| 摘要 |
PURPOSE:To perform a reliable detection of a ground fault phase irrespective of a magnitude of a ground fault resistance, by a method wherein a zero phase voltage at an occurring time of a ground fault trouble is caused to be produced within the range of a given angle based on a vector of a phase voltage whereat the ground fault occurs. CONSTITUTION:A signal from a terminal 1 obtains a zero phase voltage -V0 at a phase angle set circuit 2. In a pulse conversion circuit 3, a negative half-cycle pulse and a positive half-cycle pulse are outputted by zero cross detectors 3-1-3-3, and a reference phase angle synthesization circuit 4 synthesizes a reference and a range of a phase angle decision. If a ground fault decreases in a positive half- cycle having, for example, an A-phase and the -V0, a D flip-flop 7a-2 outputs in a succeeding negative half-cycle, and a 7a-1 in a succeeding positive half-cycle to perform an output from an OR gate 7a-3 to a a-terminal. The device permits the rapid detection of a ground fault phase without the complicated vector computation irrespective of the magnitude of a ground fault resistance. |
