AVAILABILITY BASED TARIFF
SCHEDLING PROCEEDURE
AND
SETTLEMENT MECHANISM
UNDER ABT REGIME
T. SRINIVAS
MANAGER,SRLDC
BANGALORE
LINKS
GIST OF CGS
SETTLEMENT
SYSTEM
BRIEF OF ABT
UI
SCHEDULING
PROCEDURE
SOUTHERN REGIONAL GRID
▀
Central Generating Stations in the Region are
•
Ramagundam Super Thermal Power Stn. : 2,600 MW (200x3 + 500x4)
•
Neyveli Lignite Corporation Ltd. - II
: 1,470 MW (210 x 7)
•
Madras Atomic Power Station
: 390 MW (170 x 1 + 220X1)
•
Kaiga Atomic Power Station
:
440 MW (220x2)
•
NLC EXPANSION TPS 1
:
420 MW
•
TALCHER STAGE II
: 2000 MW
▀ Beneficiaries
in southern Region are
.
ANDHRA PRADESH
•
•
•
•
•
•
KARNATAKA
KERALA
TAMIL NADU
Union Territory of Pondicherry
NLCMINES
GOA has share of 100MW from RSTPS
(210X2)
(500X4) situated
in ER
CONTROL AREAS
CS - 2
CS - 1
CS -3
REGIONAL GRID
RLDC
COORDINATES
SEB - A
STATE
IPP
SEB -B
STATE
GENR
SEB’S GRID
DISTR
-A
DISTR
-B
SEB -C
CENTRAL
SHARE
SLDC
COORDINATES
DIRECTS
DISTR
-C
AC TRANSMISSION NETWORK IN
SR
JEYPORE
SIMHADRI NTPC
8x4
400 KV LINE
PRESENTLY
OPERATED AT 220 KV
RSTPP
1
GAZUWAKA(AP)
15x2
VISAKHAPATNAM
P
HYDERABAD
P
P
KHAMMAM
P
MMDP
P
VIJAYAWADA
P
RAICHUR
NAGARJUNASAGAR
Nagjhari
SSLMM
MUNIRABAD
KODASAALY
P
KAIGA
P
SIRSI
N
KURNOOL
GOOTY
P
CUDDAPAH
DAVANAGERE
KADRA
NELLORE
HIRIYUR
NELAMANGALA BANGALORE
ALMATHI
P
KOLAR
HOSUR
HOODY
TALGUPPA
SALEM
MAPS
PONDICHERY
P
NEYVELI
UDUMALPET
TRICHUR
MADRAS
P
TRICHY
P
P
P
MADURAI
PALLOM
KAYANKULAM
2x78
THIRUVANATHAPURAM
P
THIRNELVALI
KOODANKULAM
(POWERGRID)
TALCHER
BHADRAVATI
JEYPORE
SIMHADRI NTPC
RSTPP
P
KHAMMAM
HYDERABAD
GAZUWAKA
P
P
KALPAKKA
(POWERGRID)
P
MMDP
P
RAICHUR
KURNOOL
MUNIRABAD
VIJAYAWADA
N’SAGAR
P
SSLMM
P
KAIGA
N
SIRSI
P
GOOTY
CUDDAPAH
P
1000 MW HVDC BACK TO BACK LINK
GUTTUR
NELLORE
HIRIYUR
TALGUPPA
NELAMANGALA
BANGALORE
2000 MW HVDC BIPOLE
P
P
KOLAR
HOODY
MADRAS
500 KV HVDC LINE
HOSUR
400 KV LINE POWERGRID
SALEM
NEYVELI
NEYVELI
TPS – 1 (EXP)
400 KV LINE APTRANSCO
EXP
UDUMALPET
TRICHUR
400 KV LINE KPTCL
P
TRICHY
P
400 KV LINE OPERATED AT 220 KV
MADURAI
THERMAL GENERATING STATION
400KV SUB-STATION
THIRUVANANTHAPURAM
MAJOR GENERATORS
FROM TALCHER (4 x 500MW)
SCATTERED ACROSS SR
MAJOR LOAD CENTRES SCATTERED ACROSS SR
LOAD 500-1500 MW
LOAD 200-500 MW
±500KV
KOLAR
- HYDRO
- THERMAL
GENERATORS ABOVE 1000 MW
- GAS / NAPTHA
GENERATORS 500 – 1000 MW
GENERATORS BELOW 500 MW
KUDAKULAM APP
2 x 1000MW
- NUCLEAR
BACK
CONVENTIONAL METHOD OF OPERATION


