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Description / Abstract:
The purpose of this recommended practice is to provide information on
surge voltages in low-voltage (Footnote 1) ac power circuits. With this
information, equipment designers and users can evaluate their operating
environment to determine their need for surge-protective devices. The
document characterizes electrical distribution systems in which surges
exist, based upon the data that have been recorded in interior locations
on single-phase and three-phase residential, commercial, and industrial
power distribution systems.
There are no specific models that are representative of all surge
environments; the complexities of the real world need to be simplified
to produce a manageable set of standard surge tests. To this end, a
surge environment classification scheme is presented. This
classification provides a practical basis for the selection of
surge-voltage and surge-current waveforms and amplitudes that may be
applied to evaluate the surge withstand capability of equipment
connected to these power circuits. It is important to recognize that
the proper coordination of equipment capability and environment
characteristics is required: each environment and the equipment to be
protected has to be characterized and the two reconciled.
The surges considered in this document do not exceed one-half period of
the normal mains waveform in duration. They may be periodic or random
events and may appear in any combination of line, neutral, or grounding
conductors. They include those surges with amplitudes, durations, or
rates of change sufficient to cause equipment damage or operational
upset (see Fig. 1). While surge-protective devices acting primarily on
the amplitude of the voltage are often applied to divert the damaging
surges, the upsetting surges may require other remedies.
Test procedures are described in IEEE C62.45-1987 [8], (Footnote 2) as a
companion to the present document. Other surge-related standards are
identified in Section 4; the present document is intended to complement
these standards.