Prevention Method for False Operation of the Earth Leakage Circuit Breakers due to Lightning Surges

Abstract

The unnecessary triggering of an earth leakage circuit breaker (ELB), which may occur when a lightning strike occurs (hereafter referred to as a false operation) causes an interruption of the stable supply of electricity because it leads to a power failure accident for low voltage consumers. Furthermore, in many cases, the major cause of the false operation is not the direct lightning strike, it is the rather small induced lightning surge invading through a distribution line. As a result, the problem occurs over a wide range and, therefore, it becomes one of those problems that must be solved in order to properly serve the present highly information-oriented society. The author has studied the causes and mechanisms of the false operation of ELBs due to lightning surges which may occur when lightning occurs.In this report, the author details the results of further experimental studies into the means to prevent false operation of ELBs due to lightning surges building on the study results obtained so far, and reports the results obtained.(1) Reverse-parallel diodes were applied to the secondary side of the zero phase current transformer (ZCT) of an ELB. As a result, the surge current at which false operation occurs was improved by approx 6 times, that is, from 80 to 500 A.(2) A false operation prevention device for an existing ELB was trial-manufactured and studied experimentally. As a result, the false operation performance could be improved up to a surge current of 1.4 kA.Key Word: ELB, false operation due to lightning surge, false operation prevention measure, diode, bypass method.