IEEE C62.41-1980 pdf free.IEEE Guide for Surge Voltages in Low-Voltage AC Power Circuits.
IEEE C62.41 primarily addresses ac power cir-cuits with rated voltages up to 277 V line toground，althoughsome of the conclusionsoffered could apply to higher voltages and alsoto some dc power systems. Other standardshave been established，such as ANSI/IEEEC37.90a-1974，Guide ’for Surge WithstandCapability (swc)Tests，intended for thespecial case of highvoltage substation environ-ments,and ANSI/IEEEStd 28-1974, Standardfor Surge Arresters for AC Power Circuits,covering primarily the utilities environment.This guide intends to complement, not conflictwith,existing standards,and to present a practical basis for the selection of voltage and cur-rent tests to be applied in evaluating the surgewithstand capability of equipment connectedto these power circuits, primarily in residential,commercial，and light industrial applications.Although the data have been recorded primarilyon 120，220/380，or 277/480 v systems,thegeneral conclusions may be valid for 6o0 V systems， but more data are needed for the highervoltages.
While the major purpose of this guide is todescribe the environment, a secondary purposeis to lead toward standard tests and the preparation of an application guide.Standard tests willprovide a realistic evaluation of the surge withstand capability of equipment connected to thepower circuits suitable for most installations.of necessity，the complex real situation mustbe simplified to produce a manageable set ofstandards. Proper application,or coordinationof equipment capacility and environmentalcharacteristics，of course remains the responsi-bility of manufacturers and users.
The surge voltages (see 8.1 ) considered in thisguide are those exceeding 2 per unit (or twicethe peak operating voltage) and having durations ranging from a fraction of a microsecondto a millisecond. Overvoltages of less than 2 perunit are not covered here, nor are transients oflonger duration resulting from power equipment operation and failure modes.Becausesuch low-amplitude and long-duration surgesare generally not amenable to suppression byconventionalsurge protective devices，theyrequire different protection techniques fromthose discussed in this guide.
General.Surge voltages occurring in low-voltage ac power circuits originate from twomajor sources, system switching transients anddirect or indirect lightning effects on the powersystem.
Lightining Transients. Measurements andcalculations of lightning effects have beenmade to yield data on the levels that can beproduced, even if the exact mechanism of any particular surge is unknown.The major mech-anisms by which lightning produces surge voltages are the following:
(1)A direct lightning strike to a primarycircuit injects high currents into the primarycircuit，producing voltages by either flowingthrough ground resistance or flowing throughthe surge impedance of the primary conductors.(2) A lightning strike that misses the line buthits a nearby object sets up electromagneticfields which can induce voltages on the conductors of the primary circuit.IEEE C62.41 pdf download.