POWER GRID CORPORATION OF INDIA LTD

POWER GRID CORPORATION OF INDIA LTD

SOUTHERN REGIONAL LOAD DESPATCH CENTRE

2nd MEETING OF COMMERCIAL SUB COMMITTEE OF SRPC

07TH DECEMBER 2006

BANGALORE

AGENDA

4.0 COMPUTATION OF UI EXCHANGES BETWEEN ER-SR

5.iii COMPUTATION OF TALCHER STPS-II INJECTION

6.0 LOSS ESTIMATION METHODOLOGY

Computation of Talcher STPS-II Injection

Computation of Talcher STPS-II Injection

• The computation of actual injection of Talcher STPS-II for accounting purposes was done using SEMs installed on the out going feeders till 31.03.2006.

• Clause 7.4.6 of revised IEGC effective from 1st April 2006, provided actual injection of Talcher STPS-II shall be metered on 400 kV side of Generator transformers of Talcher STPS-II units.

• CEA has issued (installation and operation of meters) Regulations, 2006 to become effective from 22.03.06 (came to notice in May, 2005).

NTPC LETTER020806

SRLDC REPLY110806

NTPC LETTER070906

SRLDC REPLY111006

CEA REGUMINUTES OF1st COMM.

AMENDMENTS BY SRLDCIEGC

GT vis a vis Feedres Inj

Computation of UI Exchanges between

ER - SR

The methodology adopted by SRLDC for computation of UI between ER-SR during the period 03.04.06 to 27.08.06 was based on the following stipulations made in IEGC (effective from 1.4.2006):

7.6.1 The regional boundaries for scheduling, metering and UI accounting of inter-regional exchanges between ER & SR shall be as follows:

400 kV Bus couplers between Talcher-I and Talcher-II

400 kV East bus of Gazuwaka HVDC.

7.6.3. No attempt shall be made to split the inter-regional schedules into linkwise schedules (where two regions have two or more interconnections).

As regards to the UI computation of Talcher Stage II, the following provisions as stated in IEGC were also taken into consideration:

7.4.2. For a clear demarcation of responsibilities and minimal to-and-fro coordination, the scheduling of Talcher-II shall be coordinated by SRLDC, and the 400 kV AC bus-couplers between Talcher-I (2x500 MW) and Talcher-II (4x500 MW) shall be treated as the interface between ER and SR.

7.4.6. …… The difference between the actual injection of Talcher II and the dispatch schedule shall constitute the UI of Talcher-II, for which payments shall be made from/into the UI pool account of Southern region operated by SRLDC, but at the UI rate corresponding to ER repeat ER frequency. The energy accounting for Talcher-II STPS shall be carried out by SRLDC.

7.4.7. While the dispatch schedule for Talcher-II shall be as advised by SRLDC, the actual generation at Talcher-II may be varied by station operators depending on ER frequency, as long as the resulting UI does not cause a transmission constraint in ER. In case of a transmission constraint being caused in ER by the UI of Talcher-II, ERLDC may advise Talcher-II to curtail its UI under intimation to SRLDC. Any such advise shall be immediately complied with by Talcher-II.

Specific Issues related to UI exchange between SR & ER vis-à-vis

between Talcher Stage II to ER :

Any UI exchange is carried out with the consent of SRLDC/ERLDC

control rooms to move power mainly from surplus to deficit region

The direction and quantum of UI between would depend on the

generation level maintained by Talcher II - irrespective of regions status

Any UI exchange is carried out depending on the frequency of both the

regions and thereby resulting into positive differential UI

Talcher II may inject UI irrespective of the frequency relationship of the

two regions and thereby at times resulting into negative differential UI

Annexure-I

Any UI exchange gives equitable benefits to the constituents in both the

regions

Injection of UI by Talcher II if clubbed with SR to ER UI, may not result

in such equitable scenario

Annexure-II

It may therefore be seen that in view of the specific location of Talcher II vis-à-vis other ISGSs, the

UI computation in respect of Talcher II is required to be followed in a manner which would be based

on the IEGC provisions as stated above and at the same time it would not defeat the basic UI

philosophy which stipulates that the UI exchange between two agencies/ regions should benefit

both the parties.

In order to achieve this, whenever UI transactions are there in respect of Talcher II with ER, the UI

calculations have to be carried out as per the IEGC provisions (clause 7.4.6 ) i.e. at ER frequency.

However as per this clause, as the payment for this UI to Talcher II has to be made from the UI

pool account operated by SR, it is natural that SR UI pool must be suitably compensated by getting

the equivalent amount from the UI pool operated by ER.

