owing to measurement and magnetizing effect for lower magnitude.

OUTPUT Action:-

The output action of the protection must isolate the Generator from grid and also removal of excitation to Generator. The conventionally action for a LBB protection is similar to the required one for Breaker Flashover condition.

The difference here is the detection at a lower magnitude of current without any trip initiation and also operating time is much less than typical LBB time of 200 to 250 mS.

Fig 5- Breaker open status Detection logic based on current threshold using AND-OR blocks.

Iph= Phase current, IN = GT Neutral current

For 1-1/2 Breaker bus, separate logic for Main and Tie breaker path current

&

IN> 10 to 20%

PU Timer = 100 mS

TRIP ALL (Class A & BUS TRIP

IPh-B <2%

IPh-c <2%

OR

IPh-A >5%

IPh-B >5%

IPh-C >5%

OR

DO Timer 200 mS

Annunciation & SOE in SCADA / DCS

IPh-A <2%

LBB Initiation

OR

TRIP ALL (Class A & BUS TRIP

Breaker Flash over O/P

I>20% Timer 250 mS

&

Fig 6: Output action for LBB and Breaker flash over protection

Annexure-IV

Page 5 of 23


(V) Solution

(b) Selectivity of Breaker Flash over for One and Half Breaker system arrangement of Bus.

The One and half breaker arrangement is mainly having advantage of redundant connectivity for feeders. As shown in fig-7, the Phase current used for Breaker flash over can be referred from Main or Tie breaker CTs. The breaker flash over may occur for Main or Tie breaker during synchronizing or after isolation from Grid. So both the paths must be

separately detected for flash arc current i.e. Main and Tie breaker. The action required after detection of flashover are different as detailed below.

(1) MAIN Breaker flash over Tripping of Generator in Class-A

to trip excitation immediately and stop prime mover for any rise in voltage due to residual magnetism.

Open all bus breaker to isolate the affected breaker from grid.

(2) TIE Breaker flash over. Tripping of Generator in Class-A

to trip excitation immediately and stop prime mover for any rise in voltage due to residual magnetism.

Trip Main breaker of Line side. Send Direct Trip Transfer signal to

isolate source from remote end.

The logic described for Current detection as Iph-A-B-C in earlier paragraphs equally used separately for Main and Tie breaker. The CT input for Main and Tie paths are indicated in fig-7.

Two separate logics should be built as conveniently in bay IEDs like, BCU or back up relay with separate set of actions as described above.

Please note that the neutral current here and elsewhere in document is indicated from GT neutral, whereas can also be used as Negative sequence current of Generator Phase connection also.

The setting values shown here are from experienced values for a 660 MW Generator, however can be considered on typical machine behavior and normal operation.

TIE

Fig 7: Current detection for selectivity for One and Half Breaker arrangement for breaker flash over protection.

Line Feeder

Y

D

Main-Line

Main-Gen

G

Iph-TIE

Iph-MAIN G

IN

Annexure-IV

Page 6 of 23


(VI) CONCLUSION;

The breaker flash over phenomena is a very typical one to detect reliably and opt for action like isolation of bus and feeder at minimum possible time. Typical logic are offered by various manufacturer as indicated earlier, however use of reliable detection and output action is a part of scheme designing and adaption of philosophy.

Reliable detection and comprehensive logic is now very easy to be built in IEDs having numerous logical blocks, I/O configuration and even use of GOOSE signals for interlocking.

Breaker flash over protection must be used as a critical protection function particularly the locations like sea shore based or saline atmosphere surrounded installations, where chances of external flash over is higher. The lower flash arc current may also cause severe oscillation and asynchronous energisation may lead to damage to TG set or transformer.

Careful design should be carried out to handle flash over detection and isolation for one and Half breaker arrangement.

(VII) REFERENCES a. IEEE Guide for AC Generator

Protection: Std C37.102-1006, 4.7.1

b. Guide for Ac Generator Protection, ANSI/IEEEC 37.102-1995.

c. Application manual AREVA Micom P34x relay.

(VIII) Acknowledgement:

Author takes opportunity to express gratitude and special thanks to HOD of P&M Group of Adani Power Ltd., his guideline & knowledge, Adani Power Training & Research Institute, APL management for granting permission and inspiration to think and present this paper.

(IX) Author:

Sanjay U. Bhatt, working as DGM (Protection) at Adani Power Ltd, Ahmedabad, (Protection Automation & Metering Department), from January 2012.

B.E. (Electrical) -1993 from L.E. College Morvi , Gujarat (India).

Worked: o In G.S.F.C.-Jamnagar, as Ele.

Maintenance Engr. o In Govt. Polytechnic, as a lecturer on

clearing GPSC. o In GSECL, Gujarat as Junior Engineer

at Sikka Power station as Electrical Testing & Maintenance engineer and at SLDC during commissioning of SCADA and related system.

o As Deputy Engineer at GSECL corporate office as Testing engineer.

Annexure-IV

Page 7 of 23

External Flashover of Generator Circuit Breaker

in Coastal Power Plants having Air Insulated

Switchyard

Bishnu Prasanna Nanda and Pramod Kumar Saxena Adani Power Training and Research Institute, Ahmedabad, India

Email: {bp.nanda; pramod.saxena}@adani.com

Abstract—The breaker flashover can be either internal or

external. External flashover is mainly due to deposition on

the external surface of the contact housings. In case of

Power Stations in coastal areas, salt deposition takes place

because of saline atmospheric pollution. Breaker flashover is

an abnormal condition and may result in severe damage to

capital equipment like Generator and Generator

Transformer. Additionally it may also result in explosion of

Circuit Breakers which can damage nearby equipment in

Switchyard and put Substation personnel at risk.

Numerical relays used for Generator Protection have the

feature to detect breaker flashover condition and quickly

isolate the equipment. This paper describes such problems

at Mundra Thermal Power Plant in western coast of India

and also dwells upon the causes, protection philosophy,

preventive measures and recommendations.

Index Terms—flashover, an unintended electric arc,

creepage distance, shortest path between two conductive

parts measured along the surface of the insulation

I. INTRODUCTION

A. Brief Description of the Plant and the Problem

Adani Power Ltd is a Private Power Utility company in

India having currently installed capacity of 6600 MW in

three geographical locations and another 2640 MW is

under installation. Mundra Thermal Power Plant is

flagship plant of Adani Group having 4620 MW installed

capacity and located in west coast of Gujarat State, India.

The Power Station has 5 units of 660 MW and 4 units of

330 MW. Two units of 330 MW are connected to 220

KV and rest all units are connected to 400 KV grid.

The Power Plant is located 0.5 KM (Arial distance)

away from sea. Humidity remains 70% in day time and

80% in night. Both 220 KV and 400 KV Switchyard are

outdoor Air Insulated Switchyard (AIS) and the bus

arrangement is Double main and Transfer and one and

half breaker scheme respectively.

The Power Station has been experiencing failures of

string and suspension insulators because of salt coating

on external surface since 2009. The salt contamination in

Manuscript received May 10, 2013, revised September 8, 2013. This paper is property of APTRI and reproduction, use or disclosure

to third parties without express authority is strictly forbidden.

combination with dust because of proximity to sea lead to

decrease in withstand voltage and dry band formation

near cap & pin by high density of leakage current.

Erosion of porcelain insulators result due to increased

leakage current and finally it develops in to overall

flashover.

Tracking along the insulator surface and consequent

failures prompted the Power Station authorities to replace

all the porcelain insulators with Composite long rod

insulators and start hot line water washing on regular

basis. The ceramic insulators of equipment like CT, PT,

CB, Isolators etc. are part of equipment and hence can not

be replaced. However these insulators have been coated

with Room Temperature Vulcanizing (RTV) Silicone

Compound.

B. Incidence

On 30/06/2012, at about 04.22 Hrs, the 330 MW Unit-

4 was getting ready for synchronization with the grid

after a forced outage. The Turbine Generator (TG) set

was at 3000 rpm and the Generator isolator in switchyard

was in closed condition. As soon as the voltage was built

up to about 24 KV, external flashover took place across

the Y-Phase Generator Circuit Breaker contacts with

heavy sound and the insulator housing of the contact got

broken. The unit got tripped on actuation of Generator

Protection.

At the same time Local Breaker Backup (LBB)

Protection of 400 KV bus also operated and all the

breakers connected with the bus also got tripped.

II. OBSERVATIONS POST OCCURENCE

Photographs of the damage Breaker pole has been

placed below as Photograph-1 and Photograph-2.

Photograph-1: Damaged Breaker Pole

119

Journal of Automation and Control Engineering Vol. 2, No. 2, June 2014

doi: 10.12720/joace.2.2.119-123

Annexure-IV

Page 8 of 23

http://en.wikipedia.org/wiki/Vulcanizing

Photograph-2: Damaged Breaker Pole

The Disturbance Recorder (DR) chart of Generator

placed below as Fig. 1 clearly showed flashover of Y-

Phase CB. The current measured was 3.21 kA (RMS) and

4.63 kA (Peak).

Figure 1. Generator disturbance recorder chart

From the above observation and seeing the physical

condition of the Circuit Breaker, it was concluded that the

flashover in Y-Pole was due to external contamination in

saline atmosphere. Since the machine was ready for

synchronization, one side of the breaker was having grid

voltage and other side voltage i.e. machine voltage was

varying with respect to the grid voltage. Under such

condition, breakdown voltage was reached across the

breaker pole and flashover took place externally.

Similar flashover incidence has also been experienced

by Mundra Thermal Power Station previously in Unit-3

and Unit-7.

III. CAUSE OF BREAKER FLASHOVER

Flashover may occur across Generator Breaker

terminals during synchronization while the breaker is

open due to:

External flashover due to contamination

Internal flashover due to low dielectric pressure

High level of humidity

Frequently, only one phase of the breaker flashes over

during synchronizing procedures. In such case-

Power system suffers an undesirable out-of-step

and single-phase synchronization

Extensive damage to generators and step-up

transformers.

During synchronization process, the out-of-phase

voltage angle between contacts changes from 0 to 360

degrees continuously. Voltage across the breaker contacts

reaches its maximum instantaneous value when the angle

difference between the voltages is 180 degrees as shown

in Fig. 2 below-.

Figure 2. Voltage across breaker contacts

The voltage across breaker contacts before

synchronization (considering connection with 400 KV

Grid) -

Line voltage = 400 KV

Phase voltage = (400 /√3) = 231 KV

Peak value of Phase voltage =√2 x 231 = 327 KV

During out of phase condition, i.e. (voltage vectors 180

degree apart), net voltage across breaker contacts = 462

KV (RMS) and 654 KV (Peak)

This voltage may cause external or internal flashover

depending upon the breaker condition.

IV. METHODS FOR FLASHOVER PROTECTION

From the power system point of view, a flashover is a

fault which is not a ground or a phase-to-phase fault, but

a condition that resembles one phase of a breaker closed,

with a residual current much lower than a phase-to-

ground fault. A flashover can lead to a power oscillation.

Multifunction Numerical Generator Protection relays

have the function to detect both inadvertent energisation

and also breaker flashover condition. However standard

breaker-failure protections effective at detecting flashover

failure require an external trip signal from another

protection device to initiate the breaker failure. Relying

on an external trip prolongs the failure until line,

generator, or transformer protection trips.

The current flow during single phase CB flashover has

been shown below in Fig. 3.

120

Journal of Automation and Control Engineering Vol. 2, No. 2, June 2014Annexure-IV

Page 9 of 23

Figure 3. Current in case of single phase CB flashover

Following parameters can be used as inputs for

detecting breaker flashover and design protection scheme

for the same-

Phase currents

Residual current

Voltages from one or both sides of the breaker,

Breaker status auxiliary contacts (52a or 52b )

Close-signal monitoring or timers

Once the flashover is detected, all the breakers in the

bus must be tripped, as in a conventional breaker-failure

scheme. Security considerations are very important to

avoid mal-operations.

A. Method-1

Based on residual-current measurement and a breaker

auxiliary contact [52a- Normally open (NO) or 52b-

Normally closed (NC)] supervision. Logic for triggering

Breaker Failure scheme is shown in Fig. 4 below.

Flashover is detected and the bus is cleared if there

is residual current and the breaker is open.

Require timer to eliminate mismatching in time of

simultaneous closing of three phases.

Figure 4. Logic for initiating breaker failure scheme

B. Method- 2

Time Limits and Close-Signal Monitoring to Detect

Flashover is shown in Fig. 5 below.

Figure 5. Logic for Detection of Breaker Flashover

In order to operate this logic requires-

Phase current greater than set value and no current

five cycles before the start of the scheme.

Breaker auxiliary contact open.

No closing signal to breaker at least six cycles

before the start.

Allows scheme operation only if latch conditions occur

in the first five cycles after current flows in the breaker.

No mal-operation where a breaker auxiliary signal is lost

during normal operation with the breaker closed and

residual or phase currents present.

Method I would trip for this condition in case of

external fault. Timer is used to confirm the flashover

condition. The timer resets once current falls set value or

close signal appears or 52a indicates a closed indication.

Unbalanced currents associated with breaker head

flashover will generally cause the generator negative-

sequence relay to operate. This will initiate tripping of the

generator breaker(s), shutting down the generator and

providing the Breaker Failure Initiation (BFI) signal. The

Breaker Failure Logic will be initiated only if the breaker

failure current detectors are set with sufficient sensitivity

to detect the flashover current.

