Surge Protection (Surge Protection Device, Surge Suppression) OVR BT2 4P In:20kA, Imax:45kA Uc:420V DescriptionOVR BT2 series Surge Protection Device (in short: ... SPD, alias: Surge Suppression, Surge Arrester) is suitable for TT, IT ... status, white means normal, red means abnormal. Surge Protection , Surge Suppression