Furthermore by following this methodology as no differential gets generated in SR/ER UI pool on

this account, there cannot be any sharing of accumulated differential UI. therefore the possible

viable approach within the framework of IEGC regulations could be:

--- to treat this transaction as a UI only between Talcher II and ER and

--- while accounting these amounts (as it is) these can be routed through the SR weekly UI

accounts

METHODOLOGY FOR ACCOUNTING OF UI BETWEEN TALCHER II AND ER

TALCHER STAGE II UI & ER AND SR FREQUENCY

-30.00

-20.00

-10.00

0.00

10.00

20.00

30.00

40.00

0000

-001

5

0100

-011

5

0200

-021

5

0300

-031

5

0400

-041

5

0500

-051

5

0600

-061

5

0700

-071

5

0800

-081

5

0900

-091

5

1000

-101

5

1100

-111

5

1200

-121

5

1300

-131

5

1400

-141

5

1500

-151

5

1600

-161

5

1700

-171

5

1800

-181

5

1900

-191

5

2000

-201

5

2100

-211

5

2200

-221

5

2300

-231

5

TIME BLOCK --->

EX

-BU

S I

N M

W -

--->

48.50

49.00

49.50

50.00

50.50

51.00

51.50

52.00

52.50

53.00

53.50

FR

EQ

UE

NC

Y I

N H

Z -

--->

UI SR FREQUENCY ER FREQUENCY 23-May-06 Tuesday

EASTERN REGION

Loss = 2.9 lakhs

Payable by ER RS. 4.3 Lakhs Receivable by SR Rs. 6.2 Lakhs

Negative Differential UI Rs.2.9 Lakhs

TALCHER STAGE II UI & ER AND SR FREQUENCY

-15.00

-10.00

-5.00

0.00

5.00

10.00

15.00

20.00

25.00

30.00

0000

-001

5

0100

-011

5

0200

-021

5

0300

-031

5

0400

-041

5

0500

-051

5

0600

-061

5

0700

-071

5

0800

-081

5

0900

-091

5

1000

-101

5

1100

-111

5

1200

-121

5

1300

-131

5

1400

-141

5

1500

-151

5

1600

-161

5

1700

-171

5

1800

-181

5

1900

-191

5

2000

-201

5

2100

-211

5

2200

-221

5

2300

-231

5

TIME BLOCK --->

EX

-BU

S I

N M

W -

--->

48.50

49.00

49.50

50.00

50.50

51.00

51.50

52.00

52.50

53.00

53.50

FR

EQ

UE

NC

Y I

N H

Z -

--->

UI SR FREQUENCY ER FREQUENCY 10-Jun-06

SaturdayEASTERN REGION

Loss = 3.8 lakhs

SR & ER FREQUENCY AND DIFFERENCE AMOUNT BETWEEN SR-ER UI RATES ON 14-10-2006

-6

-5.465

-4.93

-4.395

-3.86

-3.325

-2.79

-2.255

-1.72

-1.185

-0.65

-0.115

0.42

0.955

1.49

1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76 79 82 85 88 91 94

TIME BLOCKS

DIF

F. A

MO

UN

T B

ET

WE

EN

SR

-E

R U

I RA

TE

S

48.5

48.7

48.9

49.1

49.3

49.5

49.7

49.9

50.1

50.3

50.5

50.7

50.9

51.1

51.3

51.5

SR FREQUENCY

ER FREQUENCY

DIFFERENTIAL AMOUNT

-1.5 lakhs -48.7 lakhs

ERFreq = 49.6 HzUI Rate= Rs.3/

TalcherStage IIGen: 1600Schd: 1600

1600 MWSR

Talcher Stage I & II I/C

SR Freq = 49.16 HzUI Rate= Rs.5/

UI (SR to ER) 0 MW

0 MWER

0 MW UI (from SR to ER)

Annexure -ICASE – 1 UI from Talcher Stage II to ER when SR frequency < ER frequencyBase Case: Talcher Stage II UI =0 MW

Base Case +Talcher Stage II 50 MW UI (Talcher Stage 2 actual Generation = 1650 MW against Schd. of 1600 MW)

ERFreq = 49.6 HzUI Rate= Rs.3/

TalcherStage IIGen: 1650Schd: 1600

1600 MWSR

Talcher Stage I & II I/C

SR Freq = 49.16 HzUI Rate= Rs.5/

UI (SR to ER) 0 MW

50 MWER

0 MW UI (from SR to ER)

Issues

Considering the variable cost of Talcher Stage II as around 80 paisa it would be beneficial for Talcher Stage II to generate positive UI as the ER UI rate is more than its variable cost. For every unit of power exported to ER, Talcher Stage II would get a price of Rs 3/Unit.However if the UI by Talcher Stage II to ER is considered as UI from SR to ER, then it would be a case of –ve UI

For every unit of power exported , SR would expect a price of Rs 5/Unit while ER would be able to give a price of Rs 3/Unit only. Such transactions accumulated during that periods could cause commercial implications.

