SEMs Specification Static type Composite meter Highest accuracy available in the power industry 3 Phase – 4 wire connections/measurement Direct measurement in whrs and varh on the CT/PT secondaries –110 V Ph to Ph /63.51 V Ph – N –1 amp or 5 amp –VA burden not more than 10 on any of the phases Works on real time clock No calibration required

Share Drawal Curve

Loss Graph

Raw data WEEK FROM 0000 HRS OF TO 0837 HRS OF NP-0185-A NP-0185-A NP-0185-A

Computed Mwh data 230 kV Neyveli line at Pondicherry CTR = 600 PTR = 2091 PO-02 NP-0185-A …. ….. …..…..…

Active energy ENERGY ACCOUNTING USING SPECIAL ENERGY METER FOR TIME PONDY YANNAM Net Drawal PO-02 PO-06 IN Mwhr : : : : : : : : : : : : TOTAL

Reactive energy accounting

POSSIBLE MODES OF SCHEDULED AND UNSCHEDULED INTERCHANGES/TRADING 1)Supply of allocated shares from ISGS and jointly owned plants, as per Availability Based Tariff. 2)Transfer of an SEB’s share in Central Generation or a jointly owned plant 3)Long-term contracts with other SEBs and Generating Companies within and outside the Region, on negotiated terms specifying daily drawal schedules and price. 4)Bilateral long/short-term agreements for as-and-when available and off-peak surplus energy 5)Negotiated interchanges/trades with neighbouring Regions through Regional Power pool or consortium. 6)Unscheduled interchanges of as-and-when- available surplus to replace costlier energy at frequency-linked pool price, through the pool.

GRID INDISCPLINE CONDITIONS i)Over-drawal when frequency is below normal. ii)Generation above the given schedule when the frequency is above normal. iii)Drawal of MVARs from the EHV grid when the voltage is below normal at the drawal point. iv)Delay in payment of dues to the generating companies, transmission companies and other utilities for power/energy drawn.

CHARGE FOR REACTIVE ENERGY OBJECTIVE: To induce SEBs to install capacitors timely, and thereby reduce MVAR drawals, MVAR flows on long EHV lines, and resultant large voltage drops. Voltage-related; only for SEBs SEBs pay for MVARh drawn while voltage is low (below 97%), and get paid for MVARh drawn while voltage is high (above 103%). Nominal rate: 4p/kVARh, with escalation Recommended in ECC Report Meters already installed in S.R, E.R., N.E.R. Metering pioint: 400 kV side of ICTs, both ends of all inter- State lines.

CHARGE FOR REACTIVE ENERGY No additional earning for ISGS and POWERGRID No charge for drawal directly from ISGS’ busbars. Inter-State lines: One SEB pays to the other SEBs also get paid at the same rate for MVARh return while voltage is low, and pay for MVARh return while voltage is high. All MVARh payment collection goes into a separate pool fund, from which MVARh payments would be made, and balance would be used for system improvement schemes.

REVISION OF SCHEDULES/REQUISITIONS A)OUTAGE OF GENERATING UNIT B) REVISED DECLARATION OF AVAILABILITY BY ISGS C) OUTAGE OF A TRANSMISSION ELEMENT D)UNFORESEEN LOAD-CREASH TAKES EFFECT FROM A)4 TH TIME BLOCK IN CASE OF -FORCED OUTAGE OF A GENERATING UNIT -TRANSMISSION CONSTRAINT -GRID DISTURBANCE -SUO MOTO BY RLDC B) 6 TH TIME BLOCK IN CASE OF -REVISION OF DECLARED AVAILABILITY BY ISGS

WHAT ALL CAN HAPPEN?

What all can happen on the day of Operation? Prospective revision (upward / downward) of ISGS availability (advised by ISGS through RLDC) Schedules revision for remaining part of the day

TRIPPING OF ISGS UNIT TRIPPING OF THE SEB’S UNITS LOAD CRASH IN THE STATE FREQUENCY IS GOOD OR HIGH THE STATE IS OVERDRAWING THE STATE IS UNDERDRAWING THE ISGS IS OVER GENERATING THE ISGS IS UNDER GENERATING FREQUENCY IS LOW THE STATE IS OVERDRAWING THE STATE IS UNDER-DRAWING THE ISGS IS UNDER GENERATING THE ISGS IS OVER GENERATING What all can happen on the day of Operation?

TRIPPING OF ISGS UNIT ( Known after the event) Immediate frequency dip All operating units pick up extra MW, SEB’s drawal reduces SEBs get UI payment After the transients : An SEB has the option of adjusting his generation/load to increase/decrease his net drawal to forgo or take advantage of UI, till ISGS revises availability and new schedules come into effect.

