दूरभाषTel.- 26967840/42, 26967990, 26868681 वैबसाइट Website : www.nrpc.gov.in फै सFax : 26865206 email [email protected]भारत सरकार उƣर ेीय िवुत सिमित 18-ए, शहीद जीत िसंह सनसनवाल माग , कटवािरया सराय, नई िदãली - 110016 Government of India Northern Regional Power Committee 18-A, Shaheed Jeet Singh Marg, Katwaria Sarai, New Delhi-110016 NO. SE (O)/NRPC/Jhakri_HV/2009 Dated: 20.01.2010 Subject: “Report of the Sub-Committee on the incident of Fault in R-phase of 400 kV GIS at Line Circuit Breaker of Jhakri-Abdullapur line-I at Jhakri end on 19-11-2009”. Sir, Report of the Sub-Committee on the subject cited issue is enclosed herewith for further necessary action in the matter. The report is also available on NRPC website: www.nrpc.gov.in . Yours faithfully/भवदीय अशोक क ु मार राजप ू त (A K Rajput) SE (Operations) To: Sh A K Aggarwal, Member Secretary, NRPC Sh R P Singh, Director Electrical NJPS/SJVNL; Sh S C Singh, Executive Director, POWERGRID, NR-II, Jammu Sh Suneel Grover, Director (PR &CERC), HPSEB, Shimla; Sh V K Agrawal, General Manager, NRLDC, New Delhi; Sh Pankaj Kumar, General Manager, POWERGRID, New Delhi; Sh A K Rajput, SE (O), NRPC, New Delhi Copy for information to: Chairperson, CEA, New Delhi Member GO&D, CEA, New Delhi Director (OM), Ministry of Power New Delhi Director (O), POWERGRID, Gurgaon
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Report of the Sub-Committee on the subject cited issue · PDF fileAcknowledgement The Sub-Committee gratefully acknowledges the cooperation extended by the officials of M/S SJVNL,
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18-ए, शहीद जीत िसहं सनसनवाल मागर्, कटवािरया सराय, नई िद ली - 110016 Government of India
Northern Regional Power Committee 18-A, Shaheed Jeet Singh Marg, Katwaria Sarai, New Delhi-110016
NO. SE (O)/NRPC/Jhakri_HV/2009 Dated: 20.01.2010 Subject: “Report of the Sub-Committee on the incident of Fault in R-phase of
400 kV GIS at Line Circuit Breaker of Jhakri-Abdullapur line-I at Jhakri end on
19-11-2009”.
Sir,
Report of the Sub-Committee on the subject cited issue is enclosed herewith for further necessary action in the matter. The report is also available on NRPC website: www.nrpc.gov.in.
Yours faithfully/भवदीय
अशोक कुमार राजपूत (A K Rajput)
SE (Operations)
To:
Sh A K Aggarwal, Member Secretary, NRPC
Sh R P Singh, Director Electrical NJPS/SJVNL;
Sh S C Singh, Executive Director, POWERGRID, NR-II, Jammu
Sh Suneel Grover, Director (PR &CERC), HPSEB, Shimla;
Sh V K Agrawal, General Manager, NRLDC, New Delhi;
Sh Pankaj Kumar, General Manager, POWERGRID, New Delhi;
Sh A K Rajput, SE (O), NRPC, New Delhi
Copy for information to: Chairperson, CEA, New Delhi Member GO&D, CEA, New Delhi Director (OM), Ministry of Power New Delhi Director (O), POWERGRID, Gurgaon
REPORT OF THE SUB-COMMITTEE ON THE INCIDENT
OF FAULT IN R-PHASE OF GIS ON LINE CIRCUIT
BREAKER OF JHAKRI-ABDULLAPUR LINE-I
AT
JHAKRI END
ON 19TH NOVEMBER, 2009
IN HIMACHAL PRADESH
NRPC New Delhi
January, 2010
Acknowledgement
The Sub-Committee gratefully acknowledges the cooperation extended by the officials of M/S SJVNL, POWERGRID (NR-I/NR-II), NRLDC and HPSEB in providing the inputs for analyzing the incident of fault in GIS Circuit Breaker at Nathpa Jhakri HE Project. The Sub-Committee places on record its appreciation of the assistance provided by Shri Mukesh Khanna, DGM (POWERGRID), Shri Anoop Singh, DGM (POWERGRID, NR-II), Shri Balwant S. Negi, Dy. Manager SJVNL, Shri S R Narasimhan, DGM (SO-II), NRLDC, Shri Rajiv Porwal, Chief Manager, NRLDC, Shri Rajesh Kumar, Manager, NRLDC, Sh Ramprakash, Power Controller, HPSEB, and Shri Vikram Singh, EE of NRPC in analyzing the causes of the incident and preparation of the report.
Sh. A K Aggarwal, Member Secretary, NRPC, New Delhi
Chairman
Sh. R P Singh, Director (Electrical), SJVNL
Member
Sh. S C Singh, Executive Director, POWERGRID, NR-II, Jammu
Member
Sh. Suneel Grover, Director (PR &CERC), HPSEB, Shimla;
Member
Sh V. K. Agrawal, General Manager, NRLDC, New Delhi;
Member
Sh Pankaj Kumar, General Manager, POWERGRID, New Delhi;
Member
Sh A. K. Rajput, SE (O), NRPC, New Delhi
Convener
Report of the Sub-Committee on the incident of fault in GIS Circuit Breaker at Nathpa Jhakri HE Project.
1.0 Introduction
Nathpa Jhakri Hydro Power Station (NJHPS) has 400 kV double busbar Gas Insulated Switchgear (GIS) System which transmits 1500 MW power from NJHPS and 300 MW from Baspa HPS (BHPS) through four outgoing 400 kV circuits i.e. Nalagarh-I&II and Abdullapur-I&II to the Northern Grid. The 400 kV circuits i.e. Baspa-I&II are also terminating at 400 kV GIS of NJHPS (network shown at Exihibit-I).
SJVNL has reported that on 19-11-2009 at 09:47 PM while opening of Abdullapur-Jhakri-I line, flash over occurred in circuit breaker chamber of R-phase at Jhakri end. SJVNL has also reported that incidences of similar nature have occurred in the past. A copy of the letters received from M/s SJVNL is enclosed at Annexure- I, II, III & IV. To analyze the above incident and to suggest remedial measures in order to ensure safe and secure operation of integrated Grid as per clause 2.3 of IEGC, a sub-Committee comprising the following was constituted (refer Annexure-A):
Sh A K Aggarwal, Member Secretary, NRPC Chairman
Sh R P Singh, Director Electrical NJPS/SJVNL; Member
Sh S C Singh, Executive Director, POWERGRID, NR-II, Jammu Member
Sh Suneel Grover, Director (PR &CERC), HPSEB, Shimla; Member
Sh V K Agrawal, General Manager, NRLDC, New Delhi; Member
Sh Pankaj Kumar, General Manager, POWERGRID, New Delhi; Member
Sh A K Rajput, SE (O), NRPC, New Delhi Convener
The sub-committee had two meetings, First meeting on 02-12-2009 and Second meeting 11-12-2009.
2.0 Evacuation arrangements of NJHPS and Baspa HPS
50 MVAR Non Switchable Line reactor at Nalagarh end end on each Nathpa Jhakri line
400 kV 50 MVAR switchable Bus Reactor at Nalagarh Substation
400 kV Nathpa Jhakri –Baspa D/C Line 54 km 3.0 Description of the incident On 19-11-2009 at 2147 hrs the 400 kV Abdullapur-Jhakri -1 Line was
opened from Abdullapur end vide NRLDC code No 1306 & CPCC Hissar code No 761. The 400 KV Jhakri-Nalagarh-1 line was already opened from Nalagarh end at 21:15 Hrs.
At the of opening of line breaker at Abdullapur end at 21:47 Hrs, the direct trip (DT) command was sent to Jhakri end. The line breaker at Jhakri end was also opened on receipt of DT at 21:47 hrs. A flash over in the breaker chamber of R-Phase at Jhakri followed the opening of the breaker. Following protections also operated at Jhakri end.
LBB trip Command generated Bus coupler breaker tripped.
The direct trip command was also sent to Abdullapur and Nalagarh substations of POWERGRID due to above operation of distance/LBB protection.
4.0 The presentations given by POWERGRID (NR-II), NRLDC and SJVNL during the meeting are enclosed at Annex-V, VI &VII respectively. The gist of presentations are mentioned below:
Gist of Presentation by SJVNL:
Persistent high voltage above 420 kV (highest system voltage) is
observed in NJHPS area during every off peak seasons at 400 kV
NJHPS Bus..
The frequent switching operation (closing/opening) carried out in
every off peak seasons at NJHPS in persistent overvoltage
condition. generates the switching surges.-= Thereby all the 400 kV
equipment insulation are also - subjected to severe stress
generated by switching surges during every off peak seasons.
The list of equipment failure at NJHEP is as below:-
(i) R-Ph CB pole failure of NJ-BP-I on 10/02/05.
(ii) R-Ph CVT failure of NJ-NLG-I on 10/05/07.
(iii) Y-Ph CVT failure of NJ-ABD-I on 21/03/07.
(iv) R-Ph CVT failure on NJ-BP-I on 06/06/09.
(v) B-Ph CB pole failure of NJ-ABD-I on 04/04/09.
(vi) R-Ph CB pole failure of NJ-ABD-I on 19/11/09.
Sequence of line opening and rotation of circuits was suggested
Opening of line from NJHEP end first or bypassing of remote end line
reactor at the time of line opening (after being opened from remote
end) from NJHEP end was also suggested. However, SJVNL stated
that these suggestion could be implemented only after proper study.
Gist of Presentation by NRLDC
Voltages remained high during night off peak hours during winter, particularly in case of weather disturbances. Severe time being 2300-0400 hours.
Many 400 kV lines are regularly opened to control high voltage (8-10 lines per day) while during the day all lines had to be kept in service from the viewpoint of reliability of power stations.
Several options such as keeping all the lines to Jhakri open during night hours, keeping only one line or having a 400 kV loop were
discussed alongwith their impact on reliability of the entire power system as well as the power stations.
Need to absorb the VARs by the generators to the extent possible.
Several long term and short term measures suggested. Gist of Presentation by POWERGRID
Vide NRLDC code 1306 & CPCC code 761 dtd 19/11/2009, 400KV Abd-NJ ckt-1 was opened from Abdullapur at 21:47Hrs.
The BUS voltage before and after opening of line was 427KV and 425 KV respectively.
As per POWERGRID scheme no DR triggering is assigned for hand tripping of CBs.
