Minutes of

66th PCC meeting

Date: 09.05.2018 Eastern Regional Power Committee

14, Golf Club Road, Tollygunge Kolkata: 700 033

EASTERN REGIONAL POWER COMMITTEE

MINUTES OF 66TH PROTECTION SUB-COMMITTEE MEETING HELD AT ERPC, KOLKATA ON 25.04.2018 (WEDNESDAY) AT 10:30 HOURS

List of participants is enclosed at Annexure-A.

PART – A

ITEM NO. A.1: Confirmation of minutes of 65th Protection sub-Committee Meeting held on 28th March, 2018 at ERPC, Kolkata.

The minutes of 65th Protection Sub-Committee meeting held on 28.03.18 circulated vide letter dated 13.04.18. Members may confirm the minutes of 65th PCC meeting. Deliberation in the meeting Members confirmed the minutes of 65th PCC meeting.

PART – B

ANALYSIS & DISCUSSION ON GRID INCIDENCES OCCURRED IN MARCH, 2018 ITEM NO. B.1: Total power failure at 220/132 kV Waria S/S on 09-03-2018 at 17:15 hrs On 09-03-18 at 17:15 hrs, total power failure occurred at 220/132 kV Waria S/S due to tripping of all 220/132 kV ICTs and running units (U #4) at Waria. It is reported that Y-ph Wave Trap at 132/33 kV Ramkanali S/S caught fire at the time of the event. Analysis of PMU plots: Two faults have been observed in Durgapur PMU. First fault was seen in R & Y phases at 17:15:50 hrs which got cleared in 100ms. Three seconds after clearing the first fault, another fault was observed in R, Y & B phase which got cleared after 1000 ms. Load loss 300 MW Generation loss 180 MW DVC may explain. Deliberation in the meeting DVC gave a detailed presentation. Presentation is enclosed at Annexure-B1. DVC explained that

• There was an AB fault in 132kV DTPS-Ramkanali Line very near to Ramkanali Bus. Ramkanali end was tripped on zone 1 distance protection. Simultaneously 132kV PHS- Ramkanali D/c lines got tripped from PHS end on Zone 1 due incorrect entry of CT ratio in relay settings.

• DTPS end had identified the fault in zone 2 and given the trip command to respective CB. But CB was failed to open and clear the fault.

• As a result, 132kV DTPS-Kalipahari line got tripped from Kalipahari end on directional O/C

relay as the fault was beyond its Z2 reach. • As the initial fault current feed from 220kV DTPS end was about 2300A which was below

3000A (combined pick of ATR LV sides i.e. 3*1000A), the 220/132kV ATRs at DTPS had continued to feed the fault without tripping. This resulted in development of multiple faults in the line.

• After jumper had snapped at various locations due to continuous feeding of fault, the fault current had crossed 3000A and 220/132kV ATRs at DTPS had tripped on over current E/F.

• DTPS Burdwan Line was made OFF by hand due to extreme voltage dip as instructed by CLD.

• This caused power failure in DTPS 132KV, ASP, Jamuria and Ramkanali S/S. DVC informed that 132kV Jamuria was connected to DTPS radially hence this line didn’t trip from Jamuria. DVC added that the CBs at DTPS were 25 years old and overhauling by OEM is pending.

ATR#1,2,3O/C; P=1000A

160MVA*3

DTPS 220KV

DTPS 132KV

RAMKANALI 132KV

CB did not Trip

Z1; 3.5KM

Z2; 60.5KM

PHS 132KV

Z1

Z1

L # 90

L # 45, 46

14.4Km

73 Km

KALIPAHARI 132KV

67

67

L # 100

JAMURIA 132KV

33 Km

MADE OFF BY HAND

BURDWAN 132KV

L # 75

L # 76

L # 61

L # 60

CTPS 132KV

DVC informed that they have taken the following corrective actions:

• CT ratio in relay settings of 132kV PHS- Ramkanali D/c lines at PHS end had been corrected.

• As an additional measure to improve the reliability of 132KV system, they reviewed the overcurrent settings of 132kV Kalyaneswari-Kalipahari Line (L # 18 & 19) and 132kV PHS Ramkanali line (L # 45, 46). Whenever the current rises above 480A for 700ms in either direction, the lines would trip to prevent cascading tripping of both DTPS and Kalyaneshwary 220/132kV ATRs on overload.

PCC advised DVC to ensure the healthiness of CBs at DTPS and review the overcurrent settings of 220/132kV ATRs at DTPS to avoid the fault feeding for longer duration. ITEM NO. B.2: Total power failure at Farakka Power Station on 30th March 2018

Complete blackout occurred at 400 kV Farakka NTPC Power station on 30th March 2018 during inclement weather condition. The event started at 13:26 Hrs with the tripping of 400 kV Bus 2 of Farakka on bus fault along with 400 kV Farakka-Malda 1 circuit. Immediately after this, Farakka Unit 5 also got tripped on re-heater protection. During this event, all remaining elements remained connected through 400 kV Bus 1 through their tie. 66th PCC Minutes 2

The second event occurred at 14:26 Hrs, when this bus also tripped on Bus bar protection. With this event, both the 400 kV Bus 1 and Bus 2 at Farakka became dead, which led the tripping of Farakka Unit 1, 2, 3 and 6. Along with the units, all the 400 kV lines also tripped except 400 kV Farakka-Beharampur& 400 kV Farakka- Durgapur 1 and Farakka-Durgapur 2 & 400 kV Farakka – Kahalgaon 2 that remained in service through their tiebreakers at Farakka substation.The net generation loss during this event was 1118 MW. Following issues Observed during the event:

1. Delay in submission of information to ERLDC/ERPC on the event. 2. NTPC intimated that 400 kV Bus 2 fault occurred due to closing of bus side isolator earth

switch (4489AE) of Farakka-Gokarna Line II for all the three phases. From the switchyard snapshot submitted, it is observed that all the three phases earth switch are in close condition. NTPC/PGCIL may kindly explain how earth switch of all the three phases got closed? Further, whether the mechanical interlock scheme was healthy or not?

3. NTPC could notfind reason for fault on 400 kV Bus 1 and bus bar protection operation. The diameter /bay from which the bus bar protection activated may kindly be explained by NTPC Farakka, basedon Bus bar protection relay record.

NTPC and PGCIL may explain. Deliberation in the meeting NTPC and Powergrid explained the incident with detailed presentations. Presentations are enclosed at Annexure-B2.1 and B2.2 respectively. NTPC explained that

• During the incident, severe rain and stormy weather was prevailing at Farakka site. • At 13:56 hrs, 400 kV Bus 2 fault occurred due to closing of bus side isolator earth switch

(4489AE) of 400kV Farakka-Gokarna Line II. Heavy water ingress was observed in B-ph 4489AE MB which resulted in operation of earth switch.

• 400 kV BUS II tripped on Y PHASE differential protection and 400 KV Malda-Farakka-I Line tripped from Malda end. Farakka Unit 5 also got tripped on re-heater protection. All other elements remained connected to 400 kV Bus 1 through their tie.

• At 14:29 hrs, 400kV Bus 1 tripped on operation of bus bar protection (Y-ph differential) due to maloperation of the latchting contact of bus bar protection (zone 1).

• As a result, both 400 kV Bus 1 and Bus 2 at Farakka became dead and Farakka Unit 1, 2, 3 and 6 got tripped due to loss of evacuation path. All the 400 kV lines tripped except 400 kV Farakka-Beharampur& 400 kV Farakka- Durgapur 1 and Farakka-Durgapur 2 & 400 kV Farakka – Kahalgaon 2. The lines were remained in service through their tiebreakers at Farakka substation.

NTPC informed that 400kV Farakka-Gokarna Line II bay was recently erected and commissioned by Powergrid. Operation and Maintenance modalities are yet to be settled. Powergrid informed that joint field test was carried out on earth switch after taking 400 KV Bus-II under Shut Down on 05.04.18 and the observations are as follows:

• With all Electrical interlocks are intact; earth switch was not getting any closing command when main isolator was in closed condition.

• All mechanical interlocks are as per design and intact, i.e. by manual operation the earth switch did not operate when isolator (4489A) was in closed condition. However when put into electrical operation by Motor, bypassing all electrical interlocks, it is observed that mechanical interlock is forced to compromise and closed due to breakage of welding.

• During inspection absolute earth fault observed in both DC source.

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• Severe multi earth fault in DC system might have caused mal pick up of interlock coil

and closing coil of earth switch motor. • Welding of the mechanical interlock is an additional feature of few isolator (Make wise)

and till date generally it is not in practice to check the mechanical interlock through motorised operation as it is understood that when electrical interlock is in operation, it is not possible to operate the Earth Switch via Motor.

NTPC informed that they had taken the following remedial actions after the incident:

• RXSF relay contact of bus bar-I has been changed Powergrid informed that they had taken the following remedial actions after the incident:

• Welding has been done for Mechanical Interlock of the Earth switch (4489AE) of 400kV Farakka-Gokarna Line II

• NTPC was advised to put the AC supply all switches in off condition to avoid such incidences

ERLDC informed that the information was not received from NTPC in time. PCC opined that DC earthing could be the reason for operation of Earth Switch Motor and Busbar protection operation of Bus-I. PCC advised NTPC to ensure healthiness of the DC system at Farakka and also advised to settle the operation & Maintenance modalities with Powergrid at the earliest. CESC informed that earthing of DC system can be monitored using online monitoring system which also provides the information of fault location. This would help in maintaining the DC system at large substation. PCC requested CESC to arrange a presentation in PCC Meeting for the benefit of all ER constituents. ITEM NO. B.3: Repeated disturbances at Tashiding and Jorethang HEP

Detail report is enclosed at Annexure-B3.

1. Tripping of 220 kV Jorethang - New Melli D/C and 220 kV Tashiding -New Melli S/C lines on 22-03-2018 at 20:38 hrs

220 kV Jorethang - New Melli D/C tripped at Jorethang end on R-N fault at 20:38 hrs. At same time 220 kV Rangpo - Tashiding S/C and 220 kV Tashiding -New Melli S/C tripped at Tashiding end. 220 kV Rangpo - New Melli S/C successfully auto reclosed at same time at both the ends. Relay indications are as follows:

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Deliberation in the meeting Powergrid explained that

• There was a multi ckt fault in 220 KV New Melli-Jorethang line-I & II and Auto recloser was successfully reclosed from New Melli end. However 3-Ph tripping observed at Jorethang end.

• Similar phenomena were observed in 220kV Rangpo-Tashiding S/c line, Auto recloser was successfully reclosed from Rangpo end and 3-Ph tripping observed at Tashiding end.

• No fault was observed in 220kV New Melli-Tashiding line but Tashiding end got tripped • For both cases current was not that high but due to steep fall in voltage Zone element

picked up. DansEnergy informed that auto recloser is not in service at Tashiding and Jorethang end. PCC advised Powergrid and DansEnergy to keep the auto recloser status same in both sides to avoid unwanted autoreclose operation. PCC advised DansEnergy to check the directional feature, pick up and time settings of distance protection and over current protection of 220kV New Melli-Tashiding line at Tasheding.

2. Tripping of 220 kV Tashiding - Rangpo S/C and 220 kV Tashiding - New Melli lines on 26-03-2018 at 17:19 hrs

At 17:19 hrs 220 kV Tashiding - Rangpo S/C and 220 kV Tashiding - New Melli (Did not trip at New Melli end) S/C tripped at Tashiding end due to Y-N fault resulting S/S dead at Tashiding. Relay indications are as follows:

Powergrid and DansEnergy may explain.

