Estimation of Discharge Current Sharing Between Surge Arresters with Different Protective Characteristics Connected in Parallel

Abstract

This paper examines the effect of different protective characteristics of two metal oxide surge arresters knowingly connected in parallel. To assess the distribution of the discharge current between surge arresters, frequency-dependent models of surge arresters were used. The circuit simulation was performed using both oscillogram of real lightning current and traditional idealized lightning current waveform. If several metal oxide surge arresters are supposed to be connected in parallel, for example, to increase energy handling capability, they should be selected in the most careful way to have the same protection characteristics. It is shown that if the residual voltages, and therefore the voltage-current characteristics differ by only a few percent, this is enough for the discharge current flowing through one surge arrester to be several times greater than the current of the other one.