SHARE BASED ON ACTUAL GENERATION:
DOES NOT REFLECT THE AVAILABILITY OF
ISGS –RATHER ITS EX-BUS GENERATION

IS FIXED AND TIME INVARIANT

INSENSITIVE TO CONSTRAINTS

DOES NOT ALLOW FOCUSED CHANGES
SUB OPTIMAL UTILIZATION OF
RESOURCES
CONVENTIONAL METHOD OF ENERGY
ACCOUNTING




PAYMENTS ARE MADE AS PER THE
DRAWALS
OVER AND UNDER DRAWALS UNAVOIDABLE
UNUTILISED RESOURCES ARE OFTEN
BILLED.
INFLEXIBLE – BILATERALS, SHORT TERM
CONTRACTS – NOT ALLOWED
ADVANTAGES OF SCHEDULING








SCHEDULE REFLECTS BOTH –AVAILABILITY
OF ISGS & REQUIREMENT OF CONSTITUENT
FLEXIBILITY
TIME VARIANT - MIRRORS GRID
BEHAVIOUR
SENSITIVE TO CONSTRAINTS
FOCUSED – SCHEDULE IS NON GENERIC
OPTIMAL UTILIZATION OF RESOURCES
ECONOMIC OPERATION
INDEPENDENT OF SETTLEMENT SYSTEM.
CHAPTER-7
SCHEDULING & DESPATCHING CODE
Demarcation of Responsibilities
.
Each Region is a loose power pool and each state is a notional Control Area.
(Decentralized Scheduling and Dispatch)
.
RLDC can direct SLDCs/ISGSs in case of system contingencies, to change
drawal/injection and if time permits, RLDC will ascertain whether situation
has arisen due to
=> Deviations from schedule
=> Bilateral Exchange or Short Term Open Access
.
.
.
These can be terminated by RLDC.
All joint/bilateral agreements to be filed with RLDC/REB Secretariat
SEMs to be installed by CTU at all interconnection points for recording Actual
Interchanges and MVARh drawals.
Regional Energy Accounting to be done by REB Sectt.based on metered and
processed data (Actual net injection of ISGS and actual net drawal of each
beneficiary) received from RLDC .
SRLDC/Comml/IEGC/33
Settlement Systems*
.
Accounting on weekly basis
.
Capacity and Energy Charges billing on monthly basis
•
Billing of adjustments for deviations on weekly basis
•
RLDC to furnish data to REB Secretariat by Thursday noon for week ending
Sunday
.
REB Secretariat to finalize and issue REA by Tuesday, for seven day period
ending on penultimate Sunday
.
All data to be retained for 20 days (for RLDC & REB) for verification.
Commercial Mechanism *
Availability Based Tariff
SRLDC/Comml/IEGC/34
( a) Capacity Charge
(b) Energy Charge
(c) Adjustment for Deviations
Scheduling Process
On Day-l
10 AM
ISGSs advise foreseen plant-wise ex- . power plant MW, MWh *
capability for next day
11 AM
RLDC advises SEBs their MW, MWh* shares in foreseen ISGSs'
availability
3 PM
SLDCs furnish their ,time-wise MW requisition from the above,
and schedule of bilateral exchanges, if any
5 PM
RLDC issues' despatch schedules' for ISGSs and 'net drawal
schedules' for SEBs, for each hour the next day starting at
midnight
10 PM
SLDCs may inform any change of the above or bilateral
exchanges to RLDC, if required by any new development during
the day
11 PM
Schedules frozen for the next day. RLDC Issues final drawal
schedules to each State & Despatch schedule to each ISGS
SRLDC/Comml/IEGC/41
On Day 0
Time block t
Time block t+3
Any State may revise drawal schedule from
any/all ISGS Any ISGS may revise their
foreseen capability
RLDC to issue revised ‘drawal schedules'
and despatch schedules
On Day + 1
.
RLDC to issue before-the- fact Capacity Declaration/Schedules
finally implemented by RLDC (Datum for accounting and working out
average ex-power plant capability).
SRLDC/Comml/IEGC/42
Scheduling Process
Scheduling for the next day
• Every day by 10 AM, RLDC collects the foreseen plant-wise ex-power
plant MW capability of ISGSs for the next day
• By 11 AM, RLDC advises SEBs, on a 15 minutes blockwise level, their
entitled MW shares from each ISGSs’ availability
• By 3 PM, RLDC receives block-wise MW requisition from SLDCs and
also the schedule of bilateral exchanges, if any
• By 5 PM, RLDC issues ‘despatch schedules’ for ISGSs and ‘net drawal
schedules’ for SEBs, 15 minutes block-wise for the next day starting at
