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System Operations through National & Regional Load Dispatch Centres
2nd Interactive Workshop on
‘Transmission & Distribution’
17th-18th April 2009
at Hotel Sahara Star, Nr. Domestic Airport, MumbaiOrganized by India-Tech Foundation
Outline• Overview of Indian Power System
• System Operation
• Power Market
• Transfer Capability
• Open Access in Inter-state transmission
• Congestion Management
• Challenges and Concerns
NEW Grid
SouthGrid
South
West
North
East
Northeast
Five Regional GridsFive Frequencies
October 1991East and Northeast
synchronized
March 2003West synchronized
With East & Northeast
August 2006North synchronized
With Central Grid
Central Grid
Five Regional GridsTwo Frequencies
Installed Capacity 147 GW
MERGING OF
MARKETS
Renewable Energy : Wind Power
Total Renewable Energy Sources ~ 13 GW
Wind Installed Capacity ~ 9 GW
Estimated Wind Potential ~ 45 GW
India: 5th Largest Wind Power Producer
Growth in Inter-regional Transmission Capacity
Source: CEA
IR CAPACITY : 20800 MW
Growth of IR Exchanges
Development of Load Despatch Centres• Initial stages
– a telephone/hotline communication system and a frequency meter– Operational only during day-time– Acted mainly as an information centre
• State grid interconnections– 24x7 operation– Rudimentary data acquisition systems
• Central Sector generating stations– Interstate scheduling and energy accounting
• Regional Grid formation & CTU– Modernization of control centres
• Availability Based Tariff– 15-minute scheduling, metering settlement– Market operation
Modernization of Control Centres• 33 SLDCs, 5 RLDCs, 1 NLDC• Round-the-clock manning • Wideband speech and data communication• Fish as well as bird eye view through SCADA• Common database in SLDC/RLDC• Common Information Model (CIM) in NLDC• Classical data presentation plus alarm processing,
exception lists, animation, geographical displays• Multilayering, Trending• SoE and replay
Jurisdiction of Load Despatch CentersNLDC:Apex body to ensure integrated operation of National Power System
RLDC:Apex body to ensure integrated operation of power system in the concerned region
SLDC:Apex body to ensure integrated operation of power system in a state31
5
Jurisdiction of RLDCs/SLDCs• Control Area
• Scheduling Responsibilities – RLDCs
• State as a whole
• ISGS /UMPPs,
• Pvt. Generating Stations > 1000 MW and
having > 50% share of state outside home state#CERC Order 58/2008, Suo Moto
– SLDCs• State Utilities ( SGS / Discoms)
• Intra-State Entities
National Load Despatch Center (NLDC)
ERLDC WRLDC NERLDC
BACKUPNLDC, KOLKATA
MAIN NLDC, DELHI
SRLDCNRLDC
F.O. Cable on each 2E1 Link
Copper Cable –(Backup)
VSAT– (Backup) each 64Kb/s
Functions of Load Dispatch Centers– Optimum scheduling and dispatch of electricity
– Monitoring of operations and grid security
– Keeping accounts of the quantity of electricity transmitted through the regional grid
– Supervision and control over the transmission system
– Real time operations for grid control
– Dispatch of electricity through secure and economic operation of in accordance with the Grid Standards and the Grid Code
Electricity Act 2003
Foundation Stones
IEGC ABT
System Operation
• Two firm footings
– INDIAN ELECTRICITY GRID CODE (IEGC)
– AVAILABILITY BASED TARIFF (ABT)
Regional Grid Operation: Philosophy
• Operated as loose power pools• States have full operational autonomy• State power system treated as notional (flexible)
control area• Very tight control of actual interchange by state
utilities & Inter State Generating Stations not mandated
• Deviations from net drawal schedules appropriately priced
GRID MANAGEMENT FUNCTIONS• Ex-ante functions
– Scheduling
• Real-time functions– Supervision & control of system parameters– Facilitating Open Access transactions
• Post-facto functions– Settlement system operation
• Interaction with stakeholders
Balancing market guiding vector
UI mechanism
