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3rd PSS Meeting held on 28.06.2016

SOUTHERN REGIONAL POWER COMMITTEE BENGALURU

Record Notes of Deliberations of the 3

rd Meeting on PSS Tuning of Generators held

on 28th

June 2016

The 3rd

Meeting on PSS related issues was held at SRPC, Bengaluru on 28th June 2016. The List of

participants is furnished at Annexure-I.

Shri. S.R.Bhat, Member Secretary, SRPC welcomed the participants to the Meeting. He said that

the 2nd

Meeting on PSS tuning was held in the month of October 2015, in which, schedules and modalities

for PSS tuning for all generators of installed capacity of more than 50 MW had been finalized. He stated

that some noticeable progress had been observed from the utilities since PSS tuning for a few generators

had been completed while process had been initiated for most of the units. Step Response Test reports

received from the generators which had completed PSS tuning needed to be analyzed by PSS Study

Committee.

It was again noted that provision for PSS tuning was mandated in accordance with IEGC & CEA

(Technical Standards for Connectivity to the Grid) Amendment Regulations, 2013. The Enquiry Committee

for Grid Disturbances constituted by GoI had also emphasized on tuning of PSS (Recommendation 9.9.2).

This was also subsequently deliberated in the Meeting held in MoP (Para 1.4) to discuss the Task Force

Report.

Status of PSS:

APGENCO

Station Name Status of PSS tuning Comments/SRT report

submitted or not

Rayalaseema TPS Units 1

to U5

PSS tuning has been carried out on

13.1.2016 for U1 to U5

SRT report submitted.

Vijayawada TPS (NTTPS)

U1 to U7

PSS tuning had been carried out on

01.04.2016 for U1 to U4 & U7.

For U5 & U6, PO has been placed for

replacement of AVR with DAVR and

would be completed by December 2016.

SRT Report submitted for U1

to U4 and U7.

PSS tuning /SRT reports to be

submitted by December 2016

for Units-5 & 6.

SDSPP (Krishnapatnam

JV) U1 & U2

PSS tuning has been carried out on

07.10.2015 for U1 & 29.10.2015 for U2.

SRT Report submitted

Lower Sileru HEP U1 to

U4

Unit-1: Work order had been placed with

M/s BHEL on 4.6.2016 & PSS tuning

could be completed within a month.

Unit-2, 3 & 4 : DVR under tendering &

PSS tuning/SRT report to be

submitted by August 2016 for

Unit-1.

APGENCO was


would be completed within 6-8 months recommended to complete

the DVR replacement /PSS

tuning and submit the SRT

reports by March 2017.

Upper Sileru HEP U1 to

U4

Unit-1 & 2: Excitation systems were of

convention type and to be replaced for

making PSS provision. OERLIKON is

the OEM & not responding. Hence,

DVRs would be procured through

tenders.

Unit-3 & 4: Work order has been placed

with M/s. BHEL on 21.3.2016 & the PSS

tuning would be completed by August

2016.

APGENCO was suggested to

complete DVR replacement

/PSS tuning by Dec-2016.

SRT report to be submitted

by September 2016.

Srisailam RB HEP U1 to

U7

Work order had been placed with M/s

BHEL on 4.6.2016 for PSS tuning &

would be taken up soon after the

availability of water.

APGENCO was

recommended to ensure that

PSS tuning is completed

during water availability

(generation)

Andhra Pradesh IPPs

It was noted with concern that there was no representation from HNPCL.

Station Name Status of PSS tuning Comments/SRT graphs

submitted or not

HNPCL, Vizag PSS tuning and details as per

format not furnished. HNPCL to

furnish the details & PSS tuning

details before September 2016

GVK, Jegurupadu St–I, St

–II, Spectrum PGL, Lanco,

Kondapalli, Reliance

BSES, GMR Vemagiri,

Gowtami & Konaseema

APSLDC was requested to take

up for PSS tuning with the IPPs

of capacity above 50 MW.

TSGENCO

It was noted with concern that there was no representation from TSGENCO.

Station Name Status of PSS tuning Comments/SRT graphs

submitted or not

Kakatiya TPP U1 & 2 PSS tuning for the Unit-1 had been carried out

on 24.01.2016.

Unit-1 SRT submitted.

TSGENCO to furnish

PSS/SRT details for Unit-2.

Kothagudem TPS U5 to Unit-5 to 8: TSGENCO had informed that the TSGENCO to complete PSS


U11 units are 50 years old and already planned for

phasing out before December 2019 in the

phased manner as per the GOI No.J-

13012/24/2012-IA.II(T), Dt.16.07.2015.

