The Impact of Sine-Wave Distortions on Protective Relays

Sine wave distortions on power systems are shown to affect the performance of both electromechanical protective relays of classical designs and static relays of various designs. Digital based (computer) relay systems do not circumvent, per se, wave distortion problems. Protection relays are shown to not respond to any single parameter such as the rms value or the fundamental component, of an applied signal. It is noted that there are no wave distortion performance standards nor waveform testing standards for protective relays, other than for harmonic restraint relays. This can be attributed to the lack of recognizing as a significant factor the causal relationship between relay performance and waveform distortion. This is an interim report constituting about 20 percent of a contemplated special report, "Sine Wave Distortions on Power Systems and the Impact on, Protective Relaying". A bibliography on the larger subject is included.