INCENTIVE FOR

TRANSMISSION EFFICIENCY

- T. UMESH , SEE, RETD. KPTCL

- &

- N. RAGHUPRAKASH , EE, RA, KPTCL

IN THIS SESSION

Brief introduction to Transmission System

Efficiency Parameters in Transmission Activity

Transmission Loss & its calculation

System Availability & its calculation

Incentive Calculation by KERC.

INTRODUCTION TO TRANSMISSION NETWORK

Transmission Voltages in Karnataka

Transmission System Elements

AC/ DC lines

Power Transformers ( ICTs)

STATIC VAR Compensators

BUS REACTORS

TRANSMISSION SYSTEM EFFICIENCY

Measured in terms of

Transmission loss

Transmission system availability

TRANSMISSION LOSS

MYT Regulation , clause 3.4 deals with treatment of losses.

In the tariff order KERC stipulates the normative transmission losses to be achieved by KPTCL during MYT period.

If the loss is less, then incentive is allowed. This gain is to be shared in the ratio of 70: 30 between STU and the users of transmission system.

SLDC works out the Transmission loss month on month based on the input to the transmission system and the quantum of energy supplied to ESCOMs at the Inter Face points. This information is furnished to KERC based on which the Order for sharing of loss / gain on account of Transmission loss is issued.

INCENTIVE FOR TRANSMISSION EFFICIENCY

KERC vide its MYT Regulations -2006 Order

dated 31.05.2006 has stipulated that KPTCL

shall maintain a minimum of 98% availability for

recovery of full transmission charges.

Recovery of fixed charges below the level of target

availability shall be on pro-rata basis. At zero

availability, no transmission charges shall be

payable.

PROCEDURE FOR CALCULATION OF

AVAILABILITY

Availability shall be calculated and declared

separately for each voltage level.

The transmission elements shall be grouped

into following categories.

a) AC transmission lines: Each circuit of AC

transmission line shall be considered as one

element.

b) Inter-Connecting Transformers: Each 3ph

transformer or bank of three Sph transformer

shall form one element.

PROCEDURE FOR CALCULATION OF

AVAILABILITY

c) Static VAR Compensator: SVC along with SVC

transformer if any shall form one element.

d) Switched Bus Reactor: Each switched Bus

Reactor shall be considered as one element.

Weightage factor for each category of

transmission elements shall be as under:

a) For each circuit of AC line- Surge Impedance

loading (SIL) multiplied by Circuit Km. ( SIL

rating for various voltage level and conductor

configuration shall be as per the procedure

adopted for power system analysis)

PROCEDURE FOR CALCULATION OF

TRANSMISSION SYSTEM AVAILABILITY (TSA)

b) For each ICT- The rated MVA capacity

c) For SVC- The rated MVAR capacity

d) For switched Bus Reactor: The rated MVAR

capacity.

The availability for each category of transmission

elements shall be calculated based on the

weightage factor, total hours under consideration

and non-available hours for each element of that

category.

The transmission elements under outage due to

following reasons not attributable to KPTCL

shall be deemed to be available:

1) Shut down of transmission elements availed by

other agencies for maintenance or construction of

their transmission system.

2) Manual tripping of the line due to over voltage

and manual tripping of elements as per the

directions of the RLDC/SLDC.

Outage time of elements due to acts of God and

force majeure events beyond control of KPTCL

shall be excluded.

Outage time caused by grid disturbance not

attributable to KPTCL shall also be excluded. Eg.

Faults in substations or bays owned by other

agencies causing outage of KPTCL elements.

However, if the elements are not restored on

receipt of directions from SLDC while

normalizing the system following a grid

disturbance within reasonable time, then the

element will be considered not available for

whole period of outage and outage time shall

be attributable to KPTCL.

The % availability is calculated for each

transmission element as follows:

1st calculate Availability index= Total time under

consideration-Outage hours due to unscheduled

interruptions/Total time under consideration.

