FGMO

Restricted Governing Mode of Operation

C&I TG Group (Stage – I & II )

Free Governing Mode of Operation (FGMO) FGMO - BACKGROUND  Unique frequency band of 49.0 Hz to 50.5 Hz, as specified by IEGC  Scheduling & dispatch by RLDCs/SLDCs is based on day ahead demand & availability  Frequency control by load-generation balance in every 15 mins time block and Wide frequency variation during Grid disturbance, Unit outage, Change in demand, etc.  Emergencies caused due to frequency control only through importing /cutting load by system operator FGMO - GRID CODES  All generating units should have their speed governors in normal operation at all times to enable Grid frequency control by loading / unloading  Droop characteristic for primary response should be within 3% to 6%  Each unit shall be capable of instantaneously picking up at least 5% extra load for a minimum of 5 mins (up to 105%MCR), during fall in frequency  No dead bands and/or time delays shall be deliberately introduced  Facilities like load limiters, CMC, etc. shall not be used to suppress the normal governor action

FGMO SMOOTHEN THE WIDE FREQUENCY FLUCTUATION

FREQUENCY COMPARISION 52.0 PRE ABT REGIME WITHOUT FGMO

51.5 FREQUENCY

51.0 50.5 50.0 49.5 49.0 48.5

POST ABT REGIME WITH FGMO

48.0 0:00

26/1/04

2:24

4:48

26/1/03

7:12

9:36

12:00

TIME

14:24

16:48

19:12

21:36

0:00

Source:ERLDC Website

MAJOR ISSUES WITH FGMO IN 2004 • Perpetual oscillations in critical parameters

• M/C subjected to cyclic loading and fatigue stresses • Frequent HP/LP Bypass valve operation • Continuous manual interventions

• Self-defeating feature (Unloading when freq. improving towards 50 Hz)

What is RGMO ? Frequency profiles of power system in India has improved significantly after implementation of ABT and the same is now generally remains with in 49 to 50.5 Hz against pre ABT levels of 47.5 to 52.5 Hz. The response of Governors as a first line frequency control mechanism is practiced internationally. How ever the frequency variations will normally be +/-0.1% to 0.2% in those countries.

Hence for our country CEA has proposed a moderated from of FGMO(RGMO)

CERC Order Hon’ble CERC,vide order dated 20.08.09 has issued directions for implementing the RGMO,relevant extracts of which are furnished here below. Quote: 39.In the present scenario of deficit, it is not desirable to have any frequency response from generators by reducing generation when frequency is rising towards 50 Hz from a lower level. Reduction of generation would be necessary when frequency is already above 50 Hz and tends to rise further. Therefore suitable control logic would have to be developed to limit the governor response to situations when frequency is rising and grid frequency is below 50 Hz. Such a situation could be called a restricted governor mode of operation and not total FGMO. How ever this does not exempt the generators from getting the free governor mode in to operational state for use when required.

Salient features of the CERC Order  Load change is proposed to be limited to +/-5% of MCR in the frequency range of 49 Hz & 50.5 Hz and sustained for about 5 minutes before ramping back to original load automatically.  Small changes up to +/- 0.03Hz are ignored for load corrections.  For frequency below 49 Hz and above 50.5 Hz,5% droop of the governor would be effective with load change limited to +5% of MCR for frequency below 49 Hz and -10% of MCR above 50.5 Hz.”

Chronology of Events Sl No.

Date

Event

1

20.08.2009

CERC has given an Order dated 20.08.2009 for implementation of RGMO

2

01.03.2010 Scheduled date for putting the new scheme in to service for Thermal Sets 200 MW and above for Software based EHG Control System.

3

01.06.2010 Scheduled date for putting the new scheme in to service for Thermal Sets 200 MW and above for Hardware based EHG Control System

4

16.02.2010 Scheduled trail implementation of RGMO in Eastern Region

OS Recommendations on RGMO For machines with Hydraulic Governing, the Control logic for restricted governor mode of operation will be as follows 1. If frequency < 50 Hz, any decrease in frequency will result in increase in generation by Governor action as per droop(4-5%) 2. If the frequency < 50 Hz, any increase in frequency up to 50 Hz will result in no action. 3. If frequency > 50 Hz, any increase in frequency will be reset by a slow automatic resetting command to ramp back to MW set point @ 1% per minute. 4. A dead time of 5 to 15 minutes (Variable setting) will be provided before the next governor action is allowed. 5. The quantum of load change may be restricted to +/-5% from the original level.

