| 摘要 |
PROBLEM TO BE SOLVED: To provide a distance relay which is capable of operating at a high speed when an accident happens by inhibiting the operation of the relay having a possibility of causing a malfunction by an exciting inrush current, by comparing the summed value of the absolute value of the differences between resistance components and inductance components obtained from a formula for finding the absolute values from an impedance range finding value with a constant. SOLUTION: An impedance change is discriminated from a summed value of R and L components. First and second calculating means 11 and 12 respectively find|ΔR|=|Rm-Rn|and|ΔL|=|Lm-Ln|as the absolute values of the variation of the R and L values found at different times (m) and (n). The transition of the variation of the summed value|ΔZ|=|>=R|+|ΔL|with time is found continuously, and|ΔZ|always varies at a level higher than certain sensitivity with positive values. The discriminated result of whether or not the operating amount|ΔZ|in one period is higher than a prescribed value does not become intermittent operations but is stabilized by continuous operations. The value of a T1 timer can be realized with a time cooperative timer, which is shortened from the normal time by setting an appropriate value from the fastest operating time of a relay and the maximum time of the transient response period of the relay when an accident happens.
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