What all can happen on the day of Operation? TRIPPING OF THE SEB’S OWN GENERATING UNITS SEB’s net drawal from the grid increases SEB has to pay UI OPTIONS 1. Continue to overdraw and pay UI 2. Carry out corresponding load shedding 3. Run up all available generation 4. Increase ISGS requisition, in case it was not fully requisitioned earlier 5. Enter into a bilateral with another SEB/ISGS for any idling capacity

What all can happen on the day of Operation? LOAD CRASH IN THE STATE Under-drawal from the grid and frequency rise UI implications OPTIONS 1. Reduce own generation 2. Reduce ISGS requisition (only if frequency rises/is likely to rise so much that UI price falls below ISGS energy rate 3.Continue to under-draw, in effect supplying UI to the grid. This is advantageous as long as the frequency remains below about 50.2 Hz.

FREQUENCY IS GOOD OR HIGH AND THE STATE IS OVERDRAWING No problem and no action required Enhance optimisation, however to the extent possible 1.Reduce own generation to the extent possible, if frequency is above 49.8Hz and increase over-drawal 2. Restore consumer load that had been shed, provided tariff /realisation rate is higher than current UI rate. ( This is also increses overdrawal) 3. Increase ISGS requisition if some part of the entitlement had not been requisition earlier, provided the frequency is ( and is likely to remain) below 50.2Hz. (This would increase the drawal schedule and thereby reduce overdrawal)

FREQUENCY IS GOOD OR HIGH AND THE STATE IS UNDERDRAWING Action required 1.Reduce own generation to the extent possible, if the frequency is above abiut 49.8 Hz(This would reduce under drawal) 2. Restore consumer load that had been shed, and reduce underdrawal 3. Reduce ISGS requisition, provided the previous two actions have been taken and the frequency continues to be above 50.2 – 50.3 Hz. If frequency is likely to remain below 50.2 Hz, bilateral sell to a needy neighbour can be tried.

FREQUENCY IS LOW AND THE STATE IS OVERDRAWING Action required 1.Increase own generation to the maximum possible extent 2. Curtail customer load. Load shedding to be graded balancing between UI price and consumer category. 3. Increase ISGS requisition to full entitlement (If not requisitioned fully earlier), and arrange for bilateral purchase from another SEB/ ISGS

FREQUENCY IS LOW AND THE STATE IS UNDER-DRAWING 1.Increase own generation to the extent possible, provided the frequency is below about 49.5 Hz (Comparing variable cost with current UI price) As such no action required. However the following can be done for enhanced optimisation 2. Curtail consumer load, by shedding low priority load (provided UI earning for the SEB justifies such load shedding). This is totally optional, and helps the grid. 3. Increase ISGS requisition to full entitlement (if not requisitioned fully earlier) and earn UI. Alternately sell the surplus through a bilateral agreement.

OPTIONS OF ISGS TO EVENTS WHAT ALL CAN HAPPEN ON THE DAY OF OPERATION ? 1.PROSPECTIVE REVISION OF DRAWAL REQUISITION BY A BENEFICIARY ( UPWARD / DOWNWARD) SCHEDULE REVISED FOR REMAIING PART OF THE DAY BY RLDC 2.TRIPPING OF A GENERATING UNIT OF A STATE (KNOWN AFTER THE EVENT). IMMEDIATE FREQUENCY DIP ALL OPERATING UNITS PICK UP EXTRA MW, ALL STATIONS INJECTION INCREASES  ISGS RECEVIES UI PAYMENT

OPTIONS OF ISGS : i.GENERATE AS PER SCH. AND FOREGO ADVANTAGE OF UI ii.INCREASE NET INJECTION BY INCREAING OWN GENERATION  RECEIVE UI PAYMENT TILL THE BENEFICIARIES REVISE THEIR REQUISITIONS AND NEW SCHEDULES COME INTO EFFECT OR REDUCE THEIR DRAWALS 3.TRIPPING OF THE OWN GENERATING UNIT OF ISGS NET INJECTION OF ISGS REDUCES  STATION HAS TO PAY UI. OPTIONS OF ISGS : i. CONTINUE TO UNDER GENERATE AND PAY UI. ii. INCREASE NET INJECTION BY RUNNING UP ALL AVAILABLE GENERATION.Contd….

