| 摘要 |
PROBLEM TO BE SOLVED: To prevent the occurrence of a reactance measuring error even when the ratio of the actual resistance portion of the line constant of a transmission line to the reactance of the line is different, by calculating the voltage drop from an accident point to the installed point of a ground-fault distance relay which occurs due to a one-line ground-fault accident by resolving the voltage drop into theα-component and zero component of its own line and the zero component in other phases. SOLUTION: Six equations are set up including m=kj (j=1-6) as an arbitrary time series, and unknowns Rα, R0 , R0 ', Lα, L0 , and L0 ' are calculated by means of an 8th means 18. An 8a-th means 18A discriminates whether or not the inductance of, for example, anα-component is smaller than a set value by using the value of the unknowns and, when the inductance is smaller than the set value, the means 18A discriminates that operations are conducted and the conventional reactance relay can be realized. Therefore, a digital ground-fault distance relay which can be measured and separated with accuracy even when higher harmonics, etc., are superposed when an accident happens can be realized.
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