| 摘要 |
PURPOSE:To detect ground fault of a quadruple bus by providing means for performing differential operation based on a vector sum of zero-phase currents of all feeders fed from the quadruple bus and means for comparing the phase between the vector sum of zero-phase currents and the zero-phase voltage of each bus and allowing an output from the operating means based on an operating output from the phase comparing means. CONSTITUTION:Zero-phase currents i01-i04 and zero-phase voltages V01-V04 are obtained from quadruple buses 2-1-4. A CPU 9 operates the vector sum Iod of zero-phase currents of all feeders required for judgment of operation of a 87G element 13. Furthermore, zero-phase voltages of the buses 2-1-4 are subjected to phase comparison with the vector sum Iod. Decision is also made whether phase comparison conditions are satisfied for all bus voltages and the 87G element 13 is operated when the conditions are satisfied. According to the constitution, fault can be detected in any one of the quadruple buses. |
