ISLANDING SCHEME

UTTAR PRADESH

(February, 2013)

Uttar Pradesh Power Transmission Corporation Limited

Shakti Bhawan, 14 Ashok Marg, Lucknow

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INDEX

CHAPTER NAME Page No.

1. Introduction

3-4

2. Overview of Uttar Pradesh Transmission System 5-6

3. General Philosophy on formation of Islands 7-10

4. Islanding Scheme for 5x210 MW Unchahar

Generating Station

11-14

5. Average Generation and dedicated load details of

proposed Island Scheme for Unchahar

15-18

6.0 Major Challenges And Way Forward

19-20

APPENDIX

I Minutes of 1st Meeting of Islanding Scheme Group held on 7-Aug-2012

II Transmission Map of U.P. Transmission Network (132 KV and above voltage)

III Single Line Diagrams

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CHAPTER-1.0

1.0 Introduction

1.1. Twin grid failures on 30th & 31st July 2012 affecting the Northern Region (NR),

Eastern (ER) & North- Eastern (NER) regions stirred up the entire power sector in

the country and specially the Northern region. Considering the colossal impact of

these grid disturbances on the economy as well as on the daily life of the society,

Ministry of Power (MoP), Govt. of India (GoI), immediately constituted an enquiry

committee to investigate the reasons of these grid failures and to make suitable

recommendations to prevent its recurrence in future. The above committee

submitted its report on 16.08.2012. While deliberating on the reasons of grid

failure, the Committee, in its report, among various other recommendations also

recommended implementation of islanding schemes from grid security point of

view and its early restoration in case of any failure in future. The recommendations

of the committee in this regard are as quoted below:

"Effort should be made to design islanding scheme based on frequency sensing

relays so that in case of imminent grid failure, electrical islands can be formed.

These electrical islands can not only help in maintaining supply to essential

services but would also help in faster restoration of grid .

Action: CEA, RPCs, POWERGRID, STUs, SLDCs and Generators

Time Frame: 6 months"

1.2. The Expert Committee further formed five groups to look into various aspects

related to grid disturbances. One of the groups, headed by Member

Secretary, NRPC, was formed for exploring the possibilities and

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implementing the islanding scheme in Northern Region. First meeting of the

islanding scheme group was held at NRPC office at New Delhi on

07.08.2012. Representatives from all the constituents from the Northern

Region attended the above meeting. The group agreed on various aspects &

modalities for implementation of the islanding scheme. The Minutes of above

meeting are enclosed as Appendix I.

1.4 In order to further identify & work out the modalities for taking up design &

implementation of islanding schemes in line with the recommendations of the

enquiry committee, provisions of Electricity Grid Code, guidelines of CEA,

NRPC, PGCIL etc., UPPTCL constituted a study-cum-implementation group

consisting of officers from Transmission Planning & Power System Study

Group, SLDC and field units. Further, a meeting of officers from UPPTCL,

SLDC, Uttar Pradesh RajyaVidyutUtpadan Nigam and representatives from

the Power Grid (Operation Services Group), was organized at the head

quarter level, wherein deliberations were held on the tentative islanding

schemes prepared by Power System Study group of UPPTCL.

1.5 Based on the inputs provided by NRPC/ Power Grid and in house

deliberations, UPPTCL has finalized the islanding scheme for 5 x 210 MW

Unchahar Generating Station of NTPC.

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CHAPTER 2.0

2.0 OVERVIEW OF TRANSMISSION SYSTEM OF UTTAR PRADESH

2.1 The Transmission function in the state of Uttar Pradesh is being looked after

by U.P. Power Transmission Corporation Limited (UPPTCL), which is a State

Government owned company. UPPTCL maintains a very robust intra-State

Transmission System, which is part of the integrated “NEW” grid network. It

consists of 1 no. 765KV, 14 Nos. 400KV, 69 Nos. 220KV & 271 Nos. 132KV

substations with total transformation capacity of around 56844 MVA.

