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SOUTHERN REGIONAL POWER COMMITTEE BANGALORE

Minutes of the 24thMeeting of Protection Coordination Sub-Committee

of SRPC held on 26.09.2013 1. Introduction

1.1 The 24thmeeting of Protection Coordination Sub-Committee (PCSC) was

held on 26thSeptember 2013 in the Conference Hall of Southern Regional

Power Committee, Bangalore. The list of participants for the PCSC meeting

is enclosed as Annexure-I.

1.2 Shri S.R.Bhat, Member Secretary (I/c), SRPC welcomed the Members and

Participants and especially Shri Sandeep Sarwate, ACE (T), NPCIL to the

24thmeeting of the Protection Coordination Sub-Committee.

1.3 MS (i/c), SRPC informed the forum that the issue regarding high voltage

trippings in and around Nellore node had been discussed in the recent

meeting of OCC during which a few recommendations had been suggested

for implementation. He requested that this issue be also discussed in the

PCSC meeting. He also informed that a communication had been received

from NPCIL-Mumbai with regard to HV settings of the over voltage relays on

400 KV Kaiga-Guttur line. He noted that revised settings for the voltage

relays were proposed based on the premise of not losing critical trunk lines

in the first instance, thus maintaining system integrity. Time and voltage

staggered tripping of lines were in accordance with guidelines. However,

steps for maintaining voltage level within permissible limits ,included

installation of reactors / capacitors, suitable VAR interchange by Generating

units and also maintaining tap position of GTs corresponding to 400

KV.Time and voltage staggered tripping was therefore implemented to

ensure minimum number of lines are tripped, to bring voltage profile within

permissible limits. The lines to be tripped were prioritized based on the

lengths as well as criticality. The recommended settings were as in

accordance with the decisions of the PCSC forum. Success of such

trippings however also lies with the pickup to drop ratio of the relays. Higher

Minutes of the 24th Protection Coordination Sub Committee Meeting held on 26.09.2013 Page 2

the ratio, better may be the chances of survival. Relays with pick up to drop

ratio of around 0.95 would de energize, only in the event of voltage dropping

up to 418 KV, after pick up at 440 KV.

1.4 MS (I/c), SRPC also pointed out that since many line reactors are non-

switchable; the lines were getting tripped along with line reactor. The matter

regarding installation of additional reactors had been discussed in the

recent Meeting of Standing Committee on Power System Planning. He

added that need was for a harmonized approach as well as collective

participation of Generators and STU / CTU etc to maintain grid stability and

to address the high voltage phenomenon. He also proposed formation of a

Subgroup to study any specific issues in this regard referred by the

constituents. This Subgroup could examine the overvoltage settings issue

and submit its recommendations to the Protection Coordination Sub

Committee for ratification.

1.5 PCSC forum placed on record the valuable contribution of Shri Muthu

Kumar, Deputy Manager, and SRLDC in the process of analysis of the Grid

Disturbances / Grid Incidents during the period July 2013 to September

2013 and also during the visit to the substations as part of the Expert

Group.

2. Confirmation of the Minutes of the 23rd Protection Coordination Sub-Committee meeting held on 26thAugust, 2013

The Minutes of the 23rd PCSC meeting were confirmed, since no comments

were received from the constituents.

3. Deliberation on High Voltage tripping in 400 KV Nellore S/S and one circuit each of 400 KV Narendra- Kaiga & Narendra – Guttur. 400 KV Nellore S/S

Ø It was observed that line tripping were not as per the recommended order of tripping.

Ø Both the 400 KV lines from Nellore to Sriperumbudur and Alamathy tripped prior to tripping of lines from Vijayawada to Nellore which further reduced the power flow from Vijayawada to Nellore since there was no feed from Nellore towards Chennai, thus aggravating the


overvoltage condition in Nellore. This inappropriate tripping overshadowed the only possible change of saving the Nellore S/S from complete black out.

Ø PGCIL SR-I informed that the inappropriate tripping could be due to Line CVT errors and also inherent error margins of the Relays.

Recommendation

Ø All CVTS to be tested for drift once in a month. If drift analysis shows error more than the permissible limits, then it needs to be replaced immediately.

Ø While Over voltage relay setting are being carried out for time staggering and voltage staggering , CVT errors to be also considered for the relay settings.

Ø A common relay with highest pick up to drop ratio could be used for over voltage tripping.

One circuit of 400 KV Narendra- Kaiga & 400 KV Narendra –

Guttur Ø The issue regarding Overvoltage Grading had been discussed in the

OCC/PCSC forums and it was decided to have Voltage Grading with respect to Voltage also. In the earlier meetings it had been agreed to set non Critical lines at 109% to avoid picking up of all the relays at 110% .The remaining Lines would be graded with time grading from 5 to 10 seconds delay. Node wise / Lines wise issues raised by the constituents had been discussed and considered for implementation.

Ø SRPC stated that after the NEW Grid disturbance on July 31st last year, changes in the system operation strategy had taken place. The lines are now being tripped only as a last resort. SRLDC added that line tripping was being resorted only after due consideration and ensuring that all other possible measure have already been taken to contain the voltage. In this process at times. Lines are tripped under over voltage.

Ø MS (I/c),SRPC requested NPCIL-Kaiga to participate in the Meeting on RGMO & MVAR interchange scheduled to be held on 30.09.2013 at SRPC, Bangalore. He added that station wise and unit-wise analysis of MVAR interchange would be carried out in that Meeting. Issue regarding tap optimization would also be discussed to analyze performance of units for containing the voltage within the permissible limits.

Ø NPCIL quoted provisions from CEA Technical Standards for connectivity to Grid that “All the Hydro Generating units having rated capacity of 50 MW and above shall be capable of operation in synchronous condenser mode, wherever possible". NPCIL insisted for condenser mode operation of Kadra units of KPCL to support the grid by absorbing reactive power to contain the high voltage. NPCIL also cited condenser mode of operation of Srisailam units in the Southern Region.


Ø SRLDC opined that MVAR absorption downstream in the 220 kV system may not have desired impact on 400 kV system in Kaiga. The technical feasibility of running the units in condenser mode of operation had also to be examined.

Ø NPCIL enquired about the status of Guttur reactor. It was noted that the issue of Installation of Reactor was discussed in the recent Standing committee meeting.

Ø After discussions it was agreed that the Over Voltage settings of 400 KV Kaiga Guttur Lines I & II be swapped presently, in view of the suspected CVT problem at Guttur end.

4. Grid Disturbances in Southern Region

4.1 Grid Disturbance on 18.09.2013 at UPCL /Hassan

(i) Date and Time of event 18.09.2013 at 15.57 Hrs (ii) Location Udupi, Hassan, Karnataka

(iii) Plant and/or Equipment directly involved

UPCL Generating Station,400 KV PGCIL Hassan substation

(iv) Reported Disturbance / Fault

Tripping of 400kV Hassan-UPCL line-1&2, Generation loss at UPCL, tripping of 220kV UPCL-Kemar line-1&2. The triggering incident was fault in 220kV Kemar-Varahi line-3

(v) Generation Loss 350 MW (vi) Duration of interruption 1 Hour 32 Minutes (vii) Category GD 1

• The Grid Disturbance analysis as submitted by SRLDC is enclosed as

Annexure-II.

• The Grid Disturbance Report as submitted by KPTCL is enclosed as

Annexure-III.

Deliberations

• It was noted that transient arcing fault on 220 KV Kemar-Varahi line had

resulted in the unwarranted tripping of 220KV Kemar-UPCL lines, GTs of

UPCL and also 400 KV UPCL – Hassan lines.

• 400 KV UPCL- Hassan line had tripped due to over reach of distance

protection.220 KV UPCL Kemar line 1 had tripped on DEF protection

relay. UPCL GT had tripped on DT-Earth Fault indication.

• KPTCL informed that the protection settings of DEFR of the feeders would

be coordinated.


• KSEB opined that CT ratios at different locations had also to be

considered while deciding setting for relays. DEF protection settings

should be coordinated with distance protection.

• UPCL informed that they would be adopting IDMT characteristics for

Generator Transformers (GTs) within a week time.

Recommendations

• The PCSC forum recommended IDMT characteristics for Earth Fault

Relay of the GTs in UPCL.

• UPCL-Kemar Line Protection would be coordinated by KPTCL and UPCL

within a week's time and the same would be communicated to SRPC

Secretariat.

• KPTCL to review DEF relay settings of 220 KV UPCL Kemar line 1 and 2,

• PCSC forum recommended for reviewing the Distance protection relay

settings at 400 KV Hassan by PGCIL SR-II.

4.2 Grid Incidence on 27.08.2013 and 29.08.2013 in 400kV

Kudankulam Thirunelveli line-2

(i) Date and Time of event (i) 27.08.2013 at 17:10 hrs (ii) 29.08.2013 at 16:11 hrs

(ii) Location Kudankulam, TamilNadu

(iii) Plant and/or Equipment directly involved 400kV Kudankulam-Thirunelveli line-2

(iv) Reported Disturbance / Fault It was reported that TEED protection had operated at Kudankulam.