In order to address this issue ,the UI transactions can be considered between Talcher Stage II and ER, however the accounts can be routed through SR.

All Figures in Lakhs of Rs.FEEDER SIDE

AMOUNTGT SIDE AMOUNT

Difference in Amount

( A ) ( B ) ( A ) - ( B )2 3-Apr-06 9-Apr-06 291.43274 216.82037 74.612363 10-Apr-06 16-Apr-06 73.46811 25.22995 48.238164 17-Apr-06 23-Apr-06 89.81490 72.27806 17.536845 24-Apr-06 30-Apr-06 105.66756 83.49049 22.177076 1-May-06 7-May-06 113.62745 99.32897 14.298487 8-May-06 14-May-06 48.58721 27.36991 21.217308 15-May-06 21-May-06 69.71495 54.09509 15.619869 22-May-06 28-May-06 56.17899 46.64673 9.5322510 29-May-06 4-Jun-06 35.82640 32.16369 3.6627111 5-Jun-06 11-Jun-06 66.86442 45.91718 20.9472412 12-Jun-06 18-Jun-06 99.90392 63.87924 36.0246813 19-Jun-06 25-Jun-06 38.10369 27.79828 10.3054114 26-Jun-06 2-Jul-06 53.11659 42.96052 10.1560715 3-Jul-06 9-Jul-06 64.21370 53.65049 10.5632116 10-Jul-06 16-Jul-06 85.43378 72.12195 13.3118317 17-Jul-06 23-Jul-06 89.98447 76.41190 13.5725718 24-Jul-06 30-Jul-06 42.50377 33.01850 9.4852719 31-Jul-06 6-Aug-06 75.87518 67.59859 8.2765920 7-Aug-06 13-Aug-06 72.51191 62.21940 10.2925121 14-Aug-06 20-Aug-06 67.53881 60.10961 7.4292022 21-Aug-06 27-Aug-06 80.03954 64.46805 15.5714923 28-Aug-06 3-Sep-06 85.46760 66.26917 19.1984224 4-Sep-06 10-Sep-06 87.71533 64.78679 22.9285325 11-Sep-06 17-Sep-06 79.72710 55.62286 24.1042426 18-Sep-06 24-Sep-06 156.43500 144.68082 11.7541827 25-Sep-06 1-Oct-06 162.84152 148.70939 14.1321328 2-Oct-06 8-Oct-06 76.76704 61.45503 15.3120129 9-Oct-06 15-Oct-06 146.93006 114.97361 31.9564530 16-Oct-06 22-Oct-06 110.93182 74.29961 36.6322231 23-Oct-06 29-Oct-06 99.42321 66.87154 32.5516732 30-Oct-06 5-Nov-06 129.50666 88.98301 40.5236533 6-Nov-06 12-Nov-06 126.61883 88.25884 38.3599934 13-Nov-06 19-Nov-06 119.48294 81.38000 38.1029435 20-Nov-06 26-Nov-06 115.63621 80.44105 35.19516