In case the current detectors are set higher than the

flashover current and breaker failure is not initiated, the

result may be catastrophic failure of the generator. The

key consideration for setting the breaker failure current

detector is to set it below the level of the current expected

for breaker-pole flashovers.

One approach used to speed the detection of a breaker

flashover is to modify the breaker failure scheme as

shown in Fig-6. An instantaneous overcurrent relay (50N)

is connected in the neutral of the generator step-up

transformer and is set to respond to an Extra High

Voltage (EHV) breaker pole flashover current. The relay

output is supervised by the generator breaker “52B” NC

contact providing an additional start to the breaker failure

scheme. When the generator breaker is open and one or

two poles of the breaker flash over, the resulting

transformer neutral current is detected by the 50N relay

without the delay that would be associated with a

negative sequence relay. The current detectors (CD)

associated with the generator breaker scheme must be set

with sufficient sensitivity to detect this flashover

condition.

Figure 6. Speedy detection of Breaker Flashover

V. PROTECTION PROVIDED IN MUNDRA UNITS FOR

BREAKER FLASHOVER

121


Page 10 of 23

A. Phase 1&2 Units

In Phase-1&2 the relay used for Generator Protection

is P344 of AREVA make. In this relay, detection of

Breaker flashover condition is by a neutral current

measuring element. The relay standby earth fault

protection element has been connected to measure the

transformer HV earth fault current and provide the

breaker flashover protection, via suitable scheme logic.

B. Phase 3&4 Units

In Phase-3 & 4, the Generator Protection Relay used is

RCS 985B of Nanjing NARI Relays, China make. In this

relay single phase and two phases flashover has been

considered but three-phase flashover is ignored.

Criterion of circuit breaker flashover:

Position contacts of three phases of circuit breaker

are open

Negative sequence current is higher than setting

Excitation has been applied to generator, and

generator voltage is higher than setting.

Operation of this protection will shut off excitation and

activate BFI Protection.

VI. PREVENTIVE MEASURES TO AVOID FLASHOVER

The saline pollution environment is prevalent in all

Coastal Power Stations. The degree of pollution may be

different at different places.

Probability of breaker internal flashover is highest in

SF6 type of breaker. However since external flashover is

due to contamination, it can take place in any type of

breaker. Following preventive measures need to be taken

to avoid external flashover:

Line isolators should be closed just prior to

voltage build-up and when machine is ready for

synchronization.

Generator Breakers used in coastal areas should be

designed with higher creepage distance (about 35

mm/ KV) or else use creep extenders.

Regular cleaning of the insulator (Hot line

washing with DM water) to avoid salt deposition.

Avoid synchronization when humidity is high.

In Mundra TPP, the activity listed in 1 & 4 of above

list is being done regularly. Additionally, HVCE (High

Voltage Creepage Extenders) are being procured for use.

High Voltage Wraparound Creepage Extenders are

designed for use in highly contaminated environments.

The wrap around type cold applied variant is retained in

place on the collar of the existing porcelain disc with the

help of pressure sensitive mastic. Typically application of

one extends nominal creepage distance of the existing

insulator by 100 mm. It is also quite imperative to note

that once 20% of the creepage is added with the help of

extender, pollution withstand ability of the original

insulator without creating electrical flashover enhances

by more than double. The extenders are designed to be

resistant to conventional spray washing techniques and

will withstand most normal handling, abuse, and extreme

weather conditions. Photograph-3 below shows a typical

bushing fitted with Wraparound Creepage extender.

Photograph-3: HV Wraparound Creepage Extender

VII. CONCLUSION

Generator tripping on account of Breaker Flashover

can be very disruptive and costly to the Power Utility.

Determining the cause of the tripping and assessing

equipment damage can take lot of time and consequent

delay in returning to normal operations.

Following are the recommendations:

Presently the cost of Gas Insulated Switchgear

(GIS) has come down and indoor GIS can be

considered. The author’s strongly recommended to

go for GIS in place of AIS in Coastal Power

Stations. The capital cost of Switchyard shall be

about 50% high, but the operating cost shall very

less and payback period is about 5 years.

It is critical to have good sequence-of-events and

oscillographic data to review protective relay

performance, assess fault levels and clear the

machine of any damage. Instead of relying on fault

recording feature of Numerical relays, dedicated

DR should be installed in all large capacity

Generators.

A dedicated breaker-flashover scheme is a must

for breakers used to synchronize Generators.

ACKNOWLEDGEMENT

The authors wish to thank the management of Adani

Power Ltd for granting permission to participate in this

Conference and present this paper.

The authors also thank the personnel of Adani Power

Training and Research Institute (APTRI) for their support

and help in submission of paper and registration.

REFERENCES

[1] Guide for Ac Generator Protection, ANSI/IEEEC 37.102-1995. [2] IEEE Tutorial on The Protection of Synchronous Generators,

IEEE 95TP102.

[3] AC High-Voltage Circuit Breakers Rated on A Symmetrical Current Basis—Preferred Ratings and Related Required

Capabilities, IEEE C37.06-1987. [4] IEEE Standard for AC High-Voltage Generator Circuit Breakers

Rated on A Symmetrical Current, IEEE C37.013-1993.

122


Page 11 of 23

[5] IEEE Standard Test Procedure for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis, IEEE C37.09-

1979.

[6] IEEE Guide for AC Generator Protection, IEEE C37.102-1987. [7] Evaluation of Methods for Breaker Flashover Protection, Ramón

Sandoval Comisión Federal de Electricidad Sinaloa, México.

Bishnu Prasanna Nanda has about 32 years’ experience in Indian Power sector and has worked

in both Public and Private Power utilities. He has

done B.Tech in Electrical Engg from National Institute of Technology, Raurkela, Odisha, India

in 1981. He has also done Advanced Diploma in Management from IGNOU, New Delhi. He has

been certified as Energy Auditor by Bureau of

Energy Efficiency, New Delhi, India. During his career spanning 32 years, he worked with NTPC Ltd for 27 years in various Project sites in

Operation & Maintenance wing. Since 2008, he is with Adani Group

and presently working as Vice President (Engineering).

Pramod Kumar Saxena has more than 28 years’

experience in Indian Power sector and has

worked in both Public and Private Power utilities. He has done B.E in Electrical Engg from

Government Engineering College Rewa Madhya Pradesh, India in 1984. During his career

spanning 28 years, he worked with NTPC Ltd for

20 years in various Project sites in Operation & Maintenance wing. Since 2008, he is with Adani

Group. Up to 2012 he worked in projects and commissioned 5 units of 660 MW at Mundra. Presently he is working as General Manager

(O&M) at Mundra TPP.

123


Page 12 of 23

PRACTICAL INTERLOCK LOGICS TO PREVENT UNDESIRED CIRCUIT BREAKER CLOSING, ISOLATOR OPENING & CHARGING OF BAY

IN SUB STATION USING IEDS

Sanjay U Bhatt, Protection, Automation and Metering Department

Adani Power Ltd, Ahmedabad E-mail: [email protected]

ABSTRACT Un desired charging of a bay / equipment when is ready to charge or immediately after getting isolated, due to accidental closing of circuit breaker or breaker flash over may result in severe undefined damage / loss to equipment / system stability / human loss, as well financial burden due to huge repairing cost and outage period till normalcy.

This paper describes practical interlock logics using IEDs for (1) controlling DC negative source to circuit breaker closing circuit and (2) Auto opening of Isolators after opening of circuit breaker.

KEYWORDS Circuit Breaker closing circuit logic, DC negative source breaking for CB closing, Isolator Auto opening logic, safety interlock for CB and isolator.

1. INTRODUCTION The essential element of a protection & control circuit design is to have inclusion of all engineering aspects for control, protection, monitoring & measurement having considerations for technical & operational limitations and capabilities of equipments, system and switchgear, operation possibilities & flexibilities with safety interlocking.

Fig. 1 is a typical such circuit conventionally used for a Circuit Breaker closing purpose.

Fig 1- Typical Closing circuit of a circuit

Accidental shorting of DC+ve to close CB

Annexure-IV

Page 13 of 23

The safety interlocking involves design of circuit in a controlled manner, by which ultimately actuates the operating mechanism of relevant circuit breaker / isolators / contactors / solenoids etc. for bridging primary connections to charge or operate the equipment. CASE-I In case of a circuit breaker for closing circuit interlock, the auxiliary supply (DC +ve or Phase) is extended from source to actuating point connection of closing coil of a circuit breaker through various permissive contacts ensuring healthy operating conditions, CB readiness, and absence of any abnormalities. The cables are routed through all relevant location of interlock contacts. DC –ve or Neutral is directly connected to other end of closing coil. A typical circuit is shown at Fig. 1.

The opening of isolator on load is also such kind of operation due to similar reasons indicated above.

CASE-II

In addition to the undue closing of circuit breaker, the undesired energizing of equipment (Transformer, Generator, Line etc.) may also happen in case of breaker flash over (internal or external) , particularly in case of Generator or two charged line from different sources, when going to synchronize or after isolated from grid. This is due to external insulation failure or arcing within breaker chamber, causing out of phase connection of two vector (peak to peak twice magnitude) causing severe oscillation and damage to equipment. The detection of breaker flash over reliably and isolation is still a serious concern especially in case of one and half breaker arrangement. Fig.2 shows a typical bay arrangement for a Generator with possible peak to peak voltage vector from Grid and Generator causing flash over. .

An automatic and comprehensive logic which can detect successful opening of breaker and initiate command to open the outgoing circuit isolator with flexibility of closing operation will be very useful to be secure against such wrong energisation of equipments

Fig 2- Typical One and Half CB arrangement possible breaker flash over due to peak to peak voltage across CB open contacts Breaker

Annexure-IV

Page 14 of 23

2 A CASE STUDY FOR GENERATOR BREAKER RECLOSING AFTER TRIPPING.

Recently at one of the large power plant the Generator Transformer Bushing of a phase failed which led to tripping of unit on operation of overall differential protection with tripping of both Main & Tie breaker. Due to heavy flash over and burning of insulation & oil, there was heavy fire and hot oil spread in nearby MK box & cable trench. This led to damage of all cables as shown in the pictures. After @10 Minutes the Main breaker got closed due to shorting of cable carrying DC+ve and return for closing. However the tripping command was persisting on operation of lockout relay hence tripping of breaker was taking place immediately on closing this sequence repeated multiple times and then stopped on blowing of main DC fuse.

Due to very short time closing, opening of B phase HV bushing of GT and residual rolling of turbine, nothing further damaged occurred.

Fig-3, indicates the control cables route for CB closing from switchyard kiosk to Generator Relay Panel and Synchronizer panel located at Main C/R. The cable trench route is passing near GT area where fire took place.

The detailed closing control circuit is shown at Fig-4.

It is therefore must to review the conventional closing circuit scheme for breaker & Isolator and cabling practices.

Fig 3- Showing location of Bay Kiosk, CB, GT and Main C/R with route of control cable.

Annexure-IV

Page 15 of 23

Due to fire cable damaged and shorted core to complete the closing circuit path for DC Positive return to Circuit Breaker Closing circuit.

Generator Relay Panel interlock for closing circuit

Synchronizing interlock for closing circuit and closing command from Main Control Room

CB cubicle at Switchyard

Control cables in cable trench from Switchyard to Main C/R

Interlocks

Figure-4- A Generator Breaker Closing circuit, event of closing control cable shorted resulting in undesired closing of circuit breaker Annexure-IV

Page 16 of 23

3. ISSUES WITH CONVENTIONAL CIRCUIT BREAKER CLOSING & ISOLATOR OPEN CIRCUIT.

Please refer case study mentioned earlier, where the breaker closing circuit philosophy used is conventional as described previously. The scheme is simple and being used everywhere.

Pl. refer Fig.1, and case study occurrence, it is seen that extension of DC +ve supply to closing coil terminal is the only deciding factor for closing operation of breaker and also opening sequence of isolator . Any undue extension of DC+ve to operating coil may lead to undesired operation of equipment. The undue extension of DC+ve to closing circuit/isolator opening circuit may happen due to (1) shorting of control cable carrying DC+ve and return path after permissive and command towards CB/Isolator, and (2) Simultaneous grounding of DC+ve system and terminal connected to CB closing / Isolator Open circuit. The sample case for CB are mentioned in following sections which will also apply to Isolator open circuit with due modifications.

4. SOLUTION TO BREAKER CLOSING DUE TO UNDESIRED SHORTING OF DC+VE.

The mishap due to above indicated DC+ve shorting can be avoided by breaking DC-ve immediately after closing CB and the same can be made through just before closing CB, command through SCADA/IED.

The simple solution is to switch OFF the closing supply immediately after closing CB and make ON when required to close. The same can be made by breaking DC +ve as well with the method described here. However this may involve addition of circuits and contacts for +ve at DC source also, with simultaneous operation of contacts on both sides, adding more complexity and online monitoring of closing circuit also is not possible. So for our purpose DC-ve breaking scheme is sufficient.

.

Existing Closing Circuit

Close Guard I/P

Fig. 5a- Closing circuit DC Negative breaking with CMR operated from Logical operation of IED / circuit. CMR placed at Breaker MK box.

Fig. 5b- Closing circuit DC Negative breaking with Output of IED / Logical circuit scheme placed at Control panel

Digital / Analogue Interlock I/O

Digital / Analogue Interlock I/O

Annexure-IV

Page 17 of 23

Fig. 5a and 5b above indicate the methods of breaking DC-ve using logical operation performed from numerical IEDs or such circuit from conventional relay, contactor, timers etc.