 MINIMISE UI PAYMENT iii)REVISE AVAILABILITY DECLARATION WHILE CONTINUING TO UNDER GENERATE (AND PAY UI) TILL REVISED SCHEDULES TAKE EFFECT. iv)ENTER INTO A BILATERAL AGREEMENT WITH OTHER SEB/ISGS TO SUPPLY ANY SURPLUS/ IDLING CAPACITY. 4.LOAD CRASH IN A STATE: FREQUENCY INCREASES ISGS INJECTION REDUCES  UI IMPLICATION (NET GAIN/LOSS).

OPTIONS OF ISGS : (i)REDUCE INJECTION BY REDUCING OWN GENERATION. (IF SYSTEM FREQUENCY IS HIGHER THAN THE STATIONS THRESHOLD FREQUENCY) CONTINUE TO UNDER-INJECT, IN EFFECT SUPPLYING UI TO THE GRID. THIS IS ADVANTAGEOUS AS LONG AS THE SYSTEM FREQUENCY IS HIGHER THAN THE STATION’S THRESHOLD FREQUENCY (ii)CONTINUE TO GENERATE AS PER SCHEDULE THUS AVOID ANY UI IMPLICATION TILL THE BENEFICIARIES REVISE THEIR REQUISITION AND REVISED SCHEDULES ARE ISSUED BY RLDC. (iii)ENTER INTO A BILATERAL AGREEMENT WITH OTHER SEB/REGION TO SUPPLY SURPLUS /IDLING CAPACITY

FREQUENCY IS GOOD OR HIGH THE ISGS IS OVER GENERATING THE ISGS IS UNDER GENERATING FREQUENCY IS LOW THE ISGS IS UNDER GENERATING THE ISGS IS OVER GENERATING What all can happen on the day of Operation?

FOUR SCENARIOS A)FREQUENCY IS GOOD OR HIGH, AND THE ISGS IS UNDER GENERATING OPTIONS OF ISGS: i)INCREASE GENERATION IF THE SYSTEM FREQUENCY IS BELOW THE STATION’S THRESHOLD FREQUENCY. ii)REDUCE OWN GENERATION TO THE EXTENT POSSIBLE AND THUS REDUCES NET INJECTION SO LONG AS FREQUENCY IS ABOVE THE STATION’S THRESHOLD FREQUENCY. iii)GENERATE AS PER SCHEDULE (NO UI IMPLICATION)

FOUR SCENARIOS B.FREQUENCY IS GOOD OR HIGH, AND THE ISGS IS OVER GENERATING OPTIONS OF ISGS : i)REDUCE OWN GENERATION TO THE EXTENT POSSIBLE, IF THE FREQUENCY IS ABOVE THE STATIONS THRESHOLD FREQUENCY. ii)INCREASE GENERATION IF FREQUENCY IS BELOW THE STATION’S THRESHOLD FREQUENCY iii)GENERATE AS PER SCHEDULE (NO UI IMPLICATION) C)FREQUENCY IS LOW, AND THE STATION IS UNDER GENERATING OPTIONS OF ISGS : i)INCREASE OWN GENERATION TO THE MAXIMUM POSSIBLE EXTENT AS LONG AS THE FREQUENCY IS BELOW THE STATION’S THRESHOLD FREQUENCY (THUS RECEIVE UI). ii)GENERATE AS PER SCHEDULE – NO UI IMPLICATION.

FOUR SCENARIOS D.FREQUENCY IS LOW, AND THE ISGS IS OVER GENERATING NO ACTION REQUIRED FOLLOWING CAN BE DONE FOR ENHANCED OPTIMIZATION. 1.INCREASE OWN GENERATION TO THE EXTENT POSSIBLE, PROVIDED THE FREQUENCY IS BELOW THE STATION’S THRESHOLD FREQUENCY. (THUS RECEIVE UI) 2.GENERATE AS PER SCHEDULE – NO UI IMPLICATION. ACTION DEPENDS ON PREVAILING FREQUENCY, THE STATION’S THRESHOLD FREQUENCY AND IS INDEPENDENT OF WHETHER OVER-GENERATING OR UNDER-GENERATING. IT FOLLOWS THAT ON-LINE MEASUREMENT AND DISPLAY OF TELEMETERED DATA IS NOT ALL THAT CRITICAL

UNSCHEDULED INTERCHANGES (UI) i.e. deviation from schedules ENCOURAGE if good for the grid, DISCOURAGE if bad for the grid but allows because it enables meeting more demand and enhances merit order Good UI helps in improving frequency, and enables one constituent to help the other (for meeting more consumer demand i.e. reducing load shedding) UI provide the mechanism for on line displacement of costlier generation by cheaper generation: ULTIMATE OPTIMISATION

ACTION DEPENDS ON PREVAILING FREQUENCY, AND IS INDEPENDENT OF WHETHER OVER-DRAWING OR UNDER-DRAWING. IT FOLLOWS THAT ON LINE MEASUREMENT AND DISPLAY OF CORRECT NET DRAWAL IS NOT ALL THAT CRITICAL.

