Section 7.5 –4 – ii of Indian Electricity Grid code (IEGC): “The summation of station-wise ex-power plant drawal schedules for all ISGS after deducting the apportioned transmission losses (estimated), shall constitute the state-wise drawal schedule.”

The need for estimation of losses

Importance

• Wide difference in estimated & actual transmission losses would lead to huge mismatch in Un-scheduled Interchange (UI) payable & receivable.

• Losses also assume importance while scheduling open access customers.

Estimation of transmission losses for scheduling including inter-regional exchanges

Estimation of transmission losses for scheduling including inter-regional exchanges

• Transmission loss signifies the power lost while transferring the same from the

generator(s) to the load.

• In the context of scheduling under the Availability Based Tariff (ABT), generators above would mean the Inter- State Generating Stations (ISGS) while the load would mean the State drawals at their respective peripheries.

Estimation of transmission losses for scheduling (contd/-)

Region Peak ISGS generation (typical)

MW (% of peak)

Peak demand met

MW

North 9800 (46.7) 21000

East 3000 (35.3) 8500

West 5600 (25.5) 22000

South 3500 (18.4) 19000

Estimation of Transmission losses for scheduling (contd/-)

1. Through power flow studies (one day in advance)

- Accurate but complex as different conditions have to be envisaged. Further state level generation/load data required.

2. Based on average actual pooled losses calculated from net drawal of constituents & net injection of ISGS for previous weeks using Special Energy Meter (SEM) data.

- Simple and easy to implement.

Following to be kept in mind:

• Changes in load & Generation pattern over the time. (averaged actual losses will be more realistic if pattern does not change drastically)

Estimation of Transmission losses for scheduling (contd/-)

• In the Northern Region, the transmission losses for the ISGS portion varies by as

much as 1 to 1.5% within the day on account of variations in BBMB and ISGS hydro stations.

• However, the average transmission losses day-wise does not vary much during the

entire week except in situations like closure of hydro stations due to flushing of reservoir or forced outages.

Estimation of Transmission losses for scheduling (contd/-)

• It is suggested that we gradually move to the power flow study method to estimate the

losses for the purpose of day-ahead scheduling as it is more scientific.

• In case a clear pattern of losses is noticed in the course of the entire day, we could go in for a time block-wise figure of estimated losses.

Estimation of Transmission losses for scheduling (contd/-)

• Inter-regional exchanges through an intervening region

What should be the approach followed for the transmission losses in the intervening region?

Should it be the pooled loss percentage or the incremental loss approach?

Estimation of Transmission losses for scheduling (contd/-)

• Inter-regional exchanges through an intervening region (contd/-)

Incremental loss method, although scientific is not desirable as the base case itself varies from time to time.

In case of open access customer, the last set of customers may be at a disadvantage, if incremental transmission losses are levied.

Estimation of transmission losses for scheduling (contd/-)

• Inter-regional exchanges through an intervening region (contd/-)

• Pooled loss approach would be more simpler initially and more transparent.

• Later as we move to the system study method for loss estimation and as we

gain experience in respect of open access customers, we could move to the

incremental loss approach.

NRLDC Charges and Fees -Status

Annual Amount Approved by CERC for 2003-04

Rs. 652.70 Lacs

Monthly bill raised Rs. 54.766 Lacs

Payment Received from All constituents except J&K *

*J&K has opened LC for Rs. 5 Cr/ month while its average transmission & RLDC (4.5 Lacs) bills are in range of 7.0 Cr.

• For April & May 2002 Bills (Rs. 1437050 +Interest) raised on DVB, are not realised (time of unbundling of DVB)

Sl.No. Head Budgeted (2003-04)

Rs.

Actual (upto 30 Sep 2003) Rs.

1. Employee Cost 293.25 150.10

2. R&M 56.55 9.87

3. Power Charges 62.04 25.12

4. Training & Rect. - -

5. Print & Stationery 2.00 1.50

6. Rent - -

7. Misc. 7.50 2.81

8. Insurance 0.07 -

9. Share of Office Exp. - -

10. Communication Exp. 52.35 4.79

11. Traveling Charges 20.00 10.60

12. Hiring of Vehicle 8.62 3.97

13. Depreciation & Corporate Expense allocation.

Percentage of time frequency remained within the IEGC band (49.0-50.5 Hz) in Northern Region

81.7 80.8

72.4 72.5

77.8

70.468.8

71.7

80.679.3

83.4

88.0

79.3

84.481.7

85.888.8 88.7

82.5

91.489.5

97.5

60

65

70

75

80

85

90

95

100

Perc

enta

ge o

f tim

e

pre-ABT

post-ABT

Bilateral trading of power in Northern Region

7 11

2927.97

4483.73

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

Pre-ABT(Dec 01-Sep 02) Post-ABT(Dec02-Sep 03)

Nu

mb

er o

f b

ilat

eral

ag

reem

ents

/ E

ner

gy

Tra

ded

Average no.of Agreements/monthTotal Energy Traded (million units)

FREQUENCY PROFILE OF NORTHERN REGION

48.0

48.5

49.0

49.5

50.0

50.5

51.0

51.5

52.0

0:00

:00

1:00

:00

2:00

:00

3:00

:00

4:00

:00

5:00

:00

6:00

:00

7:00

:00

8:00

:00

9:00

:00

10:0

0:00

11:0

0:00

12:0

0:00

13:0

0:00

14:0

0:00

15:0

0:00

16:0

0:00

17:0

0:00

18:0

0:00

19:0

0:00

20:0

0:00

21:0

0:00

22:0

0:00

23:0

0:00

24:0

0:00

Time

29-Oct-2002

48.0

48.5

49.0

49.5

50.0

50.5

51.0

51.5

52.0

29-Oct-2003

Fre

qu

ency

(H

z)

Energy traded in Northern Region

ABT: Availability Based TariffThe Unscheduled Interchange (UI) market is also of the order of 500 MU every month

Generation above schedule by NTPC Stations in NR for freq. > 50.3 Hz

70741

10767

138319

7580

38806

2508

2468013637

0

20000

40000

60000

80000

100000

120000

140000

160000

Pre-ABT(Dec01-Oct02) Post-ABT(Dec02-Oct03)Ext

ra g

ener

atio

n a

bo

ve 5

0.3

Hz

(MW

h) Pit head

Unchahar-1&2Dadri (T)Combined Cycle

Backing down by NTPC Stations in NR for freq. > 50.3 Hz

29247

46521

19552 1982214736

18858

60348

35839

0

10000

20000

30000

40000

50000

60000

70000

Pre-ABT(Dec01-Oct02) Post-ABT(Dec02-Oct03)

Bac

kin

g d

ow

n a

bo

ve 5

0.3

Hz

(MW

h) Pit head

Unchahar-1&2Dadri (T)Combined Cycle

Generation above schedule by NTPC Stations in NR for freq. < 49.5 Hz

120759

20617

72462

18258

390962679026371

92153

0

20000

40000

60000

80000

100000

120000

140000

Pre-ABT(Dec01-Oct02) Post-ABT(Dec02-Oct03)

Ext

ra g

ener

atio

n b

elo

w 4

9.5

Hz

(MW

h)

Pit headUnchahar-1&2Dadri (T)Combined Cycle