Unit-9 to 11: PSS tuning had been carried out

on 22.12.2015.

tuning else approach Hon’ble

CERC for exemption.

SRT submitted for Unit-9 to

11.

Nagarjunasagar HEP U1

to U8

PSS not available for U1.

PSS tuning had been carried out for Unit-2 to

6 & 8 on 26.05.2015 & Unit-7 on 19.07.2015.

PSS details for Unit-1 were

yet to be submitted.

SRT submitted for Unit-2 to

8.

Srisailam LB HEP U1 to

U6

- TSGENCO was

recommended to complete

PSS tuning in

August/September 2016 (as

water / generation would be

available) and submit SRT

reports.

KPCL

It was noted with concern that there was no tangible progress by KPCL. KPCL representative was

suggested to appraise the Management and ensure timely compliance. KPCL to revert back with

unit/station-wise action plan within a month.

Station Name Status of PSS tuning Comments/SRT graphs submitted

or not

Raichur TPS U1 to U4 KPCL informed that Unit-4 was

equipped with AVR and to be replaced

with DVR.

KPCL was recommended to

complete PSS tuning and submit

SRT reports by September 2016 for

Unit-1 to 3.

Replacement with DVR / PSS tuning

/SRT reports to be completed by

March 2017 for Unit-4.

Raichur TPS U5 to U8 AVR to be replaced with DVR for Unit 6 KPCL was recommended to

complete PSS tuning and submit


Unit-5, 7 & 8.

Replacement with DVR / PSS tuning

/SRT reports to be completed by

March 2017 for Unit-7.

BTPS U1 & U2 KPCL had informed that Step

Response Test for Unit 1 was

completed on 15.10.2015 and Unit 2

was done on 17.07.2012. KPCL had

agreed to conduct Step Response Test

for U2 during Overhaul period before

March 2016.

It was noted that the reports

furnished were PID test (at no load)

for AVR and not PSS tuning reports.

KPCL was recommended to

complete PSS tuning and submit the


Unit-1 & 2.


KPCL was suggested to complete

the PSS tuning and submit the SRT

reports before COD for Unit-3.

Yeramarus TPP In the meeting, KPCL informed that

PSS tuning and SRT would be taken

up before COD.



report before COD.

Almathy HEP U2 to U6 In the meeting, KPCL informed that

discussion with M/s BHEL was

scheduled for discussion in August

2016.



reports by September 2016.

Sharavati Tail Race U1

to U4

In the meeting, KPCL informed that

static AVRs were to be replaced with

DVRs.

KPCL was recommended to replace

with DVRs and complete PSS tuning

and submit SRT reports by March

2017.

Varahi UGPH HEP U1

to U4

In the meeting, KPCL informed that M/s

BHEL had not come up for discussion

for Unit-1 & 2.

For Unit-3 & 4, they received the offer

and the quotes were on the higher side.




Nagjheri HEP U1 to U6 In the meeting, KPCL informed that the

OEMs were not responding.




Sharavathy HEP U1 to

U10

In the meeting, KPCL informed that the

discussions with M/s BHEL were

underway.

In view of revival of the units after

fire accident, KPCL was

recommended to complete the PSS

tuning and submit the SRT reports

by March 2017.

Karnataka IPPs

It was noted with concern that there was no representation from JSWEL.


or not

UPCL U1 & U2 Step Response Test was carried out for

Unit-1 & 2 on 04.10.2015.

SRT reports were submitted for Unit-

1 & 2.

UPCL was suggested to submit that

PSS details in the format.

JSWEL U1 to U4 In the meeting, it was noted that PSS

details were not received from JSWEL.

JSWEL was recommended to

carryout PSS tuning and submit the

SRT reports by August 2016.

JSWEL was suggested to submit that

PSS details in the format.

KSEBL


KSEBL stated that since cost for ensuring PSS (since units were very old and complete replacement of the

excitation system was required) was quite high, the expenditure could be met through PSDF as it was for

reliable grid operation.

It was noted that PSDF funding proposal needed to be submitted to NLDC and the Appraisal Committee

would take a call on it.


or not

Idukki HEP U1 to U3 In the meeting, KSEBL informed that

the RMU had been tendered and

awarded to M/s Alstom. Engineering

works were expected to be completed

in one year and another six months for

the commissioning activities. PSS have

been included in the tender document.

KSEBL was recommended to ensure

that PSS tuning is completed by

December 2017.