UPPTCL further has total line length of 411 ckms 765KV, 4260 ckms 400KV,

8099 ckms 220KV and 13800 ckms of 132KV lines. Transmission map of

Uttar Pradesh (132 KV & above voltages) is attached at Appendix II.

2.2 The total demand met by the transmission system of UPPTCL in the range of

8000 MW to 11500 MW. Out of this total demand, approximately 2500 MW is

met through State Government owned generating stations and balance 5500

to 8500 MW through IPP’s & co-generators in the State, allocations from the

centre sector generating stations, bilateral agreement and purchases through

power exchange.

2.3 To develop evacuation system for such large quantum of power, considering

dearth of funds with UPPTCL, the Government of U.P. has planned to

augment the State Transmission system through participation of private

players. Accordingly, contracts have been awarded to two private companies

to create additional transmission capacity of around 8000 MVA including 3

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nos. 765 kV sub-stations with capacity of 9630 MVA, 9 nos. of 400 kV sub-

stations with capacity of 8320 MVA 1485 ckt. kms of 765 kV lines and 1780

ckt. kms of 400 kV lines.

2.4 As the State of Uttar Pradesh is also planning to procure additional power

through IPPs and ultra Mega Power Projects situated in other States, it is

also planning major intra-State network expansion linked to the development

of inter-State transmission network for evacuating power from these IPPs

and Ultra Mega Power Projects.

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CHAPTER 3.0

3.0 GENERAL PHILOSOPHY FOR FORMATION OF ISLANDS

3.1 The Ministry of Power constituted a Committee to enquire into recent grid

disturbances on 30th& 31st July 2012. This committee in turn formed five

groups to look into various aspects related to grid disturbances. One of the

groups formed (headed by Member Secretary, NRPC) was to look into all

aspects of Islanding Scheme and explore the possibilities of its

implementation in the Northern Region.

3.2 The initial discussions of the above group were centered on the criteria for

formation of islands. In this regard some members suggested that the size of

the islands should be big as the chances its survival will be more due to high

inertia and stability. However, there was also an opinion that in order to form

bigger islands, more number of switching operations would be required, which

would considerable reduce the chances of success of Islanding. After detailed

discussion, it was agreed that criteria for formation of islands should not be

the geographical or electrical size but reliability of load-generation balance in

the islands.

3.3 The group agreed on following issues:

i. All control areas should endeavor to operationalize under frequency

based load shedding scheme as the first line of defense. Only when

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this defense mechanism fails and frequency continues to fall further,

formation of islands should be initiated.

ii. The probability of survival of islands will be realistic only when all the

generating units are on free governor or on restricted governor mode of

operation in accordance with provisions of Indian Electricity Grid Code.

iii. Islanding scheme should be a two-tier scheme. At frequency level of

say 47.9 Hz, trigger for formation of islands comprising of more than

one generating stations along with pre-identified load should be

initiated. However, if frequency continues to fall further to say to 47.7

Hz, possibilities of forming smaller islands with pre-identified loads

should be explored.

iv. Islands should be created in such a manner that possibility of

generation exceeding load is more.

v. In case of hydro generators, islanding should be considered keeping

peak generation in mind. This is because, in low hydro season,

generation may be practically nil during off-peak hours and hence

forming of island may not be feasible.

vi. As the load-generation balance in pre-identified islands may change

due to seasonality of load, there would be need to review the scheme

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on seasonal basis. Such review would also capture network changes

taking place in the interim period.

vii. As far as possible, major hospitals and other essential loads should be

incorporated in the islands. However, if this is not possible due to some

reasons, efforts should be made to extend supply from these islands to

essential loads on priority basis.

