An intuitive analysis of harmonic power flow in electrical distribution systems

Many have already written much about power quality and harmonics in particular. As nonlinear loads such as lighting ballasts, electronics and variable-speed motor drives become a larger percentage of the total power consumed, the resulting harmonic currents can damage equipment. Furthermore, the local effects of harmonics are most pronounced with higher source impedance from the power source. Unless continually monitored, the power quality can degrade as the power system changes until the situation is symptomatic-a nuisance at first followed by more costly damage. The focus of this paper is an explanation for these well documented harmonics. Presented is a procedure for identifying the source of harmonic currents in the power distribution system as measured at various feeders and loads. Also presented are explanations by example that show why some harmonics exist while others do not. Harmonic cancellation is explained along with the presentation of a tool for understanding and predicting the results