US Patent 10352984 Fault location in power distribution systems

A method of locating a fault on an electricity transmission line is disclosed. The transmission line has a known line impedance and is operable to transport electricity at one or more system frequencies. The method comprises using measurements of the current and voltage made on the line at one or more frequencies which are different to the system frequency and the known line impedance (Z) to determine a distance to the fault. The method may include monitoring the voltage and the current on the transmission line at the one or more non-system frequencies, and determining from the presence of signals at a non-system frequency on the transmission line that a fault has occurred.