3.4 Based on the recommendations of the enquiry committee constituted by

MOP, Govt. of India, to investigate the reasons of Grid failure on 30th and 31st

July 2012, and minutes of Islanding Group dated 07.08.2012, UPPTCL on its

own constituted a study-cum-implementation group consisting of officers from

Transmission Planning & Power System Study Group, SLDC and field units

of transmission. Further, a meeting of officers from UPPTCL, SLDC, Uttar

Pradesh Rajya Vidyut Utpadan Nigam and representatives from the Power

Grid was organized at the head quarter level, wherein deliberations were held

on the tentative islanding schemes prepared by Power System Study group

of UPPTCL. During the above meeting successful models of Islanding

Schemes were discussed and deliberations were held on the following main

issues:

a. Size of Island

b. Frequency level at which Islanding should take place.

c. Possibilities of formation of smaller island in case of failure of bigger

island and the frequency for the same.

d. Identification of dedicated load for the purposes of forming an island.

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e. Selection and monitoring of UFR.

f. Segregation of feeder and loads for different Schemes

g. Monitoring of Islanding Schemes for the purposes of load–Generation

balance.

h. House-load for survival of Island in case of extreme contingencies.

In the above meeting while deliberating on the above issues, it was suggested

that while Delhi may plan to implement a comprehensive Islanding Scheme

covering many generating stations the same may not be feasible for a State

like Uttar Pradesh, which has large geographical area and longer length of

lines with many inter-connections and loops. Accordingly, it was initially

decided that separate Islanding Schemes, for generating stations of

Unchhahar, Tanda, Roza&Parichha, as prepared by Power System Study

group of UPPTCL, only may be considered for its implementation. To make

the Islanding scheme fool proof it was further decided that two sets of under

frequency relays of different make and with different algorithm should be

utilized to isolate the island from the rest of the system.

Subsequently, in view of large demand supply gap in the State wherein large

quantum of load has to be shed on rotational basis to meet the load

generation balance, it was discussed that it may not be possible to provide

dedicated load for all the four generating stations, and accordingly, it was

finally decided that in the first go islanding scheme for only 5x210 MW

Unchahar generating station may be considered.

11 

 

CHAPTER-4.0

4.0 ISLANDING SCHEME FOR 5 X 210 MW UNCHAHAR THERMAL POWER

STATION

4.1 In the state of Uttar Pradesh, islanding scheme at the Narora Atomic Power

Station of NPC is in operation. This generating station was able to

successfully island itself during the grid disturbances of 30th July 2012 and

31st July 2012. Islanding for this generating station has been planned in two

stages at frequencies of 47.7Hz and 47.5Hz. At frequency of 47.7Hz the bulk

load is disconnected by sending tripping command to 220kV feeders of

Moradabad, Khurja and Atrauli from NAPS and only the 220kV Simbholi

feeder is kept in-service.

Similar methodology has been adopted for islanding of 5x210 MW Unchahar

generating station of NTPC in Uttar Pradesh. The first stage of islanding is

targeted at a frequency of 47.9 Hz with dedicated load of 610 MW and if

frequency still continues to fall the second stage of islanding is targeted at a

frequency of 47.7Hz with dedicated load of only 180-200 MW (i.e. house load

+ load of Rai Bareilly), with only one generator unit considered under

operation. For the second stage of Islanding suitable scheme would be

required for tripping of generator units and to prevent over-speeding of

balance unit due to reduced load.

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4.2 With respect of Islanding Scheme in general following philosophy was

agreed:

i) It was agreed that islanding would be initiated as a step of last resort

should the frequency continue to fall to lower levels even after the

operation of Under Frequency Relays (UFRs) under automatic load

shedding schemes in the UP system.

 ii) With respect to UFR’s to be utilized for Islanding purposes it was

decided that:

a. Two sets of Under Frequency Relays of different make and

different algorithm (like the Main – 1&2 protection relays) shall be

utilized to make the islanding scheme fool proof.

b. Remote monitoring facility of the under frequency relays for its

operational readiness shall be built in the scheme in phased

manner.

c. Development of communication system to enable the UFR data

communication to SLDC so that the load relief obtained through

UFR operations is available at the central location.

