Relay-based undervoltage load shedding scheme for Entergy´s Western Region

Fault-induced delayed voltage recovery (FIDVR) is a major concern in bulk electric systems, especially in high load growth areas of the system which may be limited in generation and transmission. As part of an overall emergency plan to manage exposure to low voltage conditions and resulting voltage instability under summer peak load conditions, a fast-acting, localized, relay-based undervoltage load shedding (UVLS) scheme has been implemented for Entergy´s Western Region. This paper describes the planning considerations and design criteria, followed by implementation details of the relay operation logic programmed using a standard microprocessor-based multi-functional relay. A number of dynamic simulations were performed using PSS/E program and the resulting voltage trajectories were used for testing the relay operation.