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Deliberation in the meeting Powergrid informed that there was a Y-N fault in 220kV Rangpo-Tashiding line and Rangpo end has seen the fault in zone 3. Rangpo end tripped immediately after receiving DT from Tashiding. 220kV Powergrid informed that there was no fault in 220kV New Melli-Tashiding Line as no pickup was observed from New Melli end. 220kV New Melli-Tashiding Line tripped from Tashiding end for the fault in 220kV Rangpo-Tashiding line. PCC advised DansEnergy to check the directional feature, pick up and time settings of distance protection and over current protection of 220kV New Melli-Tashiding line at Tasheding.

ITEM NO. B.4: Tripping of 220 KV Muzaffarpur-Hazipur D/C line on 21-03-2018 at 13:03 hrs.

On 21-03-18, 220 KV Muzaffarpur-Hazipur-I tripped on B-N fault at 12:57 hrs and 220 KV Muzaffarpur-Hazipur-II tripped due to Y-B at 13:03hrs. As Hazipur was radially fed from Muzaffarpur through 220 KV Muzaffarpur-Hazipur-D/C lines, total power failure occurred at 220/132 kV Hazipur S/S.

Load loss 175 MW BSPTCL may explain.

Deliberation in the meeting BSPTCL and Powergrid informed that due to tree touching, a B-N was initiated in 220 KV Muzaffarpur-Hazipur-II at 12:57 hrs. The line tripped from both ends on zone-1. Thereafter, Y-B fault initiated in 220 KV Muzaffarpur-Hazipur-I at 13:03 hrs. The fault got cleared from Muzaffarpur end on zone 1. Since no other source is connected at Hazipur end, no tripping was initiated from Hazipur end. ERLDC informed that no information was received from BSPTCL and Powergrid ER-I in time. PCC advised BSPTCL and Powergrid ER-I to submit the details in time as per IEGC.

ITEM NO. B.5: Disturbance at 400/220 kV Biharshariff S/s on 28-03-2018 at 18:43 hrs and 19-03-2018 at 02:02 hrs.

28-03-2018 at 18:43 Due to Y phase jumper snapping of 220 kV side of 400/220 kV ICT - III resulted tripping of all three 400/220 kV ICTs at Biharshariff and 220 kV Tenughat - Biharshariff S/C (From Tenughat in Z-III) resulting load loss at nearby area.

Load loss 560 MW Generation loss 10 MW

66th PCC Minutes 6

Deliberation in the meeting BSPTCL informed that a Y-N fault was initiated near to 220kV Bus at Biharshariff due to jumper snapping at bus side isolator. As a result the following elements tripped:

• 400/220 kV ICT – III tripped on HV side over current protection • 400/220 kV ICT – I & II tripped on over current protection due to overload after outage of

ICT-III • 220kV Fatua-Biharshariff line tripped from Biharshariff on zone 1 • 220kV Tenughat-Biharshariff line tripped from Tenughat end on zone 3 • 220/132kV ATRs tripped on over current protection

BSPTCL added that 220kV Kijasharai-Biharshariff line is radial line hence the line didn’t tripped from any end. PCC opined that 220kV Fatua-Biharshariff line should trip from Fatua end in zone 2 and 220kV Tenughat-Biharshariff line should trip from Tenughat end on zone 2. PCC advised BSPTCL and Tenughat to check the following:

• Direction feature of 220kV Fatua-Biharshariff line at biharshariff end. • Zone 2 reach setting of 220kV Tenughat-Biharshariff line at tenughat end.

BSPTCL informed that CT polarity of 220kV Fatua-Biharshariff line at biharshariff end was in reverse. The same has been corrected after the disturbance. 19-03-2018 at 02:02 hrs A heavy sound with flashing observed in switch yard area of BSPTCL Biharshariff s/s. On thorough inspection of switch yard area it was found that in 220KV Biharsharif - Fatuah Ckt-1 Y phase conductor between dead end tower and gantry got snapped on 132KV main Bus at BSPTCL Biharshariff s/s. It is apparent from both PMU and DR that initially the fault was cleared by 220 KV line protection within zone-2 time but again fault appearred within 80 ms in all the three phases. At the second instant conductor might touched the 132 KV bus and ultimately caused tripping of 400/220KV ICT – I, II & III and 220/132 kV ICT – I, II & III at Biharshariff. Relay indications are as follows:

Name of the elements End 1 relay indication End 2 relay indication 220 KV Biharshariff-Fatuah -I

Zone 1, Y-B fault Zone-2 ,Y-B fault

440/220kV ICT 1, 2 & 3 at Biharshariff (PG) Definite time over current

220/132 kV ICT 1, 2 & 3 at Biharshariff (BSPTCL) Tripped through O/C protection

Load loss 135 MW Powergrid and BSPTCL may explain.

66th PCC Minutes 7

Deliberation in the meeting BSPTCL informed that 220KV Biharsharif - Fatuah Ckt-1, Y phase conductor between dead end tower and gantry got snapped on 132KV main Bus at BSPTCL Biharshariff s/s. First the fault got cleared form both ends distance protection of 220 KV Biharshariff-Fatuah –I. Later the fault evolved into three-phase fault at 132kV bus. The following elements tripped 440/220kV ICT 1, 2 & 3 at Biharshariff (PG) tripped on over current protection with definite time of 600 ms before tripping of 220/132 kV ICT 1, 2 & 3 at Biharshariff (BSPTCL) 220/132 kV ICT 1, 2 & 3 at Biharshariff (BSPTCL) tripped on IDMT over current protection after 1.3 sec BSPTCL informed that the fault current was 3.2 kA which was less than the high set setting (3.6 kA) of 220/132 kV ICT 1, 2 & 3 at Biharshariff (BSPTCL) hence over current relays operated with delay as per IDMT characteristics. BSPTCL added that high set setting of 220/132 kV ICT 1, 2 & 3 at Biharshariff (BSPTCL) has been revised to 3 kA. PCC opined that Jumper cannot snap suddenly and there would be hot spot appear before such failures. BSPTCL should have monitor the hotspots on daily basis so that such jumper failures could be avoided. PCC enquired about the basis of changing the high set value. PCC advised BSPTCL to compute the fault level at the substation and review the over current settings accordingly. PCC advised BSPTCL and Powergrid to coordinate back up IDMT the over current settings at 220/132 kV ICTs with 440/220kV ICTs so that 220/132 kV ICTs would trip first for any downstream faults.

ITEM NO. B.6: Tripping of 132KV KAHALGAON(BSPTCL)-LALMATIA-S/C line on 28-03-2018 at 09:14 hrs and 31-03-2018 at 01:22 hrs.

1. 28-03-2018 at 09:14 hrs

At 09:14 hrs 132KV KAHALGAON(BSPTCL)-LALMATIA-S/C- tripped from Lalmatia end due E/F Over Current resulting load loss at radially connected Sahebgunj S/S. Load loss 32 MW Fault clearing time as per PMU data: 350 ms. Deliberation in the meeting JUSNL informed that both 132KV KAHALGAON(BSPTCL)-LALMATIA-S/C and 132KV KAHALGAON(NTPC)-LALMATIA-S/C lines tripped from Lalmatia (JUSNL) end on overcurrent, E/F protection. NTPC and BSPTCL informed that no tripping was initiated from their end. PCC advised JUSNL to check the healthiness of the relays at Lalmatia(JUSNL) end. 2. 31-03-2018 at 01:22 hrs

66th PCC Minutes 8

At 01:22 hrs 132 kV Kahalgaon - Lalmatia S/C tripped due to O/C & E/F resulting load loss at radially fed Sahebgunj area. Load loss 30 MW Fault clearing time as per PMU data is less than 100 ms. BSPTCL may explain. Deliberation in the meeting JUSNL informed that both 132KV KAHALGAON(BSPTCL)-LALMATIA-S/C and 132KV KAHALGAON(NTPC)-LALMATIA-S/C lines tripped from Lalmatia end on overcurrent, E/F protection. NTPC and BSPTCL informed that no tripping was initiated from their end. PCC advised JUSNL to check the healthiness of the relays at Lalmatia(JUSNL) end. ITEM NO. B.7: Disturbance at 220/132 kV Old Purnea S/S on 16-03-2018 at 11:15 hrs There was a transient fault in 132 KV Purnea (BSPTCL) -Triveniganj s/c transmission line, due to which Triveniganj end distance protection relay operated on Zone 2. But due to VT fuse failure of Purnea end relay, the purnea end relay of 132 KV Purnea (BSPTCL) - Triveniganj s/c transmission line did not operate. As a result, the following lines got tripped:

• 220 kV New Purnea - Old Purnea D/C (tripped from New Purnea end on directional E/F) • 220/132 kV ICT - I & II at Old Purnea (Tripped from O/C protection) • 132 kV Old Purnea - Purnea (B) - I & II (CKT I & II tripped on O/C from Purnea Old) • 132 kV Purnea - Kishangunj S/C (tripped from Kishangunj in Z-II)

As per PMU data, fault was cleared within 500 ms BSPTCL and Powergrid may explain. Deliberation in the meeting BSPTCL explained that there was a transient fault in 132 KV Purnea (BSPTCL) -Triveniganj s/c transmission line, due to which Triveniganj end distance protection relay operated on Zone 2. But Purnea end distance relay failed to operate due to VT fuse fail. 132kV Old Purnea - Purnea (B) line I & II tripped from Old Purnea but line III failed to identify the fault due to incorrect relay settings. 132 kV Purnea - Kishangunj S/C line also tripped from Kishangunj on Zone II. As a result, 220/132 kV ICT - I & II at Old Purnea tripped from 220kV side on O/C protection but 220/132 kV ICT – III failed to identify the fault because of in correct relay settings. Finally fault got cleared from 220kV New Purnea after tripping of 220 kV New Purnea - Old Purnea D/C line from New Purnea end on directional overcurrent E/F. PCC opined that during VT fuse failure the distance protection would change to non-directional overcurrent protection and alarm also appears on the relay. PCC advised BSPTCL to take the following actions: The relay settings of VT failure at Purnea(B) of 132 KV Purnea (BSPTCL) -Triveniganj s/c should to

66th PCC Minutes 9

be reviewed PCC advised Powergrid to take the following actions: The relay settings of 132kV Old Purnea - Purnea (B) line III and 220/132 kV ICT – III at Old Purnea should be reviewed Powergrid informed that the relay settings of 132kV Old Purnea - Purnea (B) line III and 220/132 kV ICT – III at Old Purnea have been corrected in coordination with adjacent relay settings. On enquiry, Powergrid informed that line differential protection is not yet commissioned for all three lines of 132kV Old Purnea - Purnea (B). Some work is yet to be done at Purnea(B). BSPTCL agreed to take necessary action by 30th April 2018. ITEM NO. B.8: Tripping of 132 KV Lakhisarai-Lakhisarai D/C lines on 19-03-2018 at 05:35 hrs At 5:35 hrs,132 KV Lakhisarai Lakhisarai d/c tripped on R-N fault distance protection from Lakhisarai (PG) end. Powergrid may explain. Deliberation in the meeting Powergrid informed that 132 KV Lakhisarai(PG)-Lakhisarai D/C line tripped from Lakhisarai (PG) end on R-N fault distance protection due to some fault in downstream network. Powergrid added that as per the DR, the fault distance from 132 KV Lakhisarai(PG) was 49.64 km for line 1 and 46.15 km for line 2 where as the line length is 16 km. This clearly shows that the fault was beyond the line. PCC advised BSPTCL to ensure the healthiness of protection system at 132kV Lakhisarai(B) S/s and downstream network so that the downstream faults should not get reflected at 132kV level. ITEM NO. B.9: Disturbance at 132 kV Sabour S/S on 20-03-2018 at 22:34 hrs At 22:34 Hrs, Y ph CT of 132/33 KV ICT #1 (HV side) at Sabour failed. At the same time, 132 KV Banka-Sabour D/c tripped, leading to a load loss of 52 MW. BSPTCL may explain. Deliberation in the meeting BSPTCL informed that Y-N fault initiated at 132kV Sabour S/s due to failure of HV side Y ph CT of 132/33 KV ICT #1. BSPTCL and Powergrid updated the relay indications as follows:

Name of the elements End 1 relay indication End 2 relay indication 132 KV Banka (PG) -Sabour -I

Zone 2, Y-N fault None

132 KV Banka (PG) -Sabour -II None Zone 1, Y-N fault PCC opined that 132 KV Banka (PG) -Sabour –II should trip from Banka(PG) end on zone 2 instead of tripping from Sabour end. BSPTCL informed that during analysis it was found that CT secondary star point of 132 KV Banka (PG) -Sabour –II at Sabour was in reverse. The same has been corrected.