UI = x – Scheduled Drawal G L X IMPORT X = L - G

AP DRAWAL ON A TYPICAL DAY

HYPOTHETICAL

FEATURES OF SPECIAL ENERGY METERS : ACCURACY : 0.2 S AS PER OEC -687, 1992 STATIC, TOTALLY TAMPER - PROOF, SEALED FOR LIFE GALVANIC ISLATION AND SURGE SUPRESSION TWO STANDARD MODELS : 110V, 1A AND 110V, 5A NON - VOLATILE MEMORY FOR 10 DAYS HARMONICS FILTERED OUT AND ONLY FUNDAMENTAL ENERGY RECORDED ALL MEASUREMENTS, RECORIDNG IN SECONDARY QUANTITIES. CT AND VCT RATION APPLIED IN REGIONAL COMPUTATION NET ENERGY ( WH) EXCHANGE IN EACH 15 MIN. BLOCK CUMULATIVE WH TRANSMITTAL AT EACH MIDNIGHT AVERAGE FREQUENCY IN EACH 15 MIN. BLOCK CUMULATIVE REACTIVE ENERGY EXCHANGE WHILE VOLTAGE IS 97% OR BELOW CUMULATIVE REACTIVE EXCHANGE WHILE VOLTAGE IS 103% OR ABOVE.

HIGH-ACCURACY OF INTERNAL CLOCK: ONE MINUTE/MONTH,WITH RESTRICTED ADVANCE/ RETARD FACILITY TAGGING OF DATA WITH DATE, TIME METER NO. IDENTIFICATION OF TIME BLOCK WHEN VT SUPPLY DISTRUBED NO SEPARATE AUXILIARY SUPPLY ; ONLY OPTICAL COUPLER FOR DATA COLLECTION ( WEEKLY) DISPLAYS TO APPRISE THE SUBSTATION OPERATOR AS TO WHAT IS BEING RECORDED IN METERS MEMORY

SEB’S OPTIONS TO EVENTS 1.PROSPECTIVE REVISION OF ISGS AVAILABILITY (UPWARD/DOWNWARD) SCHEDULE REVISED FOR REMAINING PART OF THE DAY 2. TRIPPING OF A ISGS UNIT (KNOWN AFTER THE EVENT) IMMEDIATE FREQUENCY DIP ALL OPERATING UNITS PICK UP EXTRA MW SEB’S DRAWAL REDUCES  SEB RECEIVES UI PAYMENT SEB’S OPTIONS: (I)DRAW AS PER SCHEDULE AND FOREGO ADVANTAGE OF UI (II)REDUCE NET DRAWAL BY INCREASING OWN GENERATION AND/OR REDUCING LOAD > RECEIVE UI PAYMENT TILL ISGS REVISES ITS AVAILABILITY AND NEW SCHEDULES COME INTO EFFECT

3.TRIPPING OF THE SEB’S OWN GENERATING UNIT SEB’S NET DRAWAL INCREASES  SEB HAS TO PAY UI SEB’S OPTIONS (I)CONTINUE TO OVERDRAW AND PAY UI (II)REDUCE NET DRAWAL BY CARRYING OUT CORRESPONDING LOAD SHEDDING AND/OR RUN UP ALL AVAILABLE GENERATION (III) INCREASE ISGS REQUISITION, IN CASE FULL ENTITLEMENT WAS NOT REQUISITIONED EARLIER (IV) ENTER INTO A BILATERAL WITH OTHER SEB/ISGS TO DRAW ANY SURPLUS/IDLING CAPACITY

4.LOAD CRASH IN THE STATE: FREQUENCY INCREASES UNDER DRAWAL FROM THE GRID  UI IMPLICATION (NET GAIN/LOSS) SEB’S OPTIONS: (I)INCREASE DRAWAL BY REDUCING OWN GENERATION (IF UI RATE IS LOWER THAN THE RESPECTIVE ENERGY RATE) RESTORE DISCONNECTED LOADS (IF UI RATE IS LOWER THAN THE RECOVERY RATE) REDUCE ISGS REQUISITION (IF UI RATE FALLS BELOW ISGS ENERGY RATE) CONTINUE TO UNDER DRAW, IN EFFECT SUPPLYING UI TO THE GRID. THIS IS ADVANTAGEOUS AS LONG AS THE UI RATE IS HIGHER THAN THE ENERGY RATE

