Prediction and Prevention of Load Encroachment for Reliable Operation of Distance Relay

Abstract

Electric power systems are complex and commonly run near their operational limits. In power systems, total or partial blackouts are unavoidable. A distance relay can provide remote backup protection by zones 2 and 3, but may mal-operate under heavy loading conditions and cause cascading trips in the network, which could further lead to a widespread blackout. Usually, load blinders or load encroachment elements block the distance relay when there is a heavy load in the system. The improved protection technique for zone 3 prevents mal-operation and, thus, power systems become more reliable. The most of the improved techniques prevents the load encroachment by blocking the performance of distance relay. Also those techniques don’t provide solution to reduce the loading limits.
In the research project, the increment of load is predicted from the load curve. If the load approaches the relay characteristics, the load on that particular line is reduced by optimal scheduling of generators or loads or both. The load encroachment phenomenon is not allowed to occur, before the load encroaches the action is taken preventing distance relay from tripping.