Abstract :
This paper discusses the behaviour of reverse-power a.c. relays of the wattmeter and allied types when applied to the protection of 3-phase generators and feeders, and it shows:- (a) The differences in behaviour produced by various systems of connections; (b) The improper operations inevitable with each system of connections; (c) The difficulties to be overcome in order to produce a reverse-power relay which will be stable with all conditions of forward power and whose operation will yet be certain under all conditions of reverse power. In addition, the paper shows that the most satisfactory results available with this class of instrument will be obtained if the potential coils of the relay be connected between line and neutral when used for generator protection, or between line and leading phase when used for feeder protection.