• Maximizes social welfare• Transparent, neutral & rigging proof• Diffuses market power • Ultimate open access• Facilitates reforms in the sector• Encourages trade and bilateral exchanges• Facilitates exchanges (arbitrage) between regional
power pools
The End Result ….• Frequency is
– collectively controlled– democratically stabilized
• Wholesale market is workably competitive – allocative efficiency– productive efficiency
• Economic signal available for – optimum utilization of resource – investments in generation capacity
• Settlement is– streamlined – dispute-free
INDIAN ELECTRICITY MARKETENABLERS
Legislation
Indian Electricity Act 2003
National Electricity Policy
12-Feb-2005, Para 5.7.1(d)
Regulation
IEGC-Feb 2000
ABT Order-Jan2000
Open Access-May-2004
Power Exchange-Aug-2007
Execution
CTU/STU, RLDC/SLDC
Grid & Market Operation
Control Centres & SEMs
ABT settlement: in stages 2002-03
STRUCTURE
Balancing Mechanism
Frequency linked
Unscheduled Interchange
Intra-day STOA
Day-ahead Power Exchange
Multiple Power Exchanges
Short-term Bilateral
Day-ahead
First-come-first served
Three-month ahead
Long-term Bilateral
Shared resources (ISGS)
Own resources
Grid CodeFeb.’2000
SettlementSystem2002-03
Open Access2004
PX 2008
Ancillaries,
Evolution of Power Market in India
Market Design
IMBALANCESCONGESTIONMANAGEMENT
ANCILLARYSERVICES
SCHEDULING &
DISPATCH
ELECTRICITY MARKET
“Making Competition Work in Electricity”, Sally Hunt
Four Pillars of Market Design
Apr 18, 2023 22
Total Transfer Capability
Voltage Limit
Thermal Limit
Stability Limit
Total Transfer Capability
Total Transfer Capability is the minimum of the Thermal Limit, Voltage Limit and the Stability Limit
Time
Power Flow
Transmission Capacity vs Transfer Capability
Transmission Capacity Transfer Capability
1 Is a physical property in isolation Is a collective behaviour of a system
2 Depends on design only Depends on design, topology, system conditions, accuracy of assumptions
3 Deterministic Probabilistic
4 Constant under a set of conditions Always varying
5 Time independent Time dependent
6 Non-directional Directional
7 Determined directly by design Estimated indirectly using simulation models
8 Declared by designer/ manufacturer Declared by the Grid Operator
9 Understood by all Frequently misunderstood
10 Considered unambiguous & sacrosanct Subject to close scrutiny by all stakeholders
Total & Available Transfer Capability
ATC = TTC – TRM – CBM
Transfer Reliability Margin (TRM)
Capacity Benefit Margin (CBM)
Long Term Open Access (LTOA)
Short Term Open Access (STOA)
TTC
ATC
“Reliability is the performance level of the elements of the bulk electric systems that results in electricity being delivered to the customers within accepted standards and in amount desired. It is expressed in terms of the frequency, duration and magnitude of adverse effects on electric supply. Reliability comprises of Adequacy and Security…Adequacy is reliability within the range of events which can be controlled by operators whereas Security is reliability under conditions beyond the control of operators.” Dr. Mohammad Shahideopour
CERC Open Access Regulations, 2008• Effective 01.04.2008
• Permits usage of spare transmission capacity through a transparent process
• Offers choice and freedom to buy & sell power
• Transactions categorized as Bilateral and
Collective (through Power Exchange)
• Transmission Charges moved from “Contract Path” to “Point of Connection” for Collective Transaction
• Thrust on Empowerment of SLDCs
Time Line
Bilateral - Advance
Bilateral - FCFS
Collective Through
PX
Day - Ahead
Bilateral - Contingency
Trade under Short-Term Open Access
17
2324
3130
778
3938
5933
11781
9560
12
14
16
18
20
22
24
26
28
30
32
2004-05 2005-06 2006-07 2007-08 2008-09
En
erg
y (
BU
s)
----
->
0
5000
10000
15000
Nu
mb
er
of
Tra
ns
ac
tio
ns
---
->
Volume of trade (BUs) No. of transactions
* 2008-09 data includes Bilateral + Collective transactions.