Regarding frequent opening of line POWEGRID follows the instruction of NRLDC as per system requirement
At Abdullapur ABB make CB is installed on this line which meets IEC: 62271-100 standard
Details of hand tripping of 400 kV Abduallapur –NJ & Nalagarh-NJ lines since commissioning: 1) 400KV ABD-NJ CKT-I = 224 nos 2) 400KV ABD-NJ CKT-II = 70 nos 3) 400KV NALAGARH-NJ CKT-I = 238 nos 4) 400KV NALAGARH-NJ CKT-II = 148 nos
5.0 Analysis of the incident 5.1 Pre incident Conditions
At 2000 hours, the generation at Jhakri was 700 MW. The voltage at Jhakri was 418 kV. The generation at Jhakri reduced to 329 MW at 2045 hours in line with the load profile of Northern Region with the 400 kV bus voltage increasing to 423 kV. The generation further dropped to 188 MW at 2100 hours and the voltage rose to 426 kV. The 400 KV Jhakri-Nalagarh-1 line was opened at 2113 Hrs considering the voltage profile and the tapering off of Jhakri generation. Voltages at 21:10 hrs (as per SCADA) 400 KV Abdullapur: 421 KV 400 KV Nalagarh : 428 KV 400 KV Jhakri: 425 KV The Power at Pot Head Yard of NJHPS at 2145 hours just before opening of 400 kV Abdullapur-Jhakri -1 line at 2147 hours was as under: Incoming Power from Baspa HEP 120 MW
Generation at NJHPS 232 MW
Total Power handled by Jhakri Bus Bar 352 MW Outgoing Power at Abdullapur Line -I 42 MW Outgoing Power at Abdullapur Line –II 42 MW Outgoing Power at Nalagarh Line – II 268 MW Voltages at 21:45 hrs (as per SCADA) 400 KV Abdullapur: 423 KV 400 KV Nalagarh : 429 KV 400 KV Jhakari: 426 KV Other conditions were normal in the grid with frequency on higher side. ( generally above 50 Hz after 2035 hours and touching 50.36 Hz at 2145 hours)
5.2 Time line and the analysis of incident Based on the inputs given by SJVNL and POWERGRID, NR-II, the sequence of event in the incident was explained as under:
NJ-ABD-I CB opening was carried out by Trip Neutral Close (TNC) switch at Abdullapur Substation at 21:47:28.758 Hrs (Opening of main CB as recorded by Event Logger {EL} at Abdullapur end. Time is not synchronized with GPS). It generated opening of Abdullapur Main CB. At 21:47:37:902 tie CB was opened & simultaneously Direct Trip Command was sent to Jhakri through PLCC.
Jhakri Received the Direct Trip (DT) Command at 21:47:11:889 hrs & CB opened at 21:47:11:922 hrs (all Jhakri end numerical relay output times for Abdullapur –I circuit. Time difference between DT received and CB opening at Jhakri is 33 msec as derived from this numerical relay output). The Abdullapur CB opened at around 21:47:11:869 (converted to Jhakri time) hrs i.e. 53 msec before Jhakri CB opening (assuming 20 ms as propagation time for command send through carrier).
Abdullapur CB was opened first and Line remained charged from Jhakri end for 53 msec & line Charging current was of the magnitude of 113 Amp. ( as indicated by Jhakri from numerical relay output).
Jhakri CB has to open under this capacitive line charging breaking current of 113 Amp (rated capacitive interrupting capability of Circuit Breakers is 600 A as per IEC 62271-100 and SJVNL in their
presentation on 2nd December 2009 has reported this figure as 400A) . As soon as Jhakri CB opened , switching surge with oscillatory voltage appeared on CB owing to generation of re-strike voltage due to capacitive breaking. This switching voltage of line capacitance oscillates with the Remote end non switchable Line reactor of 50 MVar at Abdullapur.
As per Jhakri numerical relay output, the amplitude of the Oscillatory voltage is of the order of 296 kV to 368 kV (Ph-N), and a resonant frequency of 32.25 Hz.
Oscillatory voltage with amplitude 296KV to 368KV (Ph-N) with long decay Generated after Jhakri CB opening due to Energy exchange between line capacitance To non switchable 50Mvar Reactor at remote end
Jhakri CB opened
Ground fault in R-ph CB at oscillatory voltage amplitude 368KV
2
F= 1/ 0. 031 = 32.25Hz
Abdullapur-I voltage profile Before fault on R-Ph CB. The frequency & Magnitude of Oscillatory voltage present at the CB pole on line side. The voltage on Bus side & line side pole of CB were In phase opposition of 180 Deg. Voltage across contact was 247 at 50Hz + 368 KV at 32.25 Hz = 615KV
Abdullapur-I R-Ph failure DR Snapshot
2
Abdullapur CB opening Jhakri CB opening
Direct Trip Command receive
Bus Side Pole of Jhakri CB was having 247 kV(Ph-N) at 50 Hz & Line side pole of Jhakri CB was having voltage oscillation with amplitude of 296 kV to 368 kV (Ph-N) at 32.25 Hz. The voltage across the contact of CB is 247 kV at 50 Hz + 368 kV at 32.25 Hz = 615 kV with phase opposition of 180 deg. It has been reported that this phenomenon has been happening every time with the opening of Line at remote end.
The voltage reached 368 kV (Ph-N) at 32.25 Hz , Ground fault initiated due to flashover in the CB and the magnitude of fault current at Jhakri end was 5.632 kA. The numerical relay output at Jhakri (Abdullapur-1 line) indicates that the ground fault occurred 200 msec after the breaker opened. This resulted in operation of Zone-1 distance protection at Jhakri. Direct trip command at Abdullapur was received 240 msec after the line was manually opened at this end.
It is seen from the Jhakri end relay output that the fault after flashover has persisted for approx. 11 cycles (220 msec) before being cleared by the LBB protection. As the breaker flashover would come in the zone of bus bar protection, this fault should have got cleared in 20-30 msec. However it appears that bus bar protection has not operated and this might be examined separately by SJVNL.
5.3 Similar incidents occurred in the year 2009 The same are described below.
(a) A similar nature of flash over in the circuit breaker chamber at Jhakri end of Jhakri - Abdullapur – I Phase-B (RYB) on 04-04-2009 caused due to switching surges generated on account of the opening of line at High Voltage from remote end. The detailed report of this failure prepared by SJVNL/manufacturer/third party would throw more light on the incident.
( b ) Recently on 13/12/2009 at 23:33:41 Hrs flash over took place in the breaker chamber of R-Phase of 400 kV Jhakri – Baspa-2 line at Jhakri end when the line was opened manually as Baspa generation got tapered off. This is a normal practice followed daily during the night hours as Baspa generation typically tapers off to zero value between 2300-0300 hours as per the schedule given by SLDC HPSEB Shimla. As per the SOE at NRLDC, the failure appears to have occurred 41 seconds after the Baspa-2 breaker opened at Jhakri. (gathered from the time difference between LBB action and Baspa-2 breaker opening at Jhakri). However this would have to be corroborated independently from DR/EL/numerical outputs from Jhakri and Baspa. Flashover at
Jhakri on 400 kV Baspa-2 line breaker occurring 41 seconds after breaker opening when steady state nominal power frequency voltage is applied across the breaker contacts needs to be investigated further.
5.4 It is pertinent to note that high voltage above 420 kV is observed in NJHPS
area during every off peak season at 400KV NJHPS Bus. The voltage remains more than 420 kV during each day of every off peak seasons for around 20-30% of the time
The list of equipment failures in earlier years reported by SJVNL in addition to three failures of GIS equipment mentioned above are as under:-
(i) R-Ph CB pole failure of NJ-BP-I on 10/02/05.
(ii) R-Ph CVT failure of NJ-NLG-I on 10/05/07.
(iii) Y-Ph CVT failure of NJ-ABD-I on 21/03/07.
(iv) R-Ph CVT failure on NJ-BP-I on 06/06/09.
It is pertinent to note the following aspects in respect of above four failures:
Two incidents pertain to small lines (Baspa feeder at S. nos. i and iv).
Two incidents pertain to high hydro conditions (S. nos. ii and iv) when the voltage is well below 420 kV and line opening is not required.
No failures occurred during the year 2006 and 2008 despite high voltage and line opening as indicated elsewhere in the report.
Failure analysis for the above might be submitted by SJVNL.
5.5 The Committee noted that 400 kV Jhakri - Abdullapur circuit -1 &2 and Jhakri – Nallagarh circuit -1 &2 had been manually opened several times in order to control high voltage in the past as per details given below:
400 kV Jhakri - Abdullapur circuit -1 --- 224 times 400 kV Jhakri - Abdullapur circuit -2 --- 70 times 400 kV Jhakri – Nalagarh circuit -1 --- 238 times 400 kV Jhakri – Nalagarh circuit -2 --- 148 times
The reasons for opening Ckt 1 of Abdullapur or Nalagarh circuit appear to be on account of discrimination adopted in Stage-I overvoltage settings of the parallel feeders. The overvoltage settings are as under: 400 kV Jhakri-Nalagarh-1: 110% with 4 second delay 400 kV Jhakri-Nalagarh-2: 110% with 5 second delay
400 kV Jhakri-Abdullapur-1: 110% with 4 second delay 400 kV Jhakri-Abdullapur-2: 110% with 5 second delay In many other parallel lines in Northern region, voltage gradient is adopted with circuit-1 at 110% and circuit-2 at 112%. Hence the operator generally opens circuit-1 as he feels that circuit-2 would hold for a longer period in case of any load throw off situation. The Committee feels that this might be a relevant issue. The Protection sub-committee of NRPC could examine annual/seasonal reversal of these settings so that the same equipment is not stressed repeatedly.
5.6 It was reported that 400 kV Jhakri - Abdullapur D/C line was transposed at
two locations which is supposed to be done at three locations. 5.7 NRLDC pointed out that Jhakri GIS equipment is experiencing frequent
problem even by opening of lines when the system voltages are in the range of 420 to 425 kV and even below 420 kV.
5.8 SJVNL has reported that in view of another damage of R- Phase CB at Jhakri GIS of 400 kV Baspa-Jhakri Ckt-II on 13.12.2009, there is a need to analyze the probable extent of damages in all line breaker due to switching operation on over voltage that has occurred during the last five to six years. They have requested to consider the replacement of these line breakers in phases to ensure uninterrupted power evacuation from NJHPS (1500 MW) and Baspa ( 300 MW). The following points were also deliberated in this regard.
Chamera-I HPS of NHPC is operational since 1993-94 and is experiencing similar high voltage conditions and line opening during low hydro periods, however, no GIS related failures have been reported so far.
Baspa-2 CB at Jhakri failed 41 seconds after opening when normal power frequency voltage was appearing across breaker contacts.
Stage-I overvoltage tripping of lines is set at 1.1 pu and the equipments are designed to withstand such opening.
Therefore, it was felt that the specific reasons for equipment failure(s) at Jhakri needs detailed investigation.
5.9 The Committee also noted that the transmission system is not planned in a manner that all the 400 kV lines emanating from a remote hydro plant can be kept in service with zero generation at these plants during the off peak hours. Hence opening of line(s) are already contemplated at the planning stage
5.10 The committee also deliberated on the a suggestion that the lines needed to be opened much before the voltage crosses 420 kV. It was also appreciated that this might lead to more number of line openings and consequent switching surges on the equipment(s).
5.11 Voltage and Frequency profile:
The voltage and frequency profile during Nov to Jan for the last three years is given below:
(A) Voltage profile during winter months in Jhakri and adjoining buses
2008-09 2007-08 2006-07
Nov. Dec. Jan Nov. Dec. Jan Nov. Dec. Jan
400 kV Sub-Station
Voltage % of time the voltage remained
Jhakri
> 425 kV 8.2 4.5 6.8 1.7 7.1 4.4 0.5
Data Not Available
> 420 kV to
425 kV
22.3 22.2 21.6 19.3 15.8 17.9 15.9
> 400 kV to
420 kV
69.5 73.3 71.6 79.0 77.0 77.6 75.6
Max. Voltage (kV)
435 433 435 430 433 435 428
Abdullapur
> 425 kV 1.7 0.1 0.1 0.1 0.6 1.0 0 0 0
> 420 kV to
425 kV
19.0 2.7 5.0 3.3 6.7 9.3 0.5 1.0 0.3
> 400 kV to
420 kV
78.7 89.9 88.5 94.9 90.4 87.3 86.9 94.8 95.7
Max. Voltage (kV)
430 429 431 426 429 432 425 424 425
Nalagarh
> 425 kV 10.6 4.7 4.5 7.5 6.0 5.3 6.5 14.6 3.4
> 420 kV to
425 kV
27.2 24.0 24.8 23.5 7.8 11.7 26.2 20.6 15.1
> 400 kV to
420 kV
62.1 70.6 69.1 69.0 85.9 82.8 67.3 65.3 79.3
Max. Voltage (kV)
432 431 432 431 435 434 435 436 431
Jallundhar
> 425 kV 13.7 1.9 2.6 7.9 5.5 6.2 5.3 10.5 0.6
> 420 kV to
425 kV
19.1 11.9 10.3 17.9 8.6 9.3 8.5 15.5 6.7
> 400 kV to
420 kV
67.1 84.9 84.4 74.1 82.7 80.3 85.2 74.1 91.2
Max. Voltage (kV)
433 429 431 433 435 439 431 435 429
SJVNL has reported that during off peak hours from 19.11.2009 to 23.11.2009 the maximum voltage was as high as 439 kV during the night off peak hours.