A simple way of breaking DC-ve is to route it from Master trip relay contacts where DC+ve for closing permissive is also routed.

However in case of manual opening or isolation Master Trip relay may not operate or can be reset after tripping for further interlocks and operations in a Generating Station. So it is also not covering complete risk.

In method 5a the CMR (Contact Multiplier Relay) placed in CB MK box is used to isolate the DC –ve. The CMR is operated by a separate DC/AC source from IED/ Logical device. As shown the CMR energizing supply is also wired from two separate contacts from IED at C&R panel. This will ensure complete secured operation of CMR even in case of the cable damage for CMR.

In method 5b the DC-ve is routed through contacts of IEDs/Device placed at Kiosk in Switchyard interfaced with SCADA.

Method 5a is the most appropriate one for all cases due to secured operation of CMR placed very near to CB closing circuit in MK box.

The CMR method should be used where there is no S/Y Kiosk near to CB and C&R panels are located at Main C/R directly connected with CB for control.

All above method should ensure secure operation with flexibility to operator and monitoring feedback. It should also supervise the shorting of cable or undue extension of DC+ve in closing circuit by guarding method.

5. LOGIC FOR BREAKING DC-VE USING IEDs & SCADA.

A practical logic using IEDs and SCADA interface implemented at the power station where the undesired closing of Generator Breaker happened as referred in case study is shown here at Fig. 6a and 6b.

Explanation of the logic:

Please refer Fig 6a, where a concept circuit is shown for placing of IED /CMR contact in the Negative terminal of closing coil (CC). The Guard input from DC+ve circuit is connected before CB auxiliary switch contact which is closed when breaker is OPEN or immediately after closing contact circuit. The guard input turns in high state when Close command is extended or any undue positive is extended in close circuit.

Please refer Fig 6b, the main logic part which can be built in IED (Relay/Bay Control Unit BCU / RTU having required logical blocks with IEC61850 accepting GOOSE signal and hard wired Binary I/O signal from scheme wiring and interfacing with local SCADA. This is generally available now with all IEDs installed in a switchyard.

The logic uses RS Flip Flop block having reset priority for latching output OPEN / CLOSE. The Flip Flop get reset and breaking DC-ve when

Circuit Breaker is closed successfully. Lock out / Master trip relay operated. Circuit Breaker Pole Discrepancy Relay

(PDR) operated. Circuit Breaker closeing permissive interlock

NOT OK. Negative Bypass command from Switchyard

SCADA is given for Manual Bypass purpose.

All above condition will cause Flip Flop to reset and opening of contact to break DC-ve.

Annexure-IV

Page 18 of 23

52b

CC

Various external interlocks / commands

Breaker MK / Control Box

IED/ CMR Contact

DC ‐ve

DC +ve

CB CLOSE (Except Line Bay)

CB-PDR Operated

Lock out relay Operated

RESET

SET

OUT

+ve Guard input High

‘CLOSE circuit through command’ (Pulse) from OWS

RS Flip-flop

IED Contacts to

operate CMR or to

DC‐ve circuit of CB

as per scheme

adopted.

Guard BI of BCU / IED

200 ms

NOTE: The logic can be built in IED (Relay/Bay Control Unit BCU / RTU having required logical blocks with

IEC61850 accepting GOOSE signal and hard wired Binary I/O signal from scheme wiring and interfacing with local SCADA. This is generally available now with all IEDs installed in a switchyard.

Necessary wiring / GOOSE configuration should be worked out for I/O as per logic. ‘The Close circuit through command’ from OWS (Operator Work Station of SCADA) to extend DC-ve for

manual close should be initiated before closing of breaker so that –ve circuit to closing coil will be extended. In case of any unwanted DC +ve extension in closing circuit will be monitored by Guard circuit and will not

allow the flip flop to set to extend DC –ve to closing coil. Which is monitored in SCADA also. The Guard timing is considered as 200 mS allowing closing of breaker normally. The above circuit can also be used for isolator control circuit with modification in input logic and other

interlocks.

Manual Reset (Pulse) from OWS

CB closing permissive OK

Interlock status feedback to SCADA / OWS

Fig 6b - Logic for DC-ve breaking for Circuit Breaker Closing circuit

Fig-6a- Concept Circuit for Breaker Closing circuit

Breaker Aux. contact

Annexure-IV

Page 19 of 23

The Flip Flop will be set to drive BO to extend DC-ve under following condition.

Though manual command from OWS (SCADA) when it is really required to close breaker, if the DC Guard input is NOT High more than 200 mSec.

Immediately after closing of CB the Flip Flop will get reset breaking DC-ve till a manual intervention is made which should be done just before closing the breaker. In case of line after closing of breaker to allow Auto Reclosure operation DC-ve is not being broken, however except in case of three phase tripping.

Further it is also important to have wire cores for DC +ve source of closing circuit going to external wiring and return from CB MK should be in different cable and not in same cable.

Above logic has been implemented and proven well working taking care for all possible abnormalities. The same can also be used to take care for undue opening of Isolator with some modification of logic such as the phase and neutral (OR DC +ve and –ve) will be extended simultaneous when any open command generated from valid open sequence and other interlocks.

Snap of logic and control built in SCADA database is mentioned as under for a Generator Circuit Breaker.

Annexure-IV

Page 20 of 23

6. LOGIC FOR AUTOMATIC OPENING

OF ISOLATOR AFTER TRIPPING OF CIRCUIT BREAKER.

It is well known that an Isolator is OFF Load and Circuit Breaker is ON Load circuit breaking equipments. Opening of an Isolator on load will lead to a severe damage to equipment and human also. Due to this reason to avoid accidental opening of isolator a routine practice is being adopted for an isolator, to switch OFF isolator Driving Motor supply after closing electrically or manually. However in case of ABCB earlier, due to risk of getting closing of circuit Breaker on low air pressure automatic opening of isolators on immediate opening of CB was used using hard wired CB status based logic. Now days all isolators are remotely operated from SCADA and also with concept of unmanned S/S the Isolators are kept ready to operate with all auxiliary sources in service. With this arrangement it is must for isolator to have DC-ve and also automatic opening of isolator breaking logic schemes.

Please refer Section 2 Case-II and case study of occurrence, the reclosing of Circuit Breaker due to any reason or flash over subsequent to opening of breaker or before synchronizing will defiantly damage the equipment connected. In the referred case, the immediate opening of circuit (Line) isolator on opening of CB would have saved the impact on Transformer and Generator, if so designed in the scheme. The manual opening of isolator immediately after tripping of CB is also not expected due to human action.

The logic implemented at Sub station referred earlier is mentioned at Fig 7 & 8 using Bay Control Unit, GOOSE signal for status / Analogue signal over IEC 61850.

The output of Auto OPEN Logic is configured with same output of the existing logic for OOPEN sequence of isolator taking status and feedback as per logic.

Explanation of the logic:

Please refer Fig. 8, the Auto Open sequence will be initiated after proposed time delay of 5 sec, when (i) Under current relay picks up AND (ii) Main Breaker is not CLOSED AND (iii) TIE Breaker is not CLOSED AND (iv) Isolator closed status is high. For secure operation the interlock of load current and breaker status has been incorporated. The Auto open sequence will be automatically latched for next operation when (1) Under current relay resets OR (ii) Main Breaker CLOSED OR (iii) Tie Breaker CLOSED, after a proposed time delay of 5 sec. The next closing sequence will be initiated by Manual command from SCADA OWS for SET command to the RS Flip-Flop, and when it is set will allow manual CLOSE sequence to operate making the operation more secure and enhancing the CLOSE logic also.

Again after opening of breaker and sensing of under-current will allow Auto opening of isolator as per logic.

The implemented logic screen snap is also indicated at Fig-9.

Existing CLOSE sequence

Existing OPEN sequence

AUTO OPEN Logic

BCU Output for Isolator OPEN & CLOSE

SCADA interface

Annexure-IV

Page 21 of 23

Fig 8 - Logic for Auto open of Isolator after opening of Circuit Breaker

&

I<1 Under Current

Main Breaker CLOSE

TIE Breaker CLOSE

Isolator CLOSE status

Manual SET

(Pulse) from OWS

Timer OPEN

Command

to Isolator

RESET

OUT

O

R

SET

To Isolator CLOSE logic interlock

to ensure SET condition of Auto

Open sequence

& Existing LOGIC for

Isolator CLOSE command

CLOSEE

Command to

Isolator

T

5 S

NOTE: Manual SET command from OWS SCADA should be SET before Closing of Isolator. The Logic is built in BCU and connected with existing OPEN command of isolator. Manual Set command latch O/P from flip flop is interlocked with Existing Logic for Isolator Closing Required modification & configuration of relevant relay for under current setting and Logic should be worked out. Timing for Auto Open Isolator may be set at 5 second after opening of CB.

Fig 9 – Implemented Logic for Auto open of Isolator after opening of Circuit Breaker

Annexure-IV

Page 22 of 23

7. CONCLUSION

The described engineering practice should be implemented as a standard scheme for operation of Circuit Breaker and Isolators looking to secure operation of primary switching.

Because numbers of incidences are being occurred on account of damaged cables or DC- grounding or mal-operation even during fault finding or testing of control wiring. The use of latest technology or equipment without reliable operating mechanism is waiting for a disaster always.

Availability of Numerical technological IEDs and GOOSE signals over IEC61850 protocol with SCADA has made the task very easy and secure.

(1) Circuit Breaker Closing circuit should be equipped with DC-ve breaking as near as possible to Closing Coil with Contact Multiplying relay / IED (Relay) contact with secured logic, control and monitoring facility in SCADA.

(2) Isolator OPEN circuit should also be equipped with similar above scheme logic indicated at (1).

(3) Circuit (Line) Isolator should be automatically opened immediately after tripping /Opening of CB/s. The logic should be secured enough to ensure complete OFF Loading of circuit and also with no confliction with CLOSE sequence operation.

(4) The control cables carrying DC-ve from CB / Isolator and to IED/Relay at C&R panel should be in different cable, preferably separate route to avoid any possibility of malfunction of the above discussed circuit itself.

(5) All the input / output and logical status should be configured in event of IED and SCADA for future analysis on event of occurrence.

(6) The new specification for C&R panel and scheme should be included with above said requirements.

REFERENCES:

(1) Various schemes drawing for different substations.

(2) AREVA make application manuals on BCU MICOM C264 /EN/AP/ C30, PACIS Operation Interface for Automation and other IEDs

(3) ABB make application manuals on 670 series IEDs.

AUTHOR:

.

.

.

Sanjay U. Bhatt, working as DGM (Protection) at Adani Power Ltd, Ahmedabad, (Protection Automation & Metering Department), from January 2012.

B.E. (Electrical) -1993 from L.E. College Morvi , Gujarat (India). Worked: In G.S.F.C.-Jamnagar, as Ele. Maintenance Engr. In Govt. Polytechnic, as a lecturer on clearing GPSC. In GSECL as Junior Engineer at Sikka Power station as Electrical Testing & Maintenance engineer and at SLDC during commissioning of SCADA and related system. As Deputy Engineer at GSECL corporate office as Testing engineer.

Annexure-IV

Page 23 of 23

Latest status of implementation of recommendations of PSAG-3 for

the Gird incident occurred at SGS on 18.08.2013

S.N.

Recommendations

KPCL’s Compliances

a Disturbance Recorder facility LOA issued to M/s Alstom T&D India Ltd., Chennai for Supply & Erection of Disturbance Recorder & GPS on 26.06.2015. During Fire accident on 18.2.2016 at SGS, all the equipment and panels placed in control room - control, relay, protection, metering panels, cable duct, cables, air conditioning system, fire detection system, etc., have been burnt completely. Hence, Re-engineering work to suit the upcoming DCS system at site, is in progress.

b Providing GPS (Time synchronization) facility

c To replace both bus sectionalizing BOCBs with new circuit breakers

LOA issued on 12.12.2014 to M/s ABB India Ltd., Bangalore. Supply and Erection of both the Breakers completed. Commissioning will be taken up along with commissioning of Sectionaliser panels from new Bay Control Rooms.

Annexure-V

S.N Commitee observations KPCL Compliance

5

KPCL shall take action to arrange for GPS time

synchronisation of all EL's and provide DR for all

lines.

Completed.

6KPCL shall take action for retrofitting of all old

electromagnetic relays with numerical relays.

Retrofitting electromechanical relays with Numerical version relays completed for

all 400kV lines.

Work Order placed on 26.06.2015 for retrofitting of relays for all 220kV lines at

RTPS. Commissiong of relays completed for Lines: Lingasugur -1,2 &3, raichur-1 &2,

Sedam 1 &2. Erection is in progress for Shahpur 1 & 2 Lines.

Obtained the Budgetary offer for retrofitting the electromechanical relays of

existing bus bar protection with numerical version and is under process.

12Recommondations of protection Audit conducted

on 02.11.2012 shall be carried out.

All Recommondations of protection Audit are being implemented in both 220kV &

400kV RTPS station except that the erection of Numerical relays is in progress for

Shahpur 1 & 2 Lines . The latest status of activities in phase-1 & phase-2 are

updated on bimonthly basis.

COMPLIANCES FOR THE RECOMMENDATIONS OF SPECIAL PROTECTION ANALYSIS GROUP COMMITTEE (SPAG-6) DURING THEIR VISIT TO RTPS

ON 05.02.2014.

Annexure-VI

1

The PSAG-10 members recommended to replace the Main I (Q21 static

Quadramho relay -SHPM 101) distance protection relays with Numerical relays

having DR and EL features.