(v) Duration of interruption 1 Hr 35 Minutes & 1 Hr 20 Minutes (vi) Category GI2 • The Grid Incidence analysis as submitted by SRLDC is enclosed herewith

as Annexure-IV.

Deliberations

• It was noted that twice TEED protection had operated on KKNP-TNV-2

line for transient faults once on Madurai-Udumalpet (400kV) and then on

Thirunelveli-Edamon (220kV) lines.

• It was informed that incorrect polarity wiring of CT involved in TEED

protection was corrected at KKNP end and the issue had thus been


resolved.

• SRLDC stated that stability test on bus bar at the time of commissioning

could have averted the CT polarity problems.

• SRLDC added that a testing kit with 10 kA sources (primary injection)

could be used for injecting current into bus-bars, and the actual current in

relays and its direction could be verified.

• NTPC informed that stability test would reveal incorrect wiring of CT.

• PGCIL informed the forum that in the past the line had not tripped for

through fault conditions. The same was happening now and opined that

certain changes might have been carried out at KKNPP end.

• SRLDC requested KKNPP to upload the D/R and E/L of trippings on the

SRLDC website.

• Recommendations

KKNPP, NPCIL to undertake thorough Stability test of Substation before

KKNPP Unit-1 commences generation.

4.3Grid Incidence at Talcher Kolar Link on 30.08.13

(i) Date and Time of event 30.08.2013 at 10:41 Hrs (ii) Location Talcher Kolar Link

(iii) Plant and/or Equipment directly involved PGCIL, Kolar HVDC Station

(iv) Reported Disturbance / Fault Pole-2 got blocked due to malfunction of pole control card at Talcher end. Pole-1 came to metallic return mode

(v) Injection Loss Power flow decreased from 1855MW to 695MW (1160 MW)

(vi) Duration of interruption 20 Minutes to 1 Hour 20 Minutes

(vii) SPS At Kolar Operated and Trip Signal I generated (642 MW Load relief obtained (AP: 104 MW;TN:251 MW;KAR:287 MW)

(vii) SPS at Talcher During the blocking of Pole-2, SPS at Talcher was in SPS 1000 mode. No unit tripped as per design.

(viii) Duration of interruption 1 Hr 14 Minutes (ix) Category GI 2 • The Grid Incidence analysis as submitted by SRLDC is enclosed

herewith as Annexure-V.


Deliberations

• It was noted that due to pole control card failure at Talcher, the tripping

had occurred and the card had since been replaced.

• NTPC queried about the status of the GRM (Ground Return Mode) study

on the HVDC Talcher Kolar Link and it was informed that the same was

underway.

4.4 Grid Incidence in Kaiga Kodasalli Line 2on 27.08.2013 at 01:45

Hrs

(i) Date and Time of event 27.08.2013 at 01:45 Hrs (ii) Location Kaiga-Kodasalli

(iii) Plant and/or Equipment directly involved

220kV Kaiga-Kodasalli line and 220kV Kaiga-Kadra line


Lines tripped on earth fault and back up over current protection at Kaiga end. 220kV Kadra-Karwar line-1 had tripped on zone-2, Y-N fault.

(v) Duration of interruption 35 Minutes (vi) Category GI 1

Deliberations

• It was felt that 220 KV Kaiga-Kadra line should not have tripped for

fault on Kadra-Karwar line-1. It was further informed that Kadra-Karwar

line-1Zone-2 picked up but tripped in Zone-1 time with carrier aided

tripping.

• KPTCL informed that DMT settings for backup have been implemented

at KGS instead of IDMT.

• SRLDC suggested that relay co-ordination be carried out at KGS end.

NPCIL suggested that initially testing of the relays be carried out at

Kadra & Karwar and in case there are no errors then NPCIL would

change the settings at KGS.

• SRLDC informed that D/R and E/L had not received by them to

analyze the case.


Recommendations

• PCSC forum requested Kaiga / NPCIL and KPTCL to review the

protection settings at Kaiga, Kadra and Kodasalli in coordination with

the adjoining utility settings to avert similar trippings.

4.5 Grid Incidence at 400/220 KV Guttur Substation on 02.09.2013.

(i) Date and Time of event 02.09.2013 at 11:41 Hrs (ii) Location Guttur, Karnataka

(iii) Plant and/or Equipment directly involved 400/220 KV Guttur substation of KPTCL


All connected 220kV lines, 400 kV and ICT’s at 400/220kV Guttur substation tripped. The triggering incident was fault in 220 kV Haveri-Guttur line-2

(v) Load Loss 434 MW (vi) Duration of interruption 44 Minutes to 2 Hr 39 Minutes (vii) Category GI 2

• The Grid Incidence analysis as submitted by SRLDC is enclosed

herewith as Annexure-VI.

Deliberation

• Protection Expert Group had been formed to study the Guttur incident

that had occurred on 02.09.2013.Thisgrouphad visited Guttur Substation

on 18th September.2013 and submitted its recommendations to the

Protection Coordination Subcommittee (Annexure-VII).

• It was noted that Bus Coupler (on 400KV and 220 kV) and Transfer Bus

Coupler (on 220 kV) were faulty.

• Fault on the Guttur-Haveri-2 line had resulted in LBB operation at Guttur

220 kV bus as the line breaker‘s DC supply to trip coil was faulty and both

the trip coils were fed from the same DC source.

• It was informed that during the incident, the two ICTs tripped on backup

protection (high set instantaneous) and Guttur-Kaiga-2 line had tripped

on over voltage.

• SRLDC informed that as the Bus Coupler (on 400KV and 220 kV) and

Transfer Bus Coupler (on 220 kV) were not functional at present, any


breaker stuck condition or bus fault would lead to who le substation

outage.

• KPTCL was requested to modify the trip circuit of the breaker with two DC

sources to feed two different trip coils of the breaker and not to tap power

for synchronizing socket from the trip coil circuit.

• Regarding high set operation of ICTs backup protection, APTRANSCO

said that high set relay is for internal or equipment fault and should not

have acted for through faults.

• KPTCL said that Guttur-Kaiga-1 line is using the TB/C as its CB at Guttur

end since it has failed some time back. It was also stated that 220 kV B/C

would be completed in few days and purchase order had been placed on

M/s Alstom for 400 kV B/C and TB/C.

• Member Secretary (I/c) said that Guttur being a critical Substation for

KPTCL system with number of 400 kV and 220 kV lines connected and

also for evacuation of Kaiga power, adequate care needed to be taken.

Deficiencies highlighted by expert group needed to be resolved urgently.

He also said that a letter had been addressed to Director (Transmission),

KPTCL regarding implementation of the recommendations of the

Protection Expert Group on priority basis (Annexure-VIII).

• SRLDC said that split bus operation and independent DC supply to two

trip coils of the circuit breaker of Guttur – Haveri – 2 lines have to be

implemented by KPTCL.

• KPTCL informed that Tie bus CB could be operated as B/C and this

would be arranged by January, 2014.

• With reference to the 5th recommendation of MoM dt 18.08.2013, CVT

has to be referred to OEM for resolving the issues.

• NLC informed that during the transient period since capacitance of CVT

changes, voltage transformation gets affected.

• SRLDC suggested that in case of error in CVT measurement, priority of

the lines could be swapped.

• It was also observed that Main-1 and Main-2 overvoltage relays were set

to take different type of input i.e. phase to neutral or phase to phase of

the CVT secondary voltage. In this regard KPTCL informed that both


Main-1 and Main-2 overvoltage relays picked up on over voltage but

Main-1 did not gave trip command, which need to be investigated.

• KPTCL said that they would swap the priorities and also address the CVT

problem. KSEB stated that continuous monitoring of measured value of

voltage of CVT is required.

• It was informed by PGCIL that some tests (such as voltage

measurement, drift measurement, etc.) are being carried out on CVT on a

monthly basis by them.

• MS (I/c), SRPC requested PGCIL to share the format for conducting

these tests on CVT, as part of sharing and dissemination of Best

Practices. The Drift Measurement format as submitted by PGCIL is

enclosed herewith as Annexure-IX.

Follow up data as furnished by KPTCL vide email dated 25.09.2013

(Annexure-X)

The status of compliance on the Recommendations of the Committee, as

informed by KPTCL is as follows:

1. Modification of the present breaker tripping scheme of Haveri line-2 so

that the trip coils are activated through two different DC sources. The

necessary modifications are to be carried out in the breaker panel.

KPTCL Action: Action is being taken to consult the breaker OEM for

making necessary modification in the internal wiring.

2. As per standard practice DC supply for synchronizing circuit not to be

tapped from the DC supply of trip / close circuits, modification in the

existing scheme of DC supply for Haveri line-2 same may be reviewed.

KPTCL Action: DC supply for the synchronizing socket is isolated

from the breaker DC circuit.