Idukki HEP U4 to U6 In the meeting, KSEBL informed that

the existing cards were checked and

PSS was enabled. Heavy oscillations

were observed and PSS was disabled.

As OEM assistance was not available,

they would once again attempt PSS

tuning through internal resources during

AMC & after gaining experience of PSS

at other stations.


PSS tuning else approach Hon’ble

CERC for exemption.

Lower Periyar HEP

U1

In the meeting, KSEBL informed that

tendering was underway and pre-bid

was under discussion for replacement

of exciter. It would take three months

after PO is placed.


that the replacements and PSS tuning

is completed before December 2016.

Lower Periyar HEP

U2 & U3


both M/s BHEL/Andritz had been

referred. M/s BHEL had come forward

but the offer was not conclusive. M/s

BHEL had informed that they would

assess the healthiness of the cards and

try for PSS tuning, if possible in the

available cards.

KSEBL to complete PSS tuning else

approach Hon’ble CERC for

exemption.

Sabarigiri HEPU1 to

U6


the PSS would be completed by within

three months for five units (except Unit-

4).

KSEBL to complete PSS tuning and

submit SRT reports by October 2016.

TANGEDCO


or not


NCTPS St-1 U1 to U3 PSS tuning was carried out on

14.7.2013 (U-1), 07.01.2016 (U-2) and

26.10.2015 (U-3)

TANGEDCO to take action as per the

recommendations of the Study

Committee.

NCTPS St-II U1 & U2 In the meeting, TANGEDCO informed

that PSS tuning for U-1 & 2 was

scheduled for August 2016 &

September 2016 respectively through

M/s BHEL.

TANGEDCO was suggested to submit

the SRT reports by October 2016.

Tuticorin TPS U1 to

U5

PSS tuning was completed for U-1

(28.11.2008), U-2 (20.08.2012), U-3

(10.1.2013), U-4 (03.07.2014) & U-5

(30.09.2015).

TANGEDCO was suggested to go for

PSS tuning for the units which was

taken up before August 2013 or within

three years of last PSS tuning.

Mettur St-I TPS U1 to

U4

PSS tuning was completed for U-1

(26.7.2013), U-2 (08.12. 2015),

U-3 (30.09.2012) & U-4 (09.10.2015).

TANGEDCO was suggested to go for

PSS tuning for the units which was

taken up before August 2013 or within

three years of last PSS tuning.

Mettur St-II TPS U1 In the meeting, TANGEDCO informed

that PSS tuning would be taken up

through M/s ABB.

TANGEDCO was suggested to submit

the SRT reports by October 2016.

Kundah III HEP U1 to

U3

In the meeting, TANGEDCO informed

that DAVR was not available and

requested for exemption since units

capacity was less than 100 MW.

TANGEDCO to complete PSS tuning

else approach Hon’ble CERC for

exemption.

Aliyar HEP U1

Kodayar I U1

Kadamparai HEP U1

to U4

In the meeting, TANGEDCO informed

that DAVR was available and PSS

tuning was to be taken up by OEM.

TANGEDCO was recommended to

ensure that PSS tuning is completed

before September 2016.

Kovil Kalappal (Gas) TANGEDCO informed that SRT would

be carried out after consultation with

OEM during next possible major shut

down opportunity.

TANGEDCO was suggested to

complete the SRT before September

2016.

TN IPPs


or not

STCMS TNSLDC was suggested to follow up

the PSS tuning and ensure SRT test

before September 2016. Gas IPP Stations

CGS/ISGS

It was noted with concern that there was no representation from NTPL, KGS, MAPS & KKNPP.



or not

NTPC, Ramagundam

STPS U1 to U7

In the meeting, NTPC informed that

SRT would be taken up for U1 (Dec -

16), U2 (Dec-16), U3 (Dec-16), U4

(Sep-16), U5 (Oct-16) & U6 (Aug-16) &

PO has been placed on M/s Siemens.

For U6, PO had been placed with M/s

Siemens for DAVR replacement. For

U7, PO had been placed with M/s

BHEL for SRT & PSS tuning.

NTPC, Ramagundam was suggested

to complete the works and submit the

SRT reports before December 2016.

PSS details as per format to be

furnished.

NTPC, Simhadri St-I &

II U1 to U4

In the meeting, NTPC informed that the

SRT had been taken up for

U1(14.03.2016) and for U2, U3 & U4

on 18.03.2016

NTPC, Simhadri to take up action as

per Study Committee

Recommendations.


furnished.

NTPC, Talcher STPS

St-II U 3 to U6


SRT for U3 & 6 was completed

between 04.06.2016 to 07.06.2016.