66th PCC Minutes 10

ITEM NO. B.10: Tripping of 132 kV NBU - Lebong S/C, 132 kV NBU - Rammam S/C, 132

kV Siliguri - Kurseong S/C, 132 kV Melli - Siliguri S/C and 132 kV Melli - Rangpo S/C lines on 11-03-2018 at 15:05 hrs

132kV NBU-Darjeeling and NBU-Rammam line tripped due to zone 1 operation. But 132kV bus of RHP got dead due to tripping of 132kV Rammam-Rangit line from Rangit(NHPC) end. At the same time, 132kV Siliguri(PG)-Kurseong line tripped from PG end causing total power failure at Kurseong S/s. 132 kV Melli - Siliguri S/C and 132 kV Melli - Rangpo S/C also tripped. In 65th PCC, WBSETCL and Powergrid informed that due to severe thunder storms in around Darjeeling, Siliguri and NBU, multiple faults were occurred in 132kV NBU-Darjeeling, 132kV NBU-Rammam and 132kV Siliguri(PG)-Kurseong lines. WBSETCL informed that faults in 132kV NBU-Darjeeling and 132kV NBU-Rammam lines were successfully cleared from both ends on zone 1 distance protection. Powergrid informed that 132kV Siliguri(PG)-Kurseong line tripped from PG end on high set overcurrent protection. This resulted in total power failure at 132kV Kurseong. It was informed that 132kV Rammam-Rangit line was also tripped from Rangit(NHPC) end resulted in total power failure at Rammam. Details from Rangit are yet to be received. PCC decided to discuss the disturbance in detail in next PCC Meeting and advised all the concern constituents to submit the details to ERPC and ERLDC. Details received from WBSTCL are as follows:

Sikkim, Powergrid and WBSETCL may explain. Deliberation in the meeting Powergrid informed that multiple faults occurred due to severe rain and stormy weather. Powergrid

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had placed the details as follows:

1. 132 KV SILIGURI-KURSEUNG Tripped from Siliguri end at 15:06:42 Hrs on operation of distance protection (Zone-I).

2. 132 KV SILIGURI-MELLI Tripped from Siliguri end at 15:06:42 Hrs on operation of distance protection (Zone-I).

3. 132 KV RANGPO-MELLI Tripped from Rangpo end on operation of distance protection at 15:06:43 Hrs (Zone-3) after Z3 time.

4. 132 KV SILIGURI-NBU Tripped from Siliguri end on operation of O/C element at 15:04:58 Hrs.

Powergrid added that 132 KV SILIGURI-MELLI & 132 KV SILIGURI-KURSEUNG are running on same tower. Sudden rise in earth potential was observed during lightning strike, which caused disturbance in the insulation distribution system and failure of insulators. The issue could be resolved after replacement of porcelain insulators with polymer insulators. In case of 132 kV Siliguri-NBU line, maximum portion of this line belongs to Sikim Govt., and most of the faults observed in their jurisdiction. It was informed that 132kV Rammam-Rangit line was hand tripped from Rangit end. PCC concluded that because of multiple line trippings, no evacuation path was available for Rangit generators. ITEM NO. B.11: Tripping of 132 kV Rangpo Gangtok S/C and 132 kV Chujachen -

Gangtok S/C on 26-03-2018 at 16:45 hrs There was no generation at Chujachen at the time of the disturbance. 132 kV Rangpo Gangtok S/C and 132 kV Chujachen - Gangtok S/C tripped simultaneously at 16:45 hrs due to R-Y-B-N fault and B-N fault respectively. Powergrid and Chuzachen may explain. Deliberation in the meeting Powergrid informed that 132 KV RANGPO-GANGTOK & 132 KV Chujachen-Gangtok are running on same tower and there was a fault in both the circuits.

1. 132 KV RANGPO-GANGTOK Tripped from both end at 16:45 Hrs on operation of distance protection (Zone-I) for R-Y-B-N Fault.

2. 132 KV Chujachen-Gangtok Tripped from both end at 16:45 Hrs on operation of distance protection (Zone-I).

Powergrid added that maximum portion of the line belongs to Sikim Govt., and most of the faults observed in their jurisdiction. ITEM NO. B.12: Tripping of Rangit units on 26-03-2018 at 14:40 hrs and 17:56 hrs At 14:40 hrs 132 kV Rangit - Rammam S/C and 132 kV Melli -Sagbari were out of service. 132 kV Melli - Siliguri S/C tripped at 14:22 hrs resulting formation of island with running of unit II at Rangit and load at surrounding area. Due to mismatch of load generation balance, Rangit unit started hunting and it was hand-tripped. Load loss 12 MW Generation loss 20 MW 66th PCC Minutes 12

Deliberation in the meeting Powergrid informed that 132 KV SILIGURI-MELLI tripped at 14:22 hrs from both end on dist protection, ZONE-I,R-Y FAULT, Fault Current: Ia= 1.83 KA, Ib= 1.81 KA, Ic= 0.22 KA. At 17:56 hrs 132 kV Rangit - Rammam S/C and 132 kV Melli -Sagbari were out of service. At 17:56 hrs 132 kV Melli - Silliguri S/C and 132 kV Rangit -Kurseong S/C tripped on Y-B-N fault resulting formation of island with running units at Rangit and load at surrounding area. Due to mismatch of load generation balance, Rangit unit started hunting and they were hand-tripped. Load loss 16 MW Generation loss 60 MW NHPC, Sikkim and Powergrid may explain. Deliberation in the meeting Powergrid informed that 132 KV SILIGURI-MELLI tripped at 17:56 hrs from both end on dist protection, ZONE-I,Y-B-N FAULT, 36.9 KM from siliguri, FAULT CURRENT: Ia= 0.09KA,Ib=2.58KA, Ic= 2.98KA. Powergrid added that for both the incidents massive thundering & lightening was observed in the affected area. Sudden rise in earth potential was observed during lightning strike, which caused disturbance in the insulation distribution system and failure of insulators. The issue could be resolved after replacement of porcelain insulators with polymer insulators. ITEM NO. B.13: Disturbance in North Bengal on 22.03.18 at 11:23hr On 22.03.18 at 11:23hr, generators running at Rammam and TCF HEP got tripped due to overcurrent protection causing generation loss of 10MW and 19MW. WBSETCL sub-stns. at NBU, Ujanu, Siliguri, Darjeeling, Kurseung and NJP experienced momentary blackout at that moment though no tripping of any line occurred at any S/S. UFR relays operated at 11:23hr tripping 33kv feeders at NJP, NBU and Siliguri sub-stn. At NJP, the only 160MVA TR#2 which was in service has tripped on both HV & LV side due to operation of relay 86 (Master Trip). It was presumed that some transient fault occurred at 132kv network associated with 220/132kv Siliguri(PGCIL) S/S at 11:23hr on 22.03.18 causing voltage dip at associated WBSETCL S/S. In 65th PCC, WBSETCL informed that no transmission line was tripped from their end. PCC advised Powergrid to verify and submit all the relevant details to ERPC and ERLDC for further analysis and detailed discussion in next PCC Meeting. Powergrid, WBSETCL and NHPC may explain. Deliberation in the meeting Powergrid informed that zone 3 pickup observed at Rangpo end relays of 132kV Rangpo-Melli and 132kV Rangpo-Gangtok line. It was informed that 132 kV Melli –Sagbari line was taking into service at the time of incident. Details are awaited from Sikkim. ITEM NO. B.14: Disturbance at 132 kV Patratu S/S (DVC) on 25-03-2018 at 14:25 hrs 66th PCC Minutes 13

220/132 kV ATR-II at Patratu was under shutdown. 132 kV bus at Patratu became dead after tripping of remaining 220/132 kV ATR at Patratu on E/F. DVC may explain. Deliberation in the meeting DVC informed that they are taking power from Patratu (JUSNL) and no disturbance was observed on 25-03-2018 at 14:25 hrs. ITEM NO. B.15: Unreliable operation at Motihari (DMTCL) SS

In 144th OCC, ERLDC informed that 400/132kV Motihari S/Stn is of critical importance as the two high capacity inter-regional lines (400kVBarh-Gorakhpur Qd. Moose D/C) link E. Region with N. Region at this S/Stn. The Barh-Motihari D/C Qd. Moose line is essential for reliable power evacuation from Barh STPS of 2X660MW capacity. Motihari S/Stn is also responsible for meeting about 200MW load, considering Bihar and Nepal together. Power supply to Motihari, Dhaka, Raxaul, Bettia, Ramnagar etc. S/Stns of Bihar and to Nepal at Surajpura and Parwanipur interface points failed at 09:56 Hrs of 07-04-18, due to tripping of all lines connected to Motihari 400kV (DMTCL) S/Stn on YN/BN/3-ph faults, leading to interruption of around 200MW load in Bihar and Nepal taken together. The 3-ph fault of Barh-Motihari D/C line was cleared with a delay of 400ms, which is much higher than that mandated by CEA standards (100ms). The units at Barh STPS experienced severe jerk of about 110MW during such fault. On same day at 18:25 Hrs, ICT I again tripped on overload protection. As a result 132 KV side became dead resulting in load loss of 177 MW at Ramnagar, Betiah, Raxaul, Motihari, Dhaka, Sibhar, Narkatiyaganj including 80 MW of Nepal as mentioned above As on date main CB of 125MVAR bus reactor-1, line isolator of 400kV Gorakhpur-2 line along with main and tie CBs of this line are out of service due to problem in gas duct. 400 kV Motihari – Gorakhpur – II was out of service due to unavailability of both bays at Motihari S/S.

It may be appreciated that in view of the importance of Motihari 400kV as stated above, reliable performance of this S/Stn has to be ensured under all circumstances. OCC took serious note of the issue and referred to 66th PCC Meeting scheduled to be held on 25th April 2018. 66th PCC Minutes 14

DMTCL may explain. Members may discuss. Deliberation in the meeting DMTCL has submitted a report. The report is enclosed at Annexure-B15. ERLDC informed that any fault in 400kV Barh-Motihari line is getting cleared in 500 msec. It should be cleared within 100 ms. PCC advised DMTCL to put the PLCC and inter tripping scheme is service so that the fault would be cleared within 100 ms. PCC also advised DMTCL to attend OCC & PCC meetings on regular basis. ITEM NO. B.16: Tripping incidences in the month of March, 2018 Other tripping incidences occurred in the month of March 2018 which needs explanation from constituents of either of the end is given at Annexure- B16. In 58th PCC, ERLDC informed that most of the constituents are not submitting the DR and EL data for single line trippings. PCC advised all the constituents to upload the details along with DR and EL in PDMS on-line portal and referred the issue to TCC for further guidance. In 36th TCC, all the constituents were advised to use the PDMS on-line portal for uploading the single line tripping details along with DR (comtrade files), EL and other relevant files for all trippings of August 2017 onwards. Otherwise, it will be considered as violation of compliance of clause 5.2(r) & 5.9 of IEGC. Members may discuss. Deliberation in the meeting Members explained the tripping incidences. Updated status is enclosed at Annexure-B16. ERLDC has placed the details of Disturbance at Meramundali S/s as follows: At 19:30:48.400 Hrs, 400 kV Meramundali-Sterlite – I has tripped on distance protection operation due to the failure of B phase Lightening arrester at Meramundali end. Immediately the 400/220 kV ICT 1 and 2 (each of 315 MVA capacity) at Meramundali substation also got tripped from 400 kV side on backup overcurrent protection.

