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PROCEDURE FOR:: REAL TIME CONGESTION MANAGEMENT. ASSESSMENT OF TTC. TTC/ATC assessment is carried out after construction & solution of a base case power system model for a representative scenario EHV system modelled upto 220KV level(except NER modelled upto 132KV)
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ASSESSMENT OF TTC • TTC/ATC assessment is carried out after construction & solution of a base case power system model for a representative scenario • EHV system modelled upto 220KV level(except NER modelled upto 132KV) • Normally all units > 50MW with switching at 132KV level & above would be modelled • Loads would be lumped at 220 / 132KV • Actual data or data as per CEA transmission planning criterion
ASSESSMENT OF TTC • Separate base case for export & import & TTC calculations for both peak/off-peak • Network topology :: data from CTU / STU • Unit availability:: LGBR • Actual Generation:: As per past trends/anticipation • Actual Demand:: As per data furnished/LGBR/past trends • MVAR Demand:: CEA manual on transmission criterion planning or data furnished
ASSESSMENT OF TTC • Normal operating limts for Line:: CEA manual on transmission criterion planning • Emergency operating limit of line:: 110% of Normal • ICT loading:: 90% of MCR • In case of non availability of data/additional data requirement - reasonable assumptions to be made • TTC between two areas calculated by increasing generation in exporting area and load in importing area till constraints are hit for a credible contingency
ASSESSMENT OF TTC • Credible contingency:: -Outage of a single transmission element -Outage of the largest unit in a generating station & transmission element • All base case loadings are within normal operating limits • After credible contingency all line loadings are within emergency operating limits and voltage as per IEGC defined range
ASSESSMENT OF TTC TTC would be limited by : -violation of voltages -violation of line operating limits in base case -violation of emergency limits in contingency
ASSESSMENT OF TRM/ATC • TRM kept to ensure that the system is reliable under a reasonable range of uncertainities • Computation of TRM:: - 2% of anticipated peak demand(MW) -power number in MW for the IEGC frequency range (with load damping of 4 % with/without FGMO) - size of the largest generating unit - size of largest anticipated infeed • ATC = TTC – TRM • ATC is the transfer capability commercially available for scheduling
PROCEDURE FOR ATC/TTC/RM DECLARATION • SLDCs shall assess the TTC/ATC for intra-regional corridors & exchange of power with ISTS • RLDCs shall determine TTC/ATC at regional level after receipt of above & other data for TTC computation from SLDCs. • RLDCs would determine TTC/ATC for inter-regional corridors & intra-regional corridors & between two or group control areas • TTC/ATC assessment shall be three months in advance upto the fourth month • All these data shall be forwarded to NLDC for computation/verification of intra-regional/inter-regional TTC/ATC
ISGS-II ISGS-I ISTS NETWORK STATE-A STATE-B
PROCEDURE FOR ATC/TTC/RM DECLARATION • All TTC/ATC declarations to be put on RLDC/NLDC website & also communicated as per Format-I • Revision of TTC/ATC may be done by NLDC based on: - inputs received from SLDCs/RLDCs - change in network topology - change in anticipated Load/generation - based on own observation
PROCEDURE FOR REAL TIME CONGESTION DECLARATION • SLDCs/RLDCs/NLDC would display the actual real time power flow Vis-a-Vis the TTC declared as per Format-II & voltages upstream/downstream • Reasons for Consideration of congestion:: - Grid voltage downstream/upstream beyond operating range -real time power flow exceeds the ATC for one time block for the congested corridor -loading of transmission lines beyond operating limit
PROCEDURE FOR REAL TIME CONGESTION DECLARATION • In case actual flow in inter/intra regional corridor exceeds ATC continuously for two time blocks NLDC would issue a warning notice • SLDCs on noticing congestion can inform RLDC who in turn will inform NLDC • If power flow is as per schedule but congestion is due to a forced outage :: OA transaction shall be revised first followed by TTC revision • If power flow is as per schedule and there is congestion in terms of voltages/line loadings without any forced outages, TTC shall be revised • In case of continued persistance of congestion and no action from defaulting constituents notice of application of congestion charges would be issued
APPLICABILITY OF CONGESTION CHARGE • Applicable simultaenously on all entities upstream / downstream • Payable by entities causing congestion and receivable by entities relieving congestion • Congestion charges may be applied pan india being applicable for entities in one region causing intra-regional congestion in a separate region • Shall be applicable only after two time blocks of issue of the notice • Once applied will remain in force for 8 time blocks(2 hours) • Congestion charges would not be applied for more than four times in a day to prevent continued flip-flops
APPLICABILITY OF CONGESTION CHARGE • Congestion charges levied for the fourth time would remain in force for the rest of the day. • If the congestion charges continues into next day the same shall be considered as 1st time for the day. • Shall be lifted only after the 2 hour period and when power flow falls below ATC and remains below ATC level for at least one time block • At frequency below 50 Hz, congestion charge would be levied for overdrawal in the importing control area and at frequencies above 50Hz, congestion charge would be levied for under-drawal in the exporting control area.
U/D-X O/D-Y SF > 50.00Hz A,C CAUSING CONGESTION NR U/D-A O/D-B U/D-C O/D-D NER ER WR SR SF < 50.00Hz Y CAUSING CONGESTION CONGESTED LINKS ER-NR & WR-ER
CONGESTION CHARGE-ACCOUNTING & SETTLEMENT • Congestion charge present rate:: 545 p/Kwh • At the end of the operating day RLDC/NLDC would indicate all time blocks where congestion charges applicable • Computation using SEM data and Frequency • Congestion charge account to be settled on weekly basis and maintained/operated by RLDCs • Statement of congestion charge disbursal to be issued by RPCs on weekly basis • Constituents required to pay into congestion charge account within 10 days of issue of accounts • Delay beyond 12 days will attract penalty @ 0.04% S.I per day • RLDC to release disburse towards payments within 3 days of receipt.
CONGESTION CHARGE-ACCOUNTING & SETTLEMENT • Undisbursed amount if any would be utilized as per instruction of CERC • RLDC to furnish data regarding undisbursed amount to the commission on a six monthly basis