For U4 & U5 was not completed due to

port problem. The issue would be

rectified during the annual

maintenance.

NTPC, Talcher to take up action as per

Study Committee Recommendations

for U3 & U6.

SRT for U4 & U5 to be submitted

before December 2016.


furnished.

NTPC, Kudgi NTPC, Kudgi to ensure PSS tuning

before COD.

NTPC, RGCCP,

Kayamkulam 2 GTs &

1 ST


they were ready to conduct the SRT

test at 80% load.

NTPC was suggested to carry out SRT

whenever the unit(s) are scheduled

above 80%.

NTECL, Vallur TPS U1

– U3

In the meeting, NTECL informed that

SRT of U1 (09.03.2012), U2

(09.08.2015) & U3 (28.02.2014) had

been carried out.

It was noted that the reports furnished

were PID test (at no load) for AVR

and not PSS tuning reports.

NTECL agreed to complete the PSS

tuning by July 2016 for all the three

units and submit the SRT.

NLC, Neyveli TPS I U7

to U9

In the meeting, NLC informed that M/s

BHEL would be visiting NLC next week

for discussions.

NLC TS-1, was suggested to submit

the SRT before December 2016.


furnished.

NLC, Neyveli TPS I

Exp U1 & U2

In the meeting, NLC informed that SRT

had been carried out on U-1

(12.10.2015) and U-2 (05.11.2015).

NLC TPS-1 Exp was suggested to

submit the SRT.

NLC, Neyveli TPS II

U1 to U7

In the meeting, NLC informed that the

contract for SRT was in advance stage

and SRT would be completed by

December 2016.

NLC TS-1, was suggested to submit

the SRT by December 2016.

NLC, Neyveli TPS II

Exp U1 & U2

In the meeting, NLC informed that SRT

would be completed by 15.07.2016.

NLC TS-II Exp was suggested to

submit the SRT before July 2016.



furnished.

(NLC & TN JV)NTPL

U1 & U2

In the meeting, NLC informed that as

per feedback, PSS was on. SRT

would be taken up shortly.

NTPL was suggested to complete the

SRT and submit the report before Sep

2016.


furnished.

NPCIL, KGS U1 to U4 PSS not in service for U-1 & U-2.

PSS tuning was carried out for U-3

(19.04.2007) & U-4 (17.01.2011).

KGS was suggested to enable the PSS

and complete the SRT for U-1 & U-2

and submit the report by Sep 2016.

For U-3 & U-4 complete the SRT and

submit the report by Sep 2016.

NPCIL, MAPS U1 &

U2

PSS tuning was carried out for U-1

(11.01.2006) & U-2 (03.08.2003).

MAPS to complete the SRT and submit

the report by Sep 2016.

NPCIL, KKNPP KKNPP had informed that SRT was

done on 07.06.2014.

KKNPP to take action as per Study

Committee recommendation.

KKNPP to ensure PSS tuning before

COD of U-2.

ISTS connected IPPs

It was noted with concern that there was no representation from SEL, CEPL, IL&FS and SGPL.


or not

Simhapuri Energy Ltd

(SEL) U 1 to U4

PSS not available. SEL to ensure PSS availability by

December 2016.

MEPL U1 & U2 In the meeting, MEPL informed that

PSS was not available and they were

in discussion with their OEM.

MEPL to ensure PSS availability by

December 2016.

TPCIL (Thermo Power

Tech) U1 & U2

In the meeting, TPCIL informed that

PSS was carried out on U-1

(22.12.2014) & U-2 (11.08.2015). SRT

was planned to be taken up on

20.08.2016 for U-1 and SRT for U-2

would be taken up during shut down.

It was noted that earlier reports were

PID test reports (at no load) for AVR.

SRT to be taken up by TPCIL and

complete for both the units before

December 2016.

Coastal Energen CEPL was suggested to complete the


2016.


furnished.

IL & FS SRT for U-1 was carried out on

12.04.2015.

IL&FS to take up action as per Study

Committee Recommendation for U-1.

SRT for U-2 to be carried out before

Sep 2016.


furnished.


Lanco Stage II & III LKPPL was suggested to complete the


2016.


furnished.

SGPL, Nellore SGPL to ensure PSS tuning and SRT

before COD.

Other issues:

KSEBL /TANGEDCO pointed out that many Hydro units were very old and needed exorbitant cost

to enable them with PSS. IEGC /CEA Connectivity Regulations had come up subsequently. CEA

Regulation mandates PSS only for Units above 100 MW.