Name of the elements Relay Indication Meramundali end Relay Indication at remote end

400 kV Meramundali-Sterlite 1

B-N, Z-I, 27.4 km from Meramundali, F/C 35.46 kA

B-N, Z-I, 221.9 km from SEL, F/C 1.6

kA

400/220 kV 315 MVA Meramundali I CT 1

O/C protection operated at 400 kV side and inter trip at 220 kV side.

400/220 kV 315 MVA Meramundali I CT 2

O/C protection operated at 400 kV side and inter trip at 220 kV side.

OPTCL informed that ICTs tripped on high set overcurrent protection but the fault current was not so high. They are investigating the cause. 66th PCC Minutes 15

66th PCC Minutes 16

PART- C:: OTHER ITEMS

FOLLOW-UP OF DECISIONS OF THE PREVIOUS PROTECTION SUB-COMMITTEE MEETING(S)

(The status on the follow up actions is to be furnished by respective constituents) ITEM NO. C.1: Disturbance at 220/132 kV Patratu S/S on 09-02-2018 at 15:00 hrs In 65th PCC, JUSNL was advised to take the following measures:

• Check the healthiness of the DC system including end to end cables at 220/132kV Patratu S/s

• Check the healthiness of all Circuit Breakers at 220/132kV Patratu S/s • Check the healthiness of all the relays installed at 220/132kV Patratu S/s including

220/132kV ATRs • Check Kanke end relay and CB of 132kV Patratu-Kanke line • Check the Directional feature of 132 kV Hatia I – Sikidri and 132 kV Namkum - Hatia I line

relays at Hatia-I PCC advised TVNL to verify the zone 1 reach of 220kV Patratu-TVNL line as TVNL end should trip on zone 2 in this case. JUSNL and TVNL may update. Deliberation in the meeting JUSNL informed that they had visited 220/132kV Patratu S/s on 23rd April 2018 for physical inspection of protection system. JUSNL submitted the status of protection equipment as given below:

220/132KV GSS PTPS Patratu

Sl.No. Name of feeder/Transformer Relay Status Breaker Status Setting

1 132KV HATIA-I (8C) DEFECTIVE WORKING 2 132KV HATIA-I (9C) WORKING WORKING Downloded 3 132KV BUS COUPLER WORKING WORKING Downloded 4 220KV HATIA-II CKT-1 WORKING WORKING Downloded 5 220KV HATIA-II CKT-2 WORKING WORKING Downloded 6 220KV BUS COUPLER WORKING WORKING Downloded 7 220KV TVNL MAIN 1 WORKING WORKING HAND WRITTEN 8 220KV TVNL MAIN 2 DEFECTIVE 9 150MVA AUTO TRANSFORMER NO 1 WORKING WORKING HAND WRITTEN

10 150MVA AUTO TRANSFORMER NO 2 DEFECTIVE DEFECTIVE 11 132KV DVC CKT 1 WORKING WORKING Downloded 12 132KV DVC CKT 2 IDLE CHARGE FROM DVC END Downloded

JUSNL added that the primary injection kit was defective hence they could not test the healthiness of the relays. They are planning to engage an agency for checking healthiness of the relays.

66th PCC Minutes 17

ITEM NO. C.2: Tripping of 132 kV Birpara(PG) – Birpara(WB) D/C line on 13-02-2018 at 17:53

hrs 132 kV NJP – Moinaguri S/C and 132 kV NJP - Chalsa - Moinaguri link were out of service. At 17:53 hrs 132 kV Birpara - Birpara D/C tripped from PG end resulting load loss at Birpara, Moinaguri, Alipurduar and their surrounding areas. In 65th PCC, Powergrid informed that 132 kV Birpara(PG) - Birpara D/C tripped from PG on overcurrent protection due to overload. Powergrid informed that settings at PG end have been implemented as per the data received from WBSETCL end. WBSETCL informed that CT ratio at PG end has to be changed according to present loading of the line. PCC advised Powergrid and WBSETCL to coordinate and review the CT ratio/relay settings to avoid unwanted tripping. WBSETCL and Powergrid may update. Deliberation in the meeting Powergrid informed that CT ratio at PG end is 800/1 and the PSM is at 0.75 corresponding to 600 A. As per the conductor current rating, the setting is in order. Powergrid agreed to change the setting, if required. ITEM NO. C.3: Multiple tripping around Talcher during Pole shutdown on 09-01-2018 Regarding sending of carrier signal from Rourkela to Talcher, Powergrid informed that they have tested the scheme on 17th January 2018 and the issue has been referred to OEM(Alstom) for rectification. Powergrid Odisha Project may update. Deliberation in the meeting Powergrid informed that M/s Astom has suggested to revise some settings in carrier scheme and the same had been implemented. The relay is now under observation. ITEM NO. C.4: Disturbance at 220 kV Budhipadar S/s on 01-10-17 at 09:25 hrs In 62nd PCC, OPTCL informed that Busbar protection maloperated and tripped all the elements connected 220kV bus 1 at Budhipadar. OPTCL added that the issue has been referred to OEM (Siemens) for rectification. In 63rd PCC, OPTCL informed that OEM (SIEMENS) visited the Substation on 29th December’2017 and taken the data (i.e. Trip Log, Even Log & DR) for analysis. In 64th PCC, OPTCL informed that OEM, Siemens has recommended for updating of 7SS52_MCU device firmware version to V4.73 or higher to resolve the restart automatic problems. Accordingly, Siemens will upgrade the firmware. OPTCL may update. 66th PCC Minutes 18

Deliberation in the meeting OPTCL informed that the firmware would be updated by May 2018. ITEM NO. C.5: Tripping of 220 KV Darbhanga-Motipur D/C and 220 KV Muzaffarpur (MTPS)-

Motipur D/C on 02-11-17 at 13:18 hrs In 62nd PCC, it was opined that the busbar protection should not operate in this case. BSPTCL informed that the issue of maloperation of busbar protection at 220kV Motipur has been communicated to OEM (GE) for rectification. In 65th PCC, BSPTCL informed that GIS work is in progress. The busbar protection would be tested by OEM within 2 months BSPTCL may update. Deliberation in the meeting BSPTCL informed that the busbar protection had been tested and found healthy. ITEM NO. C.6: Interim Arrangement for substations that are not having bus bar protection In

Eastern region There may be 400 kV or 220 kV substations where either the bus bar is kept out of service for planned shutdown or bus bar protection is not available due to various reasons. Further, the older substations having static busbar scheme would also undergo replacement activity witha numerical scheme for which the bus bar protection will again be required to be withdrawn for a considerable time. Under such scenario, there is need of a mechanism to reduce the bus fault clearance time as the non-availability of bus bar protection can result in delayed fault clearance.In case of any issue of the protection system at remote substations,there may bea widespread outage.

In view of this, it is proposed to adhere to the following philosophy whenever the bus bar protection is kept out or is not available for a considerable amount of time at any 765/400/220 kV substation:

1. Zone 4 (Reverse Zone) timing of all the Lines to be reduced to 300 ms. The LBB should have a high priority or the reverse zone time should be set at least equal to LBB time setting.

2. Healthiness of the carrier protection of all lines is to be ensured. 3. Zone 4 timer reset should be checked in all the relays, as its function needs to be flawless. 4. DMT high set available in the numerical backup Overcurrent (O/C) relays of all the ICTs be

properly set to clear the bus fault immediately. The backup O/C protection is coordinated with the upstream and downstream elements;therefore, it would not be possible to make it sensitive as suggested.

5. Bus Coupler overcurrent protection setting to be made lower. Whenever the Bus Bar protection is out the Buses should be operated in split bus mode, to have isolation of the elements on other Buses from feeding the Bus fault.

6. Re-trip feature if available in LBB should also be enabled to take one more attempt of breaker opening.

7. Healthiness of all Protection i.e. both Main and Backup shall be ensured. 8. All the Other Utilities at the remote ends be informed about the Bus Bar protection outage

through ERLDC/respective SLDCs

In the case where two separate bus bar protections schemes are available at the substation as Main 1 and Main 2, then the above will not be applicable in the case of the outage of any one of the bus bar protection scheme.

In 65th PCC, all the constituents were advised to send their comments to ERPC and ERLDC.

66th PCC Minutes 19

PCC may discuss. Deliberation in the meeting PCC advised all the constituents to send their comments to ERPC and ERLDC. ITEM NO. C.7: Follow Up action on Disturbance at 400kV Koderma and 400kV Bokaro-A on

30-01-18 at 10:46 Hrs ● DVC to check the neutral earthing of line CVTs: Status of CVT earthing checking at the

substation may be informed by DVC ● Root cause: If any root cause for this event has been found then may kindly be shared with

ER PCM forum Regarding CVT secondary earthing at DVC KTPS 400KV switchyard, DVC informed that the earth resistance of the electronic earth pit was measured. At present the value is 0.260 ohm. Earlier it was about 16 ohms as reported by KTPS O & M. DVC may update. Deliberation in the meeting Members noted. ITEM NO. C.8: Third Party Protection Audit 1. Status of 1st Third Party Protection Audit:

The compliance status of 1st Third Party Protection Audit observations is as follows:

Name of Constituents Total Observations Complied % of

Compliance Powergrid 54 46 85.19 NTPC 16 14 87.50 NHPC 1 1 100.00 DVC 40 26 65.00 WB 68 27 39.71 Odisha 59 42 71.19 JUSNL 34 25 73.53 BSPTCL 16 5 31.25 IPP (GMR, Sterlite and MPL) 5 5 100.00

* Pending observations of Powergrid are related to PLCC problems at other end. The substation wise status of compliance are available at ERPC website (Observations include PLCC rectification/activation which needs a comprehensive plan).

Members may update. Deliberation in the meeting WBSETCL had submitted the latest status. PCC advised all the constituents to comply the pending observations. It was informed that DVC vide letter dated 9th March 2018 submitted that they are facing frequent failure of old equipment installed at 220kV MTPS, DTPS, CTPS and BTPS S/s and requested for Third Party Protection audit.