LOA’s issued on 08.10.2015. Inspection of relays completed

and received at site. DI issued for all balance materials

except furnitures.

2The PSAG group also advised KPCL to test the Main II Relay (PZ1000

numerical relay) at the earliest .

Completed.

3

The PSAG group recommended to have a uniform Zone II time settings as

agreed in the Tripartite meeting of KPCL, KPTCL and Kaiga (NPCIL) held during

11th& 12th of December, 2013) in the Kaiga – Kali Complex.

Completed.

4

The Resistive reach of distance protection relay of Kadra – Kodasalli (both

ends), Kadra – Karwar I, Kadra – Karwar II (Kadra end), Kodasalli – Nagjheri I,

Kodasalli – Nagjheri II (both ends) lines to be increased so as to operate on high

resistance faults within the permissible limits . Since the present settings are

prone to under reach and initiating unwanted tripping at the their locations,

PSAG has recommended to suitably increase the resistive reach of all the lines.

PSAG advised KPCL to revise the settings at the earliest.

Completed.

5

PSAG recommended to make the carrier aided protection functional for 220kV

Kadra-Kodasalli, 220kV Kadra-Kaiga and 220kV Kodasalli-Kaiga lines. In

addition, since most of the faults are seen as high resistance fault, PSAG

suggested to revise the existing PUR to POR scheme for all the lines at Kali

complex.



except furnitures.

6

The PSAG group noted that most of the faults were in the ‘B’ Phase (of RYB) to

ground faults. The group observed that it may be due to thick vegetation below

Kadra – Kodasalli, Kodasalli - Kaiga line, Kadra – Kaiga line. Hence the PSAG

group members advised to have regular thorough line patrolling and clearing the

corridor (i.e. Right Of Way).

To be implemented by KPTCL

Compliance to recommendations of Meeting of Protection system Analysis Group (PSAG-10) at Kadra, Kodasalli and

Kaiga held on 12th & 13th November 2014 for discussing the Grid Disturbances occurred on 26.09.2014 and 05.10.2014

Sl. No. Recommendations KPCL Compliances

Page 1 of 2

Annexure-VII

Sl. No. Recommendations KPCL Compliances

7

PSAG had recommended to have a uniform setting for the backup earth fault

protection (67N) provided through distance relay (i.e PZ1000) and separate

back up earth fault relay (CDD21 of English Electric, electro mechanical)

immediately.

Completed.

8The PSAG group advised to disable the phase over current protection in

distance relays (i.e PZ1000 of CSPC make) immediatelyCompleted.

9

KPCL informed that installation of GPS for time synchronization of all relays and

other protection devices is under process. KPCL is requested to expedite the

same.



except furnitures.

10

It is suggested to check timings (opening and closing) on Kadra line CB test at

Kodasalli station periodically and the record of checking to be maintained in the

substation

Completed.

11

It was observed that Kodasalli – Nagjheri I & II lines were kept open at Nagjheri

end on 26.09.2014, 5.10.2014 & 14.10.2014 during bus dead conditions at

Kodasalli station. KPTCL (SLDC) is requested to clarify /review the issue

To be implemented by KPTCL/SLDC

12The DR and EL data of the line/unit tripping shall be made available for analysis

at station level / SLDC /SRLDC/SRPC level.Noted

Page 2 of 2

Annexure-VII

S.N Commitee observations KPCL Compliance

1 To check the REF scheme during next shut down

for GT of Unit -7 at RTPS

Completed.

2 To take up with OEM and check the configuration

for auto reclose in relay at RTPS end as block for

auto reclose should not initiate with fuse fail On/

Start

The PSL, Event, DR & settings files extracted from the relay have

been sent to OEM for checking & reviewing. Settings received &

have been loaded in to the relay.

3 To simulate the sequence of event for relays

which trigger Class-B master relay and also check

up the pick-up voltage of Class-B Master trip relay

of Unit-5 at RTPS.

The same was checked and found to be order.

COMPLIANCES FOR THE RECOMMENDATIONS OF SPECIAL PROTECTION ANALYSIS GROUP COMMITTEE (PSAG- 13) DURING

THEIR VISIT TO RTPS ON 23.04.2015

Annexure-VIII

Mee

ting

No /

Inde

x

Details of

Event

Date Reason PCSC Recommendations Utility

Responsible

for

implementatio

n

Status of Recommendations

as on

Remark

s

Pending Implementation of PCSC Recommendations (30th to 53rd)

Karnataka

Annexure-IX

Page 1 of 12

Pending Mail recieved on 28-05-2015:

1. e- Tender folated for the retrofit of existing static relays with

Numerical version for lines M.nagar,M.bad,ICT-1 & 2 -Technical Bid &

Price bid opened . Bid evaluation and approval to place P.O. is in

progress.

2. Retrofit of existing bus bar (CAG-34) with numerical version -

Budgetetory offers obtained and is in process.

3. Order placed on M/s Siemens to replace relays. The work will be

Completed by May - 2015.

Mail recieved on 07-07-2015:

1. Retrofit of existing static relays with Numerical version for lines

M.nagar, M.bad and ICT- 1 & 2 -- Inspection of the Numerical relays at

M/s Siemens works completed on 11-06-2015 and Dispatch clearance has

been issued. Materials received.

2. Retrofit of existing bus bar (CAG-34) with numerical version –

Budgetary offers obtained and is under process.


1. Replacement of Old electromagnetic relays with Numerical relays has

been completed for RTPS-BTPS line & commissioned on 18.03.2014.

Raichur-PG1 & Raichur-PG2 lines have already retrofitted with

numerical relays.

The retrofitting of electromechanical relays with Numerical version for

ICT-1, ICT-2 and Munirabad line has been completed.

Retrofitting work for Mehaboobnagar line is pending. Awaiting for line

shutdown.

2. Job order placed on 26.06.2015 on M/s Alstom T&D India Ltd.

Chennai for retrofitting of relays for all 220kV lines at RTPS.

3. Retrofit of existing bus bar(CAG-34) with numerical version–


Mail recieved on 21-10-2015 and 23-11-2015:

1) Replacement of Old electromagnetic relays with Numerical relays has

been completed for RTPS-BTPS line & commissioned on 18.03.2014.

Raichur-PG1 & Raichur-PG2 lines have already retrofitted with

numerical relays.

The retrofitting of electromechanical relays with Numerical version for

the following lines/ICTs have been completed/commissioned as follows:

a) ICT-2 –Commissioned on 01-08-2015

b) ICT-1 ---Commissioned on 08-08-2015

c) Munirabad line--- Commissioned on 16-08-2015.

d) Mehaboobnagar line-- Commissioned on 09-09-2015.

2. Job order placed on 26.06.2015 on M/s Alstom T&D India Ltd.

Chennai for retrofitting of relays for all 220kV lines at RTPS.

3. Retrofit of existing bus bar(CAG-34) with numerical version–


RTPS

Tripping

incidents and

the Spl

meeting held

at RTPS on

13th and 14th

March 2014

30/I/

A

KPCLThe PCSC forum recommended for replacement of existing

electromechanical relays with Numerical relays. Spl meeting held at RTPS on 13

th and 14

th

March 2014

Mar-14

Annexure-IX

Page 2 of 12


1) e-NIT floated on 28.07.2014 for procurement of Numerical distance

relays & GPS. As there is change in scope of work and quantity of relays

by more than 25%, which is not permitted as per KTPP act. Hence, tender

cancelled and refloated on 05.05.2015 with revised scope of work and

revised PQR.

2. However, as per the recommendations of PSAG, Relays were

temporarily rearranged, replaced and wired up. testing & commissioning

shall be completed with the assistance of KPTCL.


1. Cover -1 of the bid is scheduled for open eing on 25.06.2015.

2. As per the recommendations of PSAG, Relays were temporarily

rearranged. testing & commissioning completed with the assistance of

KPTCL.


NIT floated on 5.5.15 through e-portal. Bid evaluation completed.

Obtaining of Administration approval to place P.O is in progress.

However, as per therecommendationsof PSAG-10, Relays

weretemporarilyrearranged.Testing & commissioning completed with the

assistanceofKPTCL.


NIT floated on 5.5.15 through e-portal. Bid evaluation completed. LOA's

issued to M/s Schneider Electric Infrastructure Ltd. on 08.10.2015.


LOA's issued to M/s Schneider Electric Infrastructure Ltd. on 08.10.2015.

Engineering work is in progress.

Status informed during Special Meeting held on 03.06.2016:

LOA’s issued to M/s Schneider on 08.10.2015. Inspection of relays

completed and received at site. DI issued for all balance materials except

furnitures.

KPCL1. The PCSC forum requested KPCL to speed up the installation

of Numerical Distance Protection relay in Kadra –Kaiga and

Kodasalli –Kaiga.

2. The PCSC forum requested KPCL to submit the implementation

status of PSAG-10 recommendations within a week’s time.

A fault had occurred in 220 kV Kadra and

Kodasalli. As A result, de-energization of

220kV bus occurred at Kadra and

Kodasalli.

13-11-2014

at 19:31hrs

Mail received on 27-05-2015 (KPTCL) & 29-07-2015:

1.Existing Back up relays will be replaced by numerical type distance

relays.Procurement is in tendering stage. Remaining observations were

attended.

KPTCL Mail recieved on 23-01-2016:

Existing back up relays will be replaced by Main-2 protection. LOI issued

M/s Alstom for taking up the works.Remaining observations were

attended.

KPTCL Mail Recieved dated 25-05-2016:

Under the Scope of R&U. The work will be taken up by M/s Alstom

shortly.

KPTCL1. PCSC forum recommended KPTCL to replace the old static

distance protection relays with numerical relays.

2. PCSC forum also requested KPTCL to provide a broken

conductor alarm indication in Control Room.

3. Standing instruction needed to be given to the all substation

personnel for not changing the relay settings without approval of

RT/MRT wing.

Fault had occurred in 220kV

Mahalingapura-Narendra line-2. Due to

the

failure of relay operation at

Mahalingapura,

breakers at remote end tripped which

resulted in bus dead condition.

25-10-2014GD-1 at

Mahalingapur

a Substation

of KPTCL

38/G

D/3.1

Pending

Mail recieved on 27-05-2015 (KPTCL):

1. KPTCL has taken action to provide bus bar protection to 220kV buses.

2. Over current relay Settings of ICTs to be reviewed by PGCIL.

Mail received on 29-07-2015 (KPTCL):

Initial Tendering stage


Detailed estimate prepared for taking up the work. CEE, Transmission

Zone, Gulbarga will take up necessary procurement and further

execution.

1. Bus bar protection shall be provided by asset owner ( i.e

KPTCL).

2. Settings for main distance protection & Overcurrent

protection shall be examined and reviewed.

3. Time synchronization of the Substation shall be ensured.

4. Correct DR shall be submitted to the SRLDC for trip analysis.

Pending

400/220 kV

ICT-1 & 2 at

MUNIRABA

D

34/I/6 As reported directional over current relay

of ICT’s operated due to snapping of

line jumper in 220kV Lingapur line.

16-07-2014 PendingKPTCL

GD-1 at

Kadra and

Kodasalli

hydro power

station

38/G

D/3.5

Annexure-IX

Page 3 of 12

Circuit breaker of 400kV Guttur-Hiriyur

line-1 failed at Guttur end while availing

shutdown for replacement of CVT. The

failure of breaker caused bus fault at

Guttur.

05-11-2014

at 11:42 hrs

GD-1 at

Guttur

Substation of

KPTCL

38/G

D/3.2


1.Existing Back up relays will be replaced by numerical type distance

relays.Procurement is in tendering stage. Remaining observations were

attended.


Existing back up relays will be replaced by Main-2 protection. LOI issued

M/s Alstom for taking up the works.Remaining observations were

attended.


Under the Scope of R&U. The work will be taken up by M/s Alstom

shortly.

KPTCL1. PCSC forum recommended KPTCL to replace the old static

distance protection relays with numerical relays.

2. PCSC forum also requested KPTCL to provide a broken

conductor alarm indication in Control Room.

3. Standing instruction needed to be given to the all substation

personnel for not changing the relay settings without approval of

RT/MRT wing.

Fault had occurred in 220kV

Mahalingapura-Narendra line-2. Due to

the

failure of relay operation at

Mahalingapura,

breakers at remote end tripped which

resulted in bus dead condition.

25-10-2014GD-1 at

Mahalingapur

a Substation

of KPTCL

38/G

D/3.1

PendingKPTCLKPTCL was requested to expedite the early implementation of

pending recommendations of:

1. Protection Audit (Phase-I & Phase-II)

2. PSAG-4, PSAG-5, and PSAG-8

Pending

Mail received on 27-05-2015 & 29-07-2015:

Latest satus of implementatin of Phase-1 &2 recommendations, PSAG

4,5 and 8 is being obtained from field. The Status will be updated witin a

weeks time.

KPTCL mail received on 23-01-2016:

'The following works are attended at 400kV Guttur SS :

1. Replacement of Hiriyur-1 line, Bus Coupler, Tie Bus coupler breakers

by new Alstom make breakers (3 new CBs commissioned) recently.

2. New CVTs provided for 400kV Hiriyur line-1 and commissioned on

21.01.2016


The following works are attended at 400kV Guttur SS :

1. Replacement of Hiriyur-1 line, Bus Coupler, Tie Bus coupler breakers

by new Alstom make breakers (3 new CBs commissioned) recently.

2. New CVTs provided for 400kV Hiriyur line-1 and commissioned on

21.01.2016.

