The feeding circuit conservation relay manner null adaptation to the alternating current regenerative car

摘要

PURPOSE:To prevent unnecessary operation owing to a load current by securing a needful protective region when a feed current does not contain any second and third order harmonic waves, and by selecting a smaller protective region when it does. CONSTITUTION:In a distance relay, a protection region 14 needed for malfunction detection and a protection region 26 without any unnecessary operation in load regions 15, 16 are set beforehand, and impedance is computed receiving voltage value from a PT and current value from a CT at a substation. Meanwhile, the content of the first and second order harmonic waves to the fundamental wave is computed from the outputs of a fundamental wave filter 27, and second and third order harmonic wave filters 28, 29. And if it is smaller than a set value K fixed beforehand a protection region 14 is selected, and if the set value K or larger a protection region 26 is. If the computed impedance is within the protection region, a protective relay outputs a break command to operate a breaker.