A method and an apparatus for protecting a bus in a three-phase electrical power system

In the field of three-phase electrical power systems there is a need for an improved method and apparatus for protecting a bus which obviate the problems associated with conventional bus protection schemes. A method of protecting a bus (16) in a three-phase electrical power system comprises the steps of (a) sampling voltage values and current values of each phase of the or each power system element (14) within a predefined protection zone; (b) analysing at least one sampled voltage value of each phase of a power system element (14) within the protection zone to detect when a fault condition arises; (c) on detection of a fault condition, determining whether the fault condition has arisen because of a bus fault; and (d) electrically isolating the bus (16) from the or each power system element (14) within the protection zone when a bus fault is determined so as to clear the bus fault.