3) Remaining works planned under R&U will be taken up by M/s

Alstom shortly.

39/I/5 Pending

Mail received on 28-04-2015:

1. In view of operating 220kV Ambewadi SS in split bus mode, action is

being taken up by KPTCL . Problem in the 220kV bus coupler breaker is

attended and isolator overhauling work is under progress. Spilt bus

operation at Ambewadi will be made possible at the earliest.

2. ICT protection system at Ambewadi and trippings occured at Supa GS

during the instance is checked up and remedial measures already

furnished in this regard.


Action is being taken by KPTCL for operating Ambewadi in split bus

mode. Problem in bus coupler breaker is attended.Isolator overhaulling

work is completed.PTs are already provided to 220kV Bus-II. After

commissioning of Bus-II PTs, Ambewadi can be operated in split bus

mode. Pending works will be completed within a months time.

KPTCL mail recieved on 23-01-2016:

Bus-II PTs yet to be commissioned.Planned to complete before end of

April-2016.

Pending1. Till the completion of R&M works for bus bar and LBB

protection, KPTCL shall explore the possibility of having split

bus operation at Ambewadi and submit the details of the same to

PCSC forum.

2. KPTCL shall provide the details of the tripping of Supa hydro

station connected downstream from 110 kV bus.

KPTCLTriggering incident was B-phase to earth

fault in 220kV Ambewadi- Nagzari line-1.

B-pole of breaker did not open at

Ambewadi end. LBB protection not

available at Ambewadi end. All elements

tripped on Zone-2 from remote ends.

22-12-2014

at 21:22 hrs

GD-1 at

220kV

Ambewadi

Station of

KPTCL

40/I/1

Mail received on 27-05-2015 & 29-07-2015:

C&R panels of 500MVA ICT 1&2 will be replaced under scheduled

R&M works. O&M personnel are instructed to take sufficient care in

order to avoid unwarrented trippings.


New C&R panels(with numerical relays) erected for 500MVA ICT-1 &2

under R&M work, which will be commissioned shortly.


New C&R panels(with numerical relays) erected for 500MVA ICT-1 &2

under R&M work, which will be commissioned shortly.

KPTCL1. PCSC forum recommended KPTCL to replace the relay with a

different make.

2. KPTCL was also requested to train the O&M personnel

adequately before performing any maintenance works to avoid such

unwanted trippings.

Suspected mal-operation of 220kV side

Rphase

over current relay

01-12-2014Tripping of

400/220kV

ICT-2 at

Hoody

substation of

KPTCL

Annexure-IX

Page 4 of 12

Line tripped on Yphase to earth fault from

both the ends

20-12-2014

at 22:20 hrs

220kV Sedam-

Tandur line

40/IV

/1


1. Procurement of Bus bar and LBB protection is in the final tendering

stage. 2. Action is being taken to restore the carrier protection for

220kV Sedam-Tandoor line. AR will be enabled.



stage.

2. Action is being taken to restore the carrier protection for 220kV

Sedam-Tandoor line. AR will be enabled after restoration of PLCC.


1. Bus bar protection panels pocured and erected at Sedam. Wiring ,

testing ,commissioning is being taken up.Planned to complete by April

2016.



PendingKPTCL 1. KPTCL to provide Bus bar and LBB protections for 220 kV

bus at Sedam S/s.

2. KPTCL to implement A/R feature on 220 kV Sedam-Tandur

inter-state line.

R-Phase to ground fault occurred on

220kV Sedam-Shahpur line. Fault not

cleared from Sedam end due to stuck-

breaker condition. While the Sedam-

Sahapur line tripped from Shahapur end in

Zone-1, the other 220 kv lines from Sedam

tripped at remote ends in Zone-2. This

caused complete outage of 220kV Sedam

substation.

27-01-2015

at 8.00 hrs

Complete

outage at

220kV Sedam

Substation of

KPTCL (GD-

1)

41/I/4


Carrier protection is being restored for 220kV Sedam-Tandoor line at

Sedam end. After restoring the carrier protection , AR will be enabled.


Carrier protection is being restored for 220kV Sedam-Tandoor line at

Sedam end. After restoring the carrier protection , AR will be enabled.


SEE,SCADA to update the latest status

KPTCLKPTCL was requested to explore the possibility of providing A/R

feature to this line and submit the remedial measures to the PCSC

forum.

Pending


1. In view of operating 220kV Ambewadi SS in split bus mode, action is

being taken up by KPTCL . Problem in the 220kV bus coupler breaker is

attended and isolator overhauling work is under progress. Spilt bus

operation at Ambewadi will be made possible at the earliest.

2. ICT protection system at Ambewadi and trippings occured at Supa GS

during the instance is checked up and remedial measures already

furnished in this regard.


Action is being taken by KPTCL for operating Ambewadi in split bus

mode. Problem in bus coupler breaker is attended.Isolator overhaulling

work is completed.PTs are already provided to 220kV Bus-II. After

commissioning of Bus-II PTs, Ambewadi can be operated in split bus

mode. Pending works will be completed within a months time.


Bus-II PTs yet to be commissioned.Planned to complete before end of

April-2016.

Pending1. Till the completion of R&M works for bus bar and LBB

protection, KPTCL shall explore the possibility of having split

bus operation at Ambewadi and submit the details of the same to

PCSC forum.

2. KPTCL shall provide the details of the tripping of Supa hydro

station connected downstream from 110 kV bus.

KPTCLTriggering incident was B-phase to earth

fault in 220kV Ambewadi- Nagzari line-1.

B-pole of breaker did not open at

Ambewadi end. LBB protection not

available at Ambewadi end. All elements

tripped on Zone-2 from remote ends.

22-12-2014

at 21:22 hrs

GD-1 at

220kV

Ambewadi

Station of

KPTCL

40/I/1

GD-1 at

220kV Kadra

power Station

of KPCL

16-02-2015

at 12:56 hrs

KPCL Mail received on 28-05-2015:

1. Main-2 relays already installed and commissioned.

2. DC fuses are intact. Till date no such incidence occurred.

3. Possibility of DC-1 & DC-2 arrangement and splitting of DC will be

reviewed.

Mail received on 07-07-2015 , 21-10-2015 and 23-11-2015:

1. Completed.

2. Completed.

3. Possibility of DC-1 & DC-2 arrangement and splitting of DC will be

reviewed.

Triggering incident was B-phase to earth

fault had occurred in 220kV Kadra-

Kodasalli line. Line tripped from Kodasalli

end only. 220kV Kaiga-Kadra tripped in

Zone-3 from Kaiga end. Tripping of

evacuating lines caused bus shut down at

Kadra hydro station.

Pending41/I/1 1. KPCL to make functional the Main2 (EPAC) relay with the

help of KPTCL at the earliest.

2. KPCL to investigate the reason for DC fuse fail during

transient fault in 220kV Kadra-Kodasalli line including the testing/

checking of DC supply cables, breaker control cables, and trip

coils.

3. KPCL to ensure supply for Main-1& Main-2 protections, Trip

Coils (TC1, TC2) from separate battery banks.

Annexure-IX

Page 5 of 12

Fault in 220kV Ambewadi-Nagjheri line-212-03-2015

at 7:51 hrs

Complete

outage of

220kV

Ambewadi

substation of

KPTCL

42/I/2

(GD)


Carrier protection is put in to service. AR will be enabled at the earliest.


Action is taken for enabling AR for Mudashinge and Talandage lines.

Work is scheduled during first week of August 2015.


1) Replaced existing VXL by ABB make C&R panel for both interstate

lines on 21.04.2015. The ABB Engineer visited 220KV Chikodi on

05.11.2015 for enabling AR system to existing ABB make REL511 relay

for both interstate line, but AR system not enable due to internal cards

faulty. Hence action is being taken to replace the ABB,REL511 distance

relays within a months time.

KPTCL1. KPTCL to provide A/R feature on the 220 kV Chikkodi –

Talandage, and 220 kV Chikkodi –Mudashinge inter-state lines.

2. KPTCL to carry out E/F relay coordination for Chikkodi -

Talandage and Chikkodi –

Mudashinge lines in coordination with Maharashtra.

Lines tripped during test charging 220kV

Chikodi-Belgaum line-2 from Chikodi

end.

20-02-2015

at

06:40 hrs

Tripping of

220kV

Chikodi-

Talandage

and

220kV

Chikodi-

Mudshingi

line

42/II/

2



stage. 2. Action is being taken to restore the carrier protection for

220kV Sedam-Tandoor line. AR will be enabled.



stage.




1. Bus bar protection panels pocured and erected at Sedam. Wiring ,

testing ,commissioning is being taken up.Planned to complete by April

2016.



PendingKPTCL 1. KPTCL to provide Bus bar and LBB protections for 220 kV

bus at Sedam S/s.


inter-state line.

R-Phase to ground fault occurred on

220kV Sedam-Shahpur line. Fault not

cleared from Sedam end due to stuck-

breaker condition. While the Sedam-

Sahapur line tripped from Shahapur end in

Zone-1, the other 220 kv lines from Sedam

tripped at remote ends in Zone-2. This

caused complete outage of 220kV Sedam

substation.

27-01-2015

at 8.00 hrs

Complete

outage at

220kV Sedam

Substation of

KPTCL (GD-

1)

41/I/4

Pending

1. KPTCL to provide Bus Bar protection and LBB protection at

Sedam S/s and furnish

the status of their implementation to PCSC forum.


inter-state line.

Pending1. KPTCL shall provide A/R feature on Ambewadi – Ponda 220 kV

D/C inter-state line.

2. Till the completion of R&M works for bus bar and LBB

protection, KPTCL shall explore

the possibility of having split bus operation at Ambewadi and

submit the details of the

same to PCSC forum.

KPTCL

15-02-2015

at 14:24 hrs

Complete

outage of

220kV Sedam

substation of

KPTCL

42/I/1

(GD)

Mail received on 27-05-2015: 1. Bus Bar protection will be provded

under R&U.

2. A/R yet to be enabled.



stage.

2. Action is being taken to restore the carrier protection for 220kV Sedam-

Tandoor line. AR will be enabled after restoration of PLCC.

KPTCLFault occurred in 220kV Sedam-Shahpur

line

Pending



stage.

2. Action is being taken to restore the carrier protection for 220kV Sedam-

Tandoor line. AR will be enabled after restoration of PLCC.

Annexure-IX

Page 6 of 12

47/III

/8

Tripping of

220kV

Ambewadi-

Ponda line-2

02-08-2015

at 13:20 hrs

Line tripped on a transient fault in B-

phase. There is no

provision for auto reclose.

KPTCL to activate non-directional Over Current protection with a

time delay of 600-800 msec for Fuse

failure condition at Lingasugur.

Pending

ICT tripped due to operation of Over

current and Earth fault relay

14-01-2015

at 1:09

hrs

Tripping of

400/220kV

ICT-1 at

BTPS

43/II/

14

Pending

Tripping of

Unit-1&2

along with

400/220kV

ICT-2 at

Raichur TPS

06-08-2015

at 4:51 hrs

KPTCL Yet to be informed Pending


1) Anti-pumping contactors of all the nine 220KV Lines are in circuit and

tested periodically during AOH works of lines along with other

protections.

2) Completed.

3) Possibility to use both the 220kV buses as main bus under normal

operation is under review.


1) Completed

3) Two bus operation for 220kV buses : In place of existing CT switching

relays, High speed manual heavy duty change over switch of sufficient

current capacity will be retrofitted to all feeders at 220kV station and

same will be operated manually during changeover of feeder by one bus

to the other and this arrangement may facilitate to put both buses in

service. Time required for this retrofit is around 90days . However, this

work will be taken up only after retrofitting of electromagnetic relays

with numerical relays for Main-2 protection of all 220kV lines, for which

work is in progress.

KPCL1. KPCL to check the operation of anti-pumping relay on 220 kV

side and keep it in healthy condition.

2. KPCL to provide manual reset to the 220 kV side master trip

relay.

3. KPCL to use both the 220 kV buses as main buses under normal

operation, and should go for single bus operation only during

emergencies.

07-06-2015

at 01:35 hrs

Trippings at

220kV

Raichur TPS

46/II/

21

KPCL vide their mail dated 07.07.2015 informed that revised relay

settings would be incorporated in co-ordination with KPTCL.

Mail received on 07-09-2015 , 21-10-2015 and 23-11-2015:

Revised relay settings are awaited from KPTCL.

Revised relay settings furnished by KPTCL will be incorporated in co-

ordination with KPTCL shortly.

PendingKPCL to check the possibility of providing line differential

protection between RTPS and Yermarus stations.

KPCL

Yet to be informedKPTCL

220kV RTPS-Lingasugur line-2 tripped at

TPS end on operation of distance

protection zone-1. 400/220kV ICT-2 got

tripped on operation of earth fault

protection. 220kV RTPS-Lingasugur line-

1&3 tripped on distance protection

zone-2 and zone-3 respectively. Due to

tripping of ICT-2, the running units got

overloaded and it was mentioned that

under frequency occurred as units are

on load control. The Units got tripped

on under frequency.

47/II/

13

Till A/R is put into service on Ambewadi-Ponda line-1, KPTCL to

reduce Zone-2 time setting to zero sec. at Ambewadi end.

Annexure-IX

Page 7 of 12

47/III

/10

Tripping of

220kV

Ambewadi-

Ponda line-1

08-08-2015

at 10:51

hrs and 09-

08-2015 at

11:15 hrs

Line tripped on a B-phase to earth fault.