midnight.
• Upto 10 PM SLDCs may inform any change of the above or bilateral
exchanges to RLDC, if required by any new development during the day.
• At 11 PM Schedules are frozen for the next day. RLDC issues final drawal
schedules to each State & Despatch schedule to each ISGS.
Scheduling Process
Any change of schedule for the current day
• In case of any forced outage of a unit, or in case of any transmission
bottleneck or in the interest of better system operation, RLDC may revise
the schedules. The revised schedules will become effective from the 4th time
block.
• ISGSs and/or SLDCs may also revise their schedules during a day. The
revised schedules will become effective from the 6th time block.
REVISION OF SCHEDULES/REQUISITIONS
A)
B)
C)
D)
OUTAGE OF GENERATING UNIT
REVISED DECLARATION OF AVAILABILITY BY ISGS
OUTAGE OF A TRANSMISSION ELEMENT
UNFORESEEN LOAD-CRASH
TAKES EFFECT FROM
A)
-
4TH TIME BLOCK IN CASE OF
FORCED OUTAGE OF A GENERATING UNIT
TRANSMISSION CONSTRAINT
GRID DISTURBANCE
SUO MOTO BY RLDC
B) 6TH TIME BLOCK IN CASE OF
REVISION OF DECLARED AVAILABILITY BY ISGS
REVISION OF REQUISITIONS BY BENEFICIARIES
A new scheduling software in Visual Basic is
developed by SRLDC which has the following
advantages:
-
Minimize data entry errors.
Faster reconciliation of schedules
Facilitate electronic data transfer
Modularly structured, simple and practicable
SCHEDULING METHODOLOGY
The station-wise (Ex-bus) capability
would be submitted by the ISGSs in
the specified format. ISGSs would
declare the capability i.e. the MW
and MWH quantum in the absolute
values and not in the form of some
relative percentages or in any other
manner.
SCHEDULING METHODOLOGY
Based on the declared capability &
the allocations of different States /
Beneficiaries in different ISGSs, the
station wise entitlements would be
worked out and intimated to all the
States/Beneficiaries by SRLDC.
SCHEDULING METHODOLOGY
The requisitions would be submitted
by the States in the specified format.
The States would submit the
requisitions indicating the quantum
desired
against
the
given
entitlement, and not the quantum
surrendered.
The requisitions in
case of nuclear and run of the river
hydro stations would be equal to the
entitlements.
SCHEDULING METHODOLOGY
The details of the despatch and drawal
schedules and Unrequisitioned, surpluses
shall be made by SRLDC and the information
would be exchanged through fax and/or
through FTP.
SCHEDULING METHODOLOGY
In the event of any unrequisitioned
surpluses, the Owner State ( the State to
which the share actually belongs and
pays the capacity charges) may find out a
suitable Buyer/ Willing State to take such
unrequisitioned
surplus
and/or
the
Buyer/Willing
State may contact the
Owner State for such exchange.
The
agreed
Short
Term
Open
Access
Transactions be intimated / consented to
SRLDC
by
both
the
States
for
incorporating in the final schedules.
SCHEDULING METHODOLOGY
Any unrequisitioned surpluses still
available, can be agreed for Short
Term Open Access Transactions
between the concerned ISGS and
one or more desiring States. The
agreed Short Term Open Access
Transactions from ISGS to a State be
intimated to SRLDC by both the
agencies (ISGS as well as States) for
incorporation in the final schedule.
SCHEDULING METHODOLOGY
During the current day in case the
Owner State requisitions back its
surrendered share, then the same is
withdrawn from the other State/
States to which it was allocated as
surplus energy and the schedules
are revised in line with the Grid
Code.
SCHEDULING METHODOLOGY
While making or revising their
declaration
of
capability
the
generators shall ensure that the
declared capability during peak
hours is not less than during other
hours.
SCHEDULING METHODOLOGY
While communicating
States shall ensure that:


