What is Earth Fault Loop Impedance?
when there is an electrical earth fault on a circuit current flows from the Line (phase) conductor through the fault, down the CPC (earth wire) along the earthing conductor provided by the electricity company for TNS and TNCS or through the earth electrode and planet earth for a TT system into the neutral point of the supply company transformer and through the transformer winding The circuit (or loop) then is the Transformer winding (impedance) the supply company phase cable the phase cable in the installation and the return earth conductor (resistance) This complete circuit is called the earth fault loop and the Earth fault loop impedance is the value in ohms measured at the furthest point in a circuit and depends on the length and size of cables and the impednace of the supply transformer. It is measured using an earth fault loop impedance tester. Once a measurement is taken its value can be compared with a maximum value for a given protective device (fuse/circuit breaker) in IEE wir