As an immediate relief mechanism following measures should be taken to control over voltages:
(i) Line Opening Rotation and sequence in NJHPS area during lean
season in off peak hours when generation is nil/low would be monitored and optimized based on the following:
line lengths
voltage at Jhakri and neighbouring nodes
tapering of hydro generation.
overvoltage setting of parallel lines
(Action- NRLDC/SJVNL/BASPA/POWERGRID) (ii) 50 MVAR non-switchable line reactor of Jhakri-Abdullapur Circuit -1
at Abdullapur substation which is out due to CB fault at Jhakri end can be utilised as bus reactor (As a temporary measure) by using the line breaker and ensuring the protection aspects.- (Action- POWERGRID/)
(iii) One of the machines at Jhakri HEP and/or at Baspa HEP could be
kept in operation for controlling voltages when the grid frequency is continuously below nominal value of 50 Hz during the night hours. During such period the generator shall absorb the maximum possible VARS as per its capability curve. - (Action- SJVNL/BASPA/NRLDC)
(iv) The transposition of the lines emanating from Jhakri Hydro Power
Station may be checked up by POWERGRID. - (Action- POWERGRID)
(v) Baspa Hydro Power Plant (3X100 MW) which is designed for running in synchronous condenser mode may be utilized for controlling over voltages in the Baspa & Jhakri Systems. - (Action- BASPA HPS/HPSEB)
(vi) The bus bar protection at Jhakri HPS needs to be checked for satisfactory operation.- (Action: SJVNL)
(B) Long Term measures
i. The additional reactive compensation of 125 MVAR each planned at Abdullapur and Nalagarh (under proposal stage) by
POWERGRID may be commissioned on priority. - (Action- POWERGRID)
ii. Comprehensive study may be carried out by CTU to identify the
reactive power compensation at NJHPS to contain voltages and also the switching surges. The study should also consider the proposed LILO of existing Jhakri-Nalagarh line at Rampur HPS. The options of providing line vis-a-vis Bus reactor at Jhakri HPS and Rampur HPS may also be examined. - (Action- CTU)
iii. The capability of GIS equipments at Jhakri HPS to withstand design parameters particularly switching and normal over voltages needs to be examined and a comprehensive analysis may be got done through a third party-(Action- SJVNL)
iv. The condition of GIS equipments may be examined and
accordingly appropriate corrective action may be taken by SJVNL.-(Action- SJVNL)
v. The insulation coordination studies for GIS substation including
Very Fast Transient (VFT) studies or any other phenomenon related to GIS may be carried out under different operating conditions of the grid and future development.- (Action-SJVNL)
vi. 220 kV Nalagarh-Mohali D/C line must be commissioned
expeditiously by PSEB. This line would provide strong anchoring support at Nalagarh considering the proximity of Mohali to 6x210 MW Ropar TPS.-(Action: PSEB).
vii. A comprehensive study may be carried out to examine the effect of Surge Arrestor at Nathpa Jhakri end on switching phenomena with special emphasis on GIS station. For this following is suggested: (Action-SJVNL)
Study for optimized siting of SA including provision of additional SA
at suitable location.
Increase the protective margin of SA through reduced rated voltage
and higher energy capability to take into account the sustained
voltages.
(C) General
(i) The Protection sub-committee of NRPC could examine annual/seasonal reversal of the overvoltage settings on parallel lines for uniform distribution of switching impact on equipment.-(Action: NRPC)
(ii) Necessary measures to control overvoltage by using other line
reactors as bus reactors after the line is opened, may also be taken in due course of time after carrying out the necessary modifications in the protective system.-(Action: CTU)
(iii) Considering the growing number of GIS installations expected in
the country, the following measures to enhance reliability of these installations are suggested.
Sharing of best practices through user groups of all the utilities owning such installations.
Measures to reduce the Mean Time to Repair (MTTR) of such installations which otherwise are designed to have a high Mean Time Between Failures (MTBF).
Breaker and a half switching scheme may be considered for future GIS installations.
(Action: All utilities having GIS installations)
(iv) All future remote hydro projects such as Karcham Wangtoo,
Parbati, Koldam, wherever feasible, may have the capability to operate in synchronous mode. -(Action: All utilities setting up remote hydro power stations having unit size 50 MW and above).
(v) SJVNL may also explore the possibility to take up a pilot R & D
project towards retrofitting of one unit at Jhakri for synchronous condenser mode operation.-(Action: SJVNL)
Northern Regional Power Committee 18-A, Shaheed Jeet Singh Marg, Katwaria Sarai, New Delhi-110016
NO. SE (O)/NRPC/Jhakri_HV/2009 Dated: 25.11.2009
Subject: Fault in R-phase of GIS at Line Circuit Breaker of Jhakri-Abdullapur line-I at Jhakri end. Sir, It has been reported that on 19-11-2009 at 09:47 PM while opening of Abdullapur-Jhakri-I line, flash over in breaker chamber of R-phase at Line Circuit Breaker of Jhakri-Abdullapur-I line took place. The voltage prior to opening of line at Jhakri end was 431 kV. Other reported problems of similar nature in the past have been cited as: Flash over in the Gas Insulated Switchgear’s (GIS) circuit breaker
chamber (phase B) of 400 kV Jhakri-Abdullapur ckt-I on 4th April 2009 due to switching surges generated because of the opening of line at high voltage from remote end.
400 kV Tehri-Merrut-II circuit was out of operation since 8th February 2009 to 11th April, 2009 due to reported problem in Gas Insulated Bus Duct of the line at Tehri GIS.
The hydro stations are generally remotely located and on associated long evacuation lines high voltage conditions are encountered during light load period. Keeping in view the above a sub-committee comprising of following has been constituted to analyze the subject cited incidents and to suggest the immediate, short-term as well as long term measures in the mater.
Sh A K Aggarwal, Member Secretary, NRPC Chairman
Sh R P Singh, Director Electrical NJPS/SJVNL; Member
Sh S C Singh, Executive Director, POWERGRID, NR-II, Jammu Member
Sh Suneel Grover, Director (PR &CERC), HPSEB, Shimla; Member
Sh V K Agrawal, General Manager, NRLDC, New Delhi; Member
Sh Pankaj Kumar, General Manager, POWERGRID, New Delhi; Member
Sh A K Rajput, SE (O), NRPC, New Delhi Convener
Meeting of the above sub-committee is proposed to be held on 02-12-2009 at 12:00 Hrs at NRPC, Delhi. Kindly make it convenient to attend the meeting. A line of confirmation would be appreciated.
Yours faithfully/भवदीय
अशोक कुमार राजपूत (A K Rajput)
SE (Operations) To:
Sh A K Aggarwal, Member Secretary, NRPC
Sh R P Singh, Director Electrical NJPS/SJVNL;
Sh S C singh, Executive Director, POWERGRID, NR-II, Jammu
Sh Suneel Grover, Director (PR &CERC), HPSEB, Shimla;
Sh V K Agrawal, General Manager, NRLDC, New Delhi;
Sh Pankaj Kumar, General Manager, POWERGRID, New Delhi;
Sh A K Rajput, SE (O), NRPC, New Delhi
Exhibit-I
Exhibit-II Capability Curve of Generator at NJHPS
Annexure-IV SJVN/C&SO/ND- Dated:16.12.2009 To Member Secretary (NRPC),
18/A, Shaheed Jeet Singh Marg, Katwaria Sarai, New Delhi-110 016 Subject: Over Voltage Problem in NJHPS During Lean Season. Dear Sir,
The problem being faced by SJVN, due to opening of 400kV NJHPS GIS line breakers by carrier inter-tripping from remote station under high voltage condition during every lean season beyond permissible limit of 400 kV was brought to the knowledge of NRPC through specific agenda in OCC meetings. The first agenda on this issue was discussed at Amritsar on 16.11.09 and thereafter at New Delhi on 11.12.09. During the OCC meeting held at New Delhi on 11.12.2009 SJVN expressed their concern about continuous deterioration of GIS due to frequent switching operations at overvoltage beyond permissible limit of 420kV considering the past failures.
1. R-Ph CB pole failure of NJ-BP-I on 10/02/05.
2. R-Ph CVT failure of NJ-NLG-I on 10/05/07.
3. Y-Ph CVT failure of NJ-ABD-I on 21/03/2007.
4. R-Ph CVT failure of NJ-BP-I on 06/06/09
5. B-Ph CB pole failure of NJ-ABD-I on 04/04/09
6. R-PH CB pole failure of NJ-ABD-I on 19/11/09
It was also expressed that the extent of deterioration in GIS equipment is un-known and their reliability to sustain frequent opening of lines at high voltages beyond permissible limit cannot not be ascertained as following was observed from the fault analysis of 19.11.2009-
1. Abdullapur CB was opened first and Line was charged from Jhakri end for 54msec & line Charging current of magnitude 113A. The magnitude of line charging current of Abdullapur Line is dependent on Voltage in Line i.e. Ic = 2πfCV.
Jhakri CB has to open for this capacitive line charging breaking current of 113A. As soon as Jhakri CB opened, switching surge with oscillatory voltage appears on CB owing to generation of re-strike voltage due to capacitive breaking. This switching voltage of line capacitance is oscillated with the Remote end non switchable reactor of 50Mvar. This phenomenon is happening every time Line is opened from remote end.
2 The Oscillatory voltage has the amplitude of 296KV to 368KV (Ph-N),
however it is to note that the oscillatory voltage has lower resonate frequency of 32.25Hz. This is because of Oscillation between Line capacitance to the remote end Line Reactor.
Bus Side Pole of Jhakri CB was having 247KV (Ph-N) at 50Hz & Line side pole of Jhakri CB was having voltage oscillation with amplitude 296KV to 368KV (Ph-N) at 32.25Hz. It is to note that these two voltages are in phase opposition i.e. Phase angle is 180 deg. The voltage across the contact of CB is 247KV at 50Hz + 368KV at 32.25Hz = 615 KV with phase opposition of 180 deg. This phenomenon is happening every time Line is opened from remote end. However, magnitudes are varying based upon voltage oscillation amplitude.
