A study of Degradation Characteristics and Diagnostic Method of Lightning Surge Arrester for 6.6 kV Power Distribution Lines

Lightning surge arresters with a series gap are used in Japan for 6.6 kV distribution lines and are primarily comprised of a metal oxide varistor (MOV) with a series gap, and they are sealed by a metal lid and a sealing rubber. The degradation of the MOV can be determined by measuring a reference voltage equal to the terminal voltage of the MOV in small current region. However, there is currently no effective method to measure the reference voltage of an MOV without disassembling the lightning surge arrester with a series gap. This paper describes the degradation characteristics and limit of MOV as well as a method for measuring the terminal voltage of an MOV with a series gap. The authors determined a specific criterion for evaluating the degradation of an MOV and developed diagnostic device for identifying defective lightning surge arresters.