Grade D proteced power surge protective device Amp: 5-10KA,10-20 KA selected Pole: 1P,2P,3P,4P Glade D type ... TT, IT, TN-S, TN-C-S etc. power supply system of AC 50/60HZ, installed on the joint ... failure release will help electric device separate from the power system and give indication signal. White means normal, red ... service after sale are provided. Grade D protected power surge protective device