Managing harmonic emissions from small low voltage installations

Managing voltage distortion in power systems usually consists of two steps. The first step, mostly utilized outside of North America, involves limiting harmonic emissions from individual pieces of equipment. The second step, utilized worldwide in different ways, is to manage harmonic emissions on a system level. Traditionally, equipment emissions have been managed at low voltage (LV) whereas system-level electromagnetic compatibility (EMC) issues, including harmonics, have been managed at medium, high, and extra-high voltages (MV, HV, and EHV). With the continued growth of low voltage networks, it is becoming necessary to implement some type of system-level coordination strategy at low voltage. Toward this end, IEC TC77/SC77A/WG8 has developed a committee draft document outlining an EMC coordination approach for harmonics, flicker, and voltage unbalance in LV systems and networks. This work is intended to bridge the existing gap in EMC coordination between small equipment harmonic limits and (larger) installation-level limits. To effectively bridge this gap, it is necessary to borrow concepts from both equipment and system-level EMC coordination approaches while not overburdening the parties involved in the process. The possibilities of using current harmonic limits for small installations connected to LV are considered in this paper.