CEA Connectivity Regulations stipulates:

Part II

Connectivity Standards applicable to the generating stations

A. Connectivity Standards applicable to the Generating Stations other than wind and

generating stations using inverters

……………..

A1.For Generating stations which are connected on or after the date on which CEA

(Technical Standards for Connectivity of the Grid) Regulation, 2007 became effective

( 1 ) The excitation system for every generating unit:-

…………………..

( c ) The Automatic Voltage Regulator of generator of 100 MW and above shall include

Power System Stabilizer (PSS)

……………………

A2. For Generating stations which were already connected to the grid on the date on

which CEA (Technical Standards for Connectivity of the Grid) Regulation, 2007 became

effective

For all thermal generating unit having rated capacity of 200 MW and above and hydro units

of having rated capacity of 100 MW and above, the following facilities would be provided at

the time of renovation and modernization.

…………………..

( 2 ) Every generating unit of capacity having rated capacity of higher than 100 MW shall

have Power System Stabilizer.

……………………

IEGC Regulations 5.2(k) stipulates

“All generating stations shall normally have their automatic voltage regulators (AVRs) in

operation. In particular, if a generating unit of over fifty (50) MW size is required to be operated

without its AVR in service, the RLDC shall be immediately intimated about the reason and

duration, and its permission obtained. Power System Stabilizers (PSS) in AVRs of generating

units (wherever provided), shall be got properly tuned by the respective generating owner as per

a plan prepared for the purpose by the CTU/RPC from time to time. CTU/RPC will be allowed to

carry out checking of PSS and further tuning it, wherever considered necessary.”

In view of the above provisions, it was suggested that respective entities could suitably take up for

exemption with Hon’ble CERC for the applicable units.


Generators was suggested to go for PSS tuning/SRT for the units for which SRT was taken up

before August 2013 or within three years of last SRT.

It was agreed to form a PSS web group in which all the SRT/PSS details would be posted.

The following to be taken care during SRT/Report preparation :

Damping Torque to be calculated for every SRT test with and without PSS.

Power System Stabilizer Models to be given along with the implemented settings (Final).

SRT to be carried out at >80% Load and at 50% loading.

Both Step Up and Step Down tests needs to be carried out.

Real (Active) Power Scale to be within 10 % of operating point in the graphs. Proper Graphs

(soft copy) with visible scale to be provided.

Make, Type & Model of Excitation System to be provided.

Step up to be followed by Step down with a time gap of 20 sec, if taken up, simultaneously.

Station personnel to co-ordinate and be associated with the OEM/Testing Agency during the

SRT test to ensure the requirements as envisaged.

It was observed that PSS performance of brushless exciters was not evident when compared

to the PSS performance of static exciters. There was no discernible improvement observed

with PSS On with respect to PSS Off for the units equipped with brushless exciters. It was

opined that the brushless excitation system were improved version and M/s BHEL / OEM

require to be address the issue for making PSS performance more effective.

It was also noted with concern that many of the submitted graphs/reports were not legible. Hence it

was agreed that Step Response Test Reports would be furnished in the specified format /Graph as

given in Annexure- II. Active Power, Reactive Power, Terminal Voltage, Field Current and PSS

contribution in different colours would be ensured. Soft copy of the graphs/report needed to be sent

to web group and SRLDC ([email protected]) / SRPC ([email protected] )/ CTU

([email protected]) .

It was agreed that the exact schedule of testing would be communicated to SLDC/SRLDC/SRPC.

There could be representation from SRLDC, SRPC Secretariat & State during PSS tuning/ Step

Response Test being conducted by OEM.

All the utilities would take up with their OEMs/Testing Agency at the earliest to conduct Step

Response Test as per the schedule.

All new units with capacity over 50 MW must carry out PSS tuning before declaration of Date of

Commercial Operation (COD). A report in the specified format along with model parameters shall

be submitted to SRLDC/SRPC/CTU.

PSS shall be kept in service (“On” or energized and performing as designed by the manufacturer).

PSS could be taken out only under intimation to SLDC/SRLDC along with technical justification i.e.

for short duration of one week.

