| 摘要 |
A short-circuit distance relay is provided which has a high accuracy and an excellent reliability such that the relay can determine the fault phase based on impedance values measured by each phase, present misjudgment and unnecessary operation due to overreach without depending on the power system conditions, and operate even if multiple faults occur. An impedance calculation part (11) calculates an impedance value of the phase in which the direction element (SM) has operated. A minimum phase selection part (12) selects as a fault phase, the phase having a minimum impedance value. When the impedance value of the selected phase is equal to or less than the setting impedance value of the distance element of the phase, an output of the distance element of the phase is made to be valid to output an opening command to a circuit breaker. As a result, it is possible to prevent misjudgment and unnecessary operation due to overreach without depending on the power system conditions. |
