iPRD withdrawable surge arresters allow quick replacement of damaged cartridges. Type 2 surge arresters are tested with a 8/20 Ps current wave. Type 3 surge arresters are tested with a 1.2/50 Ps and 8/20 Ps combined wave. The iPRD8(r) ensures secondary protection of loads to be protected and is placed in cascade with the incoming surge arresters. This surge arrester is required when the loads to be protected are at a distance of more than 10 m from the incoming surge arrester