NTPC Kaniha comments and action plan given to OS COMMENT Sl IOM Ref No OS/CC/FGMO/09 No For Machines with EHG –Control Logic for Restricted mode of Operation

i)

If frequency < 50 Hz, any decrease in This is possible to be frequency will result in increase in Generation implemented with 5% droop. by Governor Action as per droop (4%-5%) In fact this is available in the existing logic of FGMO with a droop of 10%.

ii)

If frequency < 50 Hz, any increase in frequency This Logic modification up to 50Hz will result in NO Action. possible. To be implemented.

iii)

If frequency >50 Hz, any increase in frequency This is possible to be will result in decrease in Generation by implemented with 5% droop. Governor Action as per droop (4%-5%) In fact this is available in the existing logic of FGMO with a droop of 10%.

iv)

The increased / decreased generation will be This is possible reset by a slow automatic resetting command implemented. to ramp back to MW set point @ 1% per minute.

v)

A dead time of 5 to 15 minutes (variable It is not in line with CERC order. setting) will be provided before the next governor action is allowed.

to

is

be

NTPC Kaniha comments and action plan given to OS Sl IOM Ref No OS/CC/FGMO/09 No For Machines with EHG –Control Logic for

COMMENT

Restricted mode of Operation

vi)

IMPLEMENTAION SCHEDULE: The implementation of the suggested logic vide IOM OS/CC/FGMO/09 will be implemented after getting approval from CC-OS/Engg. However, it can be carried out during Opportunity Shutdown / Overhauling.

ii)

TSTPS_Stage-I Units (2X500 MW) In stage-I, the TG sets are of ABB make and Electro Hydraulic Governing is also of ABB make. The existing scheme is enclosed. Since the CERC order specifies only for KWU & LMZ turbines, applicability of the same for ABB turbine may be clarified. If applicable, the same scheme can be implemented after consultation with OEM (M/S ABB, Germany).

Approval from Engg./ OS NTPC Ltd. Talcher Supper Thermal Power Project. INTER OFFICE MEMO From: DGM(O&M/C&I) To:1.AGM(OS/C&I) 2. HOD( PE/C&I) EOC, NOIDA Ref: 9501/O&M/C&I/ CC: 1.ED (TK): for kind inf. pl. 2. GM (O&M): for kind inf. pl. 3. AGM (M): for kind inf. pl. Date: 13-11-2009. Sub: Implementation of restricted governing mode of operation; draft logic proposal for approval reg. With reference to above subject and IOM: OS/CC/FGMO/09 dated: Sept-10-2009, please find enclosed the modified logic for implementing restricted governing mode of operation. Approval from OS / Engineering is sought for the proposed scheme to enable us to implement the same at our site as per the schedule. For point no IV and V we have faced difficulty in proposing the scheme, this may be taken care while finalizing the logic. Since our system falls under the category of “Software based EHG system” we need to implement the same after taking all necessary approvals before 31/03/2010. This also needs unit shutdown for implementation. Early finalization and approval will enable us to implement the same with in schedule. Y.M.Basavaraju

Existing Scheme in Talcher KanihaStage-I(2X500MW) 50 25 0 -25

49.85

49.65

50

50.55

51.1

51.65

-50 -75

49.725

50.15

-100

Load Inc/Dec in MW

-125 -150 -175 -200 -225 -250 -275

5 % Droop

-300 -325 -350 -375 -400

Frequency dead band will be off automatically if: 1) Frequency Deviation is +/-1Hz. 2) Rate of Change of Frequency is greater than 25 rpm/sec

-425 -450 -475

There is no Hydraulic Governor in Main Turbine.The Droop characteristics implemented in EHC.

-500 Frequency In Hz

52.2

52.65

Modified scheme in Talcher Kaniha Stage-I (2X500MW) Speed Signal in 0-100% Range (0 – 3450 rpm)

Finds the difference between Tracking frequency O/P and the actual frequency.

Tracking @0.02Hz/Minute SWI P001=10% E P002=112 s ABG TY2=0 s OG =58.33 %( 50.5Hz) UG =33.33% (49 Hz)

FKG 0% = 0% 81.739% (2820rpm) = 0% 86.956% (3000rpm) = 50% 92.173% (3180rpm) = 100%

Ensuring that if frequency < 49.97 Hz only loading is allowed.

SMU

MAX

+

UMS

K=1

-

Scaling the frequency from 47.0 Hz to 53 Hz.

