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

The author discusses several of the practical problems involved in applying total harmonic current distortion limits to industrial and commercial power systems. It is noted that because of the complexity of the harmonic current sources and the complexity and variability of the power system impedances at the harmonic frequencies, determination of harmonic current flows becomes very difficult. The formulation of limits of harmonic current distortion at one point in the power system, the PCC (point of common coupling), will leave the system designer with great uncertainty regarding compliance of the overall system without a direct measurement after the fact. A suggested alternative or addition to the harmonic current distortion limits at the PCC is the establishment of limits for each individual nonlinear load by category. In this way, more practical limits could be established, and there would be less compliance uncertainty for the system designer.<>