Analysis of SRT reports submitted:

PSS study committee analyzed the PSS Tuning/SRT reports/graphs submitted and the

recommendations had been finalized (Analysis & recommendations are available at Annexure-III). The

SRT of following unit(s) were analyzed:

mailto:[email protected]




APGENCO

NTTPS (VTPS) Units – 1,2,3,4,&7 Krishnapatnam(SDSPP) U

– 1 & 2

Rayalasema TPP Units 1-

5

TSGENCO Kakatiya TPS Unit 1 Kothagudem TPS UNIT-9,

10 & 11

Nagarjunasagar PH Units

2-8

KPCL Bellary TPS Units 1 &2

TANGEDCO

Tuticorin TPS Units 1-5 NCTPS Stage- I Units 1 -3 Mettur TPS Stage I Units

1-4 NTPC

Talcher Stage II Units 3 & 6

Simhadri TPS Units 1-4

NTECL Vallur TPS Unit-2

NPCIL Kaiga GS Units 3 & 4 KKNPP Unit-1

IPPS/MPPS IL&FS Unit-1

UPCL Units 1 &2

TPCIL Units 1 &2

Vote of Thanks

Member Secretary, SRPC thanked the participants for their active deliberations. He again

suggested that all generators complete the PSS tuning/Step Response Test for the units as per

schedule finalized.

*****************************

server

Typewritten Text

Annexure-I

Response of Unit # 1

Step input on # 1, PSS-1 & PSS-2 OFF

Active Power

Reactive Power Output

Field Current

PSS contribution

Terminal Voltage

server

Typewritten Text

Annexure-II


Annexure- III

PSS STEP RESPONSE TEST ANALYSIS & RECOMMENDATIONS

Brief Background

PSS is a device that enhances the damping of low frequency oscillations at the synchronous

machine by controlling excitation. As a benefit of the action of several PSSs at several synchronous

machines, the stability of the whole power system increases.

The low frequency oscillations that can be damped by the PSS are divided into following modes

Local Mode – 1.0 to 2.0 Hz ( One generator swings against rest of the system)

Inter Area Mode – Around 0.3 Hz. ( Two Area’s swinging against each other)

Torsional Mode – 10 – 40 Hz. ( Generator Geometry )

Damping Torque


SR PSS MEETING- MINUTES

o The 2nd Meeting on PSS related issues was held at SRPC, Bengaluru on 30th October

2015.

o It was decided that all generating units to set PSS in such a way that it should

come into service when the unit loading is above 50 % of installed capacity

o It was agreed that step in the range of 2- 5 % could be taken at full load and at 50 % (or

at a value as suggested by OEM) load for Step Up and Step Down with PSS On & Off for

Step Response Test of each unit. PSS for the other units (of the station/stage)

would be kept Off during the test

o All generating units with a capacity over 50 MW, for which PSS have not been tuned or

Step Response Test has not been carried out during last 24 months (after August 2013),

should do so by August 2016 and submit result of Step Response Test to SRLDC/

SRPC/ CTU

SRT of 210 MW machine - PSS OFF


SRT of 210 MW machine - PSS ON

PSS Tuning/SRT analysis and recommendations:

APGENCO

NTTPS (VTPS) UNITS – 1,2,3,4,&7

For Unit 1

Step response was done with ± 3% step change in Vref.

Without PSS in-service and step change in Vref the oscillations took 4.5 second to die

down.

With PSS in-service and final Gain settings of K1 = 7.5pu & K2 = 0.5pu, the oscillation were

dying down in 1.5 secs.

For Unit – 2

Step response was done with ± 3% step change in Vref.

Without PSS, the oscillation Pout were taking almost around 4sec to settle down.

With PSS in-service, the oscillations were settling down in almost 1.5 sec.

For Unit 3

Step response test of ± 3 % were conducted.

It was observed that there were oscillations observed in Real Power. The scale is not clear.

VTPS to to discuss the results with the SRT agency /OEM. Accordingly, PSS Tuning may

be taken up again.


For Unit 4

Step response of ±3 % was conducted.

Small oscillations were observed in Pout of the Machine with and without PSS.

The same was being reflected in the PSS Output which was trying to damp down the

oscillation.

Was this a measurement error? or were there such oscillations at NTPPS Unit 4 terminal

needs to be verified.

The PSS may not be tuned properly, the Gains and Phase needs to be tuned as this is

evident as PSS is unable to damp the oscillations. VTPS to discuss the results with the

SRT agency /OEM.

For Unit 7

Step response test was conducted with different Gains with PSS in-service and without

PSS.

From the plots it was seen that the PSS was causing more sustained oscillations as evident

from the Pout and Vfield plots.

The PSS may not be tuned properly, the Gains and Phase needs to be tuned as this is

evident as PSS is unable to damp the oscillations. VTPS to discuss the results with the

SRT agency /OEM.

KRISHNAPATNAM U – 1 & 2

Unit – 1

Step response of +3 % was done at 80 % Loading of the machine.

