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
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
corridors & exchange of power with ISTS
intra-regional
• 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
computation/verification
TTC/ATC
be
of
forwarded to NLDC for
intra-regional/inter-regional
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
SF > 50.00Hz
O/D-Y
A,C CAUSING
CONGESTION
NER
SF < 50.00Hz
Y CAUSING
CONGESTION
NR
U/D-A
U/D-C
O/D-B
O/D-D
ER
WR
SR
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
FORMAT FOR DECLARING ATC/RM/TTC BY NLDC
Format-I
National
/________Regional Load Despatch Centre
Total Transfer Capability for mmmm ,yyyy
Issue Date:
Issue Time:
Revision No.
Corridor/
Control
Area
Remarks:
Date
Time
Period
Reliabili
Total
ty
Transfer Margin
Capabili (RM)
ty
(TTC)
Available
Transfer
Capability
(ATC)
DISPLAY FOR CONGESTION MONITORING
Format II
National/_________Regional Load Despatch
Centre
Congestion Monitoring Display
dd/mm/yyyy,
hh:mm
TTC
ATC
Corridor/
Control Area
Actual
PROCEDURE FOR REAL TIME CONGESTION DECLARATION
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
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
APPLICABILITY OF CONGESTION CHARGE
Format V
National/_________Regional
Notice Number: (LDC/RLDC)/yyyy/mm/….
Load Despatch Centre
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
CONGESTION CHARGE-ACCOUNTING & SETTLEMENT
Format VI
National/_________Regional Load Despatch Centre
Statement on application of congestion charge for Date:
Issued on:
Time
Time
Downstream Upstream
Block
Entities
Entities
1
2
3
0000-0015
0015-0030
0030-0045
96
2345-0000