3. The non-availability of 220kV and 400kV bus coupler is affecting the

reliability of 400/220kV Guttur substation. Hence problems in 220kV bus

coupler breaker, 400kV bus coupler breaker along with Kaiga line-1

breaker to be rectified and taken into service at the earliest.

KPTCL Action: Rectification of 220kV ABB make bus coupler breaker

problem is under process:


(i). Purchase order placed on M/s Alstom for replacement of 400kV

Bus coupler CB, Transfer CB and circuit breaker of Munirabad bay.

(ii) Action is being taken for overhauling of 400kV Kaiga-1 line circuit

breaker. Removal of Pre Insertion Resistor (PIR) and over hauling of

the breaker has been delayed on account of rainy weather conditions.

4. Committee Members had requested KPTCL to explore the possibility of

operating the 220kV system at Guttur in split mode until the 220kV bus

coupler breaker is taken into service in order to avoid complete outage of

the station in the event of a fault in 220kV bus bar or a fault during a stuck

breaker condition.

KPTCL Action: Action is being taken to rectify the problem in the

220kV bus coupler breaker, which would be taken into service soon

after completion of the work.

5.400kV Guttur-Kaiga line-2 got tripped on operation of over voltage

stage-2 in Main-2 protection relay. The Main-1 relay had sensed the over

voltage but did not give a trip command. It was observed that this was a

peculiar phenomenon as overvoltage relay of any other 400kV lines at

Guttur did not sense over voltage condition. It was advised to take up with

OEM of CVT and relay to investigate the problem.

KPTCL Action: 400kV Kaiga-2 line had tripped at Guttur end due to

operation of Over Voltage protection in Main-2 relay. But during this

instance, other lines had not sensed the over voltage. Hence the

protection expert committee suspected the mal operation of Kaiga-2

line CVTs. Measurement of CVT voltage done during normal condition

found to be in order. As per the Committee recommendations, the

matter was taken up with M/s BHEL for rectification. The Main-1 relay

also sensed the over voltage but did not give the trip command. The

relay operation tested and found to be normal.

6. The backup earth fault, 51N (high set) protection of ICT’s got operated

for a fault in 220kV Guttur- Haveri line-2. The present setting of high set of

back up earth fault relay for ICT is 2.56 kA. High set in over current and

earth fault relay is generally provided for fault on the equipment which

involves a very high current. Hence it was advised to review the High set

setting of Back up earth fault relay of ICT’s at Guttur substation.


Ø KPTCL Action: The high set settings of back up earth fault relays

of ICTs revised by considering 220kV bus fault level.

4.6 Grid Incidence at 400 KV Nellore Pooling Substation on 10.09

.2013.

(i) Date and Time of event 10.09.2013 at 03:04 Hrs (ii) Location Nellore , Andhra Pradesh

(iii) Plant and/or Equipment directly involved 400 KV Nellore substation of POWERGRID


400kV Vijayawada-Nellore line-1&2, 400kV Nellore-Sriperumbudur line, 400kV Nellore-Almatti line, 400kV Nellore pooling-Nellore line-1&2 tripped on operation of over voltage stage-1

(v) Generation Loss 480 MW (vi) Duration of interruption 45 Minutes to 12 Hr 9 Minutes (vii) Category GI 2

• The Grid Incidence analysis as submitted by SRLDC is enclosed

herewith as Annexure-XI.

Deliberation

• It was pointed out that during the High voltage tripping incident at 400 KV

Nellore substation, the lines had not tripped in the order of sequence laid

down by the OCC/PCSC forum.

• PGCIL informed that due to CVT errors, tripping were not as per set

priority order.

• SRLDC said that the design objective of Voltage and time-graded tripping

of lines under high voltage conditions, was not to lose critical lines and

hence tripping should be in the recommended order to serve the intended

purpose.

• APTRANSCO opined that some node wise engineering is required to

implement time-graded over voltage settings to obtain tripping as per

recommended order. They further added that due to these efforts some

chances are there to save the station from total outage.

• SRLDC placed on record the following three points:

(i) CVT measurement errors need to be taken into consideration

while deciding the trip setting of over voltage relays.


(ii) Drop-off to pick-up ratio of over voltage relay should be as close

to 1 and possibly at least 0.99.

(iii) Tripping sequences that were recommended by the forum to

contain high voltages have to be strictly adhered.

• PGCIL informed that in only one particular make of Siemens relay’s drop-

off to pick-up ratio is 0.99.It would thus be difficult to replace all the relays

where drop-off to pick-up ratios is less than 0.99.

• Member Secretary (I/c), SRPC requested the constituents to strictly

adhere to the Voltage and Time staggered tripping recommended by the

OCC forum to save the trunk lines.

• With regard to CVT errors, NTPC informed that the practice was to

replace the CVT in case of more than 2% error in its LV (secondary

voltage) measurement.

• SRLDC also stressed on having switchable line reactor which could be

converted to bus reactor in the eventuality of losing the line during high

voltage tripping.

• It was noted that in Eastern Region, voltage-graded tripping at 112% is

reported to be in practice.

• PGCIL stressed that voltage rating of the equipment needed to be

considered while devising voltage-graded tripping of lines.

Recommendations

• CVT measurement errors have to be taken into consideration while

deciding the trip setting of over voltage relays.

• Drop-off to pick-up ratio of over voltage relay should be close to 1 and

possibly at least 0.99.

• Drift analysis of CVTs to be carried out every month and in case drift is

more than 2%, then CVT to be replaced.

• Relays with highest Drop-off to pick-up ratio to be wired for over voltage

protection.


5. SPS for Kudankulam Nuclear Power Station

SRLDC brought to the notice of the PCSC forum that there had been re-

orientation recently in respect of 400 KV lines emanating from

Kudankulam. Three 400kV lines are now from Kudankulam to Thirunelveli

while remaining one line is from Kudankulam to Madurai. Hence the

following logic was proposed for SPS at Kudankulam, On account of the

change in the configuration:

Contingency Action

Tripping of all three lines from Kudankulam to Thirunelveli and two units in running condition at Kudankulam.

One unit at Kudankulam to go on house load and the second unit generation would be evacuated through 400kV Kudankulam-Madurai line.

Deliberations

• NPCIL requested for load flow study to be conducted with conditions of

900 MW generation at KKNP and radial connection to Madurai so that the

SPS could be clearly understood and justified.

• Proposed SPS is for a specific condition of losing three 400 kV lines to

Thirunelveli and the details are:

(i) if one unit is running, use the Kudankulam Madurai S/C line.

(ii) if two units are running, take one unit under house load and use

Madurai line for evacuation of power from one unit.

• KSEB informed that similar approach is in operation at Kuttiadi station

with 4 lines.

• It was pointed out that lengthy 400 kV line with twin moose cannot carry

the power of 1000 MW as the thermal stability of the line would be

affected and also there would be around 13 kV dip in the voltage.

• APTRANSCO and KSEB opined that the scheme should carry out

automatic ramping down of generation so as to ensure smooth

evacuation of power from Kudankulam to Madurai.


• NPCIL said that it would explore the level of ramping down at KKNP and

would submit the details in a week's time.

• SRLDC was requested to conduct the study under these conditions to

observe the power flow and voltage dip in the adjacent nodes.

6. Review of Power swing block settings of Distance protection relay. SRLDC has stated that during grid disturbances, when the network depletes,

there could be a scenario where load would be fed through long lines. Also

there would be fast changes in the system due to disturbances. During such

conditions, losing further lines on account of power swing would further

aggravate the situation and may lead to a major disturbance or blackout.

Many practices were being followed for power swing detection and blocking,

adoption of blinders etc. This would be of further importance when SR and

NEW grid get synchronized. Hence, it was important that the existing

practices in this regard be studied and harmonized.

Deliberations

• PCSC forum decided that the issue would be discussed in detail by the

Sub Group to be formed to discuss the Over voltage and staggered

tripping issues in coordination with the NEW Grid settings.

7. Compliance status of Protection Audit conducted in the

Substations of Southern Region

Deliberations

PCSC suggested that PGCIL and APTRANSCO inform the forum about the

remedial measures taken by them to address the protection Audit

Observation / Recommendations noticed during the protection audit.

8. Minor Tripping

The Minor tripping that had occurred in the Southern Region during the month

of August-September 2013 as submitted by SRLDC; POSOCO is attached

herewith as Annexure-XII.


9. SPS FOR 400 KV KOLAR - HOSUR LINE

• SRTS II, PGCIL informed that the Original Equipment Manufacturer

(OEM, i.e. Siemens) had advised not to have too many Logics (in this

instance- runback) in the HVDC system.

Deliberations

• It was agreed that the SPS for 400 KV Kolar Hosur Line would be

discussed in a Special Meeting to be convened at Kolar SS.

10. Status of implementation of various SPS proposed in the Southern Region

Sl. No.

