Uncertainties in compliance with harmonic current distortion limits in electric power systems

The recent widespread use of static power converters has brought about the need to set limits on harmonic distortion to avoid noise and interaction problems in the power system. The harmonic distortion of any repetitive voltage or current waveform is typically described by the quantity total harmonic distortion (THD). Proposals have been made to limit harmonic currents in power systems using the total harmonic distortion of the current as the criterion. This criterion, although it may be necessary, can be ambiguous and lead to compliance uncertainties. A discussion is presented on several of the practical problems by applying total harmonic current distortion limits to industrial and commercial power systems