正(zheng)常情況下(xia)，故(gu)(gu)(gu)障(zhang)指(zhi)示(shi)(shi)(shi)器(qi)不動(dong)(dong)作，故(gu)(gu)(gu)障(zhang)指(zhi)示(shi)(shi)(shi)燈不亮。當通過(guo)電(dian)(dian)(dian)纜的(de)電(dian)(dian)(dian)流(liu)達(da)到故(gu)(gu)(gu)障(zhang)指(zhi)示(shi)(shi)(shi)器(qi)設定(ding)的(de)故(gu)(gu)(gu)障(zhang)電(dian)(dian)(dian)流(liu)值時，顯示(shi)(shi)(shi)器(qi)會對(dui)由傳感器(qi)傳來的(de)電(dian)(dian)(dian)流(liu)進行判斷，如果(guo)過(guo)電(dian)(dian)(dian)流(liu)持續不到100～200 ms，則此(ci)(ci)電(dian)(dian)(dian)流(liu)可能是電(dian)(dian)(dian)機起(qi)動(dong)(dong)等因(yin)素引起(qi)的(de)瞬間起(qi)動(dong)(dong)過(guo)電(dian)(dian)(dian)流(liu)，不是故(gu)(gu)(gu)障(zhang)電(dian)(dian)(dian)流(liu)，因(yin)此(ci)(ci)顯示(shi)(shi)(shi)器(qi)不動(dong)(dong)作。如果(guo)過(guo)電(dian)(dian)(dian)流(liu)持續超(chao)過(guo)100～200 ms，則判斷為故(gu)(gu)(gu)障(zhang)電(dian)(dian)(dian)流(liu)，顯示(shi)(shi)(shi)器(qi)動(dong)(dong)作，指(zhi)示(shi)(shi)(shi)燈閃(shan)爍顯示(shi)(shi)(shi)。
顯(xian)(xian)示器動(dong)(dong)作(zuo)(zuo)后再作(zuo)(zuo)一次(ci)判斷(duan)，如果2 s內電(dian)纜電(dian)流已(yi)恢復正常(chang)，說(shuo)明(ming)上(shang)級(ji)開關重合(he)閘成功(gong)，故(gu)障點已(yi)被排除，恢復正常(chang)供電(dian)狀態，顯(xian)(xian)示器回(hui)復初始狀態，指(zhi)示燈(deng)熄滅。如果2 s內電(dian)纜電(dian)流消失，說(shuo)明(ming)故(gu)障已(yi)引發上(shang)級(ji)開關跳閘而導致電(dian)纜失壓，則確定為故(gu)障，顯(xian)(xian)示器保持動(dong)(dong)作(zuo)(zuo)，指(zhi)示燈(deng)繼(ji)續(xu)閃爍，直(zhi)到達到預設的時間限值或受到人工手動(dong)(dong)復位為止。