TOTAL 3217.89139 2464.30871 753.58268

Week No. From Date To Date

COMPUTATION OF TALCHER STAGE II UI AMOUNT FOR THE YEAR 2006-07

EASTERN REGION

SR

INTER-REGIONAL TRANSFER

EASTERN REGION

SR RATE = RS 3/

ER RATE = RS 5/

SR TO ER 100 UNITS OF UI ENERGY IS TRANSACTED

ER COLLECTS RS 500 FROM ITS CONSTITUENTS

RS 300 IS PAID TO SR

OF THE REMAINING RS 200/- 50% IS PAID TO SR AND 50%

IS RETAINED BY ER

300400

ER FREQ ~49.16 Hz

SR FREQ ~ 49.60 Hz/

100

500

TALHER STAGE II UI = 0

200

100

EASTERN REGION

SR


EASTERN REGION

SR RATE = RS 3/

ER RATE = RS 5/ER FREQ ~49.16 Hz

SR FREQ ~ 49.60 Hz/

100TALCHER

STAGE II

50

TALHER STAGE II UI = 50 UNITS


THERE COULD BE TWO METHODOLOGIES TO COMPUTE UIs

METHODOLGY 1

ER-SR UI AND TALCHER STAGE II UI IS COMBINED

METHODOLGY 2

ER-SR UI AND TALCHER STAGE II UI IS ACCOUNTED SEPERATELY

EASTERN REGION

SR


EASTERN REGION

SR RATE = RS 3/

ER RATE = RS 5/ER FREQ ~49.16 Hz

SR FREQ ~ 49.60 Hz/

100TALCHER

STAGE II

50

TALHER STAGE II UI = 50 UNITS


METHODOLGY 1

ER-SR UI AND TALCHER STAGE II UI IS COMBINED

150

ER COLLECTS RS 750 FROM ITS CONSTITUENTS 750


450

300

SR PAYS TO TALCHER STAGE II RS 250 FOR 50 UNITS UI

200

250

150


IS RETAINED BY ER

350

150

EASTERN REGION

SR


EASTERN REGION

SR RATE = RS 3/

ER RATE = RS 5/


ER COLLECTS RS 750 FROM ITS CONSTITUENTS



IS RETAINED BY ER

300400

ER FREQ ~49.16 Hz

SR FREQ ~ 49.60 Hz/

100

TALHER STAGE II UI = 50

TALCHER

STAGE II

50

METHODOLGY 2

ER-SR UI AND TALCHER STAGE II UI IS ACCOUNTED SEPERATELY

ER COLLETS RS 250 FOR 50 UNITS UI OF TALCHER STAGE II AND PAYS TO SR &

SR IN TURN PAYS TO TALCHER STAGE II

250

750450

200100

ER COLLECTS

ER PAYS TO SR

ER PAYS TO ER IRE

50 % OF ER IRE COMES TO SR

TOTAL SR RECEIVED

SR PAYS TO TALCHER STAGE II

NET AMOUNT RECEIVED

BY SR

NET BALANCE LEFT WITH ER IRE

500 300 200 100 400 0 400 100

SR TO ER UI = 100 Units, TALCHER STAGE II UI = 0 Units

ER Rate = Rs. 5/- SR Rate = Rs. 3 /-All in Rs.

METHODOLOGY 1ER COLLECTS

ER PAYS TO SR

ER PAYS TO ER IRE


TOTAL SR RECEIVED

SR PAYS TO TALCHER STAGE II

NET AMOUNT RECEIVED

BY SR


750 450 300 150 600 250 350 150

SR TO ER UI = 100 Units, TALCHER STAGE II UI = 50 Units

ER Rate = Rs. 5/- SR Rate = Rs. 3 /-

METHODOLOGY 2ER COLLECTS

ER PAYS TO SR

ER PAYS SR AND PAYS TO TALHER II

ER PAYS TO ER IRE


NET AMOUNT RECEIVED

BY TALCHER II

NET AMOUNT RECEIVED

BY SR


750 300 250 200 100 250 400 100

Loss Estimation Methodology

LOSS ESTIMATION

• Presently the notional transmission loss is taken as average actual loss in the system computed from the SEMs for the 2nd week prior to the current week.

• At times though the weekly average actual loss may come out to be quite close to the weekly average estimated loss, still there may be a large difference between payables and receivables because in real time as the system parameters (frequency) and hence the UI rate will vary.

DETAILS

IEGC CLAUSE

Extract from National Electricity Policy

DIFFERENCE BETWEEN PAYABLES AND RECEIVABLES

Contributing factors

• Drawal patterns of states

• Interregional exchanges ( Scheduled or UI)

• Geographical availability of generation

• Network availability


Presently as per 126th SREB decision, the minimum of the payables and receivables in a week is taken by keeping interregional payments/receivables taken as constant and first charge basis.


Following alternatives may be considered

Alternative 1Option 1

By keeping Inter regional Payments constant, the beneficiaries and ISGS payments may be modified by taking average of the payables and receivables in a 15 minute time block.

Option 2The same procedure of 1 may be carried out in day wise instead of 15 minute time block

Option 3The same procedure of 1 may be carried out in week wise instead of 15 minute time block


Following alternatives may be considered

Alternative 2Option 1

By keeping ISGS and Inter regional Payments constant, the beneficiaries payments may be modified by taking average of the payables and receivables in a 15 minute time block.

Option 2The same procedure of option 1 may be carried out in day wise instead of 15 minute time block

Option 3The same procedure of option 1 may be carried out in week wise instead of 15 minute time block

As per IEGC Clause 6.5.6 of II

The “net drawal schedule” to each beneficiary, in MW for different hours, for the next day. The summation of the station-wise expower plant drawal schedules for all ISGS and drawal from regional grid consequent to bilateral interchanges, after deducting the

transmission losses (estimated), shall constitute the State-wise drawal schedule.

As per National Electricity Policy 5.3.5To facilitate orderly growth and development of the power sector and also for secure and reliable operation of the grid, adequate margins in transmission system should be created. The transmission capacity would be planned and built to cater to both the redundancy levels and margins keeping in view international standards and practices. A well planned and strong transmission system will ensure not only optimal utilization of transmission capacities but also of generation facilities and would facilitate achieving ultimate objective of cost effective delivery of power. To facilitate cost effective transmission of power across the region, a national transmission tariff framework needs to be implemented by CERC. The tariff mechanism would be sensitive to distance, direction and related to quantum of flow. As far as possible, consistency needs to be maintained in transmission pricing framework in inter-State and intra-State systems. Further it should be ensured that the present network deficiencies do not result in unreasonable transmission loss compensation requirements.

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