SOUTHERN REGIONAL LOAD DESPATCH CENTER POSOCO,POWERGRID, BANGALORE

SOUTHERN REGIONAL LOAD DESPATCH CENTERPOSOCO,POWERGRID, BANGALORE

UI regulations,ATC,

congestion regulations

and experiences in SRBy

P.Bhaskara Rao, Addl G M, Shamreena Verghese , Mgr

16 May 2011

Overview• Ui_regulations• Transfer Capability• Relevance of transfer capability in Indian

electricity market• Reliability Margin• Difference between transfer capability and

Transmission Capacity• Assessment of Transfer capability• Ratio of transfer capability to transmission

capacity• Congestion regulations• overview of constraints and hotspots in SR

Transfer Capability - Definition

North American Electricity Reliability Corporation’s definition of TTC(Total Transfer

Capability )• “TTC is the amount of electric power that can

be transferred over the interconnected transmission network in a reliable manner based on all of the following conditions– all facility loadings in pre-contingency are within

normal ratings and all voltages are within normal limits

– systems stable and capable of absorbing the dynamic power swings

– before any post-contingency operator-initiated system adjustments are implemented, all transmission facility loadings are within emergency ratings and all voltages are within emergency limits”

06th Oct 2009 4NRLDC, POWERGRID

06th Oct 2009 NRLDC, POWERGRID 5

European Network of Transmission System Operators’ definition of Total Transfer Capability

(TTC)• “TTC is that maximum exchange programme

between two areas compatible with operational security standards’ applicable at each system if future network conditions, generation and load patterns were perfectly known in advance.”

• “TTC value may vary (i.e. increase or decrease) when approaching the time of programme execution as a result of a more accurate knowledge of generating unit schedules, load pattern, network topology and tie-line availability”

Transfer Capability as defined in the Indian Electricity Grid Code (IEGC)

‘Transfer Capability’ of a transmission network is the ability to transfer electric power when operated as part of the interconnected power system and may be limited by the physical and electrical characteristics of the system considering security aspects of the grid.

Total Transfer Capability as defined in the Congestion charge regulations

• “Total Transfer Capability (TTC)” means the amount of electric power that can be transferred reliably over the inter-control area transmission system under a given set of operating conditions considering the effect of occurrence of the worst credible contingency.

Available Transfer Capability as defined in the Congestion charge regulations

• “Available Transfer Capability (ATC)” means the transfer capability of the inter-control area transmission system available for scheduling commercial transactions (through long term access, medium term open access and short term open access) in a specific direction, taking into account the network security. Mathematically ATC is the Total Transfer Capability less Transmission Reliability Margin.


Simultaneous TTC

Area A Area B

Area C

2000 MW 4000 MW

5000 MW

Relevance of Transfer Capability in

Indian Electricity Market

CERC Open Access Regulations 2004

5. Criteria for allowing transmission access:

ii) The short term access shall be allowed, if request can be accommodated by utilising:(a) Inherent design margins(b) Margins available due to variation in power flows(c) Margins available due to in-built spare transmission capacity created to cater to future load growth

Tariff Policy Jan 2006

7.3 Other issues in transmission

(2) All available information should be shared with the intending users by the CTU/STU and the load dispatch centres, particularly information on available transmission capacity and load flow studies.

Open Access Theory & PracticeForum of Regulators report, Nov-08

“For successful implementation of OA, the assessment of available transfer capability (ATC) is very important. A pessimistic approach in assessing the ATC will lead to under utilisation of the transmission system. Similarly, over assessment of ATC will place the grid security in danger.”

13th October 2009 13POWERGRID

Declaration of Security Limits

• “In order to prevent the violation of security limits, System Operator SO must define the limits on commercially available transfer capacity between zones.” CIGRE_WG_5.04_TB_301

• “System Operators try to avoid such unforeseen congestion by carefully assessing the commercially available capacities and reliability margins.” CIGRE_WG_5.04_TB_301


Reliability Margin


NERC definition of Reliability Margin (RM)

• Transmission Reliability Margin (TRM)– Amount of transfer capability necessary to ensure reliable

service under a reasonable range of uncertainties in system conditions

• Capacity Benefit Margin (CBM)– Amount of transmission transfer capability reserved to ensure

access to generation from inter connected system

• Reliability Margin is time dependent• In the Indian context

– Overdrawal / Underdrawal by constituents resulting from demand forecast error

– Sudden outage of a large generator in a control area


Quote on Reliability Margin from NERC document

• “The beneficiary of this margin is the “larger community” with no single, identifiable group of users as the beneficiary.”

