| 摘要 |
PROBLEM TO BE SOLVED: To attain a digital type protective relay capable of obtaining anti-time- limit-characteristics or anti-time-limit - fixed-time-limit-characteristics in a single amount of protection relay using a converter or a transformer which is saturated by an excessive input. SOLUTION: Main converters 111 to 114 and auxiliary converters 121 to 124 are of small-sized Rogowskii-type, which is saturated by excessive input. The anti-time-limit computing part 131 of a protection computing part 13 has anti-time limit characteristics for causing a protective output when input current data exceeds a set value. Fast Fourier transform part 132 conducts frequency analysis of the input current data for obtaining a frequency component Sn which occurs with a converter saturated, and a determining part 133 determines the saturated condition of the transformer by the frequency component exceeding a fixed valueα. This determination permits an inhibition logic part 134 to inhibit a protective output from the anti-time-limit computing part. A determining part 135 determines the saturated condition based on a smaller level of input current data than the inhibition, which permits a timer part 136 to have fixed-time-limit characteristics, thereby producing a protective output.
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