Grade D proteced power surge protective device Amp: 5-10KA,10-20 KA ... for TT, IT, TN-S, TN-C-S etc. power supply system of AC 50/60HZ, installed on the joint of LPZ1 ... the failure release will help electric device separate from the power system and give indication signal. White means normal, red means abnormal ... 6. Best service after sale are provided. Grade D protected power surge protective device