Effect of Single-Phase Reclosing on Industrial Loads

Three-phase reclosers with single-phase tripping are being more widely employed on utility distribution feeders. They have the advantages of increasing reliability for the customers on the feeders, because the majority of distribution feeder faults are single-phase. However, certain difficulties may occur when three-phase industrial and commercial loads, with three-phase transformers and motor loads are interrupted on one phase only. These include overheating of motors, ferroresonance of transformers, tripping of power electronic drives and backfeeding of distribution lines. This paper examines these effects, their severity and mitigation techniques