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INTER - REGIONAL EXCHANGES

INTER - REGIONAL EXCHANGES. Technical and Commercial Aspects K.RAMAKRISHNA DGM, SRLDC. Types of Inter-connections. AC links (Synchronous mode) DC Links (Asynchronous mode) through - HVDC line and Convertors/Invertors - HVDC Back to Back system. Features of AC links.

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INTER - REGIONAL EXCHANGES

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  1. INTER - REGIONAL EXCHANGES Technical and Commercial Aspects K.RAMAKRISHNA DGM, SRLDC

  2. Types of Inter-connections • AC links (Synchronous mode) • DC Links (Asynchronous mode) through - HVDC line and Convertors/Invertors - HVDC Back to Back system

  3. Features of AC links • Low cost (up to some distance) • Increased Fault level and Inertia • Synchronous operation (same frequency) • No control on Power flow • Fault in one Region may affect other Region • Over voltage problems • Huge Power is lost in Equalizing the frequencies thereby loosing the advantage in Differential frequency • No run back schemes

  4. Features of DC Links Higher capital cost Asynchronous operation Immunity from faults in both Regions Control on Power flow Optimization through frequency Differential

  5. High lights of various HVDC links • Bypass arrangement (ex.Bhadrawati,Gazuwaka) • Power order setting • Minimum Power for deblocking • Ramping rate variation • Run Back systems / Power Demand Overrides (PDOs) • Automatic Filter switching for Reactive power requirement

  6. TALCHER KOLAR LINK • ONE OF THE LONGEST HVDC LINES IN THE WORLD • DESIGNED TO EVACUATE 2000 MW • COMMISSIONED IN ADVANCE TO UTILISE NON-PEAK SURPLUS POWER OF EASTERN REGION • COMMISSIONED 9 MONTHS AHEAD OF SCHEDULE • COST INCURRED Rs 3,100 CRORES AGAINST APPROVED COST OF Rs 3,866 CRORES:- SAVING OF NEARLY 800 CRORE RUPEES • THE PROJECT HAS USED APPROXIMATELY 90,000 TONNES OF STEEL AND 16,000 KM OF CABLES ABOUT 10,500 MU IMPORTED ON THIS LINK TILL DATE!!

  7. TALCHER-KOLAR IMPORT OF 12728MUs FROM ER THROUGH TALCHER-KOLAR UPTO OCT-04

  8. Defense Mechanism Run Back scheme in Gazuwaka HVDC Power level reduces to 250MW , - If Gazuwaka East bus Voltage <320kV - If Gazuwaka ICT O/L alarm actuates - If Jeypore ICT trips - If Jeypore-Indravati Line trips Power level reduces to 150MW, - If East side frequency <49Hz and if df/dt>=-0.3 Hz./sec.

  9. Defense Mechanism for Talcher Kolar HVDC link In case of any pole tripping, Inter-trip signal generated to trip associated AC lines at Yerraguntla(AP), Kolar, Hoody, Somanahalli(Karnataka) Sriperambadur, Salem and Hosur (TN) Mode of Oprn. Power Level for Inter-trip Mono polar >400MW and pole trips Bi-polar >800MW/pole and one pole trips Bi-polar >200MW/pole and both pole trip contd..

  10. Defense Mechanism for Talcher Kolar HVDC link Further PDOs at HVDc Kolar, Condition Power reduced to If only 2 lines are available 500MW If only 3 lines are available 1000MW If only 4 lines are available 1500MW

  11. Experience of SR in operation of IR links Congestion in associated AC network in (ex. 1)Over loading of Raipur-Rourkela, Raipur-Bhadravati, Chandrapur-Bhadravati in case of more import from WR. 2) Over loading of Chadrapur-Parli in case of more export to WR 3) Over loading of Jeypore-Jayanagar, Jeypore-Meramundali, Jeypore-Indravati, Talcher-Banjinagar(220kV), Gajuwaka-Vijayawada in case of more import from ER through Gazuwaka Reduced fault level at Jeypore contd…

  12. Experience of SR in operation of IR links • Problems in Converter transformers at Gazuwaka ( HENCE SUGGESTED FOR STANDBY CONVERTER TRANSFORMERS AT ALL THE PLACES) • Harmonics in neutral of Kolar ICT and flow of the same in associated system • Over voltage at Kolar due to Switching of filters • High losses in Monopolar- Metallic return mode. • Annual Maintenance of Poles. • CURTAILMENT OF STOA

  13. LOSSES IN HVDC SYSTEM % LOSS MIN. CAPACITY (50MW ) MAX CAPACITY POWER ORDER IN MW

  14. Loss optimization IR flows can influence SR System Loss • By importing more through Kolar • By exporting to WR from Ramagundam-Chandrapur Link • During high frequency, More import from Gazuwaka preferred.