Name of the Scheme Details of the scheme

Implementing

Agency

24th PCSC Deliberations

PCSC Recommendations

1 Proposed Modification in the SPS at Kolar SS

In the 16th PCSC the forum proposed an additional trip logic (dp/dt )to the Kolar SPS during contingencies similar to New Grid disturbance on 31.07.2012

PGCIL PGCIL informed that the SPS is under Process. Would be completed by October 2013.

The forum requested PGCIl to complete the modification within the agreed time.

2 Kudankulam SPS In case of tripping one or two units at Kudankulam nuclear power plant, trip signal-1 or Trip signal-1&2 will be generated depending on number of units tripping. Trip signal-1:793 MW and Trip Signal-2:710 MW

PGCIL Second Mock Exercise was conducted on 29th August 2013.

-

3 Modification in NTPC Talcher SPS

SPS would be modified to back down all the generating units instead of tripping the units

NTPC New Scheme with SPS 1000 may be kept in service under normal Operating conditions

The PCSC forum requested NLDC/SRLDC to convey the decision at the earliest.

* 1. The Non-receipt of Signal at Oothankarai in Tamilnadu needs to be checked. TANTRANSCO is requested to check transmission of signal from Salem to Oothnkarai and inform the status to PCSC forum at the earliest. 2. During testing of SPS signal-2, signal was received at Sriperumbudur which was not desired as per the design. SRTS II, POWERGRID is requested to check the same and inform the status to PCSC forum at the earliest.


11. Status of implementation of various SPS proposed in the Andhra Pradesh periphery

S.No

Name of the Scheme

Details of the scheme Implementin

g Agency 24th PCSC

Deliberations PCSC

Recommendations

1 Vijayawada-Nellore SPS

if one of 400kV Vijayawada-Nellore D/C line trips and before tripping flow each circuit is >550 MW then back down generation or trip one generating unit each at GMR Vemagiri, Gouthami, Konaseema, Jegurupadu-II and Lanco. Total generation back down of 430 MW. Proposed in 9th PCSC (9.07.2010)

PGCIL ./ APTRANSCO/IPPs

APTRANSCO informed that all the IPPs were given their consent for the SPS.

The forum requested PGCIl to implement the SPS at the earliest.

2 Nellore-Almatti SPS

If one of 400kV Nellore-Almatti DC line trips and before tripping flow each circuit is >520 MW then trip one generating unit each at SEPL and MEPL. Total generation back down of 300 MW. Proposed in 15th PCSC (18.07.2012)

PGCIL MEPL sent the confirmation.

The forum requested SEPL to send the confirmation at the earliest.

12. Status of implementation of various SPS proposed in the Karnataka periphery

S.No

Name of the Scheme

Details of the scheme Implementing

Agency 24th PCSC

Deliberations PCSC

Recommendations

1 Somanahally & Bangalore water supply

a) To trip all 220kV lines & 220 / 66kV trfs except 220 kV Harohalli & Tataguni lines at Somanahally and to trip Vrishabhavathi line at Tataguni when ICTs at Somanahally trip. b) To trip 220 kV Vajamangala and Madhuvanahally-1 & 2 lines at TK Hally when ICTs at Mysore trip.

KPTCL

220 kV line CVTs are being replaced under R&M work. Once the PLCC equipment are restored the SPS will be implemented.

The PCSC forum requested KPTCL to submit the SPS Logic to the SRPC Secretariat.

13. Status of implementation of various SPS proposed in the Tamil Nadu periphery

S. No

Name of the Scheme Details of the scheme

Implementing Agency

24th PCSC Deliberations

PCSC Recommendations

1 Thirunelveli SPS

To avoid overloading of Thirunelveli ICTs in the contingency of tripping of Thirunelveli-Edamon lines.

TANTRANSCO TANTRANSCO informed that the scheme would be ready by 1st week of October 2013.

The forum requested TANTRANSCO to implement the scheme within the agreed time.

2 Madurai SPS To avoid overloading of Madurai ICTs.

TANTRANSCO TANTRANSCO informed that the scheme would be ready by end of October 2013.

The forum requested TANTRANSCO to implement the scheme within the agreed time.


14. Implementation of Islanding schemes proposed in the southern region

Deliberations

The PCSC forum requested TANTRANSCO to implement the remaining

part of Stage II of the Islanding Scheme latest by end of October 2013

since other utilities had completed their part. TANTRANSCO agreed to

complete their part by the agreed time line.

15. The issue of AUFR stages and implementation in SR • In the second NPC Meeting, it had been agreed that there would be

four stages for AUFLS starting with 49.2 Hz. The various stages for AUFLS operation are 49.2 Hz, 49 Hz, 48.8 Hz and 48.6 Hz.

It was noted that all the stages had been implemented except portion of the last stage of 48.6 Hz in TN.

16. Submission of completed dynamic study data

• All SLDCs were requested to direct the embedded IPPs connected at 220 KV and above voltage level to submit completed dynamic study format to SRPC, Secretariat.

• NPCIL, MAPS was requested to submit the dynamic study data of their system.

17. Providing Synchronizing facility at key stations for Black start restoration

• The PCSC forum requested KPTCL to provide synchronizing facility in

Hubli S/S latest by January 2014.

18. Requirement of Under Voltage Relays (UVR) for SR

SRLDC had proposed for the provision of under voltage relays in various low

voltage pockets to ensure reliable power supply and grid safety

Ø Constituents were requested to install the UVR at least in a phased manner in the SRLDC specified nodes. Progress in this regard may be reported to the PCSC forum at the earliest.


19. Validation of lines: Loading on Transmission System based on the CEA "Manual On Transmission Planning Criteria" Ø Puducherry was requested to submit the validated data at the

earliest to the PCSC forum.

20. Implementation of recommendations of Grid Disturbance enquiry committee

Healthiness of Batteries: MAPS-NPCIL, and Puducherry were yet to

start reporting the status of healthiness of Batteries to the SRPC Secretariat.

21. Remedial measures taken for the critical tripping events in the

Southern Region.

The respective constituents were requested to submit the complete tripping

analysis report with (DR,EL) remedial measures taken by them for the tripping

events enclosed in the Annexure-XIII in the prescribed format (Annexure –

XIV)at the earliest.

22. Sending Agenda items for the PCSC meetings.

As per the Guidelines of CEA/MOP it had been decided to conduct the PCSC

meetings on a monthly basis .It was requested that Agenda Items for the

PCSC meetings, if any, may please be sent latest by 5th working day of every

month to SRPC Secretariat to compile and circulate the same so as to have

fruitful discussions in the PCSC meetings.

23. Date & Venue of the next Meeting

The 25th PCSC meeting would be conducted on 22.10.2013 (Tuesday).

Member Secretary i/c thanked all the Members &participants for their active

contribution in the Meeting.

*****

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ANNEXURE I (1/5)

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ANNEXURE I (2/5)

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ANNEXURE I (3/5)

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ANNEXURE I (4/5)

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ANNEXURE I (5/5)

Hassan-1

Hassan-2

UPCL 400kV Bus

power stationTripping and generation loss at Udupi

power station

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ANNEXURE II (1/3)

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ANNEXURE II (2/3)

Points for discussion

• Distance protection at Hassan end for 400kV Hassan-UPCL line-1&2 needs review.

• UPCL unit tripped on operation of Generator transformer backup earth fault protection. The settings need review.

• Review of directional earth fault relay settings of 220kV UPCL-Kemar lines

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ANNEXURE II (3/3)

KARNATAKA POWER TRANSMISSION CORPORATION LIMITED Tel: 080 – 22211537 Office of the

Fax: 080 – 22219253 Chief Engineer Electricity,

E-mail: [email protected] RT& R&D, KPTCL, Room No.508, 5th Floor,

Kaveri Bhavan, Bengaluru - 9. No. CEE/RT & R&D/KCO-79/45916/2012-13/ Date: -09-2013 To,

The Member Secretary,

Sothern Region Power Committee,

No.29, Race Course Cross Road,

A.R.Circle, Bengaluru-09.

Sir, Sub: Tripping of UPCL unit and 400kV lines at PGCIL 400kV Station Hassan on 18.09.2013 at 15.57Hrs -reg.

***** At Kemar on 18.09.2013 at 15.57Hrs there was heavy arcing in the R phase jump at

5th tower of 20kV Kemar –Varahi-3 line.150MW of power was flowing from Varahi to Kemar.

The arcing in the jump ended up in opening of the jump and the cut jump also entered

arcing zone of Y phase.

DEFR

23km

5th tower, arcing and opening of the jump & then phase-phase fault(RY)

VARAHIII

UPCL- 220kV Bus

Tripped on DPR, Zone-II

0.7km

Varahi -2

Varahi -3

KEMAR

UPCL-1

20MW each

Shimoga

UPCL-2

SHIMOGA

45MW

50MW

50MW

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ANNEXURE III (1/4)

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The line tripped at Varahi in distance protection Zone-2(fault loop: L2-L3,distance-80km, line length-80km). The line tripped at Kemar end on DEFR.

