Optimal Coordination of Distance and Overcurrent Relays

This chapter helps the industry professionals to understand the importance of coordinating distance and overcurrent relays. It discusses the variation in operating time of distance relays at different fault zones. The chapter aims to determine when do distance relays operate as primary or backup protective devices. It explores different mathematical models for the special optimal coordination problem. The reason of using over‐current relays (OCRs) instead of other relays is that OCRs can compromise between many performance criteria. In distance protection, the voltage and current at the beginning of the line are utilized to determine the fault location where the impedance can be measured through a relay comparator. The literature contains many studies about optimal coordination of distance and overcurrent relays. Conventional OCRs are widely used to protect radial distribution systems and source nodes.