the requisitions, the
maximum economy and efficiency in the
operation of the power system in the State
is achieved while requisitioning and /or
surrendering power from different ISGSs
vis-à-vis from their own stations.
the
requisitions
are
operationally
reasonable,
particularly
in
terms
of
ramping-up / ramping-down rates and ratio
between
minimum
and
maximum
generation levels, and are in line with the
agreed philosophy in the region amongst
different agencies.
SCHEDULING METHODOLOGY
In the event of despatch schedule in respect of a
particular ISGS, (as agreed between ISGS and
the State constituents in respect of thermal
units it would be taken as 70%) the changes in
requisition between two successive blocks is
higher than a ramp up/down quantum, then the
State/States due to which such anomaly is being
experienced would be requested by SRLDC to
change its/their requisition in that particular
ISGS,
to make the schedule
operationally
reasonable.
SCHEDULING METHODOLOGY
While issuing the final schedules, SRLDC
shall check that the schedules do not give
rise to any transmission constraints. In
case
any
imperssible
constraints/
anomalies are foreseen, the RLDC shall
moderate the schedules to the required
extent
, under intimation to the
concerned agencies.
SCHEDULING METHODOLOGY
During the periods of low demand in the region,
in spite of all efforts if the despatch schedule of
an ISGS(s) during certain blocks in the off-peak
period remains below the minimum agreed
value, and the concerned ISGS (s) is not able to
operate the units due to technical constraints,
then the concerned ISGS(s) may close down
some unit(s) in consultation with SRLDC and the
despatch schedule of the ISGS(s) shall be revised
accordingly. Under such a situation the net
drawal schedule of the beneficiary (ies) having
share in the ISGS(s), may get reduced during
peak hours also.
SCHEDULING METHODOLOGY
If at any
point of time SRLDC
observes that there is need for
revision of schedules in the interest
of better system operation, it may
do so on its own and make it
effective in line with the grid code
provisions.
SCHEDULING METHODOLOGY
While entering
into a bilateral
agreement, the concerned parties
shall ensure that the agreements are
clear and explicit and contains all
the relevant details which may be
necessary from scheduling and
computation of energy flow.
BACK
Payment to Inter State Generating
Stations (ISGS) from beneficiaries under
Availability Based Tariff
(ABT)



Capacity charges
Energy charges
Unscheduled Interchange (UI)
CAPACITY CHARGE
Capacity charge will be related to
‘availability’ of the generating
station and the percentage capacity
allocated to the state. ‘Availability’
for this purpose means the
readiness of the generating station
to deliver ex-bus output expressed
as a percentage of its rated ex-bus
output capability.
ENERGY CHARGE
Energy charges shall be worked out
on the basis of a paise per kwh rate
on ex-bus energy scheduled to be
sent out from the generating station
as per the following formula
Energy charges =
Rate of energy
charges
(paise/kwh) x Scheduled
Generation (ex-bus MWh)
UNSCHEDULED INTERCHANGE (U I) :



Variation in actual generation / drawal with
respect to scheduled generation / drawal
shall be accounted for through Unscheduled
Interchange (UI).
UI for generating station shall be equal to
its total actual generation minus its
scheduled generation.
UI for beneficiary shall be equal to its total
actual drawal minus its total scheduled
drawal.
UNSCHEDULED INTERCHANGE (U I) :
UI shall be worked out for each 15
minute time block.
 Charges for all UI transactions shall be
based on average frequency of the
time block.
 UI rates shall be frequency dependent
and uniform throughout the country.

UI
RATE
650
----------------->
600
Below 49.0 Hz UI rate =570 p/u
550
Rate of Unscheduled Drawal/Injection
Frequency (Hz)
Above 50.5
500
450
400
Rate (p/u)
0
50.0
150
49.8
210
49.0 and below
570
350
At 49.8 Hz UI rate =210 p/u
300
UI rate
250
200
At 50.0 Hz UI rate =150
p/u
Above 50.5 Hz UI rate =0
p/u
150
100
50
0
48.9 49
49.1 49.2 49.3 49.4 49.5 49.6 49.7 49.8 49.9
50
50.1 50.2 50.3 50.4 50.5 50.6 50.7 50.8 50.9 51
Frequency ----------->
AVAILABILITY BASED TARIFF
CAPACITY CHARGE
(B)
ENERGY CHARGE
(C)
ADJUSTMENT FOR DEVIATIONS
(U I CHARGE)
(A) = a function of the Ex-Bus MW availability of Power
(A)
Plant for the day declared before the day starts
x
SEB’s % allocation from the plant
(B) = MWh for the day as per Ex-Bus drawal schedule for the
SEB finalised before the day starts x Energy charge
rate
(C) = Σ (Actual energy interchange in a 15 minute time block
– scheduled energy interchange for the time block) x
UI rate for the time block
TOTAL PAYMENT FOR THE DAY = (A) + (B) ± (C)
FEATURES :

