Influence of High Current impulses and 50 Hz AC Bursts on the Temperature of Low-Voltage Metal-Oxide Surge Arresters

Metal-oxide surge arresters (MOSA) used as protective devices in electrical networks undergo during in-service operation aging processes that change their technical parameters. The main in-service stresses are: operating voltage, overvoltages, partial discharges and environmental factors. Exposures that result in the dissipation of electrical energy in the varistor structure cause an increase in its temperature and changes of the structure. The paper presents studies on the impact of pulsed electrical stresses, i.e. high-current surges 8/20 and 50 Hz AC bursts on the temperature of low-voltage arresters with metal-oxide varistors. During the tests, temperature contact measurements were made on a metal base of MOSA and registration of thermograms of their surface using a thermal imaging camera. Thermal processes occurring in the tested surge arresters are characterized by long time constants. For this reason, when researching these processes, AC bursts can be a suitable alternative to the use of high currents impulses.