FIX 0% „1‟ if f>50.03Hz

BEG

OG = 50.5 % UG = 49.5%

ODR

ODR

MIN

„1‟ if f 50.03 Hz only unloading is allowed.

Switching between New Scheme & Old scheme Switching between old scheme and new scheme depending on the grid frequency UMS TBT UMS

New Delta Frequency

Delta frequency from old scheme

ADS

GUG

ABS

+

P007 = G = 2% HYS = 0.5%

Speed corrected GOG

Frequency

OG = 58.33% P004 = HYS = 3.3%

If Freq > 50.5 Hz old delta Freq will come into service.

UND

SWI E1

GRD=100% TY1=P005= 3 Min ABG OG = + 100 % UG = - 100%

R Q S

If Freq > 50.5Hz, SWI output is old f will be Final output.

If Freq < 50.5 Hz, difference between old scheme O/P & new scheme O/P is  10 MW (2%) then only new f will be direct O/P. Otherwise integrated output.

Modified scheme in Talcher Kaniha Stage-I (2X500MW) 50 25 0 -25

49.65

Dynamic 49.8 Correction 50 between 49 to 50.5 Hz

50.55

51.1

51.65

-50 -75

49.725

50.15

-100

Load Inc/Dec in MW

-125 -150 -175 -200 -225 -250 -275

6 % Droop

-300 -325 -350 -375 -400

Frequency dead band will be off automatically if: 1) Frequency Deviation is +/-1Hz. 2) Rate of Change of Frequency is greater than 25 rpm/sec

-425 -450 -475

There is no Hydraulic Governor in Main Turbine.The Droop characteristics implemented in EHC.

-500 Frequency In Hz

52.2

52.65

Existing Scheme in Talcher Kaniha,Stage-II (4X500MW) 100.00 75.00 50.00 25.00 0.00 -25.00

Dynamic Correction 49.65 between 49 to 50.5 Hz 49.4 49.55 49.7 49.85

50

52.50

50.15 50.3 50.45 50.6 50.75 50.9 51.05 51.2 51.35 51.5 51.65 51.8 51.95 52.1 52.25 52.4

-50.00 -75.00

Load Increase/Decrease in MW

-100.00 -125.00 -150.00 -175.00 -200.00 -225.00 -250.00 -275.00 -300.00

Machine Droop 5%

-325.00 -350.00 -375.00 -400.00 -425.00 -450.00 -475.00 -500.00 -525.00 Frequency in Hz

Modified scheme in Talcher Kaniha Stage-II (4X500MW)

47-53 HZ

ACTUAL SPEED

TRACKING RAMP GEN

F(X)

LIMITER

TRACKING RATE 0.02 HZ/MIN

-

49 -50.5HZ

DYNAMIC FREQUENCY ERROR

FREQ DEVIATION SWITCHING

S E L E C T

M A X

0%

+

LIMITER 49 – 50.5 HZ

FREQ

FREQ ERR STATIC

< 50HZ

F(X)

FREQ 50.5 HZ

FREQ 50.5 HZ

FREQ ON /OFF DROOP @ 5% FREQ FILTER +/- .03 HZ LOQD LIMIT +/- 25 MW FOR 4950.5 +25 MW TO -50MW FOR F

+

SELECT

MIN PR MAX

0 LOAD SET POINT PRTD

LOAD 50.5 Hz loading/unloading will be limited to +50 MW & -25 MW respectively.

Implementation of the new scheme • Earlier FGMO modifications were done in Turbotrol 52 R3 processor. If any correction is to be done in the scheme, this processor is to be removed which often becomes risky. • In Stage-I Turbotrol Panel one new 70PR03 Processor was installed. • It takes the actual speed signal from the local bus and after executing the new RGMO Logic, it will give the frequency influence correction as another bus signal to TT52 Processor. • This approach facilitates easy modification of the scheme in future. • Similar RGMO program was implemented in a Drive control module card (83SR05) in the PROCONTROL 14 System and the output was given in POS Operator station for parallel observation.

Thank you

Load Set Point Memorized Gen Load delayed UMS

MW controller ON

Unit SP Turbine UMS

CMC ON

Pressure controller POS UMS

Initial Pressure Controller ON LS Pressure SP Delayed

MUL Fast Unload in action MIN Thermal Forced Unload SUM

Load SEL Corrected

Turbine Speed Droop Droop=( Speed at no load – Speed at full load) x 100% (Rated Speed) =(3150-3000)/3000 x 100% =5%