Accessories Arrester for d.c. Voltage Systems Medium-Voltage Surge Arrester Polymer Housing Porcelain Housing Transmission line Menu Accessories Arrester for d.c. Voltage Systems Medium-Voltage Surge Arrester Polymer Housing Porcelain Housing Transmission line Nominal Discharge Current 5 kA Nominal Discharge Current 10 kA Nominal Discharge Current 5 kA Protection of transformers, switchgears and transmission lines against atmospheric and switching overvoltages.iec_class_2_up_to_145_kv-unlocked Nominal Discharge Current 10 kA Protection of transformers, switchgears and transmission lines against atmospheric and switching nominal_discharge_current_10_kaovervoltages.