Open PEN fault

An open PEN fault is a break, disconnection or open-circuit condition in a combined PEN (protective earth and neutral) conductor on a low-voltage distribution network. In a TN-C-S or protective multiple earthing arrangement, that PEN conductor performs both neutral and protective functions on the network side of the supply. IET guidance explains that if this conductor is severed, a dangerous voltage can appear between earth and metalwork connected to the installation's protective conductors, and that BS 7671 requires EV charging equipment to cease charging and isolate the vehicle from the charging equipment when an open PEN conductor fault occurs on the distribution network.