Dynamic compensation in indian Power system – siting & sizing

Indian Power System is divided into 5 (five) electrical regions viz. Northern, North-eastern, Eastern, Western & Southern. Indian grid is characterized by uneven distribution of resources and load centres. The regional grids in India have been interconnected for optimal utilisation of resources. The Northern, North-eastern, Eastern & Western grids operate in synchronous mode and are commonly referred to as NEW grid. Southern Region is asynchronously connected to NEW grid through HVDC links. With the interconnection of regional grids, Indian Power System has become one of the largest Power Systems in the world. The interconnection of regional grids and transfer of power from resource rich areas to demand areas has resulted in large inter-regional power flows. The inter-regional flows on some corridors become critical during depleted system conditions in peak hours thereby causing significant voltage drop at the nodes connecting these inter-regional corridors. Any transient fault under such situation may trigger tripping of lines and may result in large disturbance. To avoid such incidences, it is necessary to provide reactive power balance and to support the recovery which follows the clearing of line faults. Therefore, need was felt to plan dynamic compensation in the Indian Grid to provide first swing stability by maintaining system voltages during large disturbances. Studies were carried out to finalize the size, type and various locations for dynamic reactive power compensation in Indian Grid. Based on the studies, the dynamic reactive power compensation has been planned at sixteen (16) no. locations spread across the regions. The size of dynamic operating range of the reactive power compensation is from about 400 Mvar to 800 Mvar. The actual range of operation is further extended by control of mechanically switched Reactors and Capacitors proposed at these locations depending on the voltage profile during normal conditions. The locations at which the dynamic compensation is provided are typically a load centre or nodes on the inter¬regional corridor. With the implementation of the above proposed dynamic reactive power compensation, it is expected that the concerns regarding voltage instability in the grid shall be addressed and the transfer capability of the inter-regional corridors shall also be enhanced.

The present paper describes the planning studies carried out to finalize the size and various locations for dynamic reactive power compensation in Western Region of Indian Grid. For dynamic simulations, a number of disturbances were applied to the system and the voltage recovery with and without dynamic reactive power compensation device were studied. The studies show the stabilizing effect of dynamic reactive power compensation during transient conditions created by temporary fault situations. The size of dynamic operating range and mechanically switched capacitors and reactors at these locations was also finalised based on these studies and operational experience.