3 As the voltage reaches 368KV (Ph-N) at 32.25Hz, Ground fault started and the magnitude of current was 5.632KA. Since the line is opened at both ends .Fault has been started in CB & this is fed by the Bus Side source Voltage of 50Hz. Reasons for oscillatory voltage with large amplitude & longer decay time at lower resonate frequency of Switching overvoltage generation while opening of line from remote end with 50Mvar reactor permanently connected at Abdullapur end:- Difference in the amplitude & resonate frequency of each phases may be caused by 50Mvar Non switchable reactor at remote end and line asymmetries (may be inadequate transposition) coupled by mutual coupling (also unsymmetrical both inductively & capacitively) between phases. Therefore it was also expressed that possibility of failures in other line breakers cannot be ruled out if we continue to stress the GIS equipment by opening lines at overvoltage beyond permissible limit. Now on 13.12.2009 another line breaker damaged (R-Phase Baspa-II) while opening lines at overvoltage beyond permissible limit. It is therefore requested that subcommittee as constituted to analyse the aspect related to the subject problem may also consider the probable extent of damages in line breakers due to switching operations on over voltage that has already taken place in last five-six years. It is requested to consider the replacement of these line breakers in phases so as uninterrupted power evacuation from NJHPS (1500 MW) and Baspa (300 MW) is ensured by safeguarding against any future failures in the overall interest of northern region. Thanking you, for and on behalf of SJVN Ltd. -sd-
'SUB:- Fauir in H.-Phus" :11 Li ne Ci)'(: ~it 13n:~akl'r of Jh nkr ·Abd_,.il\~\()Ur line ;d
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L>m" v;~:, JP~:! )l~d L:" ~A l)dL ~ l i '!l)L , r em:; vid·; NR.LDC '::0(i~ Ho 1306 & CP_CC liis;i2, i' • E ' · '-'j , '. j'l' J't I 1 .1"'11 "'\i T' 1 ~ ,,"'Ice !tJu : ~) ,I. J 1e \r ,'JJLlg' .. ~ p1'1u': i C ~ !!\.\ (\pCll li lg 0 Jlnl.~ 2.l J1 ;;,:r : 1 1 ':~ \;\.'3S 4~ . I'\. , :1!::
; C)O KV Jhakn ~ala g"lrl ., -, t Line' \\~\S <l11~ ,lUY opened fl'om~ ; ahgari l e.nd at 09 . , S P,i.,;;
The Power a: Pot I '{c~ld 'Yard c!' NJHPS befol'e op(;ning cr tl: is line ,s us under:
incoming Power from Dasp~ . HEP G~m:!'arion ofNJHPS Total Power in Bus Sa:-
OUlgoing Power at A~~;~l:lI ;~pU I Line·l OutgoingPoY-.'er utAbollli~p\.i r Lin(;·ll (~L!tgt) i ,'~ PV',ver ~~ · N8. IH g8J'h L;~(~~I!
120 \,!\V 232 ivl\V 3 5 ~! M\V
, '\2 !\'lW 268 ,\1\,/
Ai l ~ :f~ i i~ '-t\;f~' o~· OP 'l ,:I1i,; ,:!' :: ,1(,: \,,':::lh: 1 <It (\ bd\J! L:p .11' JIC! (he trip c0111;r:anu W :iS
generated. at Abdulh,pu;' t;j-,d Llr U':PPIi'lg. (If brcaktr a. n in(11e e,yj.::,o i.e at ];:,l:,;[\ enG.
, The opening of tine brpkc[' at !:iuch higl1 I/oltng,.: prob:1 bl .. had f:ilused 8. /lash O\:~ : r lr.
lh~ breaker chamber o/" R''Ph,\S'l~ ~lL Jhu\.; ri thus J<;: \un::in i : t! ,e SF6 Oas. The ev,:; '; i::>
corroborated from the :t'cl c.:l thm at tile [J1ornc llt the brc~k'~r .nstalld ut Jhnkri end of Jhakri AbduJlapur-i liii1C ,,\'HS ClFtncd tJH\)LiI.~: l rG!11o tc t; .p :or.;Ll1~\(1J; ' the :,ollowi ;lg protection had also (,)pe~'u ll;d ,ll uur end,
. 1 . .
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, LB \3 ~r(p,, \:GII}il)·,\;;ll~l;' .,:i'a tt:d, ".8t.:S cOL\pler ' bre,nt,~ { tt'.i?i) c d.
' : tl~ ' I.:':d<.:r.t ;..lr !l :j ; l,;:.\U,i: 10 l!i!' ~~y ,; ;1;1 \:", Uj' e il 'CIl )l Ulc:lkl.:( pol.e wi I Olll,y b!,; asc:ertaiil
J ' I. :,,:,- the oFening ofbrl~'lk.:r l~cm prlr\;11I.'l!t,
\l the fir::;t Bnuly::: ls thl~ ['nul ,. ~lppC:i j' t(, (;1; 0 1' $\ln\l:l l' IHl lu;,c US that (I f f1nsh over in th e: l'; i \ (:Uit 'ol'eai:er clniydJel' cl' JlH1kri i\ bd! dl" pm .- 1 el'li)'Sl': ~B (RYE) or datl;ld 04-04-0 C) caused due to ~wilching su[ ~e5 gen~ra ted bCC2t USe of the 0peoi 11g, of line 8.1 High
Voltage from remo'~e end, I
Ttlis time, it a,gain app~ars that the present i1,\d1 over in the c: : ~c\it Breaker of R· phase' of lhakri. Abdullapllr line-l is atI.riblitablc to the openin ~o ; ' J hakri~ Abdul!l.lp1,;J \ine-l from Abdull;:\pur end wh~n the systcm voltage was hIgh th iS I,:rlusing switching
over voltage at J b,akri en9
Th~ dt;to.ils 2J1J.lysis I ltIVt;~t ; l1Ci ~ l(in arcJ)1(.kr way ('lnd the ftlrtller indings / results ,,,,,ill k l11<:lde ~waii2,blc w all COl1ct.;rI1tU i!l ck:e CU ~lr se of time,
'{ola' Li;thf\.ll~y
~) g . Salljs eY "~()d ~oi~ll, 1
Addl. General Managp (Operation) NJHPS SJVN Ltd Jhtlkri
I Copy is !'orworded to to rollow;",; [or the kind information p:,"sc.
i
1, CMD, SJVN LId, Hll1lkll L~" I i!(h:g) Sh lli1la Dlre(; tor (r.leclrlc,u),SJV1'-~ Ltd Hitr.fcd Building Shim! :;
j ,/ \ L. _." _' . ... t:... '.\ j .It: .. l ,r~L _ " .
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- Pl)W tr Cirld Carpor~tlon "I India Limited '.
No rtt 8n1 ReelotlCl'I Load Despatch Centre New Delhi
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Frorn: Gs"qt~ Gfinf~rCliI ""G'nilC'~1' (SO~iJ, "~Rl.OC, New D&IIl!
To: Geron I IV .. nagar, Nathpa Jhakri HPS, SJVNL
'3aii';i'; t Mal1a'.ger (0 & M), POWERGR,!(', NR-II, Jammu Dir8, : t~ r (HR & CERe), HPSEB, Shimla
Sub : FSi!:ur6 Gl r~ -ph.u~e cl 'cu it breRker o~ 8aspa-2 lint:: at Jhakrl on 1stn One 2009
Thh~ is in reterenc3 ) letter dated 14th Dec 2\)09 from (';M Jhakri HPS, SJVNL
addrl~%ed to Men-, i)ar Sec!et: 'Y, NRPC with copy to NRLOC on the above subJ~d . ~: \ .
In ~11is connection. ) Ie )S~ ~ note ttlat at :..:038 flours or. 1~l/l r:'?c ~~COg . ~u() ;':V Jhakri·
t 'Jal<lJ~rr;~; was OP\.!ii " ,~..:.1 rita' U(} ly to centrol righ \lolt~ge , N 1(1J( in~la:1ce, the voltage i:!t
Nale.']arh (tnj Jhakr~ :;:1t3 11 ,',;.-! :! ( ,oti"! of the ()~ iN o( 420 kV <.md ~1h.~I~ri v,~~ qonerating 400 !v1VV No ar;i,reciable cn~r.~ e : 1 ttllj voitage wa~ 0bserved after cpt'.ming of the line .
At :) :33~ liOur J" Jt OC V f ,H",e:.l<ri-Saspa-2 W::l3 reportedly opened from Baspa end (as
pe, ;' lIJrmai pri:lctl:':l;;l when 8 1 9o ~:i g~,leration tapers off to LerD bgtwe~r1 2300·0300 hours)
Wf.lell tile \;Qltag~) t;it Jr; akr :.~ as of the order of 425 kV GM Nathpa Jhak{i HPS,SJVNl '$
lettei' suggl~sts that thle bri ! C(~ ~r at Jhakri end has failed dt this instant of line opening This
had !E,d to lTipping of both 1 he 400 kV evacuating lines in opera ~itJri at Jhakn viz, Abllu!la~uj .
2 an :j Nala'garh-2 lines and C' nSI~quent loss of Baspa generation. .
In order tu ar1~lyz B hE; Incid'cllit, SJV NL, PO'JVFF.G.RIf)( ~\JR"~ i'tlld 8~s~'~ !--iPS
1..09-:; I(;;:r (tL.l and nwr;tific,:: 'el;:y outputs ~(' Nf1L[IC/!'<1R?C elt ';-:'9 gclrliesi in reopdd :if
tiath pa Jh:;lkri HPS, a~f,f la nF D, ";bdullapLJ ;md ~~dlaQ;im s~;b!)tations. SJVNL iB also
t8QU1; !;\c .; ':0 ta ~~e t) r) :he r !~ ! er o~ these failure~ (:3 ;,,):,,;.) In 2f')!"g wit.h tho manufacturers of
the (3~IS Inp',t.JIE:.\~:!~ S:..'l)'.~taqol t' (G~ S ) ;.nj U',ird pal1y exp~rts at the earliest so tMt these equipment ra,kliC'3 are ~nSl yi~ :d ~) f.' ; ... 'mprl3herl3ive m~ l~er .
Matter most ument, f' 3gards ,
COP'!' to:
I • . 'j
11/ 12/ 2889 21:1 2 ~J Jl]iJDOOiJ~IU U :l .l l ... Ll .l 1J _ .L ~ : 11J<
No.:
To
(A ,Joint \,' ~1lture of Govt. of india &: Gove of H.P) Nathpa. .rhulU'I Hydro Power Station P,Q· JIiA .. KRl-l'72 ~Col , DISTI'. Shimln (H.P)
Tho Member Secretary, NRPC, Katwatia Sar-ai, New Delhi.
Fax No. 011-26865206 I ~S567341
Sub: Fault in R-Phase of Une Circuit Breaker of Jil@kli··Abdull~pur line-I at Jhakri end followed by similar fault in R Phase of 1i1\~ circuit breaker of JhHkri-Baspa-!! line at Jhakri end on 13.12 . .2009.
Sir,
On the above cited ~ubjoct. this is in continuatior1 to our lettt:r No.
SJVN/NJHPS/G.M (P)/09-383-92 dat€:d 23.11 .09 vide which it was brought to your
notice that the opening of line breaker <at Abdwllap\Jf end at a prevailing voltage of 431
KV had caused :he flastl over in the breakor chamber of R-Phase at Jhakri on
19.11.2009 and despite this, NJHPS 400 f<V bnlja~ers are ;stil! being subjectE':d to over
voltages particularly during night bours when our generation schl'!du!e is reduced to Zero
causing shooting up of system voltages beyond permissible limit It was also informed
. that under such cirt..;umstances, the I'~petition of ~uch incidents cannot be ruled
out unle~s some corrective actions are taken in this regard on 80S basis.
Through above letter, the incident of 2~311.2009 wherein the tripping of Jhakri-
8aspa-1I line at a voltage of 439 KV was also brought to your kind notice with a request
to intervene in the matter to avoid further damages to tile system of NJHPS. Taking
cogniz2!nce of the seriousness of the issue, NRPC has already constituted a high level
Stlb-Committee chaired by your good self on 25.11.2009 to suggest immediate. sholi
term & long term measures In the matter. The above Sub-Committee has already held
two meetings wherein this issue has been deliberated at lef1gth.
