LIGHTNING ARRESTER FAILURE AND FERRORESONANCE ON A DISTRIBUTION-SYSTEM

Since 1987 the Upper Peninsula Power Company (UPPCO) has been experien cing a large number of lightning arrester failures on a portion of the ir distribution system in southern Marquette County, Michigan. It was in the area of the Navy's Extremely Low Frequency (ELF) antenna where the distribution system had been recently reconfigured so that the tra nsformers were connected line-to-line in order to eliminate interferen ce from the antenna. A study was done which determined that the system was susceptible to ferroresonance during single line faults under lig htly loaded conditions and that the overvoltages experienced could be causing the lightning arrester failures. This conclusion was further s trengthened by a statistical study which compared the actual number of failures to an expected number of failures given the system loading c ondition and fault rate.