| 摘要 |
PURPOSE:To attain to detect an earth point at an early stage, by earthing mutually divided and insulated respective shield cases of high voltage machinery by plural earth wires and detecting an earth current flowing to the current detection heads attached to a pair of arbitrary earth wires. CONSTITUTION:A center conductor 2, to which high voltage is applied, is shielded by split shield cases 4 mutually insulated through insulating plates 3 and the shield cases 4 are earthed through detection heads 6a, 6b. The detection heads 6a, 6b are respectively connected to a receiver 9 at every two through optical fibers 7, 7', 8, 8'. Then, earth currents are detected as reverse phase earth induction currents by the detection heads 6a, 6b and applied to the receiver 9 through the optical fibers while subjected to electricity-light conversion and the converted lights are again converted to currents by light-electricity conversion and, thereafter, the regenerated earth induction currents are mutually added and compared with a predetermined current value to detect earth.
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