Meanwhile at UPCL one of the 220kV lines (Kemar-2) tripped on DEFR and the other line had not tripped.

Before this, 3X250MVA Generator Transformer at UPCL tripped on DEFR. The setting for this GT was 300mA at a definite time delay of 2.5seconds.However the GT tripped within 500miliseconds.

At the same time both the 400kV lines have tripped at Shantigrama on Distance Protection.

400kV Hassan-UPCL-1:DPR(Main-I),Z2, BN,218km;

400kV Hassan-UPCL-2:DPR(Main-I),Z1, BN,138km

Inference:

1. The 220kV Kemar- Varahi line 3 should have tripped at Kemar on first zone when the cut jump entered arcing zone. However since the arcing had started much earlier to this opening and EFR relay might have advanced and might have tripped before the operation of distance relays.

2. No other lines have tripped at Kemar- which is correct as the fault was in reverse zone for other lines.

VARAHI

UPCL-400kV Bus

DPR,Z2

Fault

0.7km

Varahi -2

Varahi -3

KEMAR

UPCL-220kV Bus

Shantigrama

2*315MVA ICTs

Shimoga

Gen

Hassan-1

Hassan-2

Tripped on

Main-1, Z1

Main-1,Z2

GT

Kemar-1

Kemar-2

DEFR

DEFR

DEFR

Shimoga

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ANNEXURE III (2/4)

3. Both the lines should have tripped at UPCL on distance relay or DEFR if the fault persisted until the EFR sensed the unbalance and advanced when the actual fault occurred. .

4. The GT should not have tripped. As the fault was cleared within 500 msec(at both the ends), the GT earth fault relay which

was set for 2.5sec delay should not have tripped.

Also before GT, there are two 315MVA ICTs and they should have tripped before GT if the fault current was enough and if sufficient time delay was there.

5. The reason for tripping of 400kV lines at Shantigrama is not under stood.

For Shantigrama, the fault was beyond third bus i.e. both the lines are terminated at UPCL(181km).Then there are two ICTs in between and then UPCL 220kV Bus. After this bus two 220kV lines to Kemar (23km).After Kemar bus the fault was occurred at a distance of 0.7km.

The fault current was also not high as the fault was not a metallic fault.

Also it is to be noted that only one set of relays (only Siemens relays) have acted as the other set of relays (REL670) have not acted. As ABB relays have not acted, the settings of Siemens relays are suspected.

Under the circumstances it is requested:

1. To advice UPCL to co-ordinate the relay setting between the lines,ICTs and GT, so that

the protection of GT acts after ICTs and lines.

Shimoga

UPCL 400kV Bus

Fault

0.7km

Varahi -2

Varahi -3

220kV KEMAR

UPCL-220kV Bus

2*315MVA ICTs

Shimoga-1

Hassan-1

Hassan-2

Kemar-1

Kemar-2 VARAHI

400kV Shantigrama

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ANNEXURE III (3/4)

2. To advice PGCIL to review the settings of 400kV lines.The lines should not have tripped

for the fault in the third bus (and also beyond the ICTs impedance).

3. To advice PGCIL to keep the settings of both the relays to match each other.

Meanwhile KPTCL is also testing its relays at Kemar and review the settings. The disturbance recorder reports,the SCADA event list,power flow snap shot during and after the fault is enclosed.

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ANNEXURE III (4/4)

Tripping of 400kV Kudankulam-Tirunelveli line-2 on

27th & 29th August 2013

1) Brief Details

400kV Kudankulam-Tirunelveli line-2 tripped at 17:10 hrs on 27.08.2013 and at 16:11 hrs on

29.08.2013. It was reported that TEED protection had operated at Kudankulam.

Figure 1 : Single Line diagram of 400kV Kudankulam NPP Switchyard

Figure-1 shows the single line diagram of 400V Kudankulam Nuclear Power station. The

400kV and 220kV is a Gas insulated station. At KKNPP the 400kV system has a one and half

breaker scheme and 220kV system has a double main and transfer bus scheme. 400kV

system at Kudankulam has a 5 CT scheme.

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ANNEXURE IV (1/4)

2) Brief about TEED protection scheme

Figure 2 : One and half breaker scheme

Figure.2 shows a one and half breaker scheme with a 5 CT scheme. If line -1 is out of service and for

reliability purpose if the diameter of the one and half breaker scheme is kept closed i.e., breakers

152, 252 & 352 are in service. In the event of occurrence of fault in the three terminal or teed

section between line isolator of line-1, main breaker (152) and tie breaker (252) [highlighted

section], the distance protection of line-1 would not be able to sense the fault as the voltage from

CVT is absent due line isolator in open condition. A TEED or Stub protection is provided to sense and

clear the fault under this condition of the system.

TEED protection is a high impedance differential protection which is used to take care of the above

situation. It is generally used with a 5CT scheme.

STUB protection is an overcurrent protection and it is as an inbuilt feature of numerical distance

protection relay. The STUB protection feature in distance relay gets activated through a binary input

from line isolator open condition. In the event of fault in the section shown in fig. the distance relay

will act as an instantaneous non-directional over current relay and trip the breakers.

Rajan1

ANNEXURE IV (2/4)

3) Analysis of the Incident

i) Observations from Synchrophasor data

Figure 3 : 400kV Thrissur bus voltage on 27.08.2013

It was reported that 400kV Tirunelveli-Udumalpet line-1 auto-reclosed at 17:10 hrs on

27.08.2013. It can be observed from fig.3 that transient had occurred in Y-phase and line had

successfully auto-reclosed. During occurrence of this event, it was reported that 400kV

Kudankulam-Tirunelveli line-2 tripped on operation of TEED protection at Kudankulam end

and direct trip was received at Tirunelveli end.

Figure 4 : 400kV Thrissur bus voltage on 29.08.2013

From fig.4 it can be observed that a transient fault had occurred in Y-Phase. It was reported

that 220kV Tirunelveli-Edamon line-2 auto-reclosed and 400kV Kudankulam-Tirunelveli

line-2 got tripped on operation of TEED protection at Kudankulam end at 16:11hrs on

29.08.2013. There was no fault in 400kV Kudankulam-Tirunelveli line-2 as the distance

protection at Tirunelveli and Kudankulam did not sense any fault.

Rajan1

ANNEXURE IV (3/4)

Hence it is observed that on both 27th

& 29th

August 2013, the TEED protection of 400kV

Kudankulam-Tirunelveli line-2 got operated for a through fault i.e., for an external fault

which is not desired. It is suspected that TEED protection of 400kV Kudankulam-Tirunelveli

line-2 had mal-operated which resulted in tripping of line. Mal-operation of TEED scheme

can occur due to possible wrong connection of CT polarities for the TEED scheme.

4) Restoration:

Sl.

No

Line/Equipment Date Time

1 400kV Kudankulam-Tirunelveli line-2 27-08-2013 18:45

2 400kV Kudankulam-Tirunelveli line-2 29-08-2013 17:30

5) Suggestion and remedial measures:

a. The TEED protection scheme needs to be tested at Kudankulam end.

X…………………………………….X……………………………………..X

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ANNEXURE IV (4/4)

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ANNEXURE V( 1/6)

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ANNEXURE V( 2/6)

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ANNEXURE V(3/6)

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ANNEXURE V( 4/6)

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ANNEXURE V( 5/6)

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ANNEXURE V( 6/6)

Multiple Tripping at 400/220kV Guttur substation of

KPTCL at 11:41 hrs on 2nd September 2013

Figure 1 : Single line diagram of Guttur Substation

All connected 220kV lines, 400kV Kaiga-II line and ICT-I & II and at Guttur substation tripped at 11.41

hrs on 02.09.2013. It was reported by KPTCL that there was no load loss due the tripping. The

triggering incident for the event was fault in 220kV Guttur-Haveri line-2. Figure-1 shows the single

line diagram of 400/220kV Guttur substation.

Rajan1

ANNEXURE VI (1/3)

Analysis of the incident

Observations from Synchrophasor data:

Figure 2 : 400kV Narendra bus voltage

Figure-2 shows the 400kV bus voltage of 400kV Narendra substation. It can be observed that there

was a fault in B-Phase and there was a delayed clearance of fault.

Figure 3 : Zero and negitive sequence current in 400kV narendra-Guttur line

Figure-3 shows the negative and zero sequence current in 400kV Narendra-Guttur line. Presence of

zero sequence current indicates an earth fault in B-Phase and it can be observed that there was a

delayed clearance of fault i.e., in 280 milli seconds.

Rajan1

ANNEXURE VI (2/3)

As per report of KPTCL, there was snapping of ground wire in 220kV Guttur-Haveri line-II line. The

breaker at Guttur end could not clear the fault due to failure of DC supply. The fault was cleared by

the operation of LBB protection of Haveri-2 breaker and by back up protections of ICT’s at Guttur.

400kV Kaiga-Guttur line-2 got tripped due to operation of reverse zone of distance protection at

Guttur end.

Restoration

Sl.

