| 摘要 |
PROBLEM TO BE SOLVED: To provide a two-phase bushing current transformer enabling further reduction of the installation number of current transformers and short circuit protective relays which are used to protect a three-phase AC circuit from a short circuit failure, and to provide a voltage transformer for judging failure situation and a protective relay device. SOLUTION: An R-phase and an S-phase of a power transmission line are led through in the same direction in an annular iron core of the two-phase bushing current transformer 10 installed in the power transmission line, in which the R-phase is led through only one time and the S-phase is led through two times. Upon detecting a short circuit failure on the basis of a short circuit current I<SB>Ry</SB>inputted from the two-phase bushing current transformer 10, an overcurrent relay 4 collectively interrupts first-third breakers 2<SB>1</SB>-2<SB>3</SB>installed in the R-phase, S-phase and T-phase of the power transmission line. COPYRIGHT: (C)2009,JPO&INPIT
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