Line tripped as there is no provision for

auto-reclose

47/III

/12

Tripping of

220kV

Ambewadi-

Ponda line-1

17-08-2015

at 13:20 hrs

Line tripped on a transient fault . There is

no provision for Auto reclose.

220kV Ambewadi-Nagjheri line-2 tripped

on B-phase to earth fault. This resulted in

loss of supply to 220kV Ambewadi bus.

220kV Ambewadi-Ponda line-1&2 were

hand tripped after deenergization of bus at

Ambewadi.

KPTCL to fast-track providing A/R on all 220 kV lines emanating

from Ambewadi SS to prevent Station shut-down on temporary

faults.

KPTCL KPTCL mail received on 23-01-2016:

Will be complied in a months time.

Pending30-09-2015

at 10:41 hrs

Outage of

220kV

Ambewadi

station in

Karnataka

48/I/3

(GD)

48/I/2

(GD)

Complete

outage of

220kV

Peenya

Substation in

Karnataka

27-09-2015

at 4:23:17

hrs

All connected 220kV lines and

transformers were taken on 220kV North

bus as South bus was under shut down for

conversion of strung bus to rigid bus and

isolator replacement under R&M works.

Failure of HV side Y phase CT of

150MVA Transformer-3 occurred at

Peenya Substation which resulted in

operation of Differential and HV REF

protection. The failure of CT also resulted

in a 220kV bus fault in North Bus.

KPTCL to revise distance relay settings at Nelamangala end for

220 kV Nelamangala – Hebbal - Peenya line – 1 for the effective

line length of 17 km. These new settings can be appropriately

reviewed as and when the tie-arrangement at Hebbal is done away

with.


Presentl 220kV Nelamangala -Hoody(i.e. nelamangala-Peenya-Hebbal -

Hoody line is made LIILO at Yelahanka sub station and breaker at

Peenya is kept open, necessary modification in distance relay settings

adopted for new configuration.

Pending

PendingYet to be informedKPTCLTill A/R is put into service on Ambewadi-Ponda line-1, KPTCL to

reduce Zone-2 time setting to zero sec. at Ambewadi end. Annexure-IX

Page 8 of 12

48/I/4

(GD)

Complete

outage of 220

kV HSR

substation of

Karnataka

06-10-2015

at 16:32 hrs

All connected 220kV lines at 220kV HSR

substation i.e. Somanahalli, EPIP, Hoody

and Nagnathapura tripped during the

incident. Triggering incident was fault in

220kV HSR-EPIP line

KPTCL to review distance relay settings at Naganathpura SS in

view of LILO arrangement at HSR Lay-out.


ABB make REL 670 type distance relays provided to Somanahalli and

hoody lines. Planned to commission within 10 days.

KPTCL Mail recieved dated 25-05-2016:

New REL 670 relays erected in the panel. Testing and commissionng will

be done within a month's time.

Pending

49/I/1

.3

(GD)

Complete

outage of

220kV

Ambewadi

Substation of

KPTCL

29.10.2015

at 14:34 hrs

220kV Nagjheri-Ambewadi line-1 tripped

at 13:33 hrs due to B phase to earth fault.

Ambewadi was radially fed from Nagjheri

power station through 220kV Nagjheri-

Ambewadi line-2. Tripping of this line

caused 220kV Bus shut down at

Ambewadi and remaining lines and

transformers were hand tripped

1. KPCL to provide A/R on all 220 kV lines emanating from

Nagjheri PH.

2. KPTCL to provide A/R on all 220 kV lines emanating from

Ambewadi SS.


49/II/

15

Trippings at

Raichur TPS

12-11-2015

at 00:30 hrs

Running Unit-4, 5 and Unit-8 and 400kV

RTPS-Yeramaras TPS feeder got tripped

due to de-energization of both 400kV Bus-

1&2 at Raichur TPS

1. KPCL to carry out hot-line washing of RTPS-connected lines

regularly to avoid trippings due to fog and dust.

2. KPCL may see the feasibility of providing breaker flashover

protection at RTPS, and implement the same if possible.

KPCL Status informed during Special Meeting held on 03.06.2016:

Hot line washing was done previously.tender process is on for silicon

coating of insulators.

Pending

Failure of Lightning Arrestor of Y-phase

Line Reactor of 400kV Guttur-Hiriyur line-

1 and line tripped on distance protection

Zone-1. Bus-bar protection of 400kV Bus-

2 at Guttur substation also got operated

during the event sensing this through fault.

400/220 kV ICT-1 & 2 at Guttur, 400kV

Kaiga-Guttur-2, 400kV

Guttur-Narendra-2, 400kV Guttur-Hiriyur-

2 and 400kV Guttur-Munirabad which are

on 400kV Bus-2 got tripped during the

incident. 400kV Guttur-Narendra-1 which

was on Bus-1 also tripped at the same

time.

51/II/

21

Multiple

tripping at

400kV Guttur

sub-station

17-01-2016

at 18:53 hrs

KPTCL 1. KPTCL to configure all DR’s and EL’s at 400 kV Guttur SS so

that they will also get triggered for BBP operation.

2. KPTCL to ensure time-synchronization of all DR’s and EL’s

with GPS at their 400 kV Guttur SS.

KPTCL Mail received dated 25-05-2016:

SEE,RTC,Bangalore to update the status

Pending

220kV lines from Nagjheri power house

started tripping from 11:00 hrs due to fault

in lines. The sequence of tripping is shown

in SOE list. At 12:33 hrs, 220kV Narendra-

Ambewadi lines-1&2 got tripped which

resulted in loss of evacuation path to

Nagjheri station resulting in tripping of

running Units and complete outage at

Nagjhheri power station. 220kV

Ambewadi station also got de-energized

due to tripping of source feeders i.e.

220kV Narendra-Ambewadi-1&2 and

220kV Nagjheri-Ambewadi-1&2.

1. To avoid tripping of transmission lines on transient faults,

KPCL/ KPTCL is recommended to carry out periodic patrolling of

lines, and ensure their proper maintenance by carrying out jungle/

bushing clearance and trimming of tree branches within the RoW

of transmission lines as per the SRPC transmission line patrolling

guidelines (available under the menu item "All Uploads

Operation Miscellaneous Transmission Line Patrolling

Protocol / Guidelines for Southern Region" on SRPC website).

2. KPCL/ KPTCL to review operation of SPS at NPH for

functionality (reduction of generation with tripping of evacuating

lines) and healthiness.

3. KPCL to put 220 kV Kodasalli - Nagjheri D/C lines into service

if more than 200 MW generation from Kali Complex (with Nagheri

Contribution not less than 50 MW) is ensured on sustained basis.

KPCL/ KPTCL Status informed during Special Meeting held on 03.06.2016:

SPS is in condition at NPH healthy and It is provded for non auxilliary

units ie 3 and 6 of NPH

PendingComplete

outage of

220kV

Nagjheri

power station

and 220kV

Ambewadi

substation of

KPTCL

22-02-2016

at 12:36 hrs

51/I/3

(GD)

Annexure-IX

Page 9 of 12

52/I/3

(GD)

Complete

outage of

220kV

Shimoga

substation

22-02-2016

at 15:03 hrs

220kV Bus Bar protection operated during

failure of R phase CT in DVG-2 line bay.

KPTCL to operate 220 kV Shimoga on multi-bus operation under

normal conditions, put it on single-bus operation only under

emergency conditions.


53/II/

1 (GI)

Tripping of

ICT-3 at

Raichur

Substation

15-03-2016

at 12:28 hrs

ICT-3 tripped due to operation of back-up

earth fault protection during fault in

220kV RTPS-Raichur line-1.

KPCL/ KPTCL to check the ICT’s back-up (high-set) protection

settings, and ensure that they operate with a time delay of 100

msec.

KPCL/KPTCL KPTCL Mail Recieved dated 25-05-2016:

SEE,SCADA to update the status of healthiness of carrier protection of

220kV RTPS-Raichur 1 &2 lines


Revised settings will be uploaded in co-ordination with KPTCL

Pending

220kV Peenya-Nelamangala-3 tripped on

B-E fault at both ends. At the same time,

220kV Peenya-Nelamangala-4 tripped on

R-Y fault only at Nelamangala end, and

was in service from Peenya end. Due to

tripping of these two lines, 220kV Peenya-

Nelamangala-2 tripped on overcurrent

protection.

KPTCL to furnish a report on the tripping of 220 kV Peenya-

Nelamangala line-4 Nelamangala detailing the remedial measures

taken including the settings adopted for Z1B (Zone extension) and

Power Swing Block.

KPTCL KPTCL Mail received dated 25-05-2016:

SEE,RTC,Bangalore to update the status

Pending16-03-2016

at 11:39 Hrs

Complete

outage of

220kV

Peenya

Substation of

KPTCL

53/I/1

(GD)

1. KPTCL to configure the Auto-Reclosure (A/R) scheme at

Hoody end for all lines emanating from Hoody end in such a way

that in the event of occurrence of faults during A/R dead-time, (i) it

should immediately give a 3-ph trip, and (ii) A/R should go into

lock-out state, i.e., it must not reclose after the elapse of dead-time

of A/R.

2. As regards over-reaching of Kolar and Nelamangala end relays

for the fault on 400 kV Hoody – Kolar line-2, KPTCL and PGCIL

(SR-II) are recommended to modify the Z1B settings of the relays

used (7SA522) suitably so that they operate with a Zone-2 time

delay.

3. KPTCL to check the ICT’s back-up (high-set) protection

settings, and ensure that they operate with a time delay of 100

msec.

4. KPTCL to take steps to replace the solid state relays at Hoody

end on Hoody-Nelamangala lines – 1 & 2 with numerical relays at

the earliest.

KPTCL KPTCL Mail recieved dated 25-05-2016:

1. Incorporated.

3. With the existing electromechanical relays, it's not possible to add time

delay of 100 mSec. However, ongoing R&M works of Hoody included

complete ICT1 and ICT2 panel replacement having Numerical relays.

4.The solid state relays of Nelamangala-1 and Nelamangala-2 lines will

be replaced by numerical relays for which relays have been

identified,Will be attended in a month's time.

400kV Hoody-Nelamangala line-1&2,

400kV Hoody-Kolar line-1&2, 400/220kV

ICT-2 at Hoody tripped during the

incident. ICT-1&3 were hand tripped after

the incident.

26-03-2016

at 12:42 hrs

Complete

outage of

400kV Hoody

substation of

KPTCL

53/I/1

(GD)

Pending

PendingYet to be informed53/I/3

(GD)

Complete

outage of

220kV

Ambewadi

station of

KPTCL and

220kV

Nagjheri of

KPCL

18-03-2016

at 14:40 hrs

Ambewadi Narendra line-2 tripped on

fault and 220kV ambewadi Narendra line-

1 tripped due to over-loading. Running

Units at Nagjheri also tripped during the

event due to tripping of evacuating lines

1. KPCL to furnish a report on the reasons for Unit-6 tripping at

Nagjheri PH.KPCL/ KPTCL to modify suitably the SPS at Nagjheri

Power House such that it would also factor in the over loading of

Ambewadi-Narendra lines.

2. KPCL/ KPTCL to put 220 kV Kodasalli - Nagjheri D/C lines

into service if more than 200 MW generation from Kali Complex

(with Nagheri Contribution not less than 50 MW) is ensured on

sustained basis.

KPCL/ KPTCL

Miscellaneous

Annexure-IX

Page 10 of 12

36/II/

8

400kV

Raichur-

Munirabad

line

07-09-2014 B-phase to earth fault had occurred in line.

Line auto reclosed at Munirabad end and

failed to reclose at Raichur end.

KPTCL:

PD (pole discrepancy) time delay would be changed.

PGCIL /

KPTCL

Yet to be informed Pending

with

KPTCL

43/II/

12

Multiple

tripping at

400kV

Raichur(PG)

and Raichur

thermal

11-04-

2015at

18:04 hrs

400kV Raichur(PG)-Gooty line-2,

400kV Raichur TPS-Raichur(PG)

line-1&2, 400kV Raichur-

Mahboobnagar, Unit#5 at RTPS

tripped during the incident

KPCL, KPTCL and PGCIL (SR-I) to furnish the action taken report

on the

recommendations given by PSAG members held at Raichur on 22-

04-2015 and

23-04-2015.

KPCL/KPTCL/

PGCIL(SR-I)

Yet to be informed Pending

Tripping of

Unit 1 at

NCTPS

24-05-2015

at 19:13 hrs

ID Fan trip

Tripping of

Unit 1 at

MEPL

24-05-2015

at 19:13 hrs

Coal Mill tripped

Tripping of

Unit 1 at

Krishnapatna

m

24-05-2015

at 19:17 hrs

Generator Protection operated

Mail received on 26-05-2015 from TSTRANSCO:

It is found that the main-2 ABB make REL316 type distance relay was

defective and same was replaced with MICOM P444 by M/s.PGCIL on

23.04-2015. After replacement of main-II, DR can be extracted from this

relay. For EL in to service, some field winding is pending which is being

taken up in this month.

PGCIL mail recieved on 27-04-2016:

End to end PLCC tunning carried out

1. KPCL to review REF setting (DMT or IDMTL) for unit-7 by first

week of April, 2015 and

inform the same to PCSC forum.

2. TSTRANSCO to furnish Mehaboobnagar’s DR and EL and the

reasons for distance relay

operation at their end within a week’s time.

3. PGCIL (SR-I) to rectify the issues relating to A/R operation,

relay reach (Z2), reverse reach

(Z4) and SOTF auxiliary contacts within a week’s time, and submit

the actions taken to

PCSC forum.