Next calculate availability= Availability

index*Weightage factor

% availability= availability/weightage factor

Then, % availability of category of elements=

Sum of availability of all elements/sum of

weightage factor of all elements.

Then, % System Availability is calculated as the

average of all category availabilities.

FORMULA FOR CALCULATION

% TSA = o*AV₀ + p*AVp + q*AVq + r*AVr X 100

o+p+q+r Where ,

AV = Availability

o = No. of AC lines

p = No. of ICTs

q = Capacitor Bank

r = Bus Reactors

Zone: Bangalore

Element: AC lines

Sl.

No.Name of the line

Voltage

kVConductor Ckt.kM SIL

Weightage

factor

Total time of

consideration-

hours

Un-

Scheduled

Interrupti

ons- hours

Availability

Index

Availability

(Avi)

%

Availability

A B C=A*B D E F=(D-E)/D G=C*F H=G/C*100

1 Nelamangala - Peenya I 220 Drake 17 132 2244 8760 4.87 0.999 2242.752 99.944%

2

3

4

5

290

Total 1305556.1 1304626.78

Sl.No. ZoneNo. of AC

linesWf Availability

No. of

ICT'sWf Availability

No. of

SVAR'sWf Availability

%TSA of

Zones

1 Bagalkote 311 697757.44 695026.05 471 9702.5 9684.27 22 462 460.71 99.73

2 Bangalore 290 1305556.08 1304626.78 499 15753.9 15745.99 31 688.28 688.28 99.94

3 Gulbarga 173 738584.22 734879.11 311 6021.5 6005.16 19 456 455.37 99.65

4 Hassan 198 931824.81 928881.66 268 5836.2 5834.83 16 371 356.16 99.72

5 Mysore 134 176175.12 176082.58 233 3842.6 3841.02 27 430 430 99.96

6 Tumkur 98 286133.19 285761.46 342 6079.7 6076.21 0 0 0 99.93

1204 4136030.86 4125257.64 2124 47236.4 47187.48 115 2407.28 2390.52 99.82

AVO 1204 0.997395276

AVP 2124 0.998964358

AVQ 115 0.993037785

%TSA= 99.82177037

KPTCL TOTAL

KPTCL TOTAL

INCENTIVE

KPTCL shall be entitled to incentive on achieving

annual availability beyond the target availability

of 98% as per the following formula.

Incentive= ATC* (TSA achieved-Target

availability)/Target availability

No incentive shall be payable above the

availability of 99.75%.

50% of the incentive shall be shared by the long

time customers in the ratio of their average

allotted transmission capacity for the year.

SURGE IMPEDANCE LOADING

Surge Impedance Loading (SIL) in MW’s of a long

transmission line is defined as ratio of (kVRE)²/SI

where VRE is the receiving end voltage in KV and

SI is surge impedance of the line.

SIL is typically the limit of the maximum power

that can be transmitted through the line at the

voltage level considered.

SIL can be increased by reducing the SI of the

line.

SIL VALUES AS PER KEGC 2005

Typical values of SIL are as follows:

a) 400 kV lines – Quad conductor- 1051 MW

b) 400 kV lines – Twin conductor-515 MW

c) 220kV lines – Single conductor-132 MW

d) 110kV lines – SC – 50 MW

e) 66kV lines – SC – 35 MW

SURGE IMPEDANCE

SI is defined as the √(L/C), where L and C are

Inductance and Capacitance of the line.

SI can be reduced by bundling.

Bundling is the use of two or more conductors per

phase, which reduces L and increases C.

Hence twin/quad conductors are used in

400/765kV lines.

Transmission lines produce reactive power due to their

natural capacitance.

Mvar produced = ½ CV²

Transmission lines also utilize reactive power to

maintain their magnetic fields.

Mvar used = ½ LI²

SIL is the loading of the line when Mvar produced =

Mvar used

i.e., when ½ LI² = ½ CV²

Which gives V/I = sqare root of L/C, which is nothing

but the SI of the line.

THANK YOU