A.17.5mm B.19mm C.21.6mm D.21mm
A.線路爬電距離要求 B.絕緣子串污耐壓 C.污穢物的導(dǎo)電率及吸濕性 D.遠(yuǎn)離污穢源
A.0.5% B.1% C.1.5% D.2%