KPCL/TSTRANS

CO/PGCIL (SR-I)

Pending

with SEL

400kV Raichur TPS-Raichur(PG) line-

1&2, 400kV Raichur-Mahboobnagar,

Unit#7 and ICT-2 at RTPS tripped

during the incident. B phase to earth

fault had occurred in 400kV Raichur

TPS-Raichur line-1

09-03-2015

at

06:36 hrs

Multiple

tripping at

Raichur

thermal

power station

of

KPCL

42/II/

18

Mail recieved on 28-04-2015: End to end testing of PLCC has

been done and problem in the PLCC is atttended.


End to end testing of PLCC has been done and problem in the PLCC is

atttended. Phase discrepancy in the relay operation is to be checked

jointly.


Problem is in identification of phases at Talguppa end. To be rectified by

M/s KPTCL.

Pending1. PGCIL and KPTCL to ascertain the reason for the phase

discrepancy in the relay operation and take suitable remedial

measures.

2. KPTCL to check the PLCC operation at Talaguppa end and

submit the report to the PCSC forum.

PGCIL/ KPTCLOn account of R-phase to earth fault, line

tripped at Hassan end due to operation of

distance Zone-2 and non-receipt of carrier.

From D.R of Talaguppa end it is observed

that fault had occurred in Yphase.

01-01-2015

at

13:38 hrs

Tripping of

400

kV

TALAGUPP

A

– HASSAN

line

40/II/

3

44/I/3

(GD)

1. All Tripped units, viz., Krishnapatinam, MEPL, Raichur, NCTPS

to submit a detailed report

on this event including the remedial measures taken to PCSC

forum.

2. KPCL to check the excitation system of Unit 8 of RTPS, and

submit the remedial measures

taken to PCSC forum.

KPCL/ MEPL/

APGENCO/

TNEB

TANGEDCO vide their mail dated 07.07.2015 informed that as per the

discussion and recommendation of 44th meeting of PCSC held on

28.05.2015, a time delay of 2 Sec had been introduced for the above

tripping for all the ID fans at NCTPS-II.

MEPL vide their mail dated 14.09.2015 informed that they have

implemented 2 seconds delay for under voltage tripping of all Drag Chain

Feeder Conveyors. And this has been done for both the Units.

Pending

with

KPCL,

APGENC

O

Annexure-IX

Page 11 of 12

Tripping of

Unit-8 at

RTPS

24-05-2015

at 19:19 hrs

Tripped on Overvoltage.


Availability of week end infeed with eco feature to be confirmed by

SEE,RTC,Hubli

PendingKPTCL/ KPCL/

NPCIL

44/I/3

(GD)

1. All Tripped units, viz., Krishnapatinam, MEPL, Raichur, NCTPS

to submit a detailed report

on this event including the remedial measures taken to PCSC

forum.

2. KPCL to check the excitation system of Unit 8 of RTPS, and

submit the remedial measures

taken to PCSC forum.

KPCL/ MEPL/

APGENCO/

TNEB

TANGEDCO vide their mail dated 07.07.2015 informed that as per the

discussion and recommendation of 44th meeting of PCSC held on

28.05.2015, a time delay of 2 Sec had been introduced for the above

tripping for all the ID fans at NCTPS-II.

MEPL vide their mail dated 14.09.2015 informed that they have

implemented 2 seconds delay for under voltage tripping of all Drag Chain

Feeder Conveyors. And this has been done for both the Units.

Pending

with

KPCL,

APGENC

O

1. KPTCL/ KPCL to see the possibility of implementing Weak

Infeed logic with Echo feature enabled by Under

Voltage (27) element on Kadra-Karwar lines 1 &2, and implement

the same if feasible.

2. NPCIL to time-coordinate Kaiga’s DEFR settings with (i) Zone-2

settings at Kaiga, and (ii) primary protections of the lines

emanating from Kadra and Kodasalli.

3. KPCL to ensure time-sync of EL’s, and healthiness of the Fault

Locators at Kadra.

220kV Kadra-Karwar lines-1&2 tripped

on earth fault in B-phase in zone-2.

Kaiga-Kadra line tripped at Kaiga end

only on operation of directional eath

fault protection.

31-07-2015

at

11:44 hrs

Tripping of

220kV Kadra-

Karwar line-

1&2 and

220kV

Kaiga-Kadra

line

47/II/

7

Annexure-IX

Page 12 of 12

S. No Name of

SubstationDetails of work Status of Implementation of Protection Audit Recommendations Remarks

Dead Earth fault in 220 V DC set 1 & 2. Completed Complied

relays not Synchronised with GPS.

The work will be completed by March 2015.

Latest Update as on 25-08-2015:

GPS received at site. The work will be completed by December 2015.

Latest Update vide mail on 27-01-2016:

Completed.

Complied

A/R Scheme for 220 kV Lines not available for

lines.Completed Complied

2 220 kV Kadra

(Gen) Carrier protection is out of service for Karwar 1

& 2 feedersCompleted Complied

3 220 kV Kodasalli

S/S (Gen) Carrier protection is not in service for all feeders

(the real time testing is pending).Completed Complied

4

220 kV Nagjhari

Power House

The LBB relay time & current are sdet at 1.5 sec

& 0.2 A for all feeders and generating

transformers.

Completed Complied

220 V DC earth fault persisting negative dead

grounded


Negative dead ground is removed. Partial ground is present. The work will be completed by December 2015.


Completed

Complied

LBB Relay RAICA RXKL1 setting for ICT-II is

kept at 50 mA.Completed Complied

LBB relay timing is observed to be 0.7 sec

which is high, can be reduced to 250 to 300

m.sec in coordination with pole discrepancy

relay of breaker.

Completed Complied

KPCL

Phase-I

1 220 kV BTPS

5 220 kV Raichur

TPS

6 220 kV Sharavathi

SS (Gen)

STATUS OF IMPLEMENTATION OF PROTECTION AUDIT RECOMMENDATIONS

Annexure-X

Page 1 of 14

Carrier protection should be kept in service for

the feeders having no carrier protection.

The work will be completed by July - 2015.


Completed

Complied

DC earth leakage should be arrested on top

priority to avoid spurious trippings due to DC

earth leakage.

Completed Complied

Substation GPS to be connected to event logger

and protection relays for correct recording of the

sequence of events.

e-NIT floated on 15.09.2014. The work will be completed by December-2015.


NIT was issued through e-portal. LOA for Supply & Erection of Disturbance Recorder & GPS issued to M/s Alstom

T&D India Ltd., Chennai on 26.06.2015. Contract agreement executed.


Letter of Award issued to M/s Alstom T&D India Ltd., Chennai for Supply & Erection of Disturbance Recorder &

GPS on 26.06.2015. The firm has completed site visit for collection of data’s from site and is now preparing

schematic drawings.It is estimated that the work completion period may extend until 30.12.2016.

Pending

Complied

Feeders with same Make & Type relay as Main-I

& Main-II should be changed with different

Make/Type relays for Main-I & Main-II.

LOA issued to M/s Alstom T&D India Ltd. Bengaluru. The work will be completed by December - 2015.


LOA dtd. 15.12.2014 issued to M/s Alstom T&D India Ltd. Bengaluru. Review of drawings completed. Materials

received at site. The work will be completed by December - 2015.


LOA dated: 15.12.2014 issued to M/s Alstom T&D India Ltd. Bengaluru. Erection work completed for all 8 Lines &

2 BCs except for S-2 line, which is in pregress.The erection works involve obtaining prior line clearance from the

State Load Dispatch Centre hence the erection work for remaining line is expected to complete by 31.01.2016.


Completed

Complied

6 220 kV Sharavathi

SS (Gen)

Feeders having O/C and E/F relays as Main-II to

be replaced with distance relays for good

protection coordination on 220 kV Grid.

LOA issued to M/s Alstom T&D India Ltd. Bengaluru. The work will be completed by December - 2015.


LOA dtd. 15.12.2014 issued to M/s Alstom T&D India Ltd. Bengaluru. Review of drawings completed. Materials

received at site. The work will be completed by December - 2015.


LOA dated: 15.12.2014 issued to M/s Alstom T&D India Ltd. Bengaluru. Erection work completed for all 8 Lines &

2 BCs except for S-2 line, which is in pregress.The erection works involve obtaining prior line clearance from the

State Load Dispatch Centre hence the erection work for remaining line is expected to complete by 31.01.2016.


Completed

Annexure-X

Page 2 of 14

A/R Selection switch is kept in non auto mode

for all 400 kV lines.

Dead 220 V DC Earth fault for both sets i.e.

Positive to Earth 235 V.Completed Complied

GPS time synchronisation for all the relays &

DR not carried.

The work will be completed by May 2015.


GPS received at site. The work will be completed by December 2015.


Completed.

Complied

High setting for the bus bar differential

protection i.e. 325 V.

The work will be completed by March - 2015.


Assistance of OEM required. OEM opined that the setting is in line with latest fault levels, considering fault level as

50kA.


Assistance of OEM required. OEM opined that the setting is in line with latest fault levels, considering fault level as

50kA. This shall be reviewed as per the opinion of OEM and hence may please be removed from the list.


Completed

Complied

7

A/R function for 400kV lines shall be completed by May 2015.


Timers dispatched from supplier. Software programming is completed during previous shut down availed on lines.

One more shut down is required for uploading settings and to modify wiring. A/R function for 400kV lines shall be

completed by December 2015.


Request sent to State Load Despatch Centre for availing LC for enabling A/R function for 400kV lines.The erection

works involve obtaining prior line clearance from the Sate Load Dispatch Centre hence the work completion period

may extend till 30.03.2016.


Completed.

Complied

400 kV BTPS

Annexure-X

Page 3 of 14

Pole descripency relay setting kept at 0.1 Sec for

all the lines.

The work will be completed by July - 2015.


Timers dispatched from supplier. The work will be completed by December - 2015.


Completed.

Complied

220 V DC earth fault persisting with leakage

current of 15 mACompleted Complied

PD settings for Munirabad, BTPS and

Mahboobnagar kept at 0.1 secCompleted Complied

RTPS-Munirabad line Zone-II setting (26.880

Ohm) is more than Zone-III (26.44 Ohm)Completed Complied

No fault locator working for Munirabad and

Mehboobnagar lines

The order placed on M/s.Siemens to replace relays. The work will be completed by May - 2015.


Order placed on M/s Siemens for retrofitting of electromechanical relays with Numerical relays for both the lines.

The retrofitting of electromechanical relays with Numerical version for Munirabad line has been completed. The fault

locator is incorporated in numerical Relays. Retrofitting work for Mehaboobnagar line is pending. Awaiting for line

shutdown.


Completed.

Complied

DR communication is not working for

Munirabad and Mehboobnagar lines

The order placed on M/s.Siemens to replace relays. The work will be completed by May - 2015.


Order placed on M/s Siemens for retrofitting of electromechanical relays with Numerical relays for both the lines.

Inspection of material completed. The retrofitting of electromechanical relays with Numerical version for Munirabad

line has been completed. The fault locator is incorporated in numerical Relays. Retrofitting work for Mehaboobnagar

line is pending. Awaiting for line shutdown.


Completed.

Complied

Time Synchronisation for all relays.EL & DR

are done with GPS.The order placed on M/s.Siemens to replace relays. The work will be completed by May - 2015. Pending

7 400 kV BTPS

8 400 kV Raichur

TPS SS (IS)

Annexure-X

Page 4 of 14

Name of

SubstationDetails of work Status of Implementation of Protection Audit Recommendations Remarks

Karwar 1 & 2 fereders have only R Ph CVT

available (Y and B Ph CVTs are not available).

NIT issued vide no. LOT/CEED/EE4/245kV CVT/1285 Dated: 17.07.2014. Tender finalisation will be completed by

March - 2015.The work will be completed by December - 2015.


Purchase order dtd 27.04.2015 placed on M/s Siemens ltd. Chennai. Review of technical drawings completed and are

approved. Inspection is in progress.


Purchase order dated: 27.04.2015 placed on M/s Siemens ltd. Chennai. Supply of all Materials after inspection at

firms work completed. Erection work may take 2 weeks after handing over of a line bay. However, the erection work

involves obtaining prior line clearance from the State Load Dispatch Centre and it is estimated that the work

completion period may extend until 30.12.2016.

Pending

220 kV Kadra

(Gen)

1

Phase-II

Annexure-X

Page 5 of 14

For Kaiga and Kodasalli feeders have only R &

B CVTs available. (Y Ph CVT not available)


March - 2015. The work will be completed by December - 2015.









Pending

Work order placed for Servicing of all 89T Transfer Bus isolators and Bus Coupler breaker. Control wiring works

pending due to nonavailability of cable ICS at site. Letter addressed to OEM for detailed cable schedule and all the

connected works. BUS COUPLER module will be put into service during commissioning. The work will be

completed by August 2015.


Wiring work completed partly. Work order placed for procurement of CT's and auxiliaries. The work will be



CT’s required for commission of bus coupler. Purchase order dated: 27.04.2015 placed on M/s Alstom ltd. Bengaluru

for procurement of CTs. Drawings approved and manufacturing clearance issued. Inspection call by Firm is awaited.

Erection work may take 2 weeks after handing over of Line bay. There are 13 Line bays. However, the erection works

involve obtaining prior line clearance from the State Load Dispatch Centre and Expected work completion date:

30.12.2016

Pending

Bus coupler and transfer bus are out of service,

bus coupler module on busbar protection panel

is kept out of service.

