LH-BO (nisa 18) jerin masu karewa (wanda ake magana da shi azaman SPD) ya dace da IT, TT, TN da sauran tsarin samar da wutar lantarki na tsarin rarraba wutar lantarki mai ƙarfi AC don kare walƙiya kai tsaye, walƙiya kai tsaye ko wasu tashin hankali nan take.
Masu kare hawan hawan matakin mataki na biyu da na uku da masu kariyar gwajin gwaji na Class II bisa ma'aunin IEC61643-1. SPD yana da yanayin gama gari (MC) da hanyoyin karewa na yanayin banbance (MD).
Samfuran sun cika ka'idodi kamar GB/T 18802.11 da IEC61643-1.