66th PCC Minutes 20

PCC decided to carry out the Third Party Protection Audit of these substations in May 2018. ITEM NO. C.9: Repeated pole blocking at HVDC Sasaram In 63rd PCC, Powergrid submitted the report which is enclosed at Annexure-C9. In 64th PCC, Powergrid informed that they are implementing the observations. PCC advised Powergrid update the status in monthly PCC Meetings. Powergrid informed that as per OEM recommendation they have to install air condition system to minimize the temperature of the control panels. PCC advised Powergrid to submit the details to ERPC and ERLDC. Powergrid may update. Deliberation in the meeting Powergrid informed that as per OEM recommendation they have to install air condition system to minimize the temperature of the control panels which is under procurement. ITEM NO. C.10: Non-commissioning of PLCC / OPGW and non-implementation of carrier

aided tripping in 220kV and above lines. According to CEA technical standard for construction of electric plants and electric lines -Clause 43(4) (c), transmission line of 220 KV and above should have single-phase auto-reclosing facility for improving the availability of the lines. However, from the tripping details attached June-August, 2016 it is evident that the some of 220kV above Inter & Intra-Regional lines do not having auto-reclose facility either at one end or at both ends. Out of these for some of the lines even PLCC/OPGW is not yet installed and carrier aided protection including Autorecloser facility is not yet implemented. Based on the trippings of June- August, 2016 and PMU analysis a list of such lines has been prepared and as given below:

List of line where auto reclose facility is not available(Information based on PMU data analysis)

S. No Transmission Lines name Date of

Tripping Reason of Tripping

Owner Detail Present Status

End-1 End-2 OPGW/PLCC Link available

AR facility functional

13 220KV BUDIPADAR-KORBA-II

23.06.16 Y-N FAULT OPTCL CSEB PLCC

available

will be activated in consultation with Korba

17 220 KV TSTPP-RENGALI

17.07.16

EARTH FAULT NTPC OPTCL

by March 2018

18 220KV BUDIPADAR-RAIGARH

21.07.16

EARTH FAULT OPTCL PGCIL PLCC

defective

19 400 KV KOLAGHAT-KHARAGPUR-II

03.08.16 Y-N FAULT WBPDC

L WBSETCL

20 220 KV FARAKKA-LALMATIA

03.08.16 B-N FAULT . NTPC JUNSL

Yes Old Relay and not functional. 7-8 months required for auto re-close relay

66th PCC Minutes 21

procurement.

23 220 KV MUZAFFARPUR - HAZIPUR - II

10.08.16 B-N FAULT PGCIL BSPTCL

Voice established. For carrier required shutdown

24 220 KV ROURKELA - TARKERA-II

11.08.16 B-N FAULT PGCIL OPTCL OPGW

available

Expected to install protection coupler by Jan 17

27 220 KV BIHARSARIF-TENUGHAT

07.09.16 B-N FAULT BSPTC

L TVNL

32 220KV Bidhannagar-Waria-II WBSET

CL DVC

33 220KV Jamshedpur-Jindal-SC

34th TCC advised all the respective members to update the above list along with the last tripping status in next PCC meeting. TCC further advised all the constituents to give the latest status of PLCC of other 220kV and above lines under respective control area. OPTCL:

1. 220kV Rengali(PG)-Rengali S/Y (Proposal for Commn. in OPGW is pending): PSDF appraisal committee accepted the proposal

2. 220kV Indravati(PG)-Indravati(PH) (Proposal for Commn. in OPGW pending): PSDF appraisal committee accepted the proposal

3. 132kV Baripada(PG)-Baripada ( Tendering in Progress for OPGW): Contract awarded 4. 132kV Baripada(PG)-Rairangpur (Tendering in Progress for OPGW): Contract awarded

BSPTCL:

1. 220kV Purnea (PG)-Madhepura line 2. 220 kV Biharshariff- Begusarai line Work is in progress expected to be commissioned 3. 220 kV Biharshariff- Bodhgaya line by December 2017. 4. 220kV MTPS-Motiari line 5. 220KV Madhepura-New Purnea D/C Auto recloser is out of service at Madhepura 6. 220KV Muzaffarpur-Hajipur D/C line Auto recloser is out of service at Hazipur 7. 220KV FSTPP-Lalmatia-1 Auto recloser is out of service at Lalmatia 8. 220KV Patna-Khagaul-SC Auto recloser is out of service at Khagual

In 65th PCC, Powergrid informed that they will replace the Autorecloser relay of 400 kV Rourkela-

Chaibasa 1 and 400 kV Meramundali-Sterlite 1 & 2 by April 2018.

Members may update the status. Deliberation in the meeting Powergrid informed that they will replace the Autorecloser relay of 400 kV Rourkela-Chaibasa 1 by 26th April 2018. ITEM NO. C.11: Checklist for submission of updated data for Protection Database

The network data in Protection Database needs to be updated on regular basis on account of commissioning of new elements in the CTU as well as STU networks. Accordingly a checklist has been prepared which is enclosed in Annexure-C11.

66th PCC Minutes 22

All the constituents requested to submit the checklist on monthly bases in every OCC/PCC meetings. Constituents may note. Deliberation in the meeting PCC advised all constituents to submit the checklist on monthly bases in every OCC/PCC meetings. ITEM NO. C.12: Any other issues. 1. Low Frequency Oscillation (LFO) observed at Durgapur and nearby nodes on 05th April

2018 from 14:21 hrs to 14:28 hrs. Low frequency oscillation of 0.1 Hz was observed in Durgapur and nearby nodes on 05thApril 2018 from 14:21 hrs. to 14:28 hrs. The oscillation was prominent in the Eastern region near Durgapur only based on the analysis of pan India synchrophasor data. Durgapur bus voltage from PMU is given below where oscillation can be observed. Oscillation was not significant in magnitude at other PMUs indicating some nearby local phenomenon or generator hunting at Durgapur. Based on analysis of Eastern region SCADA data, it was found that there was a large variation in the MW and MVAR of Sagardighi Unit 4 during the same time period.

Fig 1 : Durgapur Bus Voltage from PMU indicating oscillation on 5th April’ 18.

Fig 2: MW/MVAr Plot of Sagardighi Unit 4 on 05th April’ 18 (From WBPDCL)

It was observed that the Sagardighi U#4 Active power has varied by around100 MW while its reactive power varied by 160 MVAR. The associated plot of MW/MVAr based on the data received from WBPDCL is also given below. Further, at 14:47 Hrs. Sagradighi Unit 4 tripped due to turbine vibration but it was not reported at that time to ERLDC. The tripping of unit captured from ERLDC SCADA data is given in next figure.

66th PCC Minutes 23

Fig 3 :MW variation of the Sagardighi unit 4 and its subsequent tripping observed from ERLDC SCADA for 5th April’ 18.

On inquiry from ERLDC, it was found that there was some problem in the bearing (bearing and supports are designed to keep the static and dynamic forces under control) which has led to balancing problem of rotor thus causing turbine vibration. In order to mitigate this, the load set point of the unit was changed manually causing unit generation fluctuation from 150 MW to 250 MW as can be seen from the power flow and MVAR pattern attached.

The time of LFO initiation in the grid observed from PMU data and fluctuation in MW/MVAr for the Unit 4 of Sagardighi were matching. Apart from this no other unit in the Sagardighi, as well as pan India, has shown the variation in their output. In view of this, it was inferred that the oscillation has excited in the grid due to Sagardighi Unit 4.

It may further be seen that this is not the first time Sagardighi Unit 4 has caused the oscillation in the grid. On 22nd July 2017 at 22:47 Hrsalso, the same unit has excited the Low frequency oscillation of 0.083 Hz in the Indian grid. Also in this case, the MW/MVAR of the unit has widely fluctuated (Active Power: 120-250 MW and Reactive Power: 70 to 170 MVAr). The Durgapur PMU voltage and MW/MVAr plot of Sagardighi Unit 4 is also given below for reference.

Fig 4 : Durgapur Bus Voltage from PMU indicating oscillation on 22nd July’ 18.

66th PCC Minutes 24

Fig 5 : MW and MVAr Plot of Sagardighi Unit 4 on 22nd July’ 18. In view of the aboveincident, it is desired that:

1. Sagardighi (WBPDCL) may kindly explain the issue with the turbine vibration and the remedial action taken so that such event does not appear again in near future as these have an adverse impact on the entire the Indian Grid as well as on the nearby units. Being the second time in a span of one year is serious and the all the details along with the detailed report must be shared with ERLDC/ERPC.

2. PSS tuning of all the units above 100 MW may kindly be ensured as per the relevant regulation of CERC and CEA in the Eastern region and their tuning reports to be shared with ERLDC/ERPC.

Members may discuss. Deliberation in the meeting It was informed that the issue was discussed in 144th OCC Meeting wherein WBPDCL informed that oscillations were observed due to problem in Governor of Sagardhigi unit#4. WBPDCL added that the unit is under shutdown and they are investigating the root cause. OCC advised WBPDCL to submit a report for both the incidences occurred on 05 April’18 and 22nd July 2017 along with the action taken. 2. Coordination of Auto-Reclsoure on the Transmission lines emanating from generating

substation Many of the Generating stations adopt delayed Auto-reclosure scheme by sensing of the successful Auto-reclosure at the remote end through voltage buildup. In this way if the fault is persisting then it will not be attempting auto-reclosure as line will be in trip condition from the remote end thus there will be no voltage buildup. The intent of this scheme is to avoid generator to feed the fault current on more than one occasion in case of permanent nature of the fault. However, certain issues have been observed in the real-time cases, which are described below:

1. A/R Time coordination: In many instances, it has been observed that even in case of unsuccessful A/R from other end, the generating end is attempting Auto-reclosure and thus once again feeding the fault causing double voltage dip. This defies the whole purpose of this scheme. In such cases, either there should be a direct trip sent from the remote end after unsuccessful auto –reclosure or Tripping of the circuit at generating end after the delay introduced for sensing of voltage buildup after A/R timing.

2. Activation of TOR protection:Delayed feeding of Fault during A/R has been observed in case of Zone 2 fault from one of the ends. This has happened when the fault is not in the

66th PCC Minutes 25

Overlapped Zone 1area from both ends of the transmission line. Under this condition, it has been observed that if the end from where the fault is in zone 2 takes the first attempt for A/R then will see the fault in zone 2 and clear in zone 2 timing (350 ms). This has resulted in delayed fault feeding to the system, which is highly undesirable. Under such condition, if TOR (trip on reclose) protection would have been enabled/activated, then it will trip immediately irrespective of the zone for such scheme.

Example of the above two issuescan be seen in the tripping of 400 kV Jeerat-Chanditala at 19:28 Hrs on 17.04.18: Originally the above-mentionedline was 400 kV Jeerat-Kolaghat and recentlyit has beenLILOed at Chanditala. As one side of the line was Generator (Kolaghat) previously,its A/R scheme was based kept at both ends as per above-described scheme. It is suspected that the A/R timing and scheme has not been revised after the LILO work at Chanditala. On 17th March 2018 at 19:28 Hrs, B phase to earth fault has occurred on the transmission line and its PMU plot is shown in the attached figure. It can be seen that Jeerat end has attempted the A/R in 500 ms and it continuously fed the fault in Zone 2. After clearance of the fault from one end, the other end has also taken A/R attempt, which again resulted in fault feeding in the system.

Fig: 400 kV Durgapur Bus Voltage from PMU indicating the fault on 400 Jeerat-Chanditala ckt. PCC may discuss. Deliberation in the meeting PCC opined that TOR (trip on reclose) protection should be activated to minimize the fault feeding period. PCC advised WBSETCL to take appropriate action.

Meeting ended with vote of thanks to the chair.

*************** 66th PCC Minutes 26

66th PCC Minutes 27

Scanned by CamScanner

Scanned by CamScanner

DISTURBANCE AT DVC WARIA ON 09.03.2018 AT

ABOUT 12:33HRS

Annexure-B1

SLD OF CONCERNED REGION

ATR#1,2,3O/C; P=1000A

160MVA*3

DTPS 220KV

DTPS 132KV

RAMKANALI 132KV

CB did not Trip

Z1; 3.5KM

Z2; 60.5KM

PHS 132KV

Z1

Z1

L # 90

L # 45, 46

14.4Km

73 Km

KALIPAHARI 132KV

67

67

L # 100

JAMURIA 132KV

33 Km

MADE OFF BY HAND

BURDWAN 132KV

L # 75

L # 76

L # 61

L # 60

CTPS 132KV

SEQUENCE AND ANALYSIS OF RELAY OPERATION• There was a AB fault very near to Ramkanali Bus in DTPS Ramkanali

Line(L#90). Most probably the fault was in wave trap as the Y Phasewave trap had caught fire.