0
500
1000
1500
2000
2500
3000
Month -------->
En
erg
y (
MU
s)-
----
----
-> 2007-08
2006-072005-06
ENERGY APPROVED(MU) - (Nodal RLDC-NRLDC)
2008-09
0
100
200
300
400
500
600
700
800
900
1000
APRIL MAY JUNE JULY AUG SEP OCT NOV DEC JAN FEB MARMonth -------------->
App
rove
d E
nerg
y(M
Us)
----
-->
2007-08 2006-07
2005-06
2008-09
ENERGY APPROVED(MU) - (Nodal RLDC-SRLDC)
Growing Confidence in Open Access Market - Increasing Market Players
Power Exchange in India• Salient Features
– Multiple exchanges – Competition amongst Exchanges
• Indian Energy Exchange (IEX)• Power Exchange of India (PXI)• Third Power Exchange in the offing:
– Voluntary participation– Double sided bidding– Uniform pricing– Day-ahead exchange– Hourly bids– Congestion management by market splitting
Daily Energy Traded on PX
Increasing Participation on PX
Open Access: Key Success Factors• Developed in consultation with all stake holders• Control area demarcation & boundary metering• Robust transmission system• Assessment of Transfer Capability• Balancing mechanism• Methodology for transmission charge sharing• Treatment of transmission losses• Streamlined scheduling and settlement mechanism• Transparency and non-discriminatory implementation• Compliance• Dispute redressal mechanism• Congestion management
Transmission Congestion
• Characteristics of a growing power system• Sign of optimum investment• If managed and documented
– Gives signals for future investments
• If unmanaged– A pain
– Threat to grid security
– May lead to social and economic loss
– Situation gets acute in Northern Region due to indiscriminate overdrawal
Skewed Load-Generation Balance
SR
ER+NER
WR
NR
Scenarios:
1. 4S
2. 3S + 1D (Congestion)
3. 2S + 2D
4. 1S + 3D
5. 4D
SKEWED LOAD GENERATION BALANCE
FLOWGATES
Congestion Management: Bid AreaArea
Region States
N1 North JK, HP, CHD, PUN, HAR
N2 North RAJ,DEL, UP, UTT
W1 West MP, CHTG
W2 West MAH,GUJ, GOA, DD,DNH
S1 South AP, KAR, GOA
S2 South TN, KER, PONDY
E1 East WB, SIK, BIH, JHAR
E2 East ORISSA
A1 North-East
Tripura, Manipur Mizoram, Meghalya
A2 North-East
Assam, Ar. Pradesh, Nagaland
PECULIARITIES & CHALLENGES
Skewed resource distributionLong-haulage of powerResource InadequacyWeather extremesDiversity
Dynamically varying resource sharing matrixExcessive reliance on UIFreedom and choice without enforcement of obligationsUnclear jurisdiction
High growth, high uncertaintiesUnbundling and reformsEvolving market mechanismsChanging business environment
Loose Power PoolDecentralized OperationFloating FrequencyUnscheduled InterchangeVoluntary ancillary servicesWeekly settlement 21 day cycle15-minute settlement period
DAILY OPERATIONAL CHALLENGES
FLOATING FREQUENCY: 49 - 50.5 Hz VOLTAGE VARIATIONS: 380- 430
kV
HIGH RAMP RATEBI-DIRECTIONAL LINE FLOWS
Concerns• Reliability of physical system
– Adequacy, Security, Dependability
• Rapid growth– Harmonization – Jurisdiction
• Visualization and situational awareness– Dynamic system
• Deployment of technology– Automation, Information exchange
• Capacity building– Inclusive, sustainable, broad based– Human Resource
VISUALIZATION
CHALLENGES BEFORE US
Expanding requirements
Technological up gradation
Database & display updating
Maintaining data quality
Operator familiarization
SITUATIONAL AWARENESS
Expectations• Focus on reliability of the physical system• Designing markets that complement reliability• Appreciation of System Operation as an important
function– Allocation of resources
– Automation
– Capacity building
• Grid security comes before Economics– No economic theory, no legislation, no regulation can
repeal the Laws of Physics“Power markets are the only markets that can suffer a catastrophic instability that develops in less than a second...The extent and speed of the required coordination are unparalleled.” ….Steven Stoft
Building up the Immune System• Protection
– New technologies– Co-ordination
• Power System Early Warning Systems– PMU– WAMS
• Defense mechanisms– System Protection Schemes
