Patent ID: 6525543
Filing Date: 2003-02-25
Classification: H02H

Abstract:
A system for fault type identification in an electric power system, using three-phase current information on the power line, comprising:a first circuit means responsive to protective elements which recognize the presence of single line-to-ground (SLG) faults for phases A, B and C on a power transmission line, the first circuit means including a portion thereof for recognizing and asserting output indications of single line-to-ground faults, faults involving two phases and three-phase faults, in response to the occurrence of different combinations of outputs from the protective elements; a calculation circuit, responsive to an enable signal generated upon the determination of the existence of selected threshold current conditions on the line, for determining the angular difference between the total zero sequence current and the total negative sequence current for the three-phase current on the power line, for identifying high resistance faults, wherein the angular difference is in one of three pre-selected angular difference sectors, wherein an angle difference in the first sector indicates an A phase to ground fault or a BC phase-to-phase to ground fault, wherein an angle difference in the second sector indicates a B phase to ground fault or a CA phase-to-phase to ground fault, and where an angle difference in the third sector indicates a C phase to ground fault or an AB phase-to-phase to ground fault angle differences in each of the three sectors being indicated by sector signals; and processing means for determining which of the two possible fault types indicated by the determined angular difference is the actual fault type and for providing a signal indication of said actual fault type.