• Ramkanali End L # 90 trips in Distance Zone 1. Simultaneously PHSend both lines also trips in Zone 1.

• DTPS end distance relay gives trip command in Zone 2 but CB doesnot open.

• Kalipahari End clears the fault through D/O/C relay as the fault wasbeyond it’s Z2 reach.

• L # 90 DTPS end continues to feed the fault and at 955ms the faultchanges to L2-E, at 1536ms to L1-2-E and finally at 2964ms to L1-2-3-E. These changes were due to multiple faults developing on the lineas the fault remained uncleared.

SEQUENCE AND ANALYSIS OF RELAY OPERATION

• As the initial fault current was about 2300A which was below3000A(combined pick of ATR LV sides i.e. 3*1000A), the ATRscontinue to feed the fault without tripping.

• After jumper had snapped at various locations due to continuousfeeding of fault, the fault current had crossed 3000A after which theATRs had tripped. ATR tripping took place at about 9.5sec after faultinitiation through LV O/C relay which had a Pick Up of 1000A.

• DTPS Burdwan Line was made OFF by hand due to extreme voltagedip as instructed by CLD.

• This caused power failure in DTPS 132KV, ASP, Jamuria and RamkanaliS/S.

REMEDIAL MEASURES TAKEN• Investigation of PHS end distance relay settings revealed abnormality

in Zone settings. The Zone 1 reach was double than required whichhas been corrected now.

• As an additional measure of stability in our 132KV system from theincident that happened on 19.01.18 and 09.03.18, we haveintroduced isolation of Kly & DTPS systems during overloads causedby tripping of either Kly or DTPS ATRs to prevent cascading tripping ofboth DTPS and Kalyaneshwary ATRs.

• The cut points will be Kly Kalipahari Line(L # 18 & 19) and in PHSRamkanali line (L # 45, 46) which will trip whenever the current risesabove 480A for 700ms in either directions.

DR OF L # 90

STATION BLACK OUT OF FARAKKA SUPER THERMAL

POWER PROJECT ON 30.03.2018

Annexure-B2.1

SEQUENCE OF EVENTS

TIME :16:03, DATE: 30.03.2018

ATTEMPT TAKEN TO CHARGE 400 KV BUS II, BUT TRIPPED AGAIN ON BUS BAR DIFFERENTIAL

AT 16:16 HOURS 400 KV BUS I CHARGED THROUGH FARAKKA-GOKARNA LINE 1

TIME :14:29, DATE: 30.03.2018

400 kV BUS I TRIPPED ON Y PHASE DIFFERENTIAL PROTECTION TOTAL POWER LOSS AND STATION BLACK OUT

TIME :13:56, DATE:30.03.2018

400 kV BUS II TRIPPED ON Y PHASE DIFFERENTIAL PROTECTION UNIT#5 TRIPPED ON REHEATER PROTECTION

SEQUENCE OF EVENTS

FOR ASCERTAINING CAUSE OF 400KV BUS II TRIPPING, BUS II CVT WAS TESTED FOR TAN DELTA. VOLTAGE WAS

NOT GETTING BUILD UP

ON FURTHER INSPECTION, 4489AE (BUS SIDE ISOLATOR EARTH SWITCH OF 400 KV FARAKKA-GOKARNA-II) WAS FOUND IN CLOSED CONDITION WITH ISOLATOR 4489A ALSO IN CLOSED CONDITION FOR ALL THREE PHASES

EARTH SWITCHES OPENED FOR ALL THREE PHASES AND 400 KV BUS II CHARGED AT 22:52 HOURS

400 kV SWITCHYARD SLD FOR NTPC FSTPS

Gen-1 Gen-2 Gen-3Gen-4Gen-5Gen-6

TT-1

400KV Bus-II

400KV Bus-I

152

252

352 452

552

652752

852

305228522552

2652

2752

4052

4152

44524252

4352

952

Auto Tr.

3252

3152

1052

1152

1252

1452

15521652

1752

18521952

2052

2152

2252

2352

2452

3452

3552

3752

3652

1252LV

Malda-2Malda-1

Bus Reactor-2

220KV Lalmatia Line

SagardighiBerhampore

Durgapur-1

Shunt Reactor

Durgapur-2

Kahalgaon-2

Kahalgaon-1Kahalgaon-3

Kahalgaon-4

GOKARNA IGOKARNA II

BUS REACTOR#1

1352

TT#3 TT#2

4489AE EARTH SWITCH IN CLOSED CONDITION WITH ISOLATOR 4489A IN CLOSED CONDITION

FOR ALL THREE PHASES

OBSERVATIONS

OBSERVATIONS

OBSERVATIONS

BROKEN CORONA GRADING RING R PHASE EARTH SWITCH

ISOLATOR-EARTH SWITCH MECHANICAL INTERLOCK

ISOLATOR LEVER RESTRICTING THE EARTH SWITCH OPERATION

MECHANICAL INTERLOCK OF EARTH SWITCH

BROKEN WELDING BETWEEN EARTH SWITCH SHAFT AND MECHANICAL INTERLOCK

ISOLATOR-EARTH SWITCH MECHANICAL INTERLOCK

ISOLATOR LEVER TRAJECTORY FROM ISOLATOR CLOSED TO OPEN CONDITION

MECHNICAL INTERLOCK TRAJECTORY WHEN ISOLATOR IS OPEN AND EARTH SWITCH BEING CLOSED

ELECTRICAL CONTROL CIRCUIT DIAGRAM FOR EARTH SWITCH OPERATION

OBSERVATIONS AT FARAKKA-GOKARNA LINE II BAY 44

• DURING THE OCCURENCE OF THE WHOLE INCIDENT,SEVERE RAIN AND STORMY WEATHER WASPREVAILING AT FARAKKA SITE.

• ON INSPECTION IT WAS FOUND THAT EARTH SWITCHMBs FOR 4489AE (BUS SIDE ISOLATOR EARTHSWITCH FOR BAY 44) WERE IN OPEN CONDITION.

• HEAVY WATER INGRESS WAS OBSERVED IN B –PH4489AE MB.

• THIS BAY (BAY NO 44) IS NEWLY ERECTED ANDCOMMISSIONED BY M/S PGCIL UNDER ERSS(EASTERN REGION STRENGTHENING SCHEME) ANDIS MAINTAINED BY M/S PGCIL.

BUS BAR PROTECTION SCHEME

• HIGH IMPEDANCE BUS BAR DIFFERENTIAL SCHEME ISPRESENT.

• RELAY: ABB MAKE COMBIFLEX RADHA RELAY.

• THREE ZONES ARE PRESENT: MAIN I, MAIN II, CHECK ZONE(COMMON FOR BOTH ZONE OPERATION)

• CT CONNECTIONS FOR ALL BAYS

• 1. CORE 1: ALL MAIN BAY CTs FOR BOTH 400 KV BUS I&II ARECONNECTED IN PARALLEL TO CHECK ZONE BUS BARPROTECTION.

• 2. CORE 2: ALL MAIN BAY CTs FOR 400 KV BUS I CONNECTED INPARALLEL TO ZONE 1 BUS BAR PROTECTION

• ALL MAIN BAY CTs FOR 400 KV BUS II CONNECTED INPARALLEL TO ZONE II BUS BAR PROTECTION.

BUS BAR PROTECTION PANEL SCHEMATIC DRAWING

BFR 50 LBB

BFR 50 LBB

87 BC87 BM I

87 BM IISUP CH

SUP CH

SUP CH

TRIP

BU

S I

TRIP

BU

S II

STAR

T BF

R

DIRE

CT T

RIP

CARR

IER

SNED

+

TRIP RELAY

TRIP RELAY

O/C RELAYS

RXSF: SIGNAL FLAG RELAYSTRIPPING CKT

ALARM CKT

+ve DC

GENERIC SCHEME FOR RADHA (87 BB)

+ve DC

-ve DC

RXIC CHRXSF CH

CHECK ZONE RADHA

RXIC ZONE I

SUP CHECK

SUP ZONE I

RXSF ZONE I

RXIC ZONE IIRXSF ZONE II

SUP ZONE II

ZONE 1 RADHA

ZONE II RADHA

TR

IP B

US

1T

RIP

BU

S 2

TRIP RELAYS (96) OF INDIVIDUAL BAY OF

BUS I

TRIP RELAYS (96) OF INDIVIDUAL BAY OF

BUS II

RXIC: DIFFERENTIAL CURRENT RELAY (PHASE SEGREGATED)

RXSF: CURRENT (DC) OPERATED SIGNAL RELAY (PHASE SEGREGATED)

SUP: CT SUPERVISION RELAY CONTACT

400 KV BUS BAR DIFFERENTIAL PROTECTION TRIP SCHEME. DURING OPERATION OF BB PROTECTION THE RXSF RELAY REMAINS PICKED UP THROUGH ITS LATCHING CONTACT. FOR RESETING THE SAME, DC NEEDS TO BE ISOLATED AS THERE IS NO OTHER PROVISION AVAILABLE FOR RESET.

LATCHING CONTACT FOR RXSF

+ve DC

-ve DC

RXIC CHRXSF CH

CHECK ZONE RADHA

RXIC ZONE I

SUP CHECK

SUP ZONE I

RXSF ZONE I

RXIC ZONE IIRXSF ZONE II

SUP ZONE II

ZONE 1 RADHA

ZONE II RADHA

TR

IP B

US

1T

RIP

BU

S 2

TRIP RELAYS (96) OF INDIVIDUAL BAY OF

BUS I

TRIP RELAYS (96) OF INDIVIDUAL BAY OF

BUS II

RXIC: DIFFERENTIAL CURRENT RELAY (PHASE SEGREGATED)

RXSF: CURRENT (DC) OPERATED SIGNAL RELAY (PHASE SEGREGATED)

SUP: CT SUPERVISION RELAY CONTACT

DURING INITIAL 400 KV BUS BAR II TRIPPINGCHECK ZONE FOR ENTIRE SWITCHYARD IS IN OPERATED

CONDITION; ALL ASSOCIATED BREAKERS OF 400 KV BUS II TRIPPED

+ve DC

-ve DC

RXIC CHRXSF CH

CHECK ZONE RADHA

RXIC ZONE I

SUP CHECK

SUP ZONE I

RXSF ZONE I

RXIC ZONE IIRXSF ZONE II

SUP ZONE II

ZONE 1 RADHA

ZONE II RADHA

TR

IP B

US

1T

RIP

BU

S 2

TRIP RELAYS (96) OF INDIVIDUAL BAY OF

BUS I

TRIP RELAYS (96) OF INDIVIDUAL BAY OF

BUS II

RXIC: DIFFERENTIAL CURRENT RELAY (PHASE SEGREGATED)

RXSF: CURRENT (DC) OPERATED SIGNAL RELAY (PHASE SEGREGATED)

SUP: CT SUPERVISION RELAY CONTACT

CHECK ZONE (RXSF CH)FOR ENTIRE 400 KV SWITCHYARD WAS ALREADY INOPERATED CONDITION AFTER BUS II TRIPPING. SUSPECTED MAL OPERATIONOF THE LATCHING CONTACT FOR RXSF ZONE 1 RELAY LED TO THE TRIPING OF400 KV BUS I.

