IEEE Recommended Practice on Surge Voltages in Low-Voltage AC Power Circuits
|Publication Date:||1 January 1991|
industrial and residential systems and equipment. These problems have received increased attention in recent years because of the widespread application of complex semiconductor devices that are more sensitive to voltage surges than vacuum tubes, relays, and earlier generations of semiconductor devices.
Logical and economical design of circuits to protect vulnerable electronic systems from upset or failure requires knowledge of or an estimate of:
1) Transient voltage and current waveforms,
2) Frequency of occurrence of transients with various energy levels,
3) Particular environmental variations such as amplitudes, and
4) Upset or failure threshold of the particular equipment to be protected.
The previous edition of this document, IEEE C62.41-1980, "IEEE Guide for Surge Voltages in Low-Voltages AC Power Circuits" (also known as IEEE Std 587-1980), contained similar information about the surge environment. Most of the voltage surge recordings for the 1980 edition were made prior to 1975, when electronic instrumentation for surge monitoring was not readily available. Instrumentation and data-base information, while still limited in some parameters such as very short rise time and frequencies, have vastly improved, as reflected in this edition.
This document provides updated and expanded information relevant to a typical surge environment based upon location within the building, power-line impedance to the surge, and total wire length. Other parameters often adding to the surge environment include proximity and type of other electrical loads, type of electrical service, wiring quality, and geographic location.
New information on probability of surges has been added. A new waveform incorporating a shorter front and two new waveforms incorporating longer durations supplement the two standard waveforms. A new section consisting of a "how-to-use" guide has also been added to allow the reader to develop a rational approach to equipment protection by following the recommendations of this document.
It must be noted that a recommendation of test waveforms alone is not an equipment performance specification. Other documents based on the waveforms recommended herein have been or will be developed to describe the performance of equipment or protective devices in low-voltage ac power circuits.
Some manufacturers have advertised that their protective device "meets the requirements" of IEEE Std 587-1980 or IEEE C62.41-1980. Such a statement is a misuse of the document, since the document only describes surges and does not specify any specific safe level or performance of equipment during application of a test waveform. The levels given in this document reflect typical environment conditions and provide a menu from which equipment designers and users can select the values appropriate to a specific application. Any statement that a protector "meets the requirements of" or "is certified to" this document is inappropriate and misleading.
The Summary given after this Foreword is intended only for a rapid overview and therefore is not included as part of the recommended practice.
Suggestions for improvements of this recommended practice will be welcomed. They should be sent to the Secretary, IEEE Standards Board, Institute of Electrical and Electronics Engineers, 445 Hoes Lane, P.O. Box 1331, Piscataway, NJ 08855-1331, USA.
The purpose of this recommended practice is to provide information on surge voltages in low-voltage1 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 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 ,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.