PERSPECTIVE PLANNING FOR THE INDIAN NATIONAL GRID SYSTEM WITH ENHANCED RELIABILITY - CONCEPT OF A TWIN SYSTEM HAVING MULTI-POINT ASYNCHRONOUS HVDC INTER-CONNECTION

摘要

The Indian power sector is growing at an accelerated pace and in thenext 15-20years, it could increase five fold to the level of 500 GW peak demand and 700 GW of installed generation capacity. As future generation resources are away from load centers,transmission need may increase ten fold. Concept of regional planning in power sector was followed for about 35 years leading to development of five Regional grid systems. Since the advent of the current century, the planning has changed towards National grid. In National planning, the transmission requirement has increased substantially on account of quantum as well as distance. A large National grid network of 765 kV AC, 400 kV AC and HVDC bi-pole lines has been evolved. A numbers of ± 800 kV, HVDCbipole systems with 6000 MW capacity have also been envisaged and need of 1200 kV AC system is also being felt. Grid expansion is posing a number of issues such as increasing short circuit levels, operational voltage excursions due to fluctuating reactive balance, concern for risk of grid collapse with reduced probability but much higher implication. The issues are being addressed using the technologies and practice of the day. It is suggested to develop a Twin National Grid System in which the total inter-connected all-India National grid system is made up of two separate systems. The two systems would have asynchronous HVDC inter-connections at a number of points designed to be suitable for exchange of power from one system to the other. Power transfer from system to the other could be operationally regulated to optimize the operation of the twin system. The capacity of HVDC links would be determined from the consideration that operational depletion of transmission capacity in one system could be compensated by the other system. The twin system design would help to addressing short circuit level, providing HVDC control for operational regulation and contingency support from one system to other, and substantially reduce the implication of grid failure as failure of one grid would not lead to blackout. Each of the twin grid would also have its own independent hierarchical load dispatch/system control.