Patent ID: 7948241

Claim:
A method for determining the direction of fault in an electrical power system comprising the steps of: measuring a voltage (V) at a measurement node of the electrical power system, and storing at least the phase (φ PF ) of the measured voltage (V PF ) before the occurrence of a fault, characterised by the further steps of determining at least the phase (φ PF ) of the measured voltage (V PF ) at the end of a time interval (TI) following directly after a detection of said fault has been made, determining a phase offset (φ O ) as the difference between the phase (φ PF ) of the measured voltage (V PF ) before the fault and the phase (φ F ) of the measured voltage (V F ) at the end of the time interval (TI), adjusting the phase of the measured voltage (V F ) after the detection of the fault with said phase offset (φ O ), and using the adjusted measured voltage in determining the direction of fault in relation to said measurement node.