  15. Losses applicable for various transactions 1. For share from ER ISGS- ER+SR losses 2. For Talcher St-II power through Kolar, - SR losses 3. For Talcher-St-II power when wheeled • through Gazuwaka – ER+SR losses • through Bhadravati – ER+WR+SR losses 4. Wheeling of ER power through SR – ER+ SR losses

  16. Normative % Losses of Central sector in various Regions • ER ~ 3 to 3.5% • SR ~ 2.8 to 3.8% • WR ~ 6 to 6.5% • NR ~ 3 to 4%

  17. Priority of Exchanges through IR links • Long Term transactions (ISGS Allocation to Beneficiaries of the same region) Wheeling of ISGS share of Beneficiaries in other regions any other long term transactions approved • STOA Transactions

  18. PROCEDURE FOR CURTAILEMENT • In case of transmission constraint , if curtailment is necessary then, • Short term customers first • Long term customers next Within the category, OA customers have curtailment on pro rata basis

  19. Commercial Aspects Metering and Scheduling points : SR-WR South Bus of HVDC Bhadravati SR-ER East Bus of HVDC Gazuwaka AC Inter connector of Talcher St-I and St-II

  20. TSTPP St-II scheduling and Despactch • TSTPP St-II furnishes DC to SRLDC with a copy to ERLDC. • SRLDC to carry out rest of the Scheduling process • Talcher/ Gazuwaka set points to be decided in consultation with ERLDC • Talcher HVDC controlled by ERLDC. • Gazuwaka HVDC controlled by SRLDC. • In case of Talcher Pole tripping TSTPP St-II Power wheeled through Gazuwaka/Bhadrawati

  21. TSTPP St-II UI accounting • TSTPP St-II – a SR ISGS embedded in ER system • TSTPP St-II UI @ ER frequency and to pay to SR pool • Net injection of TSTPP St-II = (Talcher HVDC Energy- flow on I/C betweenTalcher St-I&II) • Variation in TSTPPSt-II Generation results in ER-SR UI, if HVDC set point not changed • Sometimes –ve UI occurs if ER – SR SCHEDULE flow is not changed in accordance with ER-SR frequency differential.

  22. Inter Regional UI settlement • IR UI calculated by each REB at respective frequency • IR UI Payment on 1st charge basis without pro-rata reduction/averaging out • Importing Region to pay on lesser of the two principle. • Differential due to difference in UI rates on a/c of frequency deposited by importing region in their IRE account. WR UI ER UI

  23. IRE Settlement • Such accrued amounts of IRE account to be shared on 50:50 basis between Beneficiaries of both Regions • By way of credit in Transmission charges of CTU

  24. Status of IRE a/c settlement in SR & other regions • 100% settled to SR constituents except for provision for Revisions • Rs. 5 cr. Released WR constituents • Release to ER will start next week.

  25. INTER-REGIONAL EXCHANGES WR A/C DETAILS UPTO 93 WKSTILL 10/10/04 • NET ENERGY TRANSACTION IS 146 MU (IMPORT BY SR). • AMOUNT ACCRUED IN SREB – IRE DUE TO DIFF. IN WR A/C = 41.83Crs • AMOUNT TO BE ACCRUED IN WREB – IRE DUE TO DIFF. IN SR A/C = 27.71Crs • AMOUNT DUE TO SR CONSTITUENTS ON 50:50 BASIS = 34.73Crs • AMOUNT ALREADY DISBURSED TO SR CONSTITUENTS = 33.39Crs

  26. Procedure for Bidding • RLDC concerned shall invite bids if transmission capacity reservation sought by short term customer is more than the availability in a particular transmission corridor • The floor price of the bids for short term customer shall be about 1/4 th rate chargeable from long term customer and will be in Rupees per MW per day. • If customer gets the quantum of power he has bid for – he has to pay the price quoted by ‘last’ customer. • If customer gets a quantum lesser than that he has bid for – he gets to pay his bid price

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