• “The benefits of reliability margin extend over a large geographical area.”

• “They are the result of uncertainties that cannot reasonably be mitigated unilaterally by a single Regional entity”

Reliability margin as defined in Congestion charge regulations

• “Transmission Reliability Margin (TRM)” means the amount of margin kept in the total transfer capability necessary to ensure that the interconnected transmission network is secure under a reasonable range of uncertainties in system conditions;

August 08, 2007 GSIOAR-2007, IT-BHU, Varanasi 19

Distinguishing features of Indian grid

• Haulage of power over long distances• Resource inadequacy leading to high uncertainty in

adhering to maintenance schedules • Pressure to meet demand even in the face of acute

shortages and freedom to deviate from the drawal schedules.

• A statutorily permitted floating frequency band of 49.5Hz to 50.2 Hz

• Non-enforcement of mandated primary response, absence of secondary response by design and inadequate tertiary response.

• No explicit ancillary services market• Inadequate safety net and defense mechanism

April 20, 2023 NRLDC, POWERGRID 20

Reliability Margins- Inference• Grid Operators’ perspective

– Reliability of the integrated system– Cushion for dynamic changes in real time– Operational flexibility

• Consumers’ perspective– Continuity of supply– Common transmission reserve to take care of contingencies– Available for use by all the transmission users in real time

• Legitimacy of RMs well documented in literature• Reliability Margins are non-negotiable• The actual power flow only demonstrates the utilization

of these margins during real-time and therefore should not be a reason for complain

Difference between Transfer Capability and Transmission

Capacity

06th Oct 2009 NRLDC, POWERGRID

Transmission Capacity Vis-à-vis Transfer Capability

Transmission Capacity Transfer Capability

1 Declared by designer/ manufacturer Declared by the Grid Operator

2 Is a physical property in isolation Is a collective behaviour of a system

3 Depends on design only Depends on design, topology, system conditions, accuracy of assumptions

4 Deterministic Probabilistic

5 Constant under a set of conditions Always varying

6 Time independent Time dependent

7 Non-directional (Scalar) Directional (Vector)

8 Determined directly by design Estimated indirectly using simulation models

9 Independent of Parallel flow Dependent on flow on the parallel path

Transfer Capability is less than transmission capacity because

• Power flow is determined by location of injection, drawal and the impedance between them

• Transfer Capability is dependent on– Network topology– Location of generator and its dispatch– Pont if connection of the customer and the quantum of demand – Other transactions through the area– Parallel flow in the network

• Transmission Capacity independent on all of the above

• When electric power is transferred between two areas such the entire network responds to the transaction

77% of electric power transfers from

Area A to Area F will flow on the transmission path

between Area A & Area C

Assume that in the initial condition, the power flow from

Area A to Area C is 160 MW on account of a generation dispatch

and the location of customer demand on the modelled

network.

When a 500 MW transfer is scheduled from Area A to Area

F, an additional 385 MW (77% of

500 MW) flows on the transmission path from

Area A to Area C, resulting in a 545 MW power flow from

Area A to Area C.

Cross border capacity available for trade

• “Physical capacity connecting zones A and B is sum of 1-3 and 2-3 physical line capacities. However, the cross border capacity available for commercial trade would be less or at most equal to the sum of capacities of cross border lines individually.” CIGRE_WG_5.04_TB_301

1

2

3

A B


Assessment of Transfer Capability

Transfer Capability Calculations must

• Give a reasonable and dependable indication of transfer capabilities,

• Recognize time variant conditions, simultaneous transfers, and parallel flows

• Recognize the dependence on points of injection/extraction

• Reflect regional coordination to include the interconnected network.

• Confirm to reliability criteria and guides.

• Accommodate reasonable uncertainties in system conditions and provide flexibility.