(A) and (B) do not depend on actual plant
generation / drawal. No metering required
for this as they are based on off-line figures.
All deviations taken care of by (C)


No
complication
generation.
regarding
deemed
Perpetual
incentive
for
maximizing
generation and reducing drawal during
deficit, but no incentive to over generate
during surplus.
BACK
UI IN SR (FROM 01/01/03 TO 04/12/05)

TOTAL UI TURNOVER :- 10141 MU

TOTAL UI AMOUNT DISBURSED:- 1933 CR

AVG WEEKLY TRANSACTION:- 66 MU

AVG WEEKLY UI AMOUNT DISBURSED:- 13 CR
Contd..
SUMMARY OF UI – 153WKS
(FROM 01/JAN/03 TO 04/DEC/05)
AP
Total UI
exported(-) /
Imported(+) in -4688
MUs
KAR
KER
TN
PONDY
4734
679
1702
-199
Total amount
paid in Crores
Rs.
-899
862
117
448
-36
Average rate of
UI in
paise/unit
192
182
173
263
183
Contd..
OD UD AND UI RATES OF CONSTITUENTS
400
379
RATE (PAISE/UNIT)
350
300
234
250
200
200
150
100
50
2
2
6
M
U
4
9
1
4
M
U
0
AP
182 184
4
3
7
1
6
MU
6
MU
KAR
OVER DRAWAL (PURCHASE)
179 185
1
3
1
5
MU
6
3
6
MU
KER
2
2
8
1
MU
149
5
7
9
M
U
TN
UNDER DRAWAL (SOLD)
Inter Regional Links
1650 MW
700 MW
1850 MW
900 MW
30,500 MW
2300
16,000
32,700 MW
1200 MW
1200MW
2000MW
34,500 MW
Present IR Capacity
= 9,500 MW
Contd..
DEVELOPMENT
OF NATIONAL
GRID
INTER REGIONAL
LINKS
TALCHER KOLAR HVDC
PHASE-I
LINE
(By 2002)
LENGTH:100 KMS
NR
NER
AURAIYA
500
500
MW
KOTLA MALANPUR
SAHUPURI
MW
SASARAM
DEHRI
VINDHYACHAL
UJJAIN
KORBA
BONGAIGAON
ER
BUDHIPADAR
CHANDRAPUR
WR
BIRPARA
MALDA
TALCHER
ORISSA)
1000
MW
BALIMELA
500
MW
KOLHAPUR
KOLHAPUR
U.SILERU
GAZUWAKA
EXISTING
CHIKKODI
BELGAUM
UNDER
CONST.
EXISTING
KOLAR
(KARNATAKA)
220 kV
HVDC STATION
N
ANDAMA
R
NICOBA
&
P
EE
DW
HA
KS
LA
SR
400 kV
INTER REGIONAL EXCHANGES
350
RATE (PAISA/KWH) - >
300
IMPORT BY SR FROM WR
(668 MU)
265
250
IMPORT BY SR FROM ER
(805 MU)
221
200
150
150
138
100
50
0
SR RATE WR RATE
SR RATE ER RATE
INTER REGIONAL EXCHANGES
350
EXPORT BY SR TO WR
(610 MU)
286
RATE (PAISA/KWH) ->
300
EXPORT BY SR TO ER
(311 MU)
295
250
200
150
146
139
100
50
0
SR RATE WR RATE
SR RATE ER RATE
INTER-REGIONAL EXCHANGES DETAILS
UPTO 151 WKS (Till 20.11.05)
Net Energy
Transaction
Amount Due to
SR Constituents
Amount Credited
TO SR
Constituents
WR
ER
57.5 MU
IMPORT BY
SR
Rs. 79.7 Cr.
493.9MU
IMPORT BY SR
Rs. 76.2 Cr.
Rs. 24.5 Cr.
Rs. 24.5 Cr.*
*from 06.09.04 (when ER exchanges computed @ respective frequencies)