220 kV Kadra

(Gen)

1

2 220 kV Kodasalli

S/S (Gen)

Double earthing of all the supporting

structures/elements is to be ensured and neutral

of generting transformers and LAs should be

exclusively earthed.

The work will be completed by July 2015.


Work order issued. Work is under progress. The work will be completed by December 2015.


Since Kodasalli is a dam based project, double earthing of ODY structures in the existing concrete area of switchyard

could not be assessed. Work Order issued has been cancelled and NIT re-floated. The work will be completed by

30.06.2016.


Completed.

Complied

Annexure-X

Page 6 of 14

220 kV Nagjhari-Ambewadi 1 & 2 lines does

not have CVTs on the line. Carrier tripping was

not available for these lines.











Pending

Pending

NIT issued on 17.07.2014. Tender finalisation will be completed by March - 2015. The work will be completed by

December - 2015.









i) Nagjheri Kodasalli line-1 having only R-ph

CVT (Y and B Ph CVTs are not available.

ii)Nagjheri Kodasalli line-2 CVTs are not

available. iii)Kodasalli-Kadra line having only R

and B Ph CVTs (Y Ph CVTs are not available.

iv) Kodasalli-Kaiga line having only R and B Ph

CVTs (Y Ph CVTs are not available.

2 220 kV Kodasalli

S/S (Gen)

3 220kv Nagjhari

Power House

Work order placed for Servicing of all 89T Transfer Bus isolators and Bus Coupler breaker. Wiring Work completed

partly. Letter addressed to OEM for detailed cable schedule and all the connected works.The work will be completed

by August 2015.


Servicing of all the 89T isolator & Bus coupler breaker carried out and kept ready. Also, action is being taken to

replace the faulty 220kV CT of Y-phase Bus coupler. Work order placed for procurement of CT's and auxiliaries.

The work will be completed by December 2015.


CT’s required for commission of bus coupler. Purchase order dated: 27.04.2015 placed on M/s Alstom ltd. Bengaluru

for procurement of CTs. Drawings approved and manufacturing clearance issued. Inspection call by Firm is awaited.

Erection work may take 2 weeks after handing over of Line bay. There are 13 Line bays. However, the erection works

involve obtaining prior line clearance from the State Load Dispatch Centre and Expected work completion date:

30.12.2016.

Pending

Bus coupler and transfer bus are out of service,

bus coupler module on busbar protection panel

is kept out of service.

Annexure-X

Page 7 of 14

Remaining six 220 kV lines have only one R-

Phase CVT and Y & B Phase CVTs are not

available.











Pending

Synchronising of 220 kV feeders is not being

done with synchroscope, only Generator

Transformer Units are being synchronised.

Synchronization of line feeders is not being done with synchronoscope. It is true that, only generator transformer units

are being synchronized at NPH. However the efforts are being made to provide synchronising facility for lines also.

The work will be completed by June 2015.


Completed

Complied

3 220kv Nagjhari

Power House

Separate 2 no's of raisers from earthmat have been provided for each unit & GT for connecting neutral to have

effective grounding. This is in line with the CBIP manual for earthing practices. However the efforts are being made

to provide separate earthing also. The work will be completed by June 2015.


Completed

Latest Update as on 25-08-2015 and mail on 27-01-2016:

CompliedThe Neutrals of generator transformers are not

earthed exclusively and all LAs also not found to

be earthed exclusively.

Annexure-X

Page 8 of 14

The Emulsifier system nozzles are not directed

towards Power Transformer body in the middle.Complied. The mulsifire nozzles are already directed towards power transformer body in the middle. Complied

3 core CTs to be replaced with 5 crore CTs to

keep the Bus Bar protection in full shape with

both Main and Check Zone.

NIT issued vide no. R &M/245kV CTs/1348 Dated: 23.07.2014. Tender finalisation will be completed by March -

2015. The work will be completed by December - 2015.


Purchase order dtd 27.04.2015 placed on M/s Alstom ltd. Bengaluru for procurement of CTs. Drawings approved and

manufacturing clearance issued.


Purchase order dated: 27.04.2015 placed on M/s Alstom ltd. Bengaluru for procurement of CTs. Drawings approved

and manufacturing clearance issued. Inspection call by Firm is awaited. Erection work may take 2 weeks after

handing over of Line bay. There are 13 Line bays. However, the erection works involve obtaining prior line clearance

from the State Load Dispatch Centre and Expected work completion date: 30.12.2016.

Pending

3 CVTs to be provided on all 220 kV feeders so

as to keep the Main-II protections on Bus PT or

CVT which increases the reliability of the

protection system.








firms work completed.Erection work may take 2 weeks after handing over of a line bay. However, the erection work



Pending

Bus bar protection panels to be replaced with

new panels of numerical relay type to have the

bus bar protection in full shape with all features

(check zone, CT fail, iso fail etc. features) as the

existing scheme is not having check zone

facility. Certain CTs with 3 cores should also be

changed to have 5 cores for bus bar protection.

Complied. Commissioning of new Bus bar protection panel is completed on 16.06.2014 Complied

Feeders having same core for Main-I and Main-

II should be separated to individual cores, i.e.

Main-I and Main-II should be on different CT

cores.

NIT issued vide no. R &M/245kV CTs/1348 Dated: 23.07.2014. Tender finalisation will be completed by March -

2015. The work will be completed by December - 2015.


Purchase order dtd 27.04.2015 placed on M/s Alstom ltd. Bengaluru for procurement of CTs. Drawings approved and

manufacturing clearance issued.


Purchase order dated: 27.04.2015 placed on M/s Alstom ltd. Bengaluru for procurement of CTs. Drawings approved

and manufacturing clearance issued. Inspection call by Firm is awaited. Erection work may take 2 weeks after

handing over of Line bay. There are 13 Line bays. However, the erection works involve obtaining prior line clearance

from the State Load Dispatch Centre and Expected work completion date: 30.12.2016.

Pending

3 220kv Nagjhari

Power House

4 220 KV

Sharavathi SS

(Gen)

Separate 2 no's of raisers from earthmat have been provided for each unit & GT for connecting neutral to have

effective grounding. This is in line with the CBIP manual for earthing practices. However the efforts are being made

to provide separate earthing also. The work will be completed by June 2015.


Completed

Latest Update as on 25-08-2015 and mail on 27-01-2016:

CompliedThe Neutrals of generator transformers are not

earthed exclusively and all LAs also not found to

be earthed exclusively.

Annexure-X

Page 9 of 14

The battery bank-II to be replaced with VRLA

(maintenance free) type batteries to increase the

reliability of DC system, as the existing both

banks are of lead acid type are under complete

deterioration condition.

Complied. Already solved by replacing with VRLA type 1000Ah batteries on 06.01.2013 & 500Ah batteries on

24.06.2013Complied

All generator transformers OTI & WT1 shall be

brought to control room for better monitoring of

the transformer performance.

The 4-20 mA temperature signals of GT 1,3,5 & 8 have already been provided to control room recorder for

monitoring. Procurement of new guages with temperatures for GT 2, 6 & 7 is in progress. GT 9 & 10 are being

replaced & the monitoring facility will be extended after replacement.The work will be completed by June 2015.


Completed

Complied

New SF6 type circuit breakers to be replaced

without door type CTs on either side of the

breaker in place of existing old BOCBs, as the

sectionaliser breakers are very vital while

clearing the very high level bus faults.

LOA issued to M/s ABB India Ltd. The work will be completed by December - 2015.


LOA dtd. 12.12.2014 issued to M/s ABB India Ltd. Review of drawings is in progress.

The work will be completed by December - 2015.


LOA issued on 12.12.2014. Supply of all Materials after inspection at firms work completed. Erection work may

take 8 weeks after handing over of each bay. There are 2 no. of bays. However, the erection works involve obtaining

prior line clearance from the Load Dispatch Centre. Expected work completion date: 30.12.2016.

Pending

5 220 kV BTPS

220 kV Bus coupler not commissioned.

Letter addressed to EPC contractor M/s. BHEL with a request to take up the work at the earliest. The work will be



Letter addressed to EPC contractor M/s. BHEL with a request to take up the work at the earliest. The firm has

accepted to take up the work. The work will be completed by December 2015.


Letter addressed to EPC contractor M/s. BHEL with a request to take up the work at the earliest. The firm has

accepted to take up the work. The work is expected to be completed by 30.06.2016.

Pending

CVT to be provided for each Phase of the

transmission lines.








Pending

4 220 KV

Sharavathi SS

(Gen)

220kv Gerusoppa

Dam Power

House

6

Annexure-X

Page 10 of 14

Main-I Distance protection (SHPM101) is not in

service due to power supply module problem for

Karwar I & II feeders.

e-NIT No. LOT/CEED/EE6/R&M/ Dist.Prot/1416 dtd: 28.07.2014 was floated through e-portal for Supply, Retrofit,

Testing & Commissioning of Numerical Distance protection relays & GPS for Varahi, Gerusoppa, Kadra & Kodasalli

Power Houses of KPCL. Bid evaluation is under progress. The work will be completed by December - 2015.


NIT issued through e-portal on 05.05.2015. Price evaluation is under progress.


LOA’s issued on 08.10.2015. Inspection of relays completed. Materials received at site.The erection works involve

obtaining prior line clearance from the State Load Dispatch Centre and it is estimated that the work completion period

may extend until 30.12.2016.

Pending

Double earthing of all the supporting

structures/elements is to be ensured.

Earth mat purchased. The work will be completed by July 2015.




Completed

Complied

Neutrals of generating transformers and LA's are

to be exclusively earthed.

Earth mat purchased. The work will be completed by July 2015.




Completed

Complied

7 220 kV Kadra

(Gen)

1. Complied for Distance Protection Scheme(Main 1) already retrofitted with Numerical relays for all lines except

Shahpur line.

2. Budget proposal is made for the year 2014-15 for replacement of old Back up protection relays with Numerical

relays for all lines and main1 & main2 for Shahpur line.

3. Budgetary offer received and under process of issuing NIT.

5. The work will be completed by December- 2015.


e- NIT floated on 03.02.2015. Job order placed on 26.06.2015 on M/s Alstom T&D India Ltd. Chennai for retrofitting

of relays for all 220kV lines at RTPS.


Work Order placed on 26.06.2015 for retrofitting of relays for all 220kV lines at RTPS. Materials received at site.

The erection works involve obtaining prior line clearance from the State Load Dispatch Centre and it is estimated that

the work completion period may extend until 30.06.2016.


Completed

Old electromagnetic relays can be replaced with

numerical relays.

220 kV Raichur

TPS

8 Complied

Pending










Different Type of Numerical Distance protection

is to be provided as Main-II in place of Static

Over current and earth fault protection.

220kv Gerusoppa

Dam Power

House

6

Annexure-X

Page 11 of 14

1. Complied for Distance Protection Scheme(Main 1) already retrofitted with Numerical relays for all lines except

Shahpur line.

2. Budget proposal is made for the year 2014-15 for replacement of old Back up protection relays with Numerical

relays for all lines and main1 & main2 for Shahpur line.

3. Budgetary offer received and under process of issuing NIT.

5. The work will be completed by December- 2015.


e- NIT floated on 03.02.2015. Job order placed on 26.06.2015 on M/s Alstom T&D India Ltd. Chennai for retrofitting

of relays for all 220kV lines at RTPS.


Work Order placed on 26.06.2015 for retrofitting of relays for all 220kV lines at RTPS. Materials received at site.

The erection works involve obtaining prior line clearance from the State Load Dispatch Centre and it is estimated that

the work completion period may extend until 30.06.2016.


Completed

Complied

Annexure-X

Page 12 of 14

DG set is not extended to 400 kV SS

The work will be completed by May 2015.


Action is being taken up


Completed

Complied

Electromechanical directional OCR & EFR

relays are existing as back up protection for

220KV line feeders. Different type of Numerical

distance relays should be replaced in place of

electromechanical relays.










Pending

There is only one CVT available on all 220KV

lines. CVTs should be provided for all the three

phases of all the 220KV lines.






Pending

10 220kV Varahi

(VUGPH

Hosangadi) (gen)

1) Complied. Replacement of Old Electro-magnetic relays with Numerical has been completed for RTPS-BTPS line

& Commissioned on 17.03.2014.

2)Complied. Raichur-PG1 & Raichur-PG2 lines have already retrofitted with numerical relays.

3) NIT issued for replacement of old Electro-magnetic relays with Numerical version for 400 KV lines of Munirabad,

Mehaboobnagar, ICT-1 & ICT-2. Bid evaluation is under progress. Work will be Completed by May -2015.


Replacement of Old electromagnetic relays with Numerical relays has been completed for RTPS-BTPS line &

commissioned on 18.03.2014.

Raichur-PG1 & Raichur-PG2 lines have already retrofitted with numerical relays.

The retrofitting of electromechanical relays with Numerical version for ICT-1, ICT-2 and Munirabad line has been

completed.

Retrofitting work for Mehaboobnagar line is pending. Awaiting for line shutdown.


Completed

Complied

Old electromagnetic relays can be replaced with

numerical relays.

400 kV Raichur

TPS

9

Annexure-X

Page 13 of 14

Time synchronisation of the distance relays with

GPS may please be reviewed.










Pending

10 220kV Varahi

(VUGPH

Hosangadi) (gen)

Annexure-X

Page 14 of 14

SOUTHERN REGIONAL POWER COMMITTEE BENGALURU · Line tripped on operation of Backup impedance...

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