iii) The islanding scheme would be devised in two stages. In the first

stage of islanding at 47.9 Hz larger island of operation would be

enabled. In case the 1st islanding attempt at 47.9 Hz does not survive

the 2nd stage islanding at 47.7Hz would be initiated with only one

generating unit running with house load of the generating station and

some local load so as to maintain load generation balance at

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frequency of 47.7Hz. Further, considering the time of relay operation

and opening of breaker a time delay 3500 mili second shall be

provided between first stage of islanding and second stage of islanding

to prevent false initiation of second stage of islanding and to provide

time for first stage islanding to stabilize.

iv) As a general philosophy it was also agreed that in case of second

stage of Islanding no traction load shall be included as it may give rise

to harmonics and lead to instability of the system.

v) For the survival of island it shall be ensured that Island always remains

slightly on generation plus side. Possibility of automatic load

reconnection/management for maintaining load-generation balance

within the island on real time basis may also be explored.

vi) For effective control of frequency Generator units will run in free

governor mode of operation.

vii) The seasonal changes shall be reviewed periodically with the real time

data at the UP - SLDC.

viii) The assessment of committed generation and connected loads in the

island shall be discussed with the representative of generating stations

also.

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ix) The major essential loads shall be identified including hospitals,

Railway Station, traction supply points, important government offices,

defence installation, cantonment etc. To the extent possible efforts

would be made to extend supply from these islands on priority to the

essential load supply stations.

x) The identified loads of the island shall not be included in the automatic

load shedding schemes through UFRs, Scheduled Rostering

Schemes, and the SPS schemes. However, rotational schemes, as

may be approved by the management, may be incorporated to provide

alternative dedicated load.

xi) The State load dispatch center (SLDC) shall be nodal control room

responsible for the island control; however, it may involve concerned

generating station and ALDS, for effective management of the Island.

xii) Islanding load to be identified shall exclude the anticipated impact of

scheduled load shedding, automatic load shedding through existing

UFR &df/dt relays when frequency starts dipping below the pre set

level of 49.7 Hz as per the norms set by NRPC and the SPS schemes

etc..

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CHAPTER-5.0

5.0 AVERAGE GENERATION AND DEDICATED LOAD DETAILS OF

PROPOSED ISLANDING SCHEME FOR UNCHAHAR:

5.1 The Unchahar (NTPC) generating station has five units of 210 MW capacities

each. Considering that one machine or load equivalent to one machine may

be not be available all the time, the average available ex-bus generation from

this generating station, after deducting auxiliary consumption, has been

considered as 760 MW. Further, to maintain the island in a generation

surplus state the dedicated load for this Island scheme has been considered

as 600 MW, i.e. approximately 80% of the average available generation from

this generating station.

5.2 Through Islanding of Unchahar Generating Station almost 50% of total load

requirement of Lucknow (i.e 380 MW ) and almost entire load of Raibareilly &

Fatehpur would be fed.

5.3 Further, through this Islanding supply to following essential loads shall be

provided:

a. State Assembly and nearby VIP areas.

b. Raj Bhawan

c. Cantonment

d. Hospitals like Sanjay Gandhi Post Graduate Institute of Medical

Sciences, Sahara, Metro, Mayo, etc.

e. Railway Station

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f. Traction load through Sarojini Nagar &SGPGI in Lucknow, Malwaon &

Bachrawan in Fatehpur,

5.2 The details of feeders and ICTs that will remain connected during first stage

of Islanding at frequency of 47.9 Hz are provided in the tables given below:

Feeders to remain connected for Intentional Islanding of 5x210 MW Unchahar TPS Power

S.