No.

Name of equipment/ line Date Time Remarks

1 220kV Guttur-Itagi 02.09.2013 12.25

2 ICT-II at Guttur 02.09.2013 12.37

3 220kV Guttur-Davangere-III 02.09.2013 12.38

4 220kV Guttur-Davangere-I & II 02.09.2013 12.40

5 220kV Guttur-Ranebennur 02.09.2013 12.42

6 220kV Guttur-Haveri-I 02.09.2013 12.45

7 220kV Gutur-Chitradurga 02.09.2013 13.00

8 400kV Guttur-Kaiga-II 02.09.2013 13.11

9 ICT-I at Guttur 02.09.2013 14.20

Suggestion and further actions required. 1) It was reported that the breaker of 220kV Guttur-Haveri line-2 did not operate due to failure of DC

supply. As per protection philosophy, two separate DC sources and two trip coils are available for

each circuit breaker. Hence further investigation is required for non-tripping of the Haveri line-2

breaker through the alternate DC source and reason for non-detection of DC failure by supervision

relay.

2) Ideally if the breaker of Haveri-2 bay failed to clear the line fault, then breaker failure protection of

Haveri-2 bay should clear the fault by tripping the breakers connected to the 220kV bus to which

Haveri line-2 is connected and tripping of bus coupler. However in this case all the 220kV lines and

ICT’s had tripped which was not desired. Reason for tripping of all the 220kV elements needs further

investigation.

3) 220kV Guttur-Davangare line-3 had tripped from both the ends. Suspected over-reach of distance

relay could have caused tripping of line-3 from Davangare end and hence needs investigation.

4) 400kV Guttur-Kaiga line-2 distance relay at Guttur end had sensed a reverse zone fault and tripped

the line. As per protection philosophy, the reverse zone of the distance protection is used to provide

backup for the local bus-bar by applying a reverse reach setting of 25 – 25% of zone-1 reach and has

time delay of 1.5 seconds. In this case the distance relay of 400kV Guttur-Kaiga line-2 at Guttur end

had sensed a fault in 220kV Haveri line and has acted along with the transformer back up protection.

Hence review is required for the reverse reach of distance relay of 400kV Guttur-Kaiga line-2 at

Guttur end along with time co-ordination with ICT back protections.

X………………………………….X………………………………………..X

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ANNEXURE VI (3/3)

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ANNEXURE VII (1/2)

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ANNEXURE VII (2/2)

Rajan1

10284-86

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ANNEXURE VIII (1/1)

Month:

R-N Y-N B-N R-Y Y-B B-R R-N Y-N B-N R-Y Y-B B-R400kV BUS - I

CORE-I 1st of Every Month 10:00 231 231 231 400 400 400 62.60 63.06 62.62 109.20 109.20 108.20 0.44CORE-I 16th of Every Month 10:50 230 230 230 398 398 398 63.08 63.56 63.17 110.00 110.00 109.20 0.39CORE-II 1st of Every Month 11:00 231 231 231 400 400 400 62.64 62.18 62.32 110.50 110.50 109.80 0.46CORE-II 16th of Every Month 10:50 230 230 230 398 398 398 63.10 63.75 63.12 110.50 110.60 110.50 0.63CORE-III 1st of Every Month 11:00 231 231 231 400 400 400 63.13 63.24 62.79 109.30 109.30 108.70 0.45CORE-III 16th of Every Month 10:50 230 230 230 398 398 398 63.67 63.67 63.19 110.20 110.30 109.30 0.48


400kV FEEDERSFeeder-I




Feeder-III

Feeder-II:

400kV BUS - II

Secondary Voltage (kV)Time

Details of instruments used

Date of Measurement

CVT SECONDARY VOLTAGE MEASUREMENTSSubstation:

PART-I - DRIFT MEASUREMENT

CVT DescriptionPrimary Voltage (kV)

Voltage Drift*

Rajan1

ANNEXURE IX (1/2)



32721

000

Trend Increasing/ Decreasing/ Stable

Note: Trend Analysis has to be done with the historical voltage drift data of the CVTs

400kV BUS-II

Slight rise in drift in core 2 has been observed

Kept under observation

Trend Increasing/ Decreasing/ Stable

Action plan in case of increasing trend

400kV BUS-I

FEEDERR-Ph CVT Y-Ph CVT


Trend Increasing/


PART - III - TREND ANALYSIS

PART - II - ANALYSIS OF RESULTSCATEGORY

No's

No of CVTs having positive drift > 2.0 VCVTs with Negative Drift

No of CVTs having negative drift < 0.8 VNo of CVTs having negative drift between 0.8 V to 4.0 V

B-Ph CVT

No of CVTs having positive drift < 0.5 V

No CVT falls in this range presently

No of CVTs having positive drift between 0.5 V to 0.8 VNo of CVTs having positive drift between 0.8 V to 1.2 VNo of CVTs having positive drift between 1.2 V to 2.0 V

No of CVTs having negative drift > 4.0 V

Action plan for CVTs having positive drift >2.0V and Negative drift > 4.0VCVTs with positive Drift

Note: * indicates the maximum value of the difference in secondary (Ph-N) between phases

Feeder-V

Feeder-IV:

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ANNEXURE IX (2/2)

Protection expert group of SRPC visited 400kV Guttur S/s on 18.09.2013 to analyze this particular grid incident. During the visit, the committee made certain observations and recommendations. Action is being taken to attend the observations of the protection expert committee. The compliance on the committee recommendations is as follows:

1. Modification of the present breaker tripping scheme of Haveri line-2 so that the trip coils are activated through two different DC sources. The necessary modifications are to be carried out in the breaker panel.

Action: Action is being taken to consult the breaker OEM for making necessary modification in the internal wiring.

2.As per standard practice DC supply for synchronizing circuit not to be tapped from the DC supply of trip/ close circuits, modification in the existing scheme of DC supply for Haveri line-2 same may be reviewed.

Action: Dc supply for the synchronizing socket is isolated from the breaker DC circuit.

3. The non-availability of 220kV and 400kV bus coupler is affecting the reliability of 400/220kV Guttur substation. Hence problems in 220kV bus coupler breaker, 400kV bus coupler breaker along with Kaiga line-1 breaker to be rectified and taken into service at the earliest.

Action:

(i). The rectification of 220kV ABB make bus coupler breaker problem is under process.

(ii). Purchase order placed on M/s Alstom for replacement of 400kV Bus coupler CB, Transfer CB and circuit breaker of Munirabad bay.

(iii) Action is being taken for overhauling of 400kV Kaiga-1 line circuit breaker. Removal of Pre Insertion Resistor and over hauling of the breaker delayed due to rainy weather conditions.

4. Committee member had asked to explore the possibility of operating the 220kV system at Guttur in split mode until the 220kV bus coupler breaker is taken into service in order to avoid complete outage of the station in the event of a fault in 220kV bus bar or a fault during a stuck breaker condition.

Action: Action is being taken to rectify the problem in the 220kV bus coupler breaker, which will be taken in to service soon after completion of the work.

5.400kV Guttur-Kaiga line-2 got tripped on operation of over voltage stage -2 in Main-2 protection relay. The Main-1 relay had sensed the over voltage but did not give a trip command. It was observed that this was a peculiar phenomenon as overvoltage relay of any other 400kV

Rajan1

ANNEXURE X (1/2)

lines at Guttur did not sense over voltage condition. It was advised to take up with OEM of CVT and relay to investigate the problem.

Action: On 18.09.2013 at 11.41 Hrs, 400kV Kaiga-2 line tripped at Guttur end due to operation of Over Voltage protection in Main-2 relay. But during this instance other lines have not sensed the over voltage. Hence the protection expert committee suspected the mal operation of Kaiga-2 line CVTs. Measurement of CVT voltage done during normal condition found to be in order. As per the committee recommendations, the matter is taken up with M/s BHEL for rectification. The Main-1 relay also sensed the over voltage but did not give the trip command. The relay operation tested and found to be normal.

6. The back up earth fault, 51N (high set) protection of ICT’s got operated for a fault in 220kV Guttur- Haveri line-2. The present setting of high set of back up earth fault relay for ICT is 2.56 kA. High set in over current and earth fault relay is generally provided for fault on the equipment which involves a very high current. Hence it was advised to review the High set setting of Back up earth fault relay of ICT’s at Guttur substation.

Action: The high set settings of back up earth fault relays of ICTs revised by considering 220kV bus fault level.

Status of implementation of various SPS proposed in the Karnataka peri phery:

At 220kV Somanahally station, 220kV line CVTs are being replaced under R&M work. PLC logic is ready, but due to the CVT replacement work the proposed SPS cannot be implemented at present. Once the PLCC equipments are restored the SPS will be implemented.

Rajan1

Rajan1

ANNEXURE X (2/2)

Multiple tripping at 400kV Nellore substation (P.G) at

03:04 hrs on 10th September 2013

Multiple tripping had occurred at 400kV Nellore substation of POWERGRID at 3:04 hrs on 10th

September 2013. As reported the lines had tripped on operation of over-voltage stage-1

protection.

