The Westinghouse Induction Time Klement Overload Relay, Type CO, a relay operating on the same principle as an alternating current watt-hour meter, is considerably affected in its time of operation when non-sinusoidal waves of potential are applied. If the potential wave applied has a flat top or depressed peak or if the wave has a lagging peak, that is, its maximum instantaneous value occurs more than 90 degrees after the beginning of the cycle, the operation of the relay is accelerated. If the wave of potential applied to the relay reaches its peak more than 90 degrees and less than 180 degrees after the beginning of the cycle, the operation of the relay is retarded from what it would be with a sinusoidal potential applied.

The operation of a General Electric Time Current Overload Relay, Type PAC, a plunger type relay with an air bellows time delay, is, in general, retarded in operation by the application of non-sinusoidal potential waves. The operation may be slightly accelerated, however, if the wave distortion is slight, the current setting is low, and the distortion is such that the peak of the wave is flat or lagging.

The effect of the wave distortion on other relays requires more study.