In this regard, it is further informed that on 1312 2009, similar flastl over tlas
taken place in the breoker chamber of R-Phese or .Jhakri-Baspa-II 400 KV line at Jilskri . end at 23:33:41 hrs. due to switching surges. During this pariod, thEl generation
, b ,.
-
-"2-
schedule of NJHPS wac Zen) but Bar.;p;;l Project was :~!G' ner;ating arDund 58 IJiW. At the
time of flash over, the vOltage at our end was 424 ,:34 KV an.:1 ~hr:) voltage ;er.;orted at the
end of Basplil was around 430 KV. This failure took plac~, when 8aspa Projec t opened
the Iin€ circuit breaker elf t!li~, line from re rnote end 0:-: account d h;gh '/oltagl:':s be ing
obselved at 8aspe.
With above failure , now there is only one 400 f<V line for evacuation of power
from Baspe. Further, in our SwltC~1 Yar~J , ¢'IS on date, two No. 400 K\/ line bays .3 1"e
under break down because of the above problem. This j~ the third Incident of line
breaker failure during the current year (2009) itself and ~I I the throe failures have taken
place during night hours of le:;n season.
In view of above grim situation, rt will be appreciated that immediate corrective
measures to keep the system voltages within permissible limits are required so as to
avoid further damages to our line equlprnen1s &. Ilkely loss of generation nOl only to
NJHPS but also to 8aspa Project whose power is also being evacuated through our
Copy is forwarded to the following for the kind information please
1. CMD. SJVN Ltd, Himfed Building, New Shirnla. 2. Director (Elect.), SJVN Ltd., Hin1fed Building, New Shimla. 3. Executive Director NRTS-II, Power Grid, Jammu. 4. General Manager, NRLDC, New Delhi. 5. General Manager, CS&O, SJVN Ltd., Shimla. 6. Add!. General Manager(pH-Op.), NJHPS, Jhakri 7. DGM(PH-Mtc.), NJHPS, Jhakri 8. OOM, 400/220 KV Substation, Abdullapur, Haryana 9. Chief Manager, CPCC, Power Grid, Hisser 10. Vice President, Baspa Hydro Power Station, Sholtu, Distt. Kinnaur (H.P)
0"
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ON 19/11/2009 AT 21:47Hrs ABOVE MENTIONED LINE ‘HAND TRIPPED FROM
ABDULLAPUR S/S ’ AS PER NRLDC INSTRUCTION
Abdullapur and NALLAGARH S/Ss wereconceived for receiving power from 1500 MWNathpa Jhakri + 300 MW Baspa H. E. Powerprojects in Himachal Pradesh. This substationsare receiving power directly through 400 KV D/Clines from Nathpa Jhakri & Baspa H.E. PowerStation. Connectivity of Abdullapur with 400KVNR GRID is shown in next slide
Tim,e AtAbd Ilap r 21:47:28:758/764/770 21:47 :37 :896/900/902 21:47:38:140/142
Event
Main CB RIY IB 0 ened Main CB BIYIR opened
DT Cb-I & II received Note:- Direct trip command was received after 240 msec of Tie CB - opening ( 37:902- 38:142)
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_______ D interpre ation of event and oint wi e rep y to i ue ra· ed y JV d.
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ISSUES RAI E BY JV LTD regarding event of 19/11/2009
1 )Frequent Closing of Line.
2) I-Ph Auto-Reclosure during Ground faults.
3) Frequent Opening of Line at High Voltage (as higb as 439KV) from remote end (Abdullapur or Nalagarb).
4) Opening is simu taneous but with different opening time owning to techno ogy invol ed in the operating mechanism. 1HPS has H draulic Mechanism itb ax Break/opening time of 40msec whereas Remote end substations has pneumatic mechanism with minimum Beak/opening time of lOOmsec ..
5) Above non simu taneous opening at ow active load (50-100MW) lead to generation of switching O/V by inductive switching at JHPS & Capacitive switching at Remote end thereby reOected superimpose Overvoltage due to travelling wave is seen by CB during each opening.
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l)Frequent Closing of Line & 3) Frequ,ent 0 ening of Line at High Voltage (as higbas 439KV) from remote end (Abdullapur or
Nalagarh). POWERGRID FOLLOWS THE INSTRUCTION OF NRLDC IN TIDS REGARD WH CH IS AS PER SYSTEM RE'QmREME T
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POWERGRID TAND. POI T WI E
2) 1,-P Auto -Reclosure dureng Gro nd fau ts. AS ER IEC CB ARE DES G ED FOR DUTYCYC EOF o 0.3 CO 3min CO
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POWE GRID STAND: POIN · E
) SJVN has Hydraulic Mechanism with Max Break/opening time of 40msec whereas Remote end substations has pneumatic mechanism wi h minimum Break/openin2 time of lOOmsec. At Abdulahpur ARB make CB is installed on t ·s line WHICH MEETS lEe: 62271-100 STANDARD and -ts tripping tiole is less than 25 msec as is evident from test report of Oct/Nov-2009
, S itchgear TS.p - SITE REPORT MAl CB.jPg
IE C .jpg
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OWE GRID TAND: OINT WI E
WHEN TIE CB WAS HAND TRIPPED FROM ABDULLAPUR, DIRECT RIP SIGNAL WAS SENT TO SJVN END, AS PE SCHEME, WHICH TRIPPED THE CB AT S I VN END. The same is confirmed by DR GIVEN BY SJVN L d.
OWE GR -I J MMU
POWERG I STA SPOINTWI E 8 mew - [C:\Program Files\AREVA T&D\LBB191109\Dated 191109\Abd,_191109_214711.dg[ - l Bl ~~
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.(!. l2 52 Y PH OPEN
.(!. L3 52 B PH OPEN 11 L8TRIP CH 1/2RE C ,u--L-.... 11 L1 5 86 LO TRIP .(!. L1 2 LBB OPTO .(!. L1 OMAIN 2 OPTO .(l. Any Start ..0. Any Trip .(!. L6BUS 1/2 UN .(!. L7 V>PROTN OPTO
DR sbows that: l)'DlRECT TRIP' command was received at SJVN ltd. end after hand tripp·ng of TIE CBatAbdullahpur. 2) Opening of CB at AbduUahpurend can be verified from the 'event logger' of Abdullahpur. 2) B·eforeCB opening at SJV Ltd. the Voltage waveform was absolutely symmetrical. 2) After opening of CD pole at SJVN Ltd. the voltage waveform got distorted and this may have to be investigated, as CBs atbotb the ends had open,ed by this time. 3) After 200msec (approx) , current rose to 4.KA, and DT command was rece"ved at, both, Nalagarh & AbduaUpur SIS of POWE GRID.
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POWE G TAND
Details of other lines emanating from Naptha Jhakri and which have been "hand tripped" at various occasion for voltage regu ations are as per next slide and as evident from the same , while there have been faults in circuit breaker at SJVN Ltd of 400KV Abdullapur Ckt-I only ~ There has been no such situation for other lines as such matter needs further
investigat·on.
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p lemen ary data
DETAILS OF HA D TRIPPING OF 400KV Abdua apur ·NJ & ' 'alagarh-, J LINES Since commi sioning 1) 400KV ABD-,NJ CKT-I == 224 nos 2) 400KV ABD-NJ CKT-II == 70 DOS
3) 400 V ALAGARH-NJ CKT-I = 238 nos 4) 400 V ALAGAR NJ C T-I - 148 nos Manua -
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IndexIndex•Nov 09‐ Load, frequency, voltageL t lt fil•Last year voltage profile
• Nov – 2008• Dec – 2008Dec 2008
•High voltage conditions and Actions to mitigate•High Voltage Conditions: Possible operational Actions•High Voltage Conditions: Long term•High Voltage Conditions: Long‐term Actions
2009
2009
2009
2009
Dehar‐Bhiwani & Dehar‐Panipat also opened regularly
Voltage profile‐ Nov/Dec‐2008Voltage profile Nov/Dec 2008400 kV Sub‐Station Voltage % of time in Nov‐08 % of time in Dec‐08
Abdullapur> 420 kV 20 % 5 %
> 410 kV 85 % 50 %
Jallundhar> 420 kV 32 % 18 %
> 410 kV 85 % 50 %
Nalagarh> 420 kV 40 % 25 %
410 kV 90 % 80 %> 410 kV 90 % 80 %
Jhakri> 420 kV 30 % 30 %
Jhakri> 410 kV 95 % 80 %
High Voltage Conditions and action Plan to mitigate
• Severe time: 2300 to 0400 hrs d d– Low demand ‐ 20000 MW
– High frequency > 50.3 HzStorable hydro kept minimum as per valuation of hydro– Storable hydro kept minimum as per valuation of hydro for controlling frequency and consequently voltages.
– BUS reactors taken into service and parallel lines are also opened.
– Tap positions has been changed with a view to control 400 kV voltages400 kV voltages.
– One circuit of double circuit lines opened during this period.
High Voltage Conditions: Some FactsHigh Voltage Conditions: Some Facts
– The large hydro station a remote locationThe large hydro station a remote location connected with long lines.
– Generation minimum during night at these stations g gas per load profile
– Thus lines lightly loaded with high reactor power g y g pgeneration and low fault level causing high voltages.
High Voltage Conditions: Possible action plan during operationaction plan during operation
– Keeping all long lines from these generating stations shut off during this period
– Difficulty in reaching to hydro station during morning or in case of any contingency.
– Opening of vital loops for handling any icontingency.
– Chances of spillage at Run of the river or with li it d d t ti d t blimited poundage stations due to above.
High Voltage Conditions: Possible l daction plan during operation
– Running of units in synchronous condenserRunning of units in synchronous condenser (motor) mode to absorb or generate reactive power based on requirement. (Dynamic Vars)
• The CEA’s connectivity Standard Part II ‐1(10) states that “ Hydro generating units having rated capacity of 50 MW and above shall be capable of operation in50 MW and above shall be capable of operation in synchronous condenser mode wherever feasible”
• The similar machine of 250 MW Francis turbine units at Tehri as that of Jhakri are capable of operating in synchronous condenser mode.
High Voltage Conditions: Importance of reliable supply at Nalagarhreliable supply at Nalagarh
– Keeping three lines (out of 4 from Jhakri , 2 each to Nalaharh and Abdullapur) off and keeping only one circuit from Abdullapurcharged (Abdullapur suggested being higher fault level of approx g ( p gg g g pp10000 MVA and Nalagarh being 5000‐6000 MVA during night time).
• However no load charged line would still result in high voltage at Jhakri. • Tripping of this line on fa lt or o er oltage o ld black o t Jhakri and• Tripping of this line on fault or over voltage would black out Jhakri and Baspa similar to keeping all lines open and all associated problem.
• Baspa would trip if running at that time. • This tripping would also be similar to the one being tried to be resolved i.e. opening of line on high voltage.
• Opening of loop. • Nalagarh substation which feeds vital load of Chandigarh would be left with only one feed from either from Patiala or Kaithal because of verywith only one feed from either from Patiala or Kaithal because of very high voltages at Patiala as well as kaithal. Thus reliability of the chandgarh supply would be affected. Further Chandigarh load is only 20‐30 MW at Nalagarh the 400 kV lines supplying this load would be lightly loaded and would further cause high voltage at Nalagarh.
