| 摘要 |
PROBLEM TO BE SOLVED: To provide an earth fault directional relay which can decide surely an electric path which carried out earth fault without being affected by a leakage current flowing while the earth fault is not generated. SOLUTION: The earth fault directional relay 1 calculates effective values and phases of a zero-phase voltage and a zero-phase current in a subcircuit (1), the newest voltage vector based on the calculated effective value and phase of the zero-phase voltage in the course of overwrite and memory of the calculated values, voltage vector difference to the voltage vector based on the effective value and the phase of the zero-phase voltage subjected to the overwrite and memory, and a current vector difference to a current vector based on the newest current vector based on the calculated effective value and phase of the zero-phase current and the effective value and phase of the zero-phase current subjected to overwrite and memory. When the effective value of the current vector difference exceeds a prescribed value, whether or not the subcircuit (1) generates earth fault is determined based on the phase of the current vector difference to the phase of the voltage vector difference. COPYRIGHT: (C)2004,JPO&NCIPI
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