... ,Arrestor) It protects the electric network shocked by the thunder or over voltage . Surge Protective Device(Surge Protector,Arrestor)Usage and application ... scopeBY40 type surge protective device (short name "SPD") is suitable for AC 50/60 Hz, ... -S, TN-C, TN-C-S. It protects the electric network shocked by the thunder or over voltage .Working condition: 1 ...