The Oscillations in Pout were well damped with PSS in-service. Damping torque

computations were showing improvement with PSS On.

Step up response was done for Unit -1 without PSS, step down is done with PSS On.

The PSS was well tuned.

Unit – 2

Step response of ±3 % was conducted at 80 % loading.

The Oscillations in Pout took almost 3.5 sec to settle down without PSS. Damping torque

computations were showing improvement with PSS On.

With PSS the oscillation settled down in 1.5 secs.

The PSS was well tuned.

RAYALASEMA TPP

Unit – 1 & 2

The PSS was not damping out the oscillations and Damping Torque was the same with and

without PSS.

In respect of Unit-2, it was noted that PSS contributions and Pout were in the same phase

and were to be ascertained. It was noted that there could be chances of reverse polarity.

APGENCO clarified that PSS contribution was in opposite phase though graphically it was


showing in the same phase (after ascertaining from M/s BHEL telephonically). APGENCO

to revert back after ascertaining the facts.

PSS needs to be tuned properly to increase the damping torque to damp out the

oscillations more quickly. RYTPP to discuss the results with the SRT agency /OEM and

SRT may be carried out again.

Unit – 3 , 4 & 5

It was observed that with the step response change in Vref , there was no change in

Electrical Output of the Machine

The reactive power of the machine may also be plotted to see whether the Machine is

responding to such Vref changes.

The PSS had no significant effect during the step response test.

RYTPP to discuss the results with the SRT agency /OEM and SRT may be carried out

again.

TSGENCO

KAKATIYA TPS

Unit – 1

A step of ±4 % in Vref was conducted

The Power Oscillations were well damped with and without PSS.

During step down in Vref there was no change in Field current , the excitation system

parameters needed to checked, had the under excitation limiter hit?

KOTHAGUDEM TPS UNIT-9, 10 & 11

Unit – 9

SRT of ±4.5 % was done with & without PSS

As observed from the SRT , there was not much significant reduction in damping, for with

and without PSS

KTPS to discuss the results with the SRT agency /OEM and SRT may be carried out again.

Unit – 10

SRT of ±5 % was done with & without PSS

The oscillations in Electrical Power Output were less without PSS

The oscillations were minimal with PSS Gain Settings of K1 = 3sec & K2 = 0

PSS Tuning needed to be carried out again as it was inducing oscillation

KTPS to discuss the results with the SRT agency /OEM and SRT may be carried out again.

Unit – 11

SRT of ±4 % was done with & without PSS

The test was done at full Load

The Machine Real Power was sufficiently well-Damped in both the scenarios.

NAGARJUNASAGAR PH


Unit – 2, 3, 5 , 6, 7 & 8

Step Up in Vref test was conducted.

The Power Oscillations were damped better with PSS in-service.

Step Down in Vref also needed to be conducted.

The Damping Torque to be calculated.

PSS response for Units 2, 3, 5 & 8 was good. One PSS response was most likely for U7

(though not mentioned in the report) was also good.

Unit – 4

PSS in-service with step up in Vref is plotted and PSS Out-off service with step down in Vref

is provided.

For Step Up in Vref both PSS in-service and Out of-service to be plotted.

For Step Down in Vref both PSS in-service and Out of-service to be plotted.


NSR/TSGENCO to discuss the results with the SRT agency /OEM and SRT may be carried

out again.

KPCL

Bellary TPS

Unit – 1 & 2

The plots/graphs were not clear

Time scale may be clearly mentioned.

It was noted that the test reports were not clear. Bellary TPS to discuss the results with

the SRT agency /OEM and SRT may be carried out again.

TANGEDCO

TUTICORIN TPS

Unit – 1

Date of Test : 29-11-2008

No Graphs Attached.

Unit – 2


SRT ±3 % & ±5 % was done.

Only with PSS in-service graphs were attached.

Unit – 3


4% PSS ON 180MW LOAD

3% PSS ON 120MW LOAD.

Unit – 4

2 % SRT was done

Unit – 5

2 % SRT was done


As Tuticorin TPS had not furnished the graphs of PSS Off, the effect of PSS was not able to be

assessed. TTPS to discuss the results with the SRT agency /OEM and furnish the clarification. If

required, SRT to be taken up again.

NCTPS Stage- I:

Unit– 1

SRT of ±3 % was done at 70 % & 40 % loading, but with and without PSS is not being

mentioned.

Since the test was carried out in July 2013, SRT to be carried out again.

Unit -2

The SRT was carried out, but the % step was not mentioned.