High Voltage Conditions: Importance of keeping Abdullapur‐Jhakri‐Nalagarh‐Patiala‐ Hissar/ Malerkotla loop
The central part of Nothern region i.e. Merrut/Dadri/Mandola/Bawana/Ballabhgarh/Bhiwadi axis is connected with the Punjab/Haryana/BBMB/HP & J&K system th h f ll i 400 kV li kthrough following 400 kV links– 400 kV Dadri‐Panipat‐Dehar‐Bhiwani– 400 kV Dadri‐Malerkotla
– 400 kV Bawana‐Bahadugarh‐Bhiwani– 400 kV Bawana‐Hissar– 400 kV Bhiwadi‐HissarThe first loop of the above is generally kept out due to HV at Deharbut Dehar is having connectivity at 220 kV level. The opening of any f h l ld i h K i i h ifurther loop would constrain the system. Keeping in the uncertainty associated with the outage during foggy conditions it is always beneficial to keep as many loops in operation as possible. The loops through higher reaches also have less chance of tripping during fog g g pp g g gdue to less pollution level.
High Voltage Conditions: Long‐term measures
• Provision of Bus reactors at these remote hydro locations at planning stage itself (to be included in Power plant package itself).
• Running of units in synchronous condensor mode mandatory. (as per connectivity condition)
• Provision of breaker and half scheme at all future GIS substations: Presently all GIS station in NR at Chamera, NJPC, Tehri, Uri, Dulhasti, Maharani Baghetc all have Two Main switching scheme This causesetc all have Two Main switching scheme. This causes constraint in keeping the line in the service problem in any breaker.in any breaker.
High Voltage Conditions: Long‐term measuresInsulation co‐ordination, dynamic, transient and temporaryover voltages due to switching or lightening.
• Any issue regarding non proper insulation coordination of various• Any issue regarding non proper insulation coordination of variousequipment or design of surge arrestor etc at Jhakri May beexamined.
– Any tripping of the line on fault or over voltage during high voltageAny tripping of the line on fault or over voltage during high voltagecondition would be same as manual opening of the line.
– EMTP studies are required to confirm the over voltages and RestrikeVoltages in the CB vis‐à‐vis BIL of the equipment.
– Opening of the beaker at 1.1 pu voltage shall not result in outage of theCB.
– In the instant case the line reactor available at Abdullapur was inserviceservice.
– EMTP studies would also be able to through light on the considerationof better side for initiating command for opening of the line generally.
The lines from Chamera are being opened regularly on high voltage since its commissioning in 1994.
High Voltage Conditions: Long‐term measures
• NRLDC proposal for LILO of 400 kV Dehar‐Panipat and Dehar‐Bhiwani lines in NRPCPanipat and Dehar‐Bhiwani lines in NRPC Board need to be looked into from
Reliability perspective– Reliability perspective.
• Early commissioning of 220 kV Nalagarh‐M h li D/CMohali D/C
• Closing of loop at from 132 kV Dehar‐Kangoo‐Kunihar
• Expertise for handling GIS related problems inExpertise for handling GIS related problems in view of increasing population of GIS substationssubstations
High Voltage Conditions: Long‐term measuresmeasures
• para 7 2 1 of planning criterion statespara 7.2.1 of planning criterion states
"Switchable reactors shall be provided at EHV substations for controlling within the limitssubstations for controlling within the limits defined in para 5 without resorting to switching off lines "to switching off lines.........
High Voltage Conditions: Long‐term measures
• In view of foregoing relook on compensation id d d dprovided needed:
• Approx 18 % Bus reactor compensation
• Approx 38% line reactor compensation
Do we need more bus reactor?
IndexIndex•Nov 09‐ Load, frequency, voltageL t lt fil•Last year voltage profile
• Nov – 2008• Dec – 2008Dec 2008
•High voltage conditions and Actions to mitigate•High Voltage Conditions: Possible operational Actions•High Voltage Conditions: Long term•High Voltage Conditions: Long‐term Actions
2009
2009
2009
2009
Dehar‐Bhiwani & Dehar‐Panipat also opened regularly
Voltage profile‐ Nov/Dec‐2008Voltage profile Nov/Dec 2008400 kV Sub‐Station Voltage % of time in Nov‐08 % of time in Dec‐08
Abdullapur> 420 kV 20 % 5 %
> 410 kV 85 % 50 %
Jallundhar> 420 kV 32 % 18 %
> 410 kV 85 % 50 %
Nalagarh> 420 kV 40 % 25 %
410 kV 90 % 80 %> 410 kV 90 % 80 %
Jhakri> 420 kV 30 % 30 %
Jhakri> 410 kV 95 % 80 %
High Voltage Conditions and action Plan to mitigate
• Severe time: 2300 to 0400 hrs d d– Low demand ‐ 20000 MW
– High frequency > 50.3 HzStorable hydro kept minimum as per valuation of hydro– Storable hydro kept minimum as per valuation of hydro for controlling frequency and consequently voltages.
– BUS reactors taken into service and parallel lines are also opened.
– Tap positions has been changed with a view to control 400 kV voltages400 kV voltages.
– One circuit of double circuit lines opened during this period.
High Voltage Conditions: Some FactsHigh Voltage Conditions: Some Facts
– The large hydro station a remote locationThe large hydro station a remote location connected with long lines.
– Generation minimum during night at these stations g gas per load profile
– Thus lines lightly loaded with high reactor power g y g pgeneration and low fault level causing high voltages.
High Voltage Conditions: Possible action plan during operationaction plan during operation
– Keeping all long lines from these generating stations shut off during this period
– Difficulty in reaching to hydro station during morning or in case of any contingency.
– Opening of vital loops for handling any icontingency.
– Chances of spillage at Run of the river or with li it d d t ti d t blimited poundage stations due to above.
High Voltage Conditions: Possible l daction plan during operation
– Running of units in synchronous condenserRunning of units in synchronous condenser (motor) mode to absorb or generate reactive power based on requirement. (Dynamic Vars)
• The CEA’s connectivity Standard Part II ‐1(10) states that “ Hydro generating units having rated capacity of 50 MW and above shall be capable of operation in50 MW and above shall be capable of operation in synchronous condenser mode wherever feasible”
• The similar machine of 250 MW Francis turbine units at Tehri as that of Jhakri are capable of operating in synchronous condenser mode.
High Voltage Conditions: Importance of reliable supply at Nalagarhreliable supply at Nalagarh
– Keeping three lines (out of 4 from Jhakri , 2 each to Nalaharh and Abdullapur) off and keeping only one circuit from Abdullapurcharged (Abdullapur suggested being higher fault level of approx g ( p gg g g pp10000 MVA and Nalagarh being 5000‐6000 MVA during night time).
• However no load charged line would still result in high voltage at Jhakri. • Tripping of this line on fa lt or o er oltage o ld black o t Jhakri and• Tripping of this line on fault or over voltage would black out Jhakri and Baspa similar to keeping all lines open and all associated problem.
• Baspa would trip if running at that time. • This tripping would also be similar to the one being tried to be resolved i.e. opening of line on high voltage.
• Opening of loop. • Nalagarh substation which feeds vital load of Chandigarh would be left with only one feed from either from Patiala or Kaithal because of verywith only one feed from either from Patiala or Kaithal because of very high voltages at Patiala as well as kaithal. Thus reliability of the chandgarh supply would be affected. Further Chandigarh load is only 20‐30 MW at Nalagarh the 400 kV lines supplying this load would be lightly loaded and would further cause high voltage at Nalagarh.
High Voltage Conditions: Importance of keeping Abdullapur‐Jhakri‐Nalagarh‐Patiala‐ Hissar/ Malerkotla loop
The central part of Nothern region i.e. Merrut/Dadri/Mandola/Bawana/Ballabhgarh/Bhiwadi axis is connected with the Punjab/Haryana/BBMB/HP & J&K system th h f ll i 400 kV li kthrough following 400 kV links– 400 kV Dadri‐Panipat‐Dehar‐Bhiwani– 400 kV Dadri‐Malerkotla
– 400 kV Bawana‐Bahadugarh‐Bhiwani– 400 kV Bawana‐Hissar– 400 kV Bhiwadi‐HissarThe first loop of the above is generally kept out due to HV at Deharbut Dehar is having connectivity at 220 kV level. The opening of any f h l ld i h K i i h ifurther loop would constrain the system. Keeping in the uncertainty associated with the outage during foggy conditions it is always beneficial to keep as many loops in operation as possible. The loops through higher reaches also have less chance of tripping during fog g g pp g g gdue to less pollution level.
High Voltage Conditions: Long‐term measures
• Provision of Bus reactors at these remote hydro locations at planning stage itself (to be included in Power plant package itself).
• Running of units in synchronous condensor mode mandatory. (as per connectivity condition)
• Provision of breaker and half scheme at all future GIS substations: Presently all GIS station in NR at Chamera, NJPC, Tehri, Uri, Dulhasti, Maharani Baghetc all have Two Main switching scheme This causesetc all have Two Main switching scheme. This causes constraint in keeping the line in the service problem in any breaker.in any breaker.
High Voltage Conditions: Long‐term measuresInsulation co‐ordination, dynamic, transient and temporaryover voltages due to switching or lightening.
• Any issue regarding non proper insulation coordination of various• Any issue regarding non proper insulation coordination of variousequipment or design of surge arrestor etc at Jhakri May beexamined.
– Any tripping of the line on fault or over voltage during high voltageAny tripping of the line on fault or over voltage during high voltagecondition would be same as manual opening of the line.
– EMTP studies are required to confirm the over voltages and RestrikeVoltages in the CB vis‐à‐vis BIL of the equipment.
– Opening of the beaker at 1.1 pu voltage shall not result in outage of theCB.
– In the instant case the line reactor available at Abdullapur was inserviceservice.
– EMTP studies would also be able to through light on the considerationof better side for initiating command for opening of the line generally.
The lines from Chamera are being opened regularly on high voltage since its commissioning in 1994.
High Voltage Conditions: Long‐term measures
• NRLDC proposal for LILO of 400 kV Dehar‐Panipat and Dehar‐Bhiwani lines in NRPCPanipat and Dehar‐Bhiwani lines in NRPC Board need to be looked into from
Reliability perspective– Reliability perspective.
• Early commissioning of 220 kV Nalagarh‐M h li D/CMohali D/C
• Closing of loop at from 132 kV Dehar‐Kangoo‐Kunihar
• Expertise for handling GIS related problems inExpertise for handling GIS related problems in view of increasing population of GIS substationssubstations
High Voltage Conditions: Long‐term measuresmeasures
• para 7 2 1 of planning criterion statespara 7.2.1 of planning criterion states
"Switchable reactors shall be provided at EHV substations for controlling within the limitssubstations for controlling within the limits defined in para 5 without resorting to switching off lines "to switching off lines.........
High Voltage Conditions: Long‐term measures
• In view of foregoing relook on compensation id d d dprovided needed:
2 Equipment Failure History2. Equipment Failure History
3. Fault Analysis of R-Ph CB failure on 19/11/09.
4. Oscillatory Voltage behavior/Pattern of Abdullapur & Nalagarh Line ( Recent DR Records )
5. Generator Capability of NJHPS
6. Francis Turbine Partial Load operating Limitation
7. Voltage Control Measures
8 Action Plan
SJVN LIMITED 2
8. Action Plan
INTRODUCTIONINTRODUCTIONMoment of Truth is that numbers of equipment failure are taking place in 400KV system atNJHPS during lean season in off peak hours. Persistent overvoltage (beyond 420KV & goingupto 438KV) and switching surge are generated while opening of line (by carrier inter-trippingfrom remote station) under high voltage condition during every lean season (Sept to May) in offfrom remote station) under high voltage condition during every lean season (Sept to May) in offpeak hours, is observed by Circuit Breaker. It may be demanding operating duty cycle to theCB during lean season in off peak hours at NJHPS and may be one of the cause point offailures.
