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, TN-S, TN ... status, white means normal, red means abnormal. Surge Protection , Surge Suppression