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)

• 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

• 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 TTC

• 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

ASSESSMENT OF TRM/ATC

• 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

PROCEDURE FOR ATC/TTC/RM DECLARATION

ISGS-I ISGS-II

STATE-A STATE-B

ISTS

NETWORK

• 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 ATC/TTC/RM 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

PROCEDURE FOR REAL TIME CONGESTION DECLARATION

• 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.

APPLICABILITY OF CONGESTION CHARGE

NER ER

NR

SR

WR

U/D-A

O/D-B

U/D-C

O/D-D

U/D-X

O/D-YSF > 50.00Hz

A,C CAUSING CONGESTION

SF < 50.00Hz

Y CAUSING CONGESTION CONGESTED LINKS

ER-NR & WR-ER

• 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

CONGESTION CHARGE-ACCOUNTING & SETTLEMENT

Format-I

Issue Date: Issue Time: Revision No.

Corridor/ Date Time Total Reliability Available

Control Period Transfer Margin Transfer

Area Capability

(RM) Capability

(TTC) (ATC)

Remarks:

National /________Regional Load Despatch Centre Total Transfer Capability for mmmm ,yyyy

FORMAT FOR DECLARING ATC/RM/TTC BY NLDC

Format II

Congestion Monitoring Display dd/mm/yyyy, hh:mm

Corridor/ Control Area

TTC ATC Actual

National/_________Regional Load Despatch Centre

DISPLAY FOR CONGESTION MONITORING

Format III

National/_________Regional Load Despatch Centre

Notice umber: (LDC/RLDC)/yyyy/mm/…. Date: dd/mm/yy Time of Issue: hh:mm To

WARNING NOTICE

The actual transfer of electricity on following corridors has crossed the ATC.

Corridor/Control Area ATC Actual Flow

The following regional entities, which are downstream of the congested corridor, are advised to reduce their drawl/increase their generation to decongest the system: 1. … m.

The following reginal entities, which are upstream of the congested corridor are advised to / increase their drawl/reduce their generation to decongest the system: 1. … n.

Shift Charge Manager

PROCEDURE FOR REAL TIME CONGESTION DECLARATION

PROCEDURE FOR REAL TIME CONGESTION DECLARATION Format -IV

National/_________Regional Load Despatch Centre

Notice umber: (LDC/RLDC)/yyyy/mm/…. Date: dd/mm/yy Time of Issue: hh:mm

To:

NOTICE FOR LEVY OF CONGESTION CHARGE

Congestion charge for Unscheduled Interchange (UI) energy as per CERC (Measures for nd

relieving congestion) Regulations 2009 dated 22 December 2009 would be applicable w.e.f time block no. ( hh:mm )of dd/mm/yyyy.

Corridor/Control Area TTC Actual Flow

Congestion charge would be applicable on the following regional entities, which are downstream of the congested corridor: 1. … m.

Congestion charge would be applicable on the following regional entities, which are upstream of the congested corridor: 1. … n.

Shift Charge Manager

Format V

National/_________Regional Load Despatch Centre Notice Number: (LDC/RLDC)/yyyy/mm/…. Date: dd/mm/yy Time of Issue: hh:mm To

NOTICE FOR LIFTING OF CONGESTION CHARGE

Congestion charge on Unscheduled Interchange (UI) energy that was applicable w.e.f hh:mm of dd/mm/yyyy vide notice umber.... issued at hh:mm of dd/mm/yyyy would be lifted w.e.f time block no. (hh:mm) of dd/mm/yyyy.

Shift Charge Manager

APPLICABILITY OF CONGESTION CHARGE

Format VINational/_________Regional Load Despatch CentreStatement on application of congestion charge for Date:Issued on:Time Block

Time Downstream Entities

Upstream Entities

1 0000 00152 0015 00303 0030 0045

96 2345 0000

CONGESTION CHARGE-ACCOUNTING & SETTLEMENT