Challenges in assessment of transfer capability under a high growth high uncertainty restructured scenario in India

摘要

The role of the system operator worldwide as well as in India has undergone a greattransformation over the last decade. From the role of ensuring that the bulk electric powersystem is operated in a reliable manner, the role has now got enlarged to ensure that thewholesale electricity markets also function efficiently. Each activity in system operationinfluences the electricity markets significantly, be it the planned or forced outage of animportant transmission line leading to constraints in flow of power or outage of a power planteither due to a fault or fuel related issues.Since 2003 when the new Electricity Act [1] came into existence, there has been a paradigmshift in system planning and operation in the Indian power sector. Non-discriminatory openaccess [2] to the transmission system has been a key part of the reform process. Therefore,assessment of transfer capability across different parts of the transmission network,broadcasting of this information for all the market players and updating it periodicallybecomes an important aspect of operational planning.These developments have posed new challenges to the system operator and the transfercapability has to be determined in a precise manner. Unrealistic assumptions could either leadto sub-optimal utilization of the transmission system or necessitate real time curtailment topreserve the network security. Frequent curtailment of transactions in a large grid also has thepotential for disputes as all market players have to be informed well before-the-fact. All thiscalls for a high level of transparency and availability of ‘common information’ to all marketplayers. This paper deals with the challenges faced by the Indian system operator in this area,particularly considering the high level of growth as well as uncertainty in the restructuredpower system.This paper describes the development of the electricity grids in India starting from regionalgrids. Initially, there were a few radial ties between the regions with power exchange takingplace only in case of emergencies. From 1989-2002, HVDC back to back ties between the regions were also established paving the way for opportunity exchanges. Gradually, theregional grids were synchronized.Non-discriminatory Open Access to transmission and development of electricity marketsresulted in an explosion in electricity trading and bringing to centre stage, the issue of thenetwork transfer capability. The physical limitations of the network had to be clearlyinformed to the market players. In a high pace of growth be it of load, new generatingcapacity or new transmission systems, a high level of uncertainty is inevitable. Theseuncertainties result in a situation where the congestion points move from corridor to corridorand necessitating the need for redefining the interface where Total Transfer Capability isdeclared. This paper highlights the above challenges for the Indian electricity grid and themanner in which it is being handled under regulatory oversight.