MALOPERATION OF LATCHING CONTACT

REMEDIAL MEASURES TAKEN

• RXSF RELAY CONTACT FOR BUS BAR-I HASBEEN CHANGED.

• 4489AE EARTH SWITCH MECHANICALINTERLOCK, WELDING HAS BEEN DONEPROPERLY.

• ALL ISOLATORS AND EARTH SWITCH MBsFOR BAY 44 (FARAKKA-GOKARNA LINEII)HAVE BEEN LOCKED, MAIN INCOMING ACSUPPLY HAS BEEN SWITCHED OFF INPRESENCE OF M/s PGCIL.

5/9/2018

1

Bus-II Tripping of Farakka on 30.03.2018.

POWERGRID/ER-II

DETAILS OF INCIDENTS• AT 13:55:41.000 Hrs, 400 KV Malda-Farakka-I Line tripped from

Malda end only however Line remains charged from Farakka end.• At the same time 400 KV Bus-II at Farakka become dead as

information received.• At 14:27:45.166 Hrs, CB at Malda end for 400 KV Malda-Farakka-I

line synchronised at Malda end.• At 14:29:37.375 Hrs, DT Command received at Malda end for both

Malda-Farakka Line and subsequently both Lines tripped.Concurrently 400 KV Bus-I also dead at Farakka causing completeloss of Generation at their end. However some lines are remains inservice through Tie CB connectivity.

Annexure-B2.2

5/9/2018

2

• As information received from NTPC, that 4489AE , i.e,Earth switch of Main Bus-II Isolator of 400 KV FKK-GOK-II got closed when isolator is in closed position.

• The subject information got received only on 02.04.18when incident occurred on 30.03.18.

• Getting the information on 02.04.18, representative ofPOWERGRID & NTPC jointly carried out some fieldtest on said isolator and earth switch after taking 400KV Bus-II under Shut Down on 05.04.18.

• Before going in details we should keep in mind thatEarth switch is purely a maintenance device and ingeneral require human intervention to operate it.

5/9/2018

3

• During detailed field testing of isolator on 05-04-2018followings are found:-

1. All Electrical interlocks are intact and earth switch did notget any closing command when main isolator is in closedcondition.

2. All mechanical interlocks are as per design and intact, i.e. bymanual operation the earth switch did not operate when isolator(4489A) is in closed condition. However when put into electricaloperation by Motor, bypassing all electrical interlocks, it isobserved that mechanical interlock is forced to compromise andclosed due to breakage of welding.3. During inspection absolute earth fault observed in both DC

source.

• As Earth switch is a maintenance device and mandatorily requirehuman intervention for operation of the equipment, in general,AC supply of Earth Switch is generally made off and only put onwhile carrying out any maintenance activity.

• Severe multi earth fault in DC system might have caused malpick up of interlock coil and closing coil of earth switch motor to

• Welding of the mechanical interlock is an additional feature offew isolator (Make wise) and till date generally it is not inpractice to check the mechanical interlock through motorisedoperation as it is understood that when electrical interlock is inoperation, electrically it is not possible to operate the EarthSwitch.

• Brief idea about mechanical interlock through pictorialrepresentation given for reference:-

5/9/2018

4

Interlock cam whenE/S in open Position

Interlock cam

Interlock Assembly

Interlock Pipe

Bracket-2Bracket-1

5/9/2018

5

Interlock link pipe assembly

Link pipe

Interlock Adjustment

Interlock Rod whenM/S in Close Position

Interlock cam whenE/S in open Position

5/9/2018

6

Interlock Position for Disconnector Closed & Earth switch open condition

Interlock lever to be adjusted and then insert dowel pin/grub screw & welding as applicable.

Interlock Position for Disconnector Open & Earth switch close condition

5/9/2018

7

WELDING GOT DETACHED DURING FORCED ELECTRICAL OPERATIONCAUSING CLOSING OF EARTH SWITCH.

CONCLUSION……….From site observation and findings it may be concluded that, earthswitch of the particular isolator (4489A) got closed due to followingreasons:-(a) Severe Multi earth fault in both DC sources is the main reason to

mal pick up the interlock coil as well as closing coil which in turnforcingly operated earth switch and damaged the mechanical interlock.

(b) For particular incident, it is evident that AC was present &aggravate the spurious operation of earth switch. It is worthy tomention that operation of the bays are solely done by NTPC only & ingeneral practice always AC supply of the Earth switch should be keptoff other than maintenance activity.

(c) Mechanical interlock is restricting the movement of the earth switchwhen tried through manual mode even in breakage of welding joints ofstopper. However when tried through electrical operation the earthswitch get closed.

5/9/2018

8

Corrective action from POWERGRID side

• Damaged welding of the subject earth switch has already beenrectified on 05.04.18 itself and adviced for putting OFF ACsupply for all earth switch. In addition to that already all thebalance isolators of 42/43/44 Bays are planned forstrengthening of welding's of mechanical interlocks andsubsequent checking of the interlocks also to ascertain desiredaction.

Incident No. 220318/1 & 260318/1 Dtd: 03-04-18

Report on repeated grid disturbances at Tashiding and Jorethang HEP during March 2018

Summary: This report is highlighting the issue of multiple blackouts of 220 kV Tashiding and 220 kV

Jorethang substations due to multiple line tripping on a single transient fault. Apart from these, several

other tripping on various faults has also occurred on 220 kV Tashiding-New Melli and 220 kV Tashiding-

Rangit in last few months. Important tripping incidents occurred in the month of March, 2018 in this

corridor are also mentioned in this report to raise the concern among the utilities for taking appropriate

actions.

Network across Tashiding:

Figure 1: Geographical diagram of the network of affected system

A. Date / Time of disturbance: 22-03-18, 20:38 hrs

1) Summary of the incident: 220 kV Jorethang - New Melli D/C tripped at Jorethang end on R-N fault at

20:38 hrs. At the same time 220 kV Rangpo - Tashiding S/C and 220 kV Tashiding -New Melli S/C

tripped at Tashiding end. Along with this, 220 kV Rangpo - New Melli S/C got successfully auto

Annexure-B3

reclosed at the same time on observing this fault from both the ends. The tripping of all lines from

Tashiding and Jorethang has led to their blackout; however, no generation loss has occurred as no

units are in operating condition at both the generating plants.

2) Category : - GD -1

3) Quantum of load/generation loss: Nil

4) Major elements tripped:

a. 220 kV Jorethang - New Melli D/C

b. 220 kV Rangpo - Tashiding S/C

c. 220 kV Tashiding - New Melli S/C

5) Details of relay flag:

Name of the elements End 1 Relay Indication End 2 Relay Indication

220 kV Jorethang - New Melli 1

(Line length 21 km)

Jorethang: R Phase to E/F, Z-I, 7.14

km

New Melli end is yet to

be received

220 kV Jorethang - New Melli 2

(Line length 21 km) Jorethang: Phase to E/F, Z-I, 7.2 km

New Melli end is yet to

be received

220 kV Rangpo - Tashiding S/C

(Line length 46 km)

Rangpo: R-N, 22.56 km, 4.2 kA, A/R

successful

Tashiding: Tripped but no

detail received.

220 kV Tashiding -New Melli S/C

(Line length 18 km)

Tashiding: Tripped but no Detail

received. No Tripping

220 kV Rangpo - New Melli S/C

(Line length 22 km)

Rangpo: R phase to E/F, Fault loc:

22.81 km, If: 6.47 kA, A/R

successful

New Melli: R phase to

E/F, Fault loc: 5.73 km,

If: 1.13 kA, A/R

successful

6) Restoration:

220 kV Jorethang - New Melli D/C was restored at 20:47 and 20:51 hrs respectively

220 kV Rangpo - Tashiding S/C was restored at 21:11 Hrs

220 kV Tashiding - New Melli S/C was restored at 21:03 Hrs

7) Analysis:

Event after constant perusal from ERLDC, no DR/EL has been made available from New Melli and Rangpo.

Jorethang and Tashiding have sent their event logger however, that is not readable due to non-standard

format. The event has been analyzed based on Preliminary information in real time and PMU plot.

From 400 kV Binguri Bus voltage from PMU (Ref Fig 2), only one fault was observed in R phase at

20:36:20.080 hrs which got cleared within 100 ms. Based on the information, it is assumed that the fault

was on 220 kV Jorethang - New Melli D/C. However, at the same time, 220 kV Rangpo - Tashiding S/C and

220 kV Tashiding –New Melli circuit have tripped from Tashiding end. Further, 220 kV Rango-New Melli

circuit has performed successful A/R from Rangpo end for this fault.

Figure 2: 400 kV Bus voltage at Binaguri indicating the fault during the disturbance

The above Information reveals the following issues:

1. Relay setting of 220 kV Rango-New Melli S/C and 220 kV Rangpo-Tashiding ckt overreached for

the fault of 220 kV Jorethang-Melli D/C from Rangpo End.

2. 220 kV Tashiding-New Melli also tripped from the Tashiding end on observing fault in reverse

direction.

3. No Auto-Reclosure on 220 kV Jorethang-New Melli circuits from both ends and 220 kV Tashiding -

New Melli from Tashiding end are observed.

B. Date / Time of disturbance: 26-03-18, 17:19 hrs

1) Summary of the incident: At 17:19 hrs, 220 kV Tashiding - Rangpo S/C and 220 kV Tashiding - New

Melli (did not trip at New Melli end) S/C tripped at the Tashiding end due to Y-N fault resulting

blackout of 220 kV Tashiding power plant. However, no generation loss has occurred due to no

generation at Tashiding generating station.

2) Category : - GD -1

3) Quantum of load/generation loss: Nil

4) Major elements tripped:

a. 220 kV Rangpo - Tashiding S/C

b. 220 kV Tashiding - New Melli S/C

5) Details of relay flag:

Name of the elements End 1 Relay Indication End 2 Relay Indication

220 kV Rangpo - Tashiding S/C

(Line length 46 km) Rangpo end: DT receipt

Tashiding end: Y Phase to E/F, Z-1,

Fault location: 9.67 km, If : 1.62 kA

220 kV Tashiding -New Melli S/C

(Line length 18 km)

Tashiding end: Y Phase to E/F, Z-

1, 4.6 kA N. Melli end: No tripping

6) Restoration

220 kV Rangpo - Tashiding S/C was restored at 17:53 hrs

220 kV Tashiding - New Melli S/C was restored at 17:47hrs

7) Analysis:

Again, for this event also, No DR/EL was shared by the Tashiding end. Based on the flash report of ERLDC

control Room and PMU plot it has been analyzed.

From 400 kV Binaguri Bus voltage from PMU (Ref Fig 3), only one fault was observed in Y phase at

17:19:12.760 hrs which got cleared within 100 ms. Based on relay indication, it is observed that fault was

on 220 kV Rangpo-Tashiding circuit.

Figure 3:400 kV Bus voltage at Binaguri indicating the Y phase fault during the disturbance

The above Information reveals the following issues:

1. The reason for direct trip being sent to Rango end for 220 kV Rangpo-Tashiding ckt by Tashiding

end was not desirable.

2. 220 kV Tashiding-New Melli also tripped from Tashiding end on observing fault in reverse

direction.

3. No Auto-Reclosure on 220 kV Rangpo-Tashiding and 220 kV Tashiding -New Melli from Tashiding

end are observed.

As per information received, the fault was on 220 kV Rangpo - Tashiding S/C and 220 kV Rangpo - New

Melli S/C as per available relay indication. POWERGRID/Tashiding/ JLHEP may share the exact location of

the fault in the circuit.