SJVN’ I t tSJVN’s Intent
1. Find the way out to control the persistent overvoltage at NJHPS area during every lean
season (Sept to May) in off peak hours.
1.1 Immediate Measure
1.2 Short Term Measure
1 3 Long Term Measure1.3 Long Term Measure
2. Find the solution to mitigate the oscillatory voltage behavior of Abdullapur & Nalagarh Line
3. Feasibility of minimizing the switching operation.
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4. Feasibility of Opening of Line at low voltage as low as 400KV (ideal situation).
Equipment Failure History at NJHPS due to impact of Dynamic &Transient Overvoltage during lean Seasons ( Sept. to May) in offa s e t O e o tage du g ea Seaso s ( Sept to ay) opeak hours
A. R-Ph CB pole failure of NJ-BP-I on 10/02/05.
B. R-Ph CVT failure of NJ-NLG-I on 10/05/07.
C. Y-Ph CVT failure of NJ-ABD-I on 21/03/2007.
D. R-Ph CVT failure of NJ-BP-I on 06/06/09
E. B-Ph CB pole failure of NJ-ABD-I on 04/04/09
F R PH CB pole failure of NJ ABD I on 19/11/09F. R-PH CB pole failure of NJ-ABD-I on 19/11/09
Observations from past failures:-
1. Faults occurred during lean season (September to May).g ( p y)
2. Persistent Overvoltage at NJHPS i.e. more than 420KV.
3. Equipment failure of NJ-ABD-I while opening line at overvoltage.
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Fault Analysis of NJ-ABD-I R-ph CB failure on 19/11/09
Sequence of Events (SOE) of fault Creation:-Sequence of Events (SOE) of fault Creation:-1. NJ-ABD-I CB opening was carried out by TNC switch at Abdullapur Substation. It generated opening
of Abdullapur CB & simultaneously Direct Trip Command was sent to Jhakri for CB opening through
PLCCPLCC.
2. Jhakri Receives the Direct Trip(DT) Command at 21:47:11:889 hrs & CB opened at 21:47:11:922 hrs
(Time difference between DT receive and CB opening is 33msec) . The Abdullapur CB opened at
around 21:47:11:868 hrs i.e. 54 msec before Jhakri CB opening.
3. Abdullapur CB was opened first and Line was charged from Jhakri end for 54msec & line Charging
current of magnitude 113A. The magnitude of line charging current of Abdullapur Line is dependant
on Voltage in Line i.e. Ic = 2πfCV.
4. Jhakri CB has to open for this capacitive line charging breaking current of 113A. As soon as Jhakri
CB opened , switching surge with oscillatory voltage appears on CB owing to generation of re-strike
voltage due to capacitive breaking. This switching voltage of line capacitance is oscillated with the
Remote end non switchable reactor of 50Mvar This phenomenon is happening every time Line isRemote end non switchable reactor of 50Mvar. This phenomenon is happening every time Line is
opened from remote end.
Contd…….. To page 6
SJVN LIMITED5
Sequence of Events (SOE) of fault Creation:- Contd……. From Page 5
5. The Oscillatory voltage has the amplitude of 296KV to 368KV (Ph-N), however it is to note that the
oscillatory voltage has lower resonate frequency of 32.25Hz. This is because of Oscillation between
Line capacitance to the remote end Line Reactor.
6. It is note that Reactor reactance is XL = 2πfL & at the resonate frequency of 32.25Hz , reactance
become smaller & Current drawn will be large. The current has to be supplied by capacitive charging
current (Ic) of line, this high demand charging current will boost the voltage of system. The energy
exchange between line capacitance & 50Mvar Reactor has no damping device thereby large
oscillation & with longer decay time Damping is taking place only by Iron losses of reactor leakageoscillation & with longer decay time. Damping is taking place only by Iron losses of reactor, leakage
current through insulator of OHL, corona loss of OHL etc.
7. Bus Side Pole of Jhakri CB was having 247KV(Ph-N) at 50Hz & Line side pole of Jhakri CB was
having voltage oscillation with amplitude 296KV to 368KV (Ph-N) at 32.25Hz. It is to note that theseg g p ( )
two voltages are in phase opposition i.e. Phase angle is 180 deg. The voltage across the contact of
CB is 247KV at 50Hz + 368KV at 32.25Hz = 615 KV with phase opposition of 180 deg. This
phenomenon is happening every time Line is opened from remote end. However, magnitudes
are varying based upon voltage oscillation amplitude.
6. As the voltage reaches 368KV (Ph-N)at 32.25Hz , Ground fault started and the magnitude of current
was 5.632KA. Since the line is opened at both end .Fault has been started in CB & this is fed by the
S f
SJVN LIMITED6
Bus Side source Voltage of 50Hz.
Contd……… to page 7 to 11
Abdullapur-I R-Ph failure DR Snapshot
Oscillatory voltage with amplitudeGround fault in R-ph CB atoscillatory voltage amplitude Osc ato y o tage t a p tude
296KV to 368KV (Ph-N) with long decayGenerated after Jhakri CB opening due toEnergy exchange between line capacitanceTo non switchable 50Mvar Reactor at remote end
Jhakri CB opened
oscillatory voltage amplitude368KV
SJVN LIMITED7
Abdullapur-I R-Ph failure DR Snapshot
Di t T i C d i
Jhakri CB opening
Direct Trip Command receive
Abdullapur CB opening Jhakri CB opening
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Abdullapur-I R-Ph failure DR Snapshot
Jhakri CB has to open the line charging C rrent magnit de of 113 ACurrent magnitude of 113 A.
SJVN LIMITED9
Abdullapur-II DR Snapshot
Abdullapur-II voltage profile bdu apu o tage p o eBefore fault on R-Ph CB of Abdullapur-I. The frequency & Magnitude of supply which werePresent at the R Ph CB pole ofPresent at the R-Ph CB pole of Abdullapur-I on Bus Side
SJVN LIMITED10
F= 1/ 0.20 = 50Hz
Abdullapur-I R-Ph failure DR Snapshot
Abdullapur-I voltage profile Before fault on R-Ph CB. The frequency & Magnitude of Oscillatory voltage present at theOscillatory voltage present at theCB pole on line side. The voltage onBus side & line side pole of CB wereIn phase opposition of 180 Deg.
Voltage across contact was 247 at 50Hz+ 368 KV at 32.25 Hz = 615KV
SJVN LIMITED11
F= 1/ 0. 031 = 32.25Hz
Line SideBus Side
FB 16D Line Circuit Breaker in GIS II
SJVN LIMITED12
FB 16D Line Circuit Breaker in GIS-II
R-Ph CB failure of NJ-ABD-I on 19/11/09
Arching Contact
Main Contact
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R-Ph CB failure of NJ-ABD-I on 19/11/09
Main ContactDamage Finger
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R-Ph CB failure of NJ-ABD-I on 19/11/09
Interrupting Chamber
SJVN LIMITED15
R-Ph CB failure of NJ-ABD-I on 19/11/09
Interrupting chamber with puffer cylinder
Single Pressure Axial Heat Dissipation Puffer Type arc quenching techniqueSingle Pressure, Axial Heat Dissipation, Puffer Type arc quenching technique
Contact Travel during tripping 14 mtr/secContact Travel during closing 6 mtr/sec
SJVN LIMITED16
g gSF6 gas quantity 108KGSF6 Pressure 6.3 Bar at 20 deg
R-Ph CB failure of NJ-ABD-I on 19/11/09
Pre Insertion Resistor (PIR)Pre Insertion Resistor (PIR)400 ohm , 8 msec insertion time
SJVN LIMITED17
Reasons for oscillatory voltage with large amplitude & longer decay time at
lower resonate frequency of Switching overvoltage generation while openinglower resonate frequency of Switching overvoltage generation while opening
of line from remote end with 50Mvar reactor permanently connected at
Abdullapur end:-
1 Difference in the amplitude & resonate frequency of each phases are caused by1. Difference in the amplitude & resonate frequency of each phases are caused by
50Mvar Non switchable reactor at remote end and line asymmetries ( inadequate
transposition) coupled by mutual coupling ( also unsymmetrical both inductively &
i i l ) b hcapacitivly ) between phases.
Elimination of Oscillatory Voltage:-1. Symmetry of system should improve the situation.
2. Damping must speed up the decay and thereby lower both duration and Amplitude of
switching overvoltage.
3. Shifting the 50MVar Non switchable reactor at remote substation to Bus in such ag
way that during opening of line at both ends , LC oscillation should not take place.
However, it need to be studied deeper before treating it as a solution.
SJVN LIMITED18Contd….. To page 13
Contd……… from page 12
Is Line CB opening from Jhakri End provide Solution for EliminatingIs Line CB opening from Jhakri End provide Solution for Eliminating
the Oscillatory Voltage generated during inter tripping from remote
sub station ?
Prima –Facie it may appear to be a solution. But, there is a serious concern which
can not be simply ignored & ruled out i.e. 3 x 102 MVA , 15.75/420KV Generator
Transformer ( GT) is connected to the 400KV Bus at NJHPS. Frequent Line opening( ) q p g
are taking place during every lean season in off peak hours at NJHPS area . Six (06)
lean seasons years ( starting Sept 2003 to Sept 2008) has resulted into numbers of
equipment failure at NJHPS. It may happen that GT may fail if line CB opening isequipment failure at NJHPS. It may happen that GT may fail if line CB opening is
taking place from Jhakri end.
Recommendation to mitigate Oscillatory voltage:-
Proper Over Voltage study of 400KV Network at NJHPS area may reveal the
actual solution for damping the oscillatory voltage phenomenon & Impact on
GT HV windings for the line opening sequence from Jhakri end.
SJVN LIMITED19
Oscillatory Voltage behavior/Patternin Abdullapur & Nalagarh Line {p g {Recent Disturbance Recorder (DR)Records}Records}
SJVN LIMITED20
Recent DR Records of all six lines especially Abdullapur &
Nalagarh Line:Nalagarh Line:-
Importance of DR records:-
It is a vital tool that provides better understanding of the behavior ofp g
power network after a disturbance.
Further, it gives useful information to improve the existing equipment
and planning/designing new installation.
DR is an integrated facility in Main-I ( Micom P442) relay at NJHPS
& Mi P442 f ll i li ti h i d th h GPS& Micom P442 of all six lines are time synchronized through GPS
clock. DR has the capability of recording 08 analogue input 32
binary signal per line (16 nos of external binary signal has beenbinary signal per line (16 nos of external binary signal has been
connected to Micom P442 & 16 are internally generated signal of
relay).
SJVN LIMITED21
All required events of Line protection are accommodated in DR.
Cont….. To page 22
Contd….from page 21
Th O ill l b h i / i Abd ll & N l h Li fThe Oscillatory voltage behavior/pattern in Abdullapur & Nalagarh Lines after
CB opening sequence from remote end at NJHPS are similar in nature but
with varying magnitude of voltage oscillation as charging current in Nalagarh
is around 70A and it is 115A in Abdullapur line.
1) Oscillatory voltage with large amplitude & longer decay time at lower
t f f S it hi lt ti hilresonate frequency of Switching overvoltages are generation while
opening of line from remote end with 50Mvar reactor permanently
connected at Abdullapur & Nalagarh. The oscillatory voltage is appearing
at CB pole on line side with phase opposition ( 180 deg) to the voltage of
CB pole on Bus side. This is happening every time in every lean
seasonsseasons.
2) The above phenomenon is not observed while opening of Jhakri Baspa
Line. Because there is no reactor to create an oscillatory voltage. The line
SJVN LIMITED22
charging current is 54A.