13th October 2009 POWERGRID 27

Courtesy: Transmission Transfer Capability Task Force, "Available Transfer Capability Definitions and Determination", North American Electric Reliability Council, Princeton, New Jersey, June 1996 NERC

April 20, 2023 NRLDC, POWERGRID 28

Total Transfer Capability: TTC

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

29

Transfer Capability assessment

AnticipatedNetwork topology +Capacity additions

Anticipated Substation Load

Anticipated Ex bus

Thermal Generation

Anticipated Ex busHydro generation

LGBR

Last Year

Reports

WeatherForecast

Trans.Plan +

approv.S/D

Last Year

patternOperator

experience

Planning criteria

Operating limits

Credible contingencies

Simulation

Analysis

Brainstorming

Transfer Capability

ReliabilityMargin

less

AvailableTransfer

Capability

equals

Planning Criteria is strictly followed during simulations06th Oct 2009 29NRLDC, POWERGRID

30

Steady State Voltage Limits

Voltage (kV rms)

Nominal Maximum Minimum

765 800 728

400 420 380

220 245 198

132 145 122

From Section 5 of Transmission Planning Criteria

31

Credible contingencies

• From Section 3.5 of IEGC– Outage of a 132 kV D/C line or– Outage of a 220 kV D/C line or– Outage of a 400 kV S/C line or– Outage of a single ICT or– Outage of one pole of HVDC bi pole or– Outage of 765 kV S/C line

without necessitating load shedding or rescheduling of generation during steady state operation

Input Data and Source

06th Oct 2009 32

S No. Input Data Suggested Source

1 Planning Criteria Manual on Transmission Planning Criteria issued by CEA

2 Network Topology Existing network with full elements available

Planned outages during the entire assessment period

New transmission elements expected

3 Transmission line limits Minimum of thermal limit, stability limit and voltage limit

4 Thermal unit availability Load Generation Balance report, Maintenance schedule

Anticipated new generating units

5 Thermal despatch Ex bus after deducting the normative auxiliary consumption

Output could be further discounted by the performance index of generating units of a particular size as compiled by CEA

6 Gas based thermal despatch

Past trend

7 Hydro despatch Peak and off peak actual hydro generation on median consumption day of same month last year

The current inflow pattern to be duly accounted

8 Load Anticipated load

9 Credible contingencies Planning criteria + Operator experience

NRLDC, POWERGRID

Process for assessment

• Base case construction (The biggest challenge) – Anticipated network representation– Anticipated load generation– Anticipated trades

• Simulations– Increase generation in exporting area with

corresponding decrease in importing area till network constraint observed

06th Oct 2009 33NRLDC, POWERGRID

Concerns-1• Wide range of permissible frequency band

– Significant interplay of frequency and voltage in a large grid

• ‘UI’ considered as an infinite source / sink

• Limited voluntary participation by utilities for congestion management in real-time– Primary response, Reactive Support

• Availability norm falling short of ensuring Dependability– Outage of complete power station– Outage of complete EHV substation

Concerns-2 • Changes in long-term allocations

• Uncertainties in planned outages of shared resources

• Medium-term inadequacies in transmission/generation – Open Loops, Switching arrangement

• Safety net– Relay settings/ behavior: – Credible N-1 contingency getting converted into simultaneous

multiple outages in real-time

• Frequent large scale contingencies– Fog, Widespread rains, Cyclone, Silt– Limited support from online tools in case of fast events


Intra-day STOA

Day-ahead STOA

Collective (PX) STOA

First Come First Served STOA

Advance Short Term Open Access (STOA)

Medium Term Open Access (MTOA)

Long Term Open Access (LTOA)

Reliability Margin (RM)

Available Transfer Capability is

Total Transfer Capability less Reliability Margin

TTC ATC

RM

Ratio of transfer capability to transmission capacity

Congestion

Congestion in Power System

“Congestion is a situation where the demand for transmission capacity exceeds the transmission network capabilities, which

might lead to violation of network security limits, being thermal, voltage stability limits

or a (N-1) contingency condition.”

CIGRE_WG_5.04_TB_301


Visibility of congestion

• Visible to the market players– “If for a given interconnection, there is more demand

for cross border capacity than commercially available, the interconnection is also treated as congested, meaning no additional power can be transferred. This congestion is visible for market players as a limit on their cross-border transactions.”- CIGRE_WG_5.04_TB_301

• Invisible to the market players– “It is possible that even though the available

commercial interconnection capacity is not fully allocated to market players, some lines, being internal or cross-border, become overloaded. This physical congestion is a problem of the System Operator and has to be dealt with by this entity.” CIGRE_WG_5.04_TB_301


To be handled before-the fact

To be handled in real-time

Congestion visible to the market• “The more transactions and the more

meshed the network, the higher the chance for mismatch between commercial exchange and physical flows.” CIGRE_WG_5.04_TB_301 Congestion