Figure 1 : Single line diagram of Nellore Station

Nellore Pooling Station has one and half breaker scheme. It has six 400kV circuits i.e. two 400kV

circuits to Nellore pooling station and Vijayawada, One 400kV circuit to Almathy and

Sriperambadur. The 400kV bus is extended to Nellore APTRANSCO substation through 400kV bus

coupler breakers. 400kV Nellore(APTRANSCO) is connected with two circuits to Krishnapatnam

power station.

Sl.

No

Name of line/ equipment Date of

tripping

Time of

tripping

1 400kV Nellore pooling-Nellore line-1 10-09-2013 2:46


3 400kV Vijayawada-Nellore line-1 10-09-2013 3:04


5 400kV Nellore-Sriperambadur line 10-09-2013 3:04

6 400kV Nellore-Almathi line 10-09-2013 3:04

7 400kV Krishnapatnam-Nellore(A.P) line-1 10-09-2013 3:04

Generation loss of 260 MW had occurred at Simhapuri power station & 220MW at Meenakshi power

station due to loss of evacuating lines.

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ANNEXURE XI (1/3)

Figure 2 : 400kV Bus voltage at Gooty Substation

As reported, 400kV lines connected to Nellore had tripped on operation of over voltage stage-1

protection. The 400kV bus voltage (figure-1) from synchrophasor at Gooty indicates a high

voltage. It can also be inferred that there was no fault in the system prior the multiple tripping.

Figure 3 : Frequency profile

The change in frequency due to generation loss at Simhapuri and Meenakshi power stations was

0.24 Hz.

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ANNEXURE XI(2/3)

Suggestion and further actions required:

a) CVT’s at Nellore substation to be checked for errors and the same to be kept within

permissible limits.

b) Grading in voltage as well as time to be provided for over voltage protection in-order to

avoid multiple tripping of lines.

c) Testing of drop off to pick-up ratios of over voltage relays to be done and the ratio should be

as high as possible (99%).

d) Four units at Srisailam were running under condenser mode and two units were out of

service during the disturbance. If there is no generation then all the units at Srisailam hydro

station to be put under synchronous condenser mode of operation to contain the over

voltage in grid.

Restoration

Sl.

No

Name of line/ equipment Date of

restoration

Time of

restoration


2 400kV Nellore-Almathi line 10-09-2013 3:47



5 400kV Nellore-Sriperambadur line 10-09-2013 4:40


7 400kV Krishnapatnam-Nellore(A.P) line-1 10-09-2013 6:53

8 SEPL Unit-2 10-09-2013 6:05

9 SEPL Unit-1 10-09-2013 9:12

10 MEPL Unit-1 10-09-2013 10:18

11 MEPL Unit-2 10-09-2013 15:13

X----------------------------------------------X-----------------------------------------------X

Rajan1

ANNEXURE XI (3/3)

MINOR TRIPPING DETAILS INTHE SOUTHERN REGION DURING SEPTEMBER 2013

TRIPPING DETAILS FOR SEP 2013 Nc:Correct Operation Nu:Unwanted OperationY: AVAILABLE with in 24 HR D: Available After 24 HR N: Not Available Nf:Fail to Operate at internal Power System Fault

S.NO. ELEMENT NAME TRIPPING DATETRIPPING TIME FIR (S) DR (S) EL (S) TR (S) FIR ( R ) DR ( R) EL ( R) TR ( R)IN ORDER AVAILABILITY CATEGORY Remarks

1 220 kV AMBEWADI - PONDA 1 29-Sep-13 21:47 N N N N N N N N2 220 kV KAIGA - KODASALLY 29-Sep-13 21:47 N N N N N N N N3 400 kV MYSORE - HASAN 2 29-Sep-13 17:59 Y Y Y Y Y D D D Y Nc4 400 kV KAIGA - GUTTUR 2 29-Sep-13 15:12 N N N N N N N N5 400 kV KHAMMAM - MAMIDIPALLY 1 28-Sep-13 19:44 Y Y Y Y D D D N Y Nc6 220 kV AMBEWADI - PONDA 1 28-Sep-13 15:23 N N N N N N N N7 220 kV KANIAMPET - KADAKOLA 28-Sep-13 12:08 D D D N N N N N Y Nc8 220 kV IDUKKI - UDUMALPET 27-Sep-13 13:07 N N N N N N N N9 400 kV TIRUNELVELI - KUDAMKULAM 3 27-Sep-13 12:41 D D Y Y Y N N D N Nu

10 400/220 kV ICT-1 AT KHAMMAM 25-Sep-13 11:45 Y Y Y Y N N N N Nu11 400/220 kV ICT-2 AT KHAMMAM 25-Sep-13 11:45 Y Y Y Y N N N N Nu12 400 kV TALAGUPPA - HASSAN 24-Sep-13 22:17 Y N N Y D D D D N Nc13 400/230 kV ICT-1 AT NEYVELI 24-Sep-13 14:06 N N N N N N N N14 400 kV KAIGA - GUTTUR 1 24-Sep-13 0:16 N N N N NA Y Y D Y15 400 Kv HASSAN - UPCL 2 23-Sep-13 23:44 D D D D N N N N N Nc16 400 Kv GOOTY - NPS 1 22-Sep-13 3:02 Y Y Y Y Y Y Y Y N Nc17 400 kV KAIGA - NARENDRA 1 21-Sep-13 23:51 N N N N D D D D Y Nc18 400kV SIMHADRI-GAZUWAKA 2 21-Sep-13 22:39 N N N N Y N Y Y Y Nf19 400 kV RAMAGUNDAM - GAJWEL 20-Sep-13 17:09 N N N N Y D D N N Nc20 220 kV SEDAM - TANDUR 20-Sep-13 7:23 N N N N N N N N21 400 kV TALAGUPPA - NEELAMANGALA 20-Sep-13 2:10 N N N N N N N N22 400 kV VTPS IV - SRISAILAM 2 19-Sep-13 10:05 N N N N N N N N23 400 Kv VTPS - MALKARAM 2 19-Sep-13 9:54 N N N N N N N N24 400 kV TALAGUPPA - HASSAN 18-Sep-13 23:56 Y N N N Y Y Y Y N Nc25 400 kV MYSORE - HASAN 1 18-Sep-13 23:29 Y Y Y Y Y Y Y Y Y Nc26 400 kV KAIGA - NARENDRA 1 18-Sep-13 23:20 N N N N Y Y Y Y Y Nc27 400 Kv HASSAN - UPCL 2 18-Sep-13 16:00 Y Y Y Y D D D D N Nu28 400 Kv HASSAN - UPCL 1 18-Sep-13 16:00 Y Y Y Y D D D D N Nu29 400 kV RAMAGUNDAM - N'SAGAR 1 18-Sep-13 3:23 N N N N D D D D N Nu30 400 kV MADURAI - PUGALUR 1 17-Sep-13 15:01 Y D D D Y Y Y Y N Nf31 400 Kv HIRIYUR-BTPS 1 17-Sep-13 4:33 D NA NA NA D D N N N Nu32 400 kV TALAGUPPA - HASSAN 16-Sep-13 23:43 Y N N Y D D D D N Nc33 400 kV GOOTY - NELAMANGALA 16-Sep-13 23:16 D D D D Y Y Y Y N Nf

1

Rajan1

ANNEXURE XII (1/3)


