Upload
raja-ramachandran
View
12
Download
1
Embed Size (px)
DESCRIPTION
congestion
Citation preview
NLDC 2
Outline Overview
Causes of Congestion
Congestion in Indian Context
Measures to Relieve Congestion
Regulatory Initiatives
International Experience
Discussion
Congestion Definition
“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
“Congestion” means a situation where the demand for transmission capacity exceeds the Available Transfer Capability (ATC)…..CERC regulation
NLDC 3
NLDC 4
Unique Characteristics of Indian Power System Floating Frequency Band (49.2 Hz – 50.3 Hz)
Availability Based Tariff (Unscheduled Interchange)
Weak/Absent Primary Response (FGMO) Continuous Fluctuation of Frequency
Absence of Automatic Generation Control (AGC) by Design
Inadequacy : Generation & Transmission
NLDC 5
Causes of Congestion in Real Time Different from congestion in STOA
Deviation from planned activities
Large interconnected grid Fast growing network Coupling between voltage and frequency accentuates the problem
in a large grid Skewed scenarios
Weather diversity, seasonal demand variation
Interplay with UI mechanism
Scenarios
4D
3D 1S
2D 2S
1D 3S (Congestion)
4S
Skewed Load-Generation Balance
SR
ER+NER
WR
NR
D=> Deficit Region S=> Surplus Region
Seasonal Variation in Power Flow Patterns
NR
WR
ERNER
SR
Bhutan
Scenario-1: Normal Monsoon
NR
WR
ERNER
SR
Bhutan
Scenario-2: Low Load in NR
NR
WR
ERNER
SR
Bhutan
Scenario-3: Low Load in WR
NR
WR
ERNER
SR
Bhutan
Scenario-4: Peak winter
FLOWGATESNR:
Central UP-Western UP
UP-Haryana/Punjab
WR:
Chandrapur-Padghe
Chandrapur-Parli
Bina-Gwalior
Soja-Zerda
SR:
Vijayawada-Nellore
Hossur-Selam
Gutty-Neelamangala
Gutty-Huddy
ER:
Farakka-Malda
Malda-Purnea
Talcher-Rourkela
Jamshedpur-Rourkela
Farakka-Kahalgaon
Kolaghat-Baripada-Rengali
NLDC 10
Measures to Relieve Congestion in Real Time Hydro Rescheduling HVDC set points Topology Change Instructions/ Messages Commercial Mechanisms
Congestion Charge Ancillary Services Counter Trade
Curtailment
Relevant IEGC clauses (1) Clause 5.4.2
(a) …”As mentioned elsewhere, the constituents shall endeavour to restrict their net drawal from the grid to within their respective drawal schedules whenever the system frequency is below 49.5 Hz. When the frequency falls below 49.2 Hz, requisite load shedding (manual) shall be carried out in the concerned State to curtail the over-drawal.”
(b) …” Further, in case of certain contingencies and/or threat to system security, the RLDC may direct an SLDC to decrease its drawal by a certain quantum. Such directions shall immediately be acted upon.”
(c)…” Each Regional constituent shall make arrangements that will enable manual demand disconnection to take place, as instructed by the RLDC/SLDC, under normal and/or contingent conditions. ”
(d)…” The measures taken to reduce the constituents’ drawal from the grid shall not be withdrawn as long as the frequency/voltage remains at a low level, unless specifically permitted by the RLDC. ”
NLDC 11
Relevant IEGC clauses (2)
Clause 6.4.12 “However, notwithstanding the above, the RLDC may direct
the SLDCs/ISGS/other regional entities to increase/decrease their drawal/generation in case of contingencies e.g. overloading of lines/transformers, abnormal voltages, threat to system security. Such directions shall immediately be acted upon. In case the situation does not call for very urgent action, and RLDC has some time for analysis, it shall be checked whether the situation has arisen due to deviations from schedules, or due to any power flows pursuant to short-term open access. These shall be got terminated first, in the above sequence, before an action, which would affect the scheduled supplies from ISGS to the long term customers is initiated..”
NLDC 12
Relevant IEGC clauses (3) Clause 6.5.18
In the event of bottleneck in evacuation of power due to any constraint, outage, failure or limitation in the transmission system, associated switchyard and substations owned by the Central Transmission Utility or any other transmission licensee involved in inter-state transmission (as certified by the RLDC) necessitating reduction in generation, the RLDC shall revise the schedules which shall become effective from the 4th time block, counting the time block in which the bottleneck in evacuation of power has taken place to be the first one. Also , during the first, second and third time blocks of such an event, the scheduled generation of the ISGS shall be deemed to have been revised to be equal to actual generation, and the scheduled drawals of the beneficiaries shall be deemed to have been revised to be equal to their actual drawals.
NLDC 13
CERC(Measures to relieve congestion in real time operation) Regulations, 2009 NLDC to assess TTC, ATC and TRM of inter-regional
corridors in consultation with RLDCs RLDCs to assess TTC, ATC and TRM of regional
control areas Availability in public domain Provision of revision Charge both payable and receivable Warning notice and application of congestion charge Withdrawal of congestion charge Congestion charge account
NLDC 14
Rate of Congestion Charge Order
Rate of Congestion Charge – Rs 5.45/kWh Rate higher than the difference between maximum UI
charge and UI charge at 50 Hz Application of congestion charge
Below 50 Hz – downstream overdrawing entities Above 50 Hz – upstream underdrawing entities
Congestion caused by forced outage of a line in a corridor (after finalisation of drawl scheduled) No congestion charge shall be levied Provided the power flow on the corridor is as per the
schedule Such contingencies to be tackled through emergency
instructions by concerned SLDCs/RLDCs/NLDCs
NLDC 15
NLDC 16
Real Time Congestion Management
Procedure
Prepared in compliance to Section 4(2) ofThe Central Electricity Regulatory
Commission(Measures to relieve congestion in real time
operation)Regulations, 2009
NLDC 17
Transfer Capability Assessment
Total Transfer Capability Simulation Studies for Assessment
Network Modeling Input data for Basecase Preparation Operating and Emergency Limits Limiting Conditions
Basecase Violations (N-1) contingency Violations
Transmission Reliability Margin (TRM) Available Transfer Capability Import and Export Capability
Declaration of Congestion
Congestion in Real Time Voltage violations ATC violation in a corridor High loading of transmission elements
ATC violation for 2 time blocks – warning notice by NLDC
Curtailment of open access transactions Revision of Transfer Capability Application of Congestion Charge
Congestion persists after issuance of warning notice No affirmative action by defaulting agency foreseen
NLDC 18
Applicability of Congestion Charge
Applied simultaneously upstream and downstream
Applicable after 2 time blocks from notice
Remain in force for atleast 8 time blocks
Maximum upto 4 times a day
NLDC 19