Sign of growth and vibrant market Natural corollary to Open Access

Existing transmission system was not planned with short-term open access in mind

Security margins have been squeezed ‘Pseudo congestion’ needs to be checked


Congestion in real-time is a security threat

• Phenomenon common to large meshed grids

• Coupling between voltage and frequency accentuates the problem in a large grid


Real-time Congestion types

• Internal congestion (Intra-zonal)– Within a single System Operator’s control area

• Cross-border (Inter zonal)– Also called seams issue– Several System Operators involved

Was not experienced -Regional grids were small

-Trades were limited


Experienced occasionally under- Grid Contingencies

- Skewed conditions in gridAggressive Open Access trades

Types of congestion in Indian context

• 3 / 2 / 1 month (s) ahead – advance

• First come first served

• Day ahead PX

• Day ahead bilateral

• Contingency transaction

• Real time

Reasons for congestion in India

• Fuel / resources related constraints– Long haulage of power• Physical network limitations– Fast growing network, transition, mismatch• Inadequate compliance to reliability

standards– Inadequacy in Safety net • Market Design/Interplay and behavior of

players13th October 2009 46POWERGRID

Causes of congestion• Inadequate transmission – including outages

• Inadequate reactive support

• Weather diversity, seasonal demand variation

• Skewed generation availability – monsoon, planned / forced outages

• Uneven purchasing power of utilities in a shortage scenario

• Compulsion to meet load at all costs (agriculture, festival, election etc.) – Aggressive buying

• Economy (cheaper generation to replace costlier generation)

• Inflated sale / purchase requirement – Pseudo congestion

• Inter play with UI mechanism – Bids based on anticipated UI price

Regulatory initiatives• Modifications in Grid Code & other regulations

– Frequency band tightening – Cap on UI volume, Additional UI charge– Inclusion of new definitions (TTC, ATC, Congestion)

• Congestion Charge Regulation– Congestion Charge Value, Geographical

discrimination – Procedure for Assessment of Transfer Capability– Procedure for Implementation of Congestion Charge


Suggestions for improving transfer capability-1

• installation of shunt capacitors in pockets prone to high reactive drawal & low voltage

• strengthening of intra-state transmission and distribution system

• improving generation at load centre based generating stations by R&M and better O & M practices

• avoiding prolonged outage of generation/transmission elements

• reduction in outage time of transmission system particularly those owned by utilities where system availability norms are not available

Suggestions for improving transfer capability-1

• minimising outage of existing transmission system for facilitating construction of new lines

• expediting commissioning of transmission system-planned but delayed execution

• enhance transmission system reliability by stregthening of protection system

• strengthening the safety net- Under voltage load shedding schemes, system protection schemes

AN OVERVIEW CONSTRAINTS AND HOTSPOTS in

SR

ELECTRICITY, n. The power that causes all natural phenomena not known to be caused by something else. Ambrose Bierce, The Devil’s Dictionary, 1881–1906

SALIENT FEATURES OF SOUTHERN REGIONAL GRID

• BEST HYDRO-THERMAL MIX 30-70 %• HYDRO GENERATION TO MEET THE BASE LOAD• CONSIDERABLE IPP CONTRIBUTION • PUMPED STORAGE SCHEMES IN SRISAILAM-AP (900 MW) &

KADAMPARAI-TN (400 MW)– FAST RAMPS– SKEWED FLOWS

• HIGHEST WIND GENERATION AMONGST ALL THE REGIONS(>3500 MW WITH 1500 MW VARIATION)

• HEAVILY DEPENDENT ON MONSOON• VOLTAGES CHANGE FROM 370 KV TO 425 KV AT SOME

BUSES OVER THE YEAR.• 1000 MW NUCLEAR UNITS EXPECTED AT KUDANKULAM (TN)-

RELIABILITY IMPACT

• CONGESTION RELATIVELY NEW CONCEPT FOR SR IN RECENT YEARS.

NORTH EAST MONSOON

(WINTER MONSOON)

SOUTH WEST MONSOON

(SUMMER MONSOON)

IMPORT FROM CENTRAL GRIDCONTINGENCY CONDITIONS

• SR HAS BEEN ABLE TO ACCOMMODATE IMPORTS FROM

OTHER REGIONS TO..

