A sequence relay for network protectors

USELESS operations of protectors on low voltage distribution networks are practically eliminated when controlled by a relay that has been designed in accordance with the principles laid down in the companion paper “Application of Phase Sequence Principles to Relaying of Low Voltage Secondary Networks.” This relay consists of a single phase induction disk directional element, 2 overcurrent control elements of the contactor type, and suitable current and voltage filters to make it operative on 3-phase circuits. All parts, with the exception of 2 resistors and a phasing lamp, are mounted in a standard relay case.