Grade D proteced power surge protective device Amp: 5-10KA,10-20 KA selected Pole: ... protection device (SPD, surge protector, surge arrester) is suitable for TT, IT, TN-S, TN-C-S etc. power ... -current, the failure release will help electric device separate from the power system and give indication signal. White means ... service after sale are provided. Grade D protected power surge protective device