– RELIEVE LINE LOADINGS IN THAT REGION (EXAMPLE SR IMPORTED

POWER TO RELIEVE LOADING OF FARRAKA-MALDA AND TALCHER –

ROURKELA ON MANY OCCASIONS)

– NATURAL CALAMITIES : SMOG PROBLEM CAUSING UNFORSEEN TRIPPINGS

IN NR IN DEC-JAN EVERY YEAR – SR IMPORTS POWER TO THE MAXIMUM

TO ASSURE SAFETY OF INDIAN GRID

– CORRIDOR INSUFFICIENCY : SR HAS WHEELED POWER FROM ER TO WR

ON MANY OCCASSIONS

– MAJOR L/C’S IN NEW GRID

– SYSTEM DISTURBANCES IN NEW GRID

THE SOUTHERN REGION GRID

ATC ISSUES AND HOTSPOTS

SOUTHERN REGION

WESTERNREGION

EASTERN REGION

NORTHERN REGION

NORTH-EASTERN REGION

1

2

TWO ELECTRICAL REGIONS w.e.f Aug. 2006

‘NEW’ GRID

HVDC INTERCONNECTS

AC INTERCONNECTS

MAJOR INTERCONNECTIONS

2X500 MW BACK TO BACK STATION AT

GAZUWAKA(SR)

1000 MW BACK TO BACK STATION AT

BHADRAWATI(WR)