34 400/220 kV ICT-1 AT CUDDAPAH 16-Sep-13 4:14 D D D D N N N N N Nc35 400/220 kV ICT-2 AT CUDDAPAH 16-Sep-13 4:14 D D D D N N N N N Nc36 400 kV GUTTUR - HIRIYUR 1 16-Sep-13 1:56 Y NA NA NA D NA D D N Nc37 400 Kv GOOTY - NPS 1 16-Sep-13 0:01 D D D D D D D D N Nf38 400 kV MYSORE - HASAN 1 15-Sep-13 23:31 Y Y Y Y Y D D D Y Nc39 220 kV CHITTOR - THIRUVALEM 15-Sep-13 22:45 N N N N N N N N40 400 kV GUTTUR - NARENDRA 1 15-Sep-13 0:01 N N N N Y Y Y Y N Nc41 400 kV KAIGA - NARENDRA 1 15-Sep-13 0:01 N N N N Y D Y Y Y Nc42 400 kV MYSORE - HASAN 1 15-Sep-13 0:01 Y Y Y Y Y Y Y Y Y Nc43 400/230 kV ICT 1 AT PONDYCHERRY 13-Sep-13 12:52 D NA NA NA NA NA NA NA N Nu44 400 kV HASSAN - NEELAMANGALA 1 13-Sep-13 3:02 Y Y Y Y N N N N N Nf45 400 kV KAIGA - GUTTUR 2 13-Sep-13 0:05 N N N N D NA NA NA46 400 kV MYSORE - HASAN 1 12-Sep-13 23:10 Y Y Y Y Y Y Y Y Y Nc47 400 Kv GOOTY - NPS 2 12-Sep-13 2:55 D D D D Y D Y Y N Nf48 400/220 kV ICT-1 AT HOODY 12-Sep-13 0:04 N N N N N N N N49 400 kV MYSORE - HASAN 1 12-Sep-13 0:01 Y Y Y Y Y Y Y Y Y Nc50 400 kV MYSORE - HASAN 1 11-Sep-13 0:01 Y Y Y Y Y Y Y Y Y Nc51 400 kV VIJAYAWADA - NELLORE 1 10-Sep-13 3:04 Y D D D Y Y Y D Y Nc52 400 Kv KRISHNAPATNAM - NELLORE 1 10-Sep-13 3:04 Y D D D D Y Y D Y Nc53 400 Kv NPS - NELLORE -2 10-Sep-13 3:04 Y D Y D Y Y D D Y Nc54 400 kV VIJAYAWADA - NELLORE 2 10-Sep-13 3:04 Y D D D Y Y Y D Y Nc55 400 Kv GOOTY - NPS 2 10-Sep-13 3:04 D Y Y D Y Y Y D Y Nc56 400 kV NELLORE - ALAMATHI 10-Sep-13 3:04 D D Y D N N N N Y Nc57 400 Kv NELLORE - SPDR 10-Sep-13 3:04 Y Y Y D Y D D D Y Nc58 400 kV KURNOOL - GOOTY 10-Sep-13 3:04 Y N N N D Y Y D N Nc59 400 Kv NPS - NELLORE -1 10-Sep-13 2:46 Y Y Y D Y D Y D Y Nc60 400 kV HASSAN - NEELAMANGALA 1 9-Sep-13 23:59 Y D D D N N N N Y Nc61 400 kV MYSORE - HASAN 1 9-Sep-13 23:49 Y Y Y Y Y D D D Y Nc62 400 kV VIJAYAWADA - NELLORE 2 9-Sep-13 2:24 Y Y Y Y Y Y Y Y Y Nc63 400 Kv KRISHNAPATNAM - NELLORE 2 9-Sep-13 1:34 D D D N Y Y Y Y Y Nc64 400 Kv NPS - NELLORE -2 9-Sep-13 1:34 Y Y Y Y Y Y Y Y Y Nc65 400 kV NELLORE - ALAMATHI 9-Sep-13 1:34 Y Y Y Y N N N N Y Nc66 400 kV VIJAYAWADA - NELLORE 1 9-Sep-13 1:34 Y Y Y Y Y Y Y Y Y Nc67 400 Kv NELLORE - SPDR 9-Sep-13 1:33 Y Y Y Y Y Y Y N Y Nc68 400 Kv NPS - NELLORE -1 9-Sep-13 1:01 Y Y Y Y Y Y Y Y Y Nc69 400 kV MYSORE - HASAN 1 8-Sep-13 22:57 Y Y Y Y Y D D D Y Nc70 400 kV MYSORE - HASAN 1 7-Sep-13 23:56 D D D D D D D D Y Nc

2

Rajan1

ANNEXURE XII (2/3)


71 400/220 kV ICT-2 AT N'SAGAR 7-Sep-13 17:16 D NA D D N N N N Y Nc72 400 kV RAMAGUNDAM - N'SAGAR 1 7-Sep-13 17:16 N N N N D D D D N Nu73 220 kV SEDAM - TANDUR 7-Sep-13 0:13 N N N N N N N Y N74 400 Kv NPS - NELLORE -1 6-Sep-13 4:03 Y Y Y Y Y Y Y Y Y Nc75 220 kV PONDYCHERRY- VILLIANUR 5-Sep-13 18:51 D D D D N N N N N Nc76 400/230 kV ICT-3 AT S'PUDUR 5-Sep-13 9:15 N N N N N N N N77 400 Kv GOOTY - NPS 2 4-Sep-13 0:24 D D D D Y Y Y Y N Nc78 400 kV HASSAN - NEELAMANGALA 1 3-Sep-13 23:58 Y Y Y Y D D D N Y Nc79 400 Kv KOLAR - SPDR 3-Sep-13 23:58 Y Y Y Y Y Y Y Y Y Nc80 400 Kv NPS - NELLORE -1 3-Sep-13 23:55 Y Y Y Y Y Y Y Y Y Nc81 400 kV MYSORE - HASAN 1 3-Sep-13 23:48 Y Y Y Y Y Y Y Y Y Nc82 400/220 kV ICT-1 AT HYDERABAD 3-Sep-13 18:15 D NA D D N N N N N Nu83 220 kV KANIAMPET - KADAKOLA 3-Sep-13 12:57 D D D N N N N N N84 220 kV AMBEWADI - PONDA 2 3-Sep-13 12:52 N N N NA N N N N N85 400 kV TALAGUPPA - HASSAN 1 2-Sep-13 22:42 D D D N D D D D Y Nc86 400 Kv HIRIYUR-BTPS 2 2-Sep-13 22:36 D NA NA NA N N N N N Data not avaible for analysis87 400 kV KAIGA - GUTTUR 2 2-Sep-13 11:41 N N N N D D D D N88 400/220 kV ICT-1 AT GUTTUR 2-Sep-13 11:41 D NA NA D N N N N N Nc89 400/220 kV ICT-2 AT GUTTUR 2-Sep-13 11:41 D NA NA D N N N N N Nc90 400 kV UDUMALPET - TIRUNELVELI 1 1-Sep-13 17:59 D Y Y Y D Y Y Y Y Nc91 220 kV AMBEWADI - PONDA 2 1-Sep-13 3:05 N N N N N N N N N92 400 Kv KRISHNAPATNAM - NELLORE 1 1-Sep-13 2:13 N N N N D N N N N93 400 Kv NELLORE - SPDR 1-Sep-13 2:01 Y Y Y Y D D D D Y Nc94 400 Kv NPS - NELLORE -1 1-Sep-13 2:01 Y Y Y Y Y Y Y Y Y Nc95 400 kV VIJAYAWADA - NELLORE 2 1-Sep-13 2:01 Y Y Y Y Y Y Y Y Y Nc

3

Rajan1

Rajan1

ANNEXURE XII (3/3)

ANNEXURE XIII (1/1)

THE REMEDIAL MEASURES TAKEN FOR THE FOLLOWING TRIPPINGS MAY PLEASE BE SENT TO SRPC SECRETARIAT AT THE EARLIEST

Sl. No.

Element Name Date & Time of outage

Date & time of revival

Reason for outage

Remedial measure

1 400/230 KV ICT-1 at Neyveli

24-Sep-2013 14:06

24-Sep-2013 15:00

due to tripping of 220 kv line

To be discussed

2 220 kV AMBEWADI - PONDA 2

02-OCT-2013 14:37 Hrs

02-OCT-2013 14:48 Hrs

tripped on earth fault

To be discussed

3 220 kV GUMMUDIPUNDI - SULLURPET

02-OCT-2013 14:00 Hrs

02-OCT-2013 15:31 Hrs

tripped during taking lc supply

To be discussed

4 400 kv Mahaboob nagar - Raichur

04-Oct-2013 10:25

04-Oct-2013 10:48

tripped on carrier lock out

To be discussed

5 400 kv Kaiga - Guttur 1

07-Oct-2013 12:47

07-Oct-2013 13:36

tripped due to y-n fault

to be discussed

6 400/220 kv ict-1 at N'sagar

07-Oct-2013 23:57

08-Oct-2013 01:18

fault at 220 kv N sagar stn

to be discussed

7 400 kv Kaiga - Guttur 1

08-Oct-2013 10:19

tripped on r-n fault

to be discussed

8 400 kv Trichur - Kochi 1

08-Oct-2013 13:310 08

08-Oct-2013 13:50

transient fault to be discussed

9 400 kv Kurnool - Srisailam

08-Oct-2013 15:53

08-Oct-2013 16:11

distance protection

to be discussed

10 400 kv Srisailam-Mamidipalli 2

08-Oct-2013 15:51

08-Oct-2013 16:35

distance protection

to be discussed

11 400/220 kv ICT-1 at Cuddapah

09-Oct-2013 12:00

09-Oct-2013 12:46

tripped while erecting panels

to be discussed

12 400 kv NCTPS - Vallur 2

10-Oct-2013 16:05

10-Oct-2013 18:14

tripped at Vallur end

To be discussed

13 400 kv Klvdpt - Vallur 1

13-Oct-2013 19:03

13-Oct-2013 20:11

tripped on distance protn

To be discussed

ANNEXURE XIVDetails of Trippings /Grid Disturbances/ Incidents to be furnished to SRPC from July-2013:

S. No.

Elements Tripped

Date & Time Reasons

Restoration (Date & Time ) Category

Any SPS Available

SPS operated coorectly or not

Remarks on SPS action

Remedial Action taken

Difficulties arised while restoring the system if any Remarks

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