Grade D proteced power surge protective device Amp: 5-10KA,10-20 KA selected Pole: ... 2P,3P,4P Glade D type surge protective device 1. Description:Surge protection device (SPD, surge protector, surge arrester) is ... SPD fails in breakdown for over-heat and over-current, the failure release will help electric device separate from the power system ... provided. Grade D protected power surge protective device