No. Details of Sub-station No of

Circuits Load (MW) at Originating S/s

From To

1 2 3 4 5 A Generating Stn. end 1 220 kV Unchahar Gen Stn. 220 kV Raibareilly PG 3 510 2 220 kV Unchahar Gen Stn. 220 kV Fatehpur 2 150 Total 660

B 220 kV Rai Bareilly PG Details

520

1 220 kV Rai Bareilly PG 220 kV Chinhat 1

2 220 kV Rai Bareilly PG 220 kV Sarojini Nagar (Lko) 1

3 220 kV Chinhat 220 kV Gomti Nagar 1

4 220 kV Gomti Nagar 220 kV Sarojini Nagar (Lko) 1 40

5 132 kV Sarojini Nagar (Lko) 132 kV SGPGI 3 150

6 132 kV Chinhat 132 kV Gomti Nagar 1 120 (50 MW Martin purwah) 7 132 kV Chinhat 132 kV Martinpurwa 1

8 132 kV Gomti Nagar 132 kV SGPGI 1 70 9 132 kV Martinpurwa 132 kV SGPGI 1

10 132 kV Rai Bareilly PG 132 kV Rai Bareilly New 105 (10 MW Rai Bareilly New +25 MW Bachrawan)

11 132 kV Rai Bareilly New 132 kV Rai Bareilly Old 2

12 132 kV Rai Bareilly New 132 kV Bachrawan 1

14 132 kV Rai Bareilly Old 132 kV Dalmau 25 (15 MW Dalmau)

15 132 kV Fatehpur 132 kV Malwa 2 150 (60 MW Fatehpur + 60 MW Malwa + 20 MW Jahanabad+ 10

16 132 kV Fatehpur 132 kV Khaga 1

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S. No.

Details of Sub-station No of Circuits

Load (MW) at Originating S/s

From To

MW Khaga)

17 132 kV Malwa 132 kV Jahanabad

Total 670

ICTs to remain connected during first stage of Islanding of Unchahar

S. NO.

Name of the Sub-station ICTs to remain connected (Capacity /Voltage Ratio)

1 220 kV Rai Bareilly PG 2x 100 MVA, 220/132 kV 2 220 kV Fatehpur (U.P.) 1x160 MVA, 1x100 MVA, 220/132 kV

3 220 kVSarojini Nagar 2x100 MVA, 1x160 MVA, 220/132 kV

4 220 kVChinhat 2x160 MVA, 220/132 kV

5.3 Similarly, for the second stage of the islanding at 47.7Hz (i.e. with only one

generating unit of 210 MW running) feeders with dedicated load of say 180-

200 MW have been identified and tabulated in the table given below:

5.4 Further, for isolation of island from rest of the grid following lines and Inter-

connecting transformers would be required to be opened through operation of

UFRs:

S. No.

Details of Sub-station No of Circuits

Load (MW) at Originating S/s From To

1 2 3 4 5

1 Self Load Unchahar - - 60

2 220 kV Rai Bareilly (PG) 132 kV Raibareilly New 1 20

3 132 kV Raibareilly (New) 132 kV Raibareilly (Old) 2 60

4 132 kV Raibareilly (Old) 132 kV Dalmau 1 15

5 132 kV Raibareilly (New) 132 kV Bachrawa 1 25

Total 180

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Lines to Remain open on Islanding of Unchahar

1 Unchahar (NTPC) Generating Stn. Switchyard i 4x220 Kanpur PG 2 220 kV Chinhat S/S UP i Lucknow UP (Chinhat) - Lucknow PG ii 220 kV Hardoi Rd. UP S/S iii 132 kV Barabanki iv 132 kV NKN v 132 kV Khuramnagar 3 400/220/132 kV Sarojini Nagar S/S i 220 kV Hardoi Road ii 2x220 kV Unnao iii 2x132 kV TRT iv 1x132 kV Sandila v 1x132 kV Kundan Rd. 4 132 kV Raibareilly S/S (New) (Amawan) i 1x132 kV GauriGanj ii 1x132 kV Jagdishpur 5 220 kV Fatehpur S/S i 220 kV Rewa Rd. ii 220 kV Allahabad Cantt. iii 2x220 kV Fatehpur PG iv 220 Banda 6 132 kV Malwa S/S i 2x132 kV Naubasta 7 132 kV Jahanabad S/S i 132 kV BharwaSumerpur

ICT to remain open on Islanding of Unchahar

S. NO. Name of the Sub-stationICT to remain Open (Voltage Ratio/ Capacity)

400 kV

1 Sarojini Nagar S/S 400/220 kV , 2x240 MVA ICTs

19 

 

CHAPTER-6

6.0 MAJOR CHALLENGES AND WAY FORWARD

6.1 Maintaining load Generation balance for the island throughout the year in

view of changing demand during different seasons. This shall require regular

review and re-adjustments.

