Simulating and testing of incoming overvoltage using SPDs in electrical power circuits

In scenarios involving an increased risk of damage to electrical and electronic equipment due to lightning, it is important to protect equipment by employing protection mechanisms such as surge protective devices (SPDs). However, it is difficult to achieve effective protection when the protective devices have incorrect specifications, or when incorrect connections are made for the equipment to be protected. In this study, we develop circuit simulation models to investigate how the selection and installation conditions of SPDs affect their protective effect. We perform experiments and analyses using power-supply circuits of actual equipment where a single-phase alternating current (AC) voltage of 200 V was supplied outdoors. By modeling in detail a varistor as a nonlinear resistance, we were able to analyze the protective effect of varistors in power-supply circuits. By installing the varistors before and after the filter unit in the power supply circuit, we can realize the protective coordination of multiple varistors because the filter unit functions as a decoupling element. © 2015 The Institute of Electrical Engineers of Japan.