A Guideline on Surge Voltages in AC Power Circuits Rated up to 600 V

Surge voltages occurring in ac power circuits can be the cause of misoperation or product failure for residential as well as industrial systems. The problem has received increased attention in recent years because miniaturized solid state devices are more sensitive to voltage surges (spikes and transients) than were their predecessors. Although surge voltage amplitudes and their frequency of occurrence on unprotected circuits are well known, their waveshapes and energy content are less well known. On the basis of measurements, statistics, and theoretical considerations, a practical guideline for outlining the environment for use in predicting extreme waveshapes and energy content can nevertheless be established. The Surge Protective Device Committee of the Institute of Electrical and Electronics Engineers has been developing such a guideline, the essential elements of which are presented in this paper. Surge voltages [1] occurring in ac power circuits rated up to 600 V can be represented by various waveshapes in an attempt to duplicate actual surge voltages. Two major types of surges reflecting differences in the environment are described to represent the situation realistically. Systems located inside a building and separated from the overhead lines by some line impedance experience surge voltages of waveshapes and energy levels that differ from those of the outdoor environment. Outside systems exposed to direct lightning strikes or lightning-induced surges—typically overhead lines—experience levels implied by IEEE standards for secondary arresters. This guideline addresses particularly the hazards to these two types of systems [2].