Research on Surge Voltage Withstand of Medium Voltage Vacuum Reed Relay

This paper presents results of experiments carried out in order to determine surge voltage withstand of vacuum reed relay which is not given in the catalogue notes. Three MV vacuum switches were tested with standardized 1.2/50 μs voltage surge. Breakdown voltages of each analyzed reed relay were determined. The same devices (after breakdown) were tested once more in order to examine the insulation properties. As it was observed, after two electrical breakdowns, electric withstand of each reed relay decreased significantly. Based on conducted measurements it was determined that the breakdown voltage is twice as high as 60 s DC withstand voltage provided by the manufacturer. The paper also presents the analysis of electric arc erosion of electric contacts after the electrical breakdown. An optical microscope was used to perform observations of damaged surfaces. Additionally, roughness profiles of damaged contact surface were measured.