| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a distance relay that prevents malfunction at the time of a back three-phase accident and can further protect a short distance transmission line. <P>SOLUTION: The distance relay 1 includes: relay elements 6, 7 that carry out predetermined computation and direction determination using a voltage V and a current I inputted from an electric power system; a polarity voltage computing means 4 for using the voltage V to compute a polarity voltage V<SB>P</SB>; polarity voltage sensitivity determining means 8, 12 that generate an output signal when the polarity voltage V<SB>P</SB>is equal to or higher than a predetermined set value of voltage sensitivity; and a relay operation determining means 9 that determines the result of computation by the relay elements 6, 7 when there are generated output signals from the polarity voltage sensitivity determining means 8, 12. In response to the result of the operation of the relay operation determining means 9, the set value of voltage sensitivity on the polarity voltage sensitivity determining means is switched from the low side to the high side. <P>COPYRIGHT: (C)2008,JPO&INPIT |
