Degradation analysis of MOV type SPDs with surge supurposing AC operating voltage

There are various kinds of surges in LV system superposing the AC operating voltage. This document presents the test on MOV type SPDs to discover the possible reasons for fire under operation that are observed in field. The tests are including the AC test, surge test, surge on AC voltage and multiple surges. The test results lead to the solutions on how to deal with the safety problem.