Over all from both the events, following issues need immediate attention:

1. What was the reason of fault on these circuits? PGCIL ERTS-2 /Tashiding/ JLHEP May kindly

respond with details.

2. Issue of the direct trip from Tashiding end to Rangpo end. Tashiding/PGCIL ERTS-2 may kindly

respond.

3. Issue of overreaching of distance protection from 220 kV Rango substation. PGCIL ERTS-2 may

kindly respond.

4. Issue of the non-directional trip of 220 kV Tashiding-New Melli circuits. Tashiding may kindly

respond.

5. No Auto-Reclosure on 220 kV Rangpo-Tashiding and 220 kV Tashiding -New Melli from Tashiding

end and 220 kV Jorethang-New Melli circuits from both ends. PGCIL ERTS-2 /Tashiding/ JLHEP

May kindly respond with details.

6. No DR/EL are being received from the PGCIL ERTS-2/Tashiding/JLHEP substation violating the

IEGC 5.2.r and CEA grid standard 15.3. Tashiding/JLHEP have sent event logger, however, those

are not readable as differ from standard event logger. PGCIL ERTS-2 /Tashiding/ JLHEP May

kindly respond with details.

Over all Non-Compliance of regulation observed from the utilities during both the events:

Issues Regulation Non-Compliance Utility

DR/EL not provided

within 24 Hours

1. IEGC 5.2 (r)

2. CEA grid Standard 15.3

PGCIL ERTS-2, JLHEP, Tashiding

(EL received from JLHEP &

Tashiding but not in standard

format)

Non-Submission of

Details for the tripping

which is required for

appropriate analysis for

GD/GI

1. IEGC 5.2 (r), 5.9.6.c (VI)

2. CEA grid Standard 15.3

3.CEA (Technical standards for

connectivity to the Grid) Regulation,

2007-6. 4.d

PGCIL ERTS-2, JLHEP, Tashiding

Single phase A/R in

transmission lines at

220 kV and above levels

is not present/enable

1. CEA Technical standards for

construction of electric plants and

electric lines –Clause 43(4) (c).

2. CEA Transmission Planning Criteria

PGCIL ERTS-2, JLHEP, Tashiding

Incorrect/ mis-

operation / unwanted

operation of Protection

system

1. CEA Technical Standard for Construction of Electrical Plants and Electric Lines: 43.4 .A. 2. CEA (Technical standards for

connectivity to the Grid) Regulation,

2007: Schedule Part 1. ( 6.1, 6.2, 6.3)

PGCIL ERTS-2, JLHEP, Tashiding

Remedial Measures to be taken:

It has been observed that DR in comtrade format is not being received from PGCIL ERTS-

2/JLHEP/Tashiding HEP for all the major events resulting in non-compliance of regulations by CERC

and CEA. Further, in the absence of details, the analysis is also incomplete. This is not desirable from

grid security point of view. In view of the above JLHEP/Tashiding HEP/POWERGRID are advised to

find out the root cause of repeated multiple tripping at 220 kV JLHEP – New Melli – Tashiding –

Rangpo section and to ensure submission of DR (in comtrade format)/EL for any line tripping

incident within 24 hours to ERLDC as per IEGC and CEA Grid Standard to facilitate the detailed

analysis for the events. The details should be sent to the following email id:

erldcprotection@posoco.in

Along with these major five issues have been highlighted in this report. PGCIL ERTS-2/Tashiding and

JLHEP must immediately take action on these issues to improve the reliability in the area. After

taking remedial action, communication may also be given to ERLDC/ERPC. Important tripping

incidents occurred in the month of March, 2018 in this corridor are as follows:

LINE NAME TRIP

DATE

TRIP

TIME

RESTORATION

DATE RESTORATIO

N TIME

Reason

220KV TASHIDING-

RANGPO-SC

09-03-

18

17:22 09-03-18 18:06 R-Y-N FAULT

220KV TASHIDING-

RANGPO-SC

12-03-

18

13:22 12-03-18 14:05 R-Y Fault

220KV NEW MELLI-

JORETHANG-I

22-03-

18

20:38 22-03-18 20:47 TRIPPING AT

JORETHANG ONLY

220KV JORETHANG-

NEW MELLI-II

22-03-

18

20:38 22-03-18 20:51 TRIPPING AT

TASHIDING ONLY

220KV TASHIDING-

RANGPO-SC

26-03-

18

17:19 26-03-18 17:53 Y-N Fault

220KV NEW MELLI-

TASHIDING-SC

26-03-

18

17:19 26-03-18 17:47 Y-N Fault

220KV NEW MELLI-

JORETHANG-I

30-03-

18

17:45 30-03-18 17:47 B-N FAULT

220KV TASHIDING-

RANGPO-SC

30-03-

18

17:50 30-03-18 17:50 B-N FAULT

220KV NEW MELLI-

TASHIDING-SC

30-03-

18

17:50 30-03-18 17:50 B-N FAULT

220KV NEW MELLI-

TASHIDING-SC

31-03-

18

13:09 31-03-18 13:16 Y-N FAULT

Annexure-B15

S.NO

LINE NAME TRIP DATETRIP TIME

RESTORATION DATE

RESTORATION TIME

Relay Indication LOCAL END

Relay Indication REMOTE END

Reason

Fault Clearance

time in msec

Deliberation in the meeting

1 400KV BAHARAMPUR-SAGARDIGHI-II 15-03-2018 20:05 15-03-2018 20:25 Did not trippedTRIPPED FROM SAGARDIGHI

END ONLY--

DT sent from Baharampur end due to some problem in

BCU. The same has been rectified.

2 400KV FSTPP-BAHARAMPUR-SC 15-03-2018 21:15 15-03-2018 21:42 Did not trippedTRIPPED FROM SAGARDIGHI

END ONLY--

First time charging after shutdown. No fault int he

line.

3 132KV RANGPO-MELLI-SC 22-03-2018 18:03 22-03-2018 18:26R_Y,2.6 KM,R-1.67

KA;Y-1.56 KAR-Y FAULT <100

4 132KV MELLI-SILIGURI-SC 22-03-2018 18:03 22-03-2018 18:43R_Y,104.9 KM,Z2,R-1.43 KA,Y-1.29 KA

R-Y FAULT <100

5 220KV TASHIDING-RANGPO-SC 30-03-2018 17:50 30-03-2018 17:50B_N;Z-1,27.28 KM,1.356 KA

Did not tripped B-N FAULT --

6 220KV NEW MELLI-TASHIDING-SC 30-03-2018 17:50 30-03-2018 17:50Z1,B_N,9.926 KM,1.653

KA B-N FAULT --

7 220KV ATRI-PANDIABILI-II 31-03-2018 18:48 31-03-2018 19:21 86 RELAY OPERATED 86 RELAY OPERATED AT ATRI <100

8 220KV PANDIABILI-SAMANGARA-I 31-03-2018 18:48 31-03-2018 19:43 R-N fault, f/c=1.1 KA R-N FAULT <100

Miscellaneous: Tripping on DT, No reason furnished, No Fault observed in PMU

List of important transmission lines in ER which tripped in March 2018

Multiple tripping at the same time

Discussed in main agenda

Trip ckt supervision problem at Pandiabil. The same has been rectified on 15th April

2018

9 400KV RANCHI-SIPAT-I 07-03-2018 7:09 07-03-2018 7:33 DT RECEIVED DT RECEIVED AT RANCHI --Problem in PLCC at Ranchi

and same has been rectified.

10 765KV NEW RANCHI-DHARAMJAIGARH-I 12-03-2018 16:56 12-03-2018 20:30 DT RECEIVED DT RECEIVED AT NEW RANCHI -- Bus fault at Dharamjaigarh

11 220KV ATRI-PANDIABILI-II 20-03-2018 12:26 20-03-2018 12:51MASTER TRIP RELAY

OPERATEDDid not tripped

MASTER TRIP RELAY OPERATED AT ATRI

--

Trip ckt supervision problem at Pandiabil. The same has been rectified on 15th April

2018

12 220KV PUSAULI-NADHOKAR-SC 26-03-2018 0:30 26-03-2018 0:53Transient Fault,

Distance tripDistance protection at Pasuali --

Fault not observed in PMU data

13 400KV DARBHANGA (DMTCL)-MUZAFFARPUR-I 26-03-2018 18:31 26-03-2018 19:06 DT received DT received at Muzaffarpur --DT initiated due to wrong

operation DMTCL

14 220KV ATRI-PANDIABILI-II 28-03-2018 11:58 28-03-2018 12:2286 a b operated, carrier

received DT received DT received at Pandialili --

Trip ckt supervision problem at Pandiabil. The same has been rectified on 15th April

2018

Miscellaneous: Tripping on DT, No reason furnished, No Fault observed in PMU

Annexure-B16

S.NO

LINE NAME TRIP DATETRIP TIME

RESTORATION DATE

RESTORATION TIME

Relay Indication LOCAL END

Relay Indication REMOTE END

Reason

Fault Clearance

time in msec

Deliberation in the meeting

15 220KV NEW MELLI-JORETHANG-I 30-03-2018 17:45 30-03-2018 17:47 Did not tripped831.4 A,ZONE 1,B-

N,1.749 KM B-N FAULT --

Fault not observed in PMU data

16 400KV BINAGURI-NEW PURNEA-I 06-03-2018 13:14 06-03-2018 13:31 B-N , 30KM , 5 KA B-N FAULT < 200DTPC problem at Binaguri

PLCC. Tendering is in process for new DTPC.

17 400KV MOTIHARI-BARH-II 19-03-2018 11:26 19-03-2018 11:53 B-N, 4.33 KA, DIST 22.3 B-N,219 KM, 1.6 KA B-N FAULT <100 No autoreclose operation

observed in PMU data

18 400KV MEERAMUNDALI-STERLITE-I 19-03-2018 11:30 19-03-2018 17:56 B-N, 174.2 KM, 2.24 KA B-N FAULT <100 No autoreclose operation

observed in PMU data

19 400KV JHARSUGUDA-ROURKELA-II 20-03-2018 12:58 20-03-2018 13:44 R-N, 48. km, 5.7kA R-N, 72 km, 3.11 kA R-N FAULT <100 No autoreclose operation

observed in PMU data

20 400KV MALDA-NEW PURNEA-I 23-03-2018 6:49 23-03-2018 7:20 B-N, 63.48 KM, B-N, 74.81 KM, 3.78 KA B-N FAULT <100 Breaker status mismatch at Malda. The same has been

rectified.

No Autoreclose operation observed in PMU data

Annexure-C9

Checklist for Submission of new transmission elements for updation in Protection Database

NAME OF ORGANISATION:FOR THE MONTH OF:

SUBSTATION DETAIL:

Sl No DETAILS OF ELEMENTS DATA TYPEStatus of

Submission (Y/N)

Remarks

1 TRANSMISSION LINE LINE LENGTH, CONDUCTOR TYPE, VOLTAGE GRADE2 POWER TRANSFORMER NAMEPLATE DETAILS3 GENERATOR TECHNICAL PARAMETERS4 CURRENT TRANSFORMER NAMEPLATE DETAILS5 VOLTAGE TRANSFORMER NAMEPLATE DETAILS6 RELAY DATA MAKE, MODEL and FEEDER NAME

7 RELAY SETTINGS NUMERICAL RELAYS: CSV or XML file extracted from Relay

ELECTROMECHANICAL RELAYS: SNAPSHOT of RELAY8 REACTOR NAMEPLATE DETAILS9 CAPACITOR NAMEPLATE DETAILS9 UPDATED SLD

SIGNATURE:NAME OF REPRESENTATIVE:

DESIGNATION:CONTACT:E-MAIL ID:

Annexure-C11