DR Snapshot Abdullapur-I on 15/11/09 at 21:45:38 hrs
Oscillatory voltage with large amplitudewith long decay Generated after Jhakri CB openingdue to Energy exchange between line capacitanceT it h bl 50M R t t t d
Jhakri CB openedTo non switchable 50Mvar Reactor at remote end
Line Voltage 431KV, Line Charging current 112A, Oscillatory Voltage Amplitude varyingF 278KV t 322KV (Ph N) i Bl Ph & t f i 31 25 H i Bl hFrom 278KV to 322KV (Ph-N) in Blue Phase & resonate frequency is 31.25 Hz in Blue phase.This oscillatory voltage Is appearing in CB pole in line side which is in phase opposition (180 deg)To the voltage on CB pole on Bus Side.
SJVN LIMITED23
DR Snapshot Abdullapur-II on 16/11/09 at 21: 55:01 hrs
Oscillatory voltage with large amplitudewith long decay Generated after Jhakri CB openingdue to Energy exchange between line capacitanceT it h bl 50M R t t t d
Jhakri CB opened
To non switchable 50Mvar Reactor at remote end
Line Voltage 429 KV, Line Charging current 101A, Oscillatory Voltage Amplitude varyingF 278KV t 371 KV (Ph N) i R d Ph & t f i 31 25 H i R d hFrom 278KV to 371 KV (Ph-N) in Red Phase & resonate frequency is 31.25 Hz in Red phase.This oscillatory voltage Is appearing in CB pole in line side which is in phase opposition (180 deg)To the voltage on CB pole on Bus Side.
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DR Snapshot Nalagarh-I on 29/11/09 at 21:03:26 hrs
Oscillatory voltage with large amplitudeOscillatory voltage with large amplitudewith long decay Generated after Jhakri CB openingdue to Energy exchange between line capacitanceTo non switchable 50Mvar Reactor at remote end
Jhakri CB opened
Line Voltage 424 KV, Line Charging current 74A, Oscillatory Voltage Amplitude varyingFrom 261KV to 333 KV (Ph-N) in Red Phase & resonate frequency is 34.5 Hz in Red phase.This oscillatory voltage Is appearing in CB pole in line side which is in phase opposition (180 deg)To the voltage on CB pole on Bus Side.
SJVN LIMITED25
DR Snapshot Nalagarh-II on 28/11/09 at 21:29:15 hrs
Oscillatory voltage with large amplitudeOscillatory voltage with large amplitudewith long decay Generated after Jhakri CB openingdue to Energy exchange between line capacitanceTo non switchable 50Mvar Reactor at remote end
Jhakri CB opened
Line Voltage 429KV, Line Charging current 83A, Oscillatory Voltage Amplitude varyingFrom 267KV to 367 KV (Ph-N) in Blue Phase & resonate frequency is 35.7 Hz in Red phase.This oscillatory voltage Is appearing in CB pole in line side which is in phase opposition (180 deg)To the voltage on CB pole on Bus Side.
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DR Snapshot Baspa-I on 28/11/09 at 00:06:09 hrs
Negligible Oscillatory voltage but only transientRecovery voltage due to capacitive braking
Jhakri CB opened
Line Voltage 431KV, Line Charging current 55A,.
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DR Snapshot Baspa-II on 26/11/09 at 02:14:02 hrs
Negligible Oscillatory voltage but only transientRecovery voltage due to capacitive braking
Jhakri CB opened
Line Voltage 436KV, Line Charging current 57A,.
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Observations/Conclusions from DR records:Observations/Conclusions from DR records:-
The DR records approves that oscillatory voltage of varying
magnitude with longer decay time & is in phase opposition (180g g y p pp (
deg) is appearing across the CB pole of line side to the voltage on
CB pole of Bus side every time when line is opened from remote
end. This behavior may the cause point of failure in CB.
Recommendation to mitigate Oscillatory voltage:-Recommendation to mitigate Oscillatory voltage:Proper Over Voltage study of 400KV Network at NJHPS area may
reveal the actual solution for mitigating such behavior of line & The
study must be carried out immediately.
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Generator Capability of 250MWGenerator Capability of 250MW Machine of NJHPS
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Capability Curve of NJHPS Generator
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Generator Capability Curve forGenerator Capability Curve for Under exciter Limiter
The maximum Mvar Absorption capability ofp p yNJHPS is -140Mvar at 150MW. However, forstability point of view ,NJHPS machine shallnot be run at this operating point forcontinuously & safe continuous operationcontinuously & safe continuous operationshall be around 60% of -140Mvar i.e. -84Mvar.Note:-operating generator in excessive underexcitation mode lead to cause of pole slippingeven for small network disturbances as it willincreases the rotor angular position beyondthe generator transient stability limit &
At 150MW Ma reacti e po er
the generator transient stability limit &machine may trip by pole slipping protection(98).
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At 150MW, Max reactive power absorption capability is -140Mvar
Francis Turbine Partial LoadFrancis Turbine Partial Loadoperating Limitation
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Francis Turbine Partial Load Operation Limitations:-HYDRAULIC TURBINES FOR MEDIUM AND LARGE POWER HOUSES-GUIDELINES FOR SELECTION Indian Standard IS 12837:1989FOR SELECTION Indian Standard IS 12837:1989
Type of Turbine Range of Maximum Net HeadsPelton Above 300 mFrancis , 30 to 400 m ( sometimes even up to 500 to 600 m )Francis , 30 to 400 m ( sometimes even up to 500 to 600 m )Kaplan 10 to 60mBulb 3 to 20 mDeriaz 50 to I50mIn the o erlapping head ranges more detailed anal sis shall be carried o t to optimise
Minimum load up to which turbine may be continuously operated without unduecavitations and vibration is dictated by type of turbine. Normal range for continuous
In the overlapping head ranges more detailed analysis shall be carried out to optimise cost for selecting the exact type of turbine
ca tat o s a d b at o s d ctated by type o tu b e o a a ge o co t uousoperation for various types of turbines from this criteria is given below:Type of Turbine Minimum Output for
Continuous Operation( Percent )( Percent )
Pelton 30-50Francis 50Kaplan/Bulb 30-40
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Propeller 85Deriaz 40
Operation at small gate openingsresult in low efficiency andresult in low efficiency andaccelerated damage from
it ti O ti i f blcavitations. Operation is preferablyrestricted to a power range havingan efficiency of 80 percent or more.
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NJHPS Francis Turbine Data
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NJHPS Francis Turbinedesigned fordesigned forGuaranteed Efficiency atrated Output at 60% to110% of rated Turbineoutputoutput
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NJHPS Francis Turbinedesigned for smooth,Stable quite operation &Stable, quite operation &noise limit above 60%of Load
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NJHPS Francis Turbineperformance Guaranteesperformance Guarantees
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NJHPS Francis Turbine performance Efficiency, Power outputand flow graph
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Voltage Control Measures:-Voltage Control Measures:
1 I di t M1. Immediate Measure
2. Short Term Measure
3. Long Term Measure
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R Ph CB pole of NJ ABD I has failed by switching overvoltage during line1. Immediate Measure
R-Ph CB pole of NJ-ABD-I has failed by switching overvoltage during line
opening from remote end on 19/11/09. It is unlikely to get replace it before
May 2010(CB is as GIS component supplied by M/s Areva T&D France)May 2010(CB is as GIS component, supplied by M/s Areva T&D France).
The available spare pole was replaced during the similar fault appear in
B-Ph CB pole of NJ-ABD-I on 04/04/09. Presently, NJHPS does not havep y,
spare pole to replace.
It is submitted that 50Mvar non switchable Reactor of NJ-ABD-I at
Abdullapur substation shall be utilized as switchable bus reactor by using
a line breaker and keeping all protection intact. This is possible by
permanently (Dec 09 to May 10) removing the Line Jumpers at
appropriate place. This temporary provision will provide the relief of
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50Mvar with switchable operational flexibility at Abdullapur.
2. Short Term MeasureS it hi ti t NJHPS h ll b i d t b l 420KV b lt t lSwitching operation at NJHPS shall be carried out below 420KV by voltage controlby utilizing the Mvar absorbing capability of generator as far as possible. Themaximum Mvar Absorption capability of NJHPS is -140Mvar at 150MW. However,for stability point of view ,NJHPS machine shall not be run at this operating point foro stab ty po t o e , J S ac e s a ot be u at t s ope at g po t ocontinuously & safe continuous operation shall be around 60% of -140Mvar i.e. -84Mvar. NRLDC shall coordinate NJHPS & ensure the operation of opening of linebelow 420KV. It is also pertinent to mentioned that NJHPS machine are FrancisTurbine These machine cannot be run below 60% of 250 i e 150 MW forTurbine. These machine cannot be run below 60% of 250 i.e. 150 MW forcontinuous operation owning to high vibration, noise and cavitations etc. This is thelimiting parameter of every Francis Turbine in the world.
Baspa Hydro Power Plant (3X100) is designed for running in synchronouscondenser mode. The possibility of utilizing their capability to bring overvoltagebelow 420KV shall be explored.
When one of the line is in opened condition at Abdullapur & Nalagarh Substations,the possibility of Utilizing this 50Mvar Line reactor by suitable switching scheme it toact as bus reactor to get relief shall be explored.
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3. Long Term MeasureI d t ti ti i li t NJHPS h ll b t th d bInadequate reactive compensation in line at NJHPS shall be strengthened byproviding the line reactor at NJHPS in Abdullapur Line. PGCIL may explore thesame by carrying out necessary overvoltage study by considering the practicaloperational circumstance arising due to running the power flow fromp g g pAbdullapur to Nalagarh Via Jhakri with NJHPS & Baspa Power as Zero duringevery off peak seasons.
The possibility of strengthening the reactive compensation of line at RampurThe possibility of strengthening the reactive compensation of line at Rampurowing to the LILO of existing Nathpa Jhakri Nalagarh Line shall be explored byPGCIL.
Reactive compensation improvement policy as suggested by PGCIL at remotesubstations shall be brought at the earliest.
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Feasibility of Minimizing the switching operation
Line Opening Sequence & Line Opening Rotation during lean season ( Sept to
May) in off peak hours in NJHPS area shall be monitored for uniform distribution
f it hi ( i ) i t th Li B k t NJHPSof switching ( opening) impact on the Line Breaker at NJHPS.
Sequence of Line opening shall be as :-
1) Abdullapur Line shall be opened first when expected Mvar Relief from1) Abdullapur Line shall be opened first when expected Mvar Relief from
system is highest.
2) Nalagarh Line Shall follow afterwards.
3) Baspa Line shall be at the end
Sequence of Line opening Rotation shall be as :-
1) Circuit 1 & 2 shall be open on rotational basis i e Circuit 1 & 2 shall be1) Circuit -1 & 2 shall be open on rotational basis i.e. Circuit -1 & 2 shall be
opened at alternate day if daily opening of line is scheduled.
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Action Plan:-1) Switching surge generated during capacitive breaking by NJHPS CB creates
an Oscillatory voltage of varying magnitude with longer decay time is
subjected to CB pole on line side & is in phase opposition(180) to the voltage
on CB pole on Bus side, when line is open from remote end . Over Voltage
Study of 400KV NJHPS area Network shall be carried out immediately toStudy of 400KV NJHPS area Network shall be carried out immediately to
mitigate oscillatory voltage behavior of Abdullapur & Nalagarh line which has
the permanently connected 50Mvar Reactors. The study will reveal the
method of mitigation & switching sequence of line.
2) Voltage control measures shall be expedited on priority basis.
3) I di t li f h i ( D 09 t M 10) f il bl3) Immediate relief mechanism ( Dec 09 to May 10) from available resources
shall be applied with standing order & monitoring thereof.