FOUR SCENARIOS …1 A.FREQUENCY IS GOOD OR HIGH, AND THE STATE IS OVERDRAWING: -NO PROBLEM, AND NO ACTION REQUIRED FOR ENHANCED OPTIMIZATION, HOWEVER TO THE EXTENT POSSIBLE. (I)REDUCE OWN GENERATION TO THE EXTENT POSSIBLE AND INCREASE OVERDRAWAL SO LONG AS FREQUENCY IS ABOVE ABOUT 49.8 HZ. (II) RESTORE CONSUMER LOAD THAT HAD BEEN SHED, PROVIDED TARIFF/REALIZATION RATE IS HIGHER THAN CURRENT UI RATE. (THIS ALSO INCREASES OVERDRAWAL) (III) INCREASE ISGS REQUISITION, IF SOME PART OF THE ENTITLEMENTS HAD NOT BEEN REQUISITIONED EARLIER, PROVIDED THE FREQUENCY IS (AND IS LIKELY TO REMAIN) BELOW ABOUT 50.2 Hz. (THIS WOULD INCREASE THE DRAWAL SCHEDULE AND THEREBY REDUCE OVERDRAWAL)

FOUR SCENARIOS …2 B. FREQUENCY IS GOOD OR HIGH, AND THE STATE IS UNDER DRAWING: ACTION REQUIRED (I)REDUCE OWN GENERATION TO THE EXTENT POSSIBLE, IF THE FREQUENCY IS ABOVE ABOUT 49.8 HZ. (THIS WOULD REDUCE UNDERDRAWAL) (II) RESTORE CONSUMER LOAD THAT HAD BEEN SHED, AND REDUCE UNDERDRAWAL (III) REDUCE ISGS REQUISITION, PROVIDED THE PREVIOUS TWO ACTIONS HAVE BEEN TAKEN AND THE FREQUENCY CONTINUES TO BE ABOVE HZ. IF FREQUENCY IS LIKELY TO REMAIN ABOVE 50.2 HZ., BILATERAL SALE TO A NEEDY NEIGHBOUR CAN BE TRIED C. FREQUENCY IS LOW, AND THE STATE IS OVERDRAWING: ACTION REQUIRED (I)INCREASE OWN GENERATION TO THE MAXIMUM POSSIBLE EXTENT (II) CURTAIL CONSUMER LOAD, LOAD SHEDDING TO BE GRADED BALANCING BETWEEN UI PRICE AND CONSUMER CATEGORY (III) INCREASE ISGS REQUISITION TO FULL ENTITLEMENT (IF NOT REQUISITIONED FULLY EARLIER), AND ARRANGE FOR BILATERAL PURCHASE FROM ANOTHER SEB/ISGS

FOUR SCENARIOS …3 D. FREQUENCY IS LOW, AND THE STATE IS UNDERDRAWING: NO ACTION REQUIRED; FOLLOWING CAN BE DONE FOR ENHANCED OPTIMIZATION. (I)INCREASE OWN GENERATION TO THE EXTENT POSSIBLE, PROVIDED THE FREQUENCY IS BELOW ABOUT 49.5 HZ. (COMPARING VARIABLE COST WITH CURRENT UI PRICE) (II) CURTAIL CONSUMER LOAD,BY SHEDDING LOW PRIORITY LOAD (PROVIDED UI EARNING FOR THE SEB JUSTIFIES SUCH LOAD SHEDDING). THIS IS TOTALLY OPTIONAL, AND HELPS THE GRID (III) INCREASE ISGS REQUISITION TO FULL ENTITLEMENT (IF NOT REQUISITIONED) FULLY EARLIER), AND EARN UI OR SELL THE SURPLUS THROUGH A BILATERAL AGREEMENT ACTION DEPENDS ON PREVAILING FREQUENCY, AND IS INDEPENDENT OF SHETHER OVERDRAWING OR UNDERDRAWING. IT FOLLOWS THAT ON-LINE MEASUREMENT AND DISPLAY OF CORRECT NET DRAWAL IS NOT ALL THAT CRITICAL.

MANAGEMENT OF DRAWALS CURTAILMENT OF DRAWAL BY SEB A)IF UI RATE IS HIGHER THAN THE HIGHEST ENERGY RATE OF THE STATIONS SCHEDULED, THEN CURTAIL DRAWAL BY MAXIMISING CHEAPER GENERATION B) IF UI RATE IS HIGHER THAN CONSUMER LOAD NET RECOVERY RATE THEN CURTAIL DRAWAL BY LOAD SHEDDING