6.2 Availability of dedicated load for the success of Islanding Scheme in view of

massive demand supply gap and large scale scheduled and unscheduled

rostering.

6.3 Day today system contingencies.

6.4 Commitment of the generators for Free Governor Mode Operation of

Generating Stations to effectively control frequency on real time basis.

6.5 Monitoring of healthiness of Under Frequency Relays for their operation at

the set frequency.

6.6 Availability of dedicated trained staff at SLDC to monitor the scheme on daily

basis and make necessary adjustments.

6.7 Training and Mock Drills at SLDC and Generating Stations to familiarize for

handling real time situation during grid disturbance.

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6.8 To suitably plan and implement islanding schemes for other generating

stations considering the availability of dedicated load.

  

 

 

 

 

 

 

 

 

 

 

APPENDICES  

 

Single Line Diagram of First Stage of Islanding Scheme of 5x210 MW Unchahar Generating Station at Frequency of 47.9 Hz 

 

 

 

 

 

 

 

  

 

 

 

UNCHAHAR (5x210 MW)   Ex Bus Avg. Generation 760 MW with 4 unit in operation 

G‐1, 2, 3, 4, 5

220 kV Rai Bareilly PG S/S 

220 kV LKN – UP Sarojini Nagar  220 kV Chinhat S/S

Hardoi   Road  Gomti Ngr

SGPGI

Unnao

220 kV Kanpur (PG) S/S 

Kundan Rd.

Sandila 

TRT 

132 kV Raibareilly (New) S/S 

Fatehpur (PG) 

Banda

220 kV Fatehpur S/S 

Allhd. Cant 

Rewa Rd 

400/220 kv ICT 

400/220  kv ICT2x 160 MVA 220/132 kv ICT

220/132 kV  ICT

G. Nagar 

220 KV BUS Unchahar Generating Station 

To be disconnected for Islanding  

132 kV Raibareilly (Old) S/S

Bachrawan 

Dalmau

Malwa 

Jahanabad

Gauriganj

Khaga 

Bharwah Sumerpur 

Martinpurwa

220/132 kv ICT

Khurram Nagar 

NKN

Barabanki 

132 kV LKN‐UP

Jagdishpur

132 kV Chinhat 

Single Line Diagram of Second Stage of Islanding Scheme of 5x210 MW Unchahar Generating Station at Frequency of 47.7 Hz 

 

 

 

 

 

 

 

  

 

 

 

UNCHAHAR (5x210 MW)  Ex Bus Avg. Generation 180 MW with 1 unit in operation 

G‐1, 2, 3, 4, 5

Rai Bareilly PG 

LKN ‐ UP  Chinhat 

Hardoi Road  Gomti 

Ngr

 To Chibra Mau 

Unnao

  Open 

BithoorRPH 

Panki 

Rai Bareilly (New) 

Fatehpur(PG) 

 To Shahjahanpur 

Kanpur (South) 

Banda 

220 kV Fatehpur S/S 

Allhd. Cant 

Rewa Rd

 To Allahabad   To Obra 400/220 kv ICT 400/220 

kv ICT

400/220 kv ICT 

400/220 kv ICT

LKN (PG) 

Sitapur 

220 KV BUS 

To be disconnected for Islanding  

Rai Bareilly (Old) 

Bachrawan

Dalmau 

Malwan

Jahanabad

Gauriganj

Khaga

Bharwah Sumerpu

2x 160 MVA 220/132 kv ICT

400 KV220 KV132 KV

Advisor(Power System)

Updated :-

LEGEND

.

765 KV