The damping seems slightly better with PSS out of service.

Small oscillations were observed in the Electrical Output of the Machine always.

NCTPS Stage I to discuss the results with the SRT agency /OEM and furnish the

clarification. If required, SRT to be taken up again.

Unit -3

The SRT was out, but the % step is not mentioned.

Small oscillations were observed in the Electrical Output of the Machine always

No change in Electrical Output Damping, with and without PSS

NCTPS Stage I to discuss the results with the SRT agency /OEM and furnish the

clarification. If required, SRT to be taken up again.

Mettur TPS Stage I

Unit - 1

The % Step Change in Vref was not mentioned.

SRT with PSS & without PSS was done

Oscillation in Electrical Output were well damped with PSS in-service.

Unit – 2

Step Up and Step down Tests were done, but with and without PSS was not done.

MTPS to discuss the results with the SRT agency /OEM and SRT may be carried out

again.

Unit – 3

The Electrical Output was not being visualized.

The SRT with proper scales may be re-submitted.


again.

Unit – 4

The % step change in Vref was not mentioned

There were sustained oscillations observed in Electrical Output of the Machine.



again.

NTPC

Talcher Stage II

Unit – 3

Step Response of ±3% was done.

There was no much change in Electrical Output Oscillations of the Machine for PSS – OFF

& PSS – In-service. Noted as brushless exciter.

It was observed that the PSS Output in complete Phase opposition to the Electrical Output

of the Machine.

Unit – 6

Step Response of ±3% is done.

It is observed that the PSS Output in complete Phase opposition to the Electrical Output of

the Machine.

Simhadri TPS

Unit – 1, 2, 3 & 4

Step Response of ±2% was done

There was no change in Electrical Output of the Machine when there was change in Vref.

Hence, a higher step change may be done to compare the Damping for both PSS IN & Out

Plots may be given with Proper Scale.

Simhadri TPS to discuss the results with the SRT agency /OEM and SRT may be carried

out again.

NTECL

VALLUR TPS

Unit – 2

No Load SRT of ±5 % & ±10 % was conducted.

Field Current , Vref , Vactual were plotted

Machine Real & Reactive power to be plotted.


It was noted that the test report submitted was for PID for AVR (at no load). NTECL to

discuss the results with the SRT agency /OEM and SRT may be carried out again.

NPCIL

KAIGA GS

Unit – 3 & 4

The test report is dated 19th April 2007

The graphs corresponds to which unit was not mentioned.

In one unit, Electrical Output was well damped without PSS, but has large settling time,

whereas with PSS there were oscillations observed.

Are these correct legends?? The PSS SRT needs to be done every 3 years.

For other Unit, after the SRT, the oscillations were well damped with PSS.

Time reduced from 2.5 secs to around 1.5 secs.


The Magnitude of the oscillation is also reduced.

Since the tests were conducted in 2007, KGS to take up the SRT/PSS tuning again.

KKNPP Unit-1

Step Response of 1% step was carried out with PSS On and Off

Step Response of 3% step was also carried out but with PSS On only, PSS Off was not

done

PSS output graphs were not plotted.

KKNPP may kindly provide the graphs/plots consisting the parameters Field current,

Filed Voltage, P, Q and PSS output.

IPPS/MPPs

IL&FS

Unit – 1

SRT of ±3 % AT 50% loading and 90% loading was conducted.

The Oscillations in Pout were well damped with PSS in-service.

SRT of Higher % change also to be done.


IL&FS has submitted the photographs of the SRT. IL&FS was suggested to furnish the

test report (preferably the soft copy of the downloadable version).

Udupi Power Corporation Limited

Unit – 1

SRT ±3 % & ±4 % was done with PSS and without PSS

It was observed that Machine Real Power output was sufficiently damped.

PSS Activation test was done

PSS was taken into service , and no change observed in Pout of the Machine

Also the Channel Changeover test was also conducted at full load.

Unit – 2

SRT ±2 % , ±3 % & ±4 % was done with PSS and without PSS

It was observed that Machine Real Power output was sufficiently damped for all the SRT.

The damping torque to be calculated.

The above test were done at 290 MW loading, the same may be carried out full Load

during the next SRT.

TPCIL

Unit – 1 & 2

No Load SRT ±5 % was done with PSS and without PSS

The Legend of the signals plotted was not clear. ( Field Current, Vref )

With and without PSS, the SRT were not conducted.

It was noted that the test report submitted was for PID for AVR at no load. TPCIL to

discuss the results with the SRT agency /OEM and SRT may be carried out again.

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