Future Distribution Feeder Protection Using Directional Overcurrent Elements

Abstract

Distribution feeder protection could soon be complicated by nonradial flows of real and reactive power available from high penetration distributed generation and potentially from microgrids. Nondirectional overcurrent protection may not provide necessary security and sensitivity for faults on remote points of the circuit. Directional supervision is necessary to set overcurrent pickups with adequate sensitivity for remote faults. Setting the directional element by traditional means provides a reliability risk at varying VAR flows within reach of specific types of distributed generation. This paper will demonstrate the limitations of nondirectional overcurrent protection and the pitfalls of an improperly configured directional element. A unique solution using directional overcurrent elements further secured by a load encroachment function can solve these problems. This approach has been validated in renewable plant collector circuit protection applications over a wide range of operating conditions.