Lightning overvoltage suppression to UHV power transformer by ferromagnetic ring

Abstract: Lightning overvoltage protection is of great importance to the safety of devices in UHV GIS. In practice, insulation failure of UHV transformer due to lightning strike is often reported. The widely used UHV metal-oxide arresters can suppress the magnitude of lightning overvoltage but lack effectiveness on alleviating the steepness. A new protection method is proposed in this paper using ferromagnetic ring as supplement to the arresters in suppressing lightning overvoltage within UHV GIS. Moreover, equivalent model based on the characteristic of ferromagnetic material and factual dimensions of the ring is established. Simulation of an actual 1000kV GIS is carried out to thoroughly evaluate the lightning overvoltage suppressing effect of ferromagnetic rings with different materials and structure parameters. [Copyright &y& Elsevier]