Patent ID: 6459960
Filing Date: 2002-10-01
Classification: H02H

Abstract:
A distance relay equipment for detecting a protective region having a fault, among a protective zone that includes a plurality of protective regions, based on a status of a power system, comprising:an operation decision unit having short-circuit fault distance relay elements that input respectively an electrical quantity from an AC power system of three phases a, b and c, the operation decision unit calculating a fault impedance from each of the electrical quantity to compare said fault impedance, which correspond to ab-phase, bc-phase and ca-phase, with a set impedance, to produce a judging signal of each ZIS (zone first for phase fault) element (ZIS element-ab, ZIS element-bc and ZIS element-ca), depending on said result of said comparison; a calculating unit for calculating a phase-to-phase voltage amplitudes(|Vab|, |Vbc|, |Vca|) in said ab-phase, bc-phase and ca-phase; a minimum phase voltage selection unit for selecting a minimum voltage phase (V&Dgr;min) for the phase-to-phase voltage amplitudes(|Vab|, |Vbc|, |Vca|) determined by said calculating unit; a fault phase element output unit for having an AND function, which is set to each of the phases (ab-phase, bc-phase, ca-phase) of said minimum voltage phase (V&Dgr;min) selected by said minimum phase voltage selection unit and said judging signal (ZIS element-ab, ZIS element-bc and ZIS element-ca), and outputs an operation signal, to separate, the protective region having the fault, from the protective zone, of said ZIS element-ab, said ZIS element-bc and said ZIS element-ca, if said AND condition is satisfied; and an operation output unit for judging whether or not two or more operated phases of the ZIS elements are present, to output an operation signal of said ZIS elements to separate the protective region having the fault from the other protective zones.