Acti9 iPRD Quick Surge Arresters. Acti 9 iPRD DIN rail Surge Protector Devices are geared to absolute safety and improved continuity of service. Maximum discharge current 8 to 65 kA Integrated disconnector for short-circuit current withstand, Isc, up to 25 kA Maximum steady state voltage, Uc:260, 440 V Fixed or withdrawable surge arresters