Abstract: The present invention is directed to a protective relay for providing protective control to a power system carrying three-phase power. The protective relay performs a faulted phase detection method wherein signal values representative of electrical properties of the power carried by the power system are received and are processed to produce processed signals, respectively. The processed signals have components of the signal values removed that are the same frequency as the nominal operating frequency of the power system. The process signal values are added to produce a sum, which is then divided by a predetermined number to yield a quotient. A determination is made whether the quotient falls within one of a plurality of predetermined ranges. This determination is used to determine whether the power system has a single-phase fault, a two-phase fault, or a three-phase fault.

Abstract: The present invention is directed to a protective relay for providing protective control to a power system carrying three-phase power. The protective relay performs a faulted phase detection method wherein signal values representative of electrical properties of the power carried by the power system are received and are processed to produce processed signals, respectively. The processed signals have components of the signal values removed that are the same frequency as the nominal operating frequency of the power system. The process signal values are added to produce a sum, which is then divided by a predetermined number to yield a quotient. A determination is made whether the quotient falls within one of a plurality of predetermined ranges. This determination is used to determine whether the power system has a single-phase fault, a two-phase fault, or a three-phase fault.