Petition No. 188/suo-motu/2012. Case: Calculation of Total Transfer Capacity, Available Transfer Capability and Transmission Reliability Margin Vs National Load Despatch Centre, New Delhi. Central Electricity Regulatory Commission
| Case Number | Petition No. 188/suo-motu/2012 |
| Judges | Dr. Pramod Deo, Chairperson, Shri S. Jayaraman, Member, Shri V.S. Verma and Member Shri M. Deena Dayalan, Member |
| Issue | Electricity Law |
| Judgement Date | August 31, 2012 |
| Court | Central Electricity Regulatory Commission |
Order:
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National Load Despatch Centre in its letter No. POSOCO/NLDC/Tr. Cap dated 2.8.2012, addressed to Member (PS) and Member (G&O), Central Electricity Authority and Executive Director (Engg.-SEF). Central Transmission Utility, with copy endorsed to the Secretary of this Commission, has forwarded a note on "Loading of Extra High Voltage (EHV) transmission elements on the network and its impact on the grid security". It has been proposed in the said letter, that subsequent to the grid disturbance, the basis of assessment of Transfer Capability has been taken as Surge Impendence Limits (SIL) of the lines, instead of stability limit evaluated from St. Clair's curve, or thermal limit, depending upon the line length. The revised limits based on the said methodology have been implemented w.e.f. 1.8.2012. It has been mentioned in the note that in the antecedent grid conditions of the grid disturbance on 30.7.2012 and 31.7.2012, there was heavy power flow on the Bina-Gwalior-Agra section crossing 1000 MW on the single circuit available. It has been further stated that the 400 KV Gwalior-Agra line is 128 km. long and as per CEA planning criteria, it could be loaded up to the thermal limit of the order of 2500 MW and above. However, it was witnessed in the grid disturbance on the said dates that the antecedent loading of 1000 MW and above on the section had led to cascading effect. Accordingly, NLDC is stated to have reviewed (in consultation with CEA and CTU) the transfer capability of inter-regional and other critical links keeping in view the CERC Regulations and experience during the two grid collapses, till the incidents of grid disturbance are analyzed in detail and the shortcomings in the protective systems in different regions are identified. The Detailed Procedures under the CERC (Grant of Connectivity, long-term access and medium term open access in inter-state transmission & related matters) Regulations, 2009 (Connectivity Regulation) and the CERC (Measures to relieve congestion in real-time operation)...
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