Determination of Effective Protection Distance in Front of Surge Protective Devices in Low Voltage Systems

Abstract

Surge protective devices (SPDs) is widely used in low-voltage power systems for protection of devices and equipment against surges. The SPDs provide the optimized protection level only if it is installed directly across the terminals of the equipment to be protected. However, it is not always possible to locate SPD close to the protected equipment, and an inevitable separation distance along connecting cable exists. Maximum distance along cable from point of SPD connection for which desirable protective characteristics are still fulfilled represents effective protection distance of SPD. Effective protection distance is usually determined for cable length after location of SPDs toward protected equipment. However, it is known that SPD provides protective effects also on devices installed at certain distance before location of SPDs. Determination of effective protection distance in front of SPD installed in low-voltage power system has been given in the paper. Analyses are performed with extensive number of simulations in MATLAB and ATP/EMTP with different influencing parameters in wide ranges of values, and with application of standard surge testing waveforms.