Innovative distribution feeder protection and control schemes using new capabilities of microprocessor relays

Currently distribution feeder protection and control (P&C) schemes are designed using previous generation of the microprocessor relays, electromechanical switches, and separate annunciation and metering panels. This paper describes development of an innovative redundant protection and control schemes utilizing the state of the art features offered by the new microprocessor relays for distribution feeder application for one of the major utilities in the United States. In the process of designing and implementing this new distribution P&C schemes, there were numerous challenges. Special consideration and efforts were extended to comply with the utility's philosophies in relay redundancy, reclosing practices, underfrequency load shedding, overfrequency restoration and protection against "single phasing" conditions in the fused bank applications. The paper also discusses the operational experiences gained from the feeder installations employing this scheme, which validates the merits in the engineering approach as well as design and implementation