Grade D proteced power surge protective device Amp: 5-10KA,10-20 KA ... suitable for TT, IT, TN-S, TN-C-S etc. power supply system of AC 50/60HZ, installed on the joint ... over-current, the failure release will help electric device separate from the power system and give indication signal. White means normal, red ... 6. Best service after sale are provided. Grade D protected power surge protective device