TALCHER

KOLAR

TALCHER-II TO KOLAR

2000 MW BIPOLE LINK

INTER REGIONAL TRANSFER CAPACITY SR WITH OTHER REGIONS

• WITH ER• JEYPORE-GAZUWAKA 1000 MW• TALCHER-KOLAR 2000 MW

• WITH WR• RAMAGUNDAM-CHANDRAPUR 1000 MW

TOTAL CAPACITY IS 4000 MW

220 KV LINKS ARE IGNORED BECAUSE THEY ARE NOT IN ACTIVE USE

OVERLOAD CAPACITY AT KOLAR IS NOT CONSIDERED EXCEPT IN AN EMERGENCY

ALLOCATIONS OF SR PEAK

SR ISGS/ SR BENIFICIARY

RSTPS STAGE-1&2

RSTPS STAGE-3

TALCHER

STAGE-2

NLC TSII

STAGE-1

NLCTSII

STAGE-2

NLC TS1 EXP

MAPS KGS KGS3

FARAKKA

KAHALGAON

TALCHER-1

Installed Capacity @

2100 500 2000 630 840 420 440 440 2201600 840 1000

APTRANSCO 34.00 35.73 21.29 21.16 27.08 0.00 10.42 32.67 34.48 2.48 2.45 2.48

KPTCL 19.19 20.22 18.57 22.35 22.16 26.45 7.36 27.37 29.87

KSEB 11.66 12.20 21.00 10.86 11.39 14.00 5.23 8.64 7.96

TNEB 26.50 27.82 25.46 33.20 36.30 55.32 75.47 28.08 24.90 1.46 1.44 1.46

PONDY 3.78 4.03 3.48 12.43 3.07 4.23 1.52 3.24 2.79 0.73 0.72 0.73

GOA 4.76

NLC MINES

HVDC 0.11 0.20

ORISSA 10.00

TOTAL 100.00 100.00 100.00100.0

0 100.00 100.00 100.00 100.00 100.00 4.67 4.61 4.67

APTRANSCO SYSTEM

KPTCL SYSTEM

KSEB SYSTEM

Ramagundam2480 MW

ER ISGS143 MW

MAPS Nuclear 265 MW

TALCHER STG II1640 MW

KAIGA Nuclear 450 MW

NEYVELI IINEY EXP1642 MW

GAZUWAKA HVDCBHADRAWATI HVDC

TALCHER-KOLAR HVDC

SCHEDULE OF INTER STATE FLOWS AT PEAK HOUR WHEN ISGS DESPATCH IS FULL

895 MW

Pondy262 MW

585 MW

940 MW

1480MW

25 MW

TNEB SYSTEM

3 Nos. 400 kV lines &2 Nos 220 kV lines

Goa

95 MW

4 Nos. 400 kV lines &3 Nos 230 kV line

6 Nos. 400 kV lines &2 Nos 220 kV lines

*WITHOUT POOL LOSSES

4 Nos. 400 kV lines &1 Nos 220 kV line

ENT: 1728 MW

ENT: 2185 MWENT: 1385 MW

ENT: 965 MW

HYDERABAD URBAN AREA

YEDUMAILARAM

MAMIDAPALLI

MALKARAM

MOULALI

GHANAPUR GHANAPUR

MAMIDAPALLI

SIVARAMPALLI C.H.GUTTA

G BOWLI

245 MW X2

262 MWX3

66 MW

98 MW80 MW

127 MW 80 MWX2

162 MWX2

45 MWX2

COIMBATOREHEAVILY LOADED DURING LOW HYDRO

WILL BE SOLVED WITH COMMISSIONING OF ARASUR 400 Kv

TTPS

SR PUDUR

TTP AUTO

PARAMAKUDY

THENI

PASUMALAI

MADURAI

A-KULAM

K-KURUCHI

VEERANAM

KAYATHAR

SANGANERI

STERLITE

SIPCOT

TO EDAMON

TO SABARIFIRI

WIND ENERGY IN S. TAMILNADU- LINE LOADINGS

BASE CASE

1. 5 UNITS AT TTPS

2. WIND 1000 MW APPROX

3. KSEB NORMAL DRAWAL

4. WITHOUT STEPPING UP AT ICT’s AT TIRUNELVELI

5. REG. LOSSES 853 mw

137

146110

111

189

87

110

OPEN

180

6977 8

46

174

180

17

7

174

121

17

16

MAJOR WIND INJECTION POINTS

UDAYATHURKANARPATTY

THIRUNELVELI

9

141

55

TRIVANDRUM

113

223

128

26

AMUTHAPURAM

290

152

212

WIND

KODI KORICHI : 100

VEERANAM : 260

UDAYATHUR : 140

AMUTHAPURAM : 138

SANGANERI : 130

140

276

OPEN

EVOLUTION OF A CONSTRAINT

S1-S2 BID AREA SPLIT

EVOLUTION OF S1-S2 BID AREA CONSTRAINTS

• SR APPROACHING PEAK LOADS

• TN+KERALA SHORT OF POWER– PARTICIPATE AGGRESSIVELY IN STOA

AND PX– TN ISGS ENTITLEMENT IS AROUND 2000

MW– TRADES 2300 MW AT A POINT!

Congestion Management in SR: Between S1, S2 bid areaSnapshot of 400kV Hosur-Salem flow 725MW and the Drawl by S2 area constituents on 19-01-2010 at18:52Hrs

Congestion Management in SR: Between S1, S2 bid area

Snapshot of 400kV Hosur-Salem flow 725MW on 19-Jan-2010 18:52 Hrs


• During the period 18-22Hrs the schedules of TN and Kerala was around 4200 MW and 950 MW respectively.

• At this levels, 400kV Hosur-Salem flow is greater than 750 with no N-1 reliability.

• In case of tripping of 400kV Hosur-Salem or 400kV Somanahalli-Salem, other circuit get severely loaded.

• Worsens with low generation in TN-Kerala area

• In N-1 condition, 400kV Hosur-Salem and 400kV Somanahalli-Salem getting severely loaded.

• To limit the flow below 800MW, it was decided to put limit on schedule.

• After conducting load flow study, Schedule decided for S2 area constituents was 5000MW.


• Schedule breakup margin for individual constituents(approx.):

TNEB- 3700 MWKSEB- 900 MWPONDY-270 MW

• In case all NeyveliTS2 and TS1Exp units are there the limit increases to 5000MW as 60% counter flow towards S1 area will be there.

• The limit=flow sum(400kV SMN-Salem,400kV Kolar-Hosur,400kV Kolar-KVPattu,400kV Chittur-SRPD,400kV Nellore-Almatti)+Generation at NeyveliTS2+Generation at Neyveli TS1Exp


Sample Calculation of limit between S1,S2 bid area PX margin

A=S1,S2 bid area limit set (MW)

B= ISGS Entitlements after loss (MW)

C= STOA bilaterals approved after loss (MW)

D=available Px Margin for S2 area constituents

::D=A-B-C


IMPROVING THE TRANSFER CAPABILITY• SPS TO LIMIT POST CONTINGENCY

VIOLATION– SUGGESTED FOR S1-S2

• SPS TO RE-ARRANGE NETWORK IN KERALA TO LIMIT LOADS BEYOND A THRESHOLD– BEING WORKED OUT FOR KERALA

• SPS ARMING AND DISARMING BASED ON PRE-CONTINGENCY EVALUATION– Ex: SPS 450/1000

• SPLITTING THE NETWORK– NEYVELI-MADRAS CASE- 230 KV PARALLEL IS

KEPT OPEN WHEN FLOW EXCEEDS 350 MW

CLOSING THE 220 KV KADKOLA-KANIYAMPETTA LINE

SHIFTING OF CONGESTION!

