A rational approach to dealing with harmonics

Although the number of power system problems caused by harmonics is not yet a significant widespread problem, the effects of nonlinear loads are, nonetheless, becoming an increasing concern in many parts of the world today. Fortunately, harmonic sources tend to cause more localized concerns. With a limited number of major harmonic sources, they can usually be analyzed in advance and, when they represent a significant load, they can be dealt with by more traditional measures, like filters or dual transformations (e.g., converting a harmful 6-pulse system to a more benign 12-pulse system). For the most part, the major sources of harmonics up until now have been large three-phase power converters. However, the increasing use of power electronics is revolutionizing even the likely appliances that may be plugged into future power systems. Ranging up the power scale, these relatively new power system polluters include switchmode power supplies (found in a variety of devices like computers, TVs, VCRs, etc.), fluorescent lamps with electronic ballasts, variable speed control of space heating and air-conditioning and chargers for electric vehicles. While most power systems generally tolerate a fair amount of harmonics, what begs the issue is: what is a reasonable approach to dealing with harmonics? In the author's opinion, equipment harmonic limits are needed, particularly because of the distribution system, and these limits should be based on the characteristics of the power system. The main emphasis of the paper is harmonic limits for single-phase equipment.