Base Case

1.Sharavathi Gen-Full2. Varahi-3 Units3.400kV Nelamangala-Talaguppa-one ckt-out4.220kV Kadakola-Kanyampet-out

108MWx2

256 MW137MWx4

62MWx2

66MWx2

45MWx2

129MWx2

108MW

60MW

50MWx2

61MW

159MWx2

10MW

Talguppa

Sharavathi

STRP

Varahi

Nelamangala

Huyyaganahalli

Mysor

Hootgalli

Kadakola

Kaniyampet

105MW

Mysore ICT flow 129MWx2

Case-1

1.Sharavathi Gen-Full2. Varahi-3 Units3.400kV Nelamangala-Talaguppa-one ckt-out4.220kV Kadakola-Kanyampet-in with flow 193MW

123MWx2

252 MW140MWx4

60MWx2

66MWx2

45MWx2

129MWx2

121MW

75MW

122MWx2

22MW

164MWx2

40MW

Talguppa

Sharavathi

STRP

Varahi

Nelamangala

Huyyaganahalli

Mysor

Hootgalli

Kadakola

Kaniyampet

122MW

193MW

After closing 220kV Kadakola KaniyampetThe line flow shared by following:1.Mysore ICTs- 120MW (62%)2.From shimoga-30 MW (16%)3.220kV TkHalli-Hootgalli-40 MW(21%)


77MWx2

149x2 MW146MWx4

84MWx2

66MWx2

114MWx2

152MWx2

74MW

30MW

49MWx2

48MW

152MWx2

9MW

Talguppa

Sharavathi

STRP

Varahi

Nelamangala

Huyyaganahalli

Mysor

Hootgalli

Kadakola

Kaniyampet

75MW

Case-2

1.Sharavathi Gen-Full2. Varahi-zero Generation3.220kV Kadakola-Kanyampet-out


91MWx2

147x2 MW149MWx4

81MWx2

66MWx2

114MWx2

204MWx2

89MW

45MW

112MWx2

14MW

157MWx2

35MW

Talguppa

Sharavathi

STRP

Varahi

Nelamangala

Huyyaganahalli

Mysor

Hootgalli

Kadakola

Kaniyampet

90MW

Case-3

1.Sharavathi Gen-Full2. Varahi-zero Generation3.220kV Kadakola-Kanyampet-out


168 MW

Conclusion

• It is impossible to plan / design a large congestion-free system

• Mild / occasional congestion indicates optimum investment in transmission

• Regular congestion indicates inadequacy– Generation– Transmission– Reactive compensation

The balance needs to be restored !

06th Oct 2009 NRLDC, POWERGRID

Grid SecurityMarket

References• Central Electricity Authority

– Manual on Transmission Planning Criteria, Jun-94• Central Bureau for Irrigation and Power

– Thermal limits of various conductors used in transmission system, Technical Report no. 77, May 1991

• North American Electric Reliability Corporation– ‘Transmission Transfer Capability A Reference Document for Calculating and

Reporting the Electric Power Transfer Capability of Interconnected Electric Systems ’ –May 1995

– ‘Available Transfer Capability Definitions and Determination’ -June 1996– ‘Transmission Capability Margins and their use in ATC determination –White

Paper’, 17th June 1999– ‘Reliability Criteria and Operating Limits Concepts’, Version 4 Draft 8, 2nd May

2007

• Power System Engineering Research Centre– ‘Electric Power Transfer Capability: Concepts, Applications, Sensitivity and

Uncertainty’, PSERC publication 01-34, November 2001, http://www.pserc.wisc.edu

• European Network of Transmission System Operators for Electricity– NTC and ATC in the internal market of Electricity in Europe, Mar 2000– Definitions of Transfer Capacities- Final Report, April 2001– Procedures for Cross border transmission capacity asssessments, Oct 2001 8406th Oct 2009 NRLDC, POWERGRID

http://www.pserc.wisc.edu/

http://www.pserc.wisc.edu/

SOUTHERN REGIONAL LOAD DESPATCH CENTER POSOCO,POWERGRID, BANGALORE

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