| 摘要 |
PURPOSE:To permit inexpensive and easy specification of a deteriorated phase by subjecting the currents flowing in respective phases to 3-phase vector synthesis and determining the composite waveform of only the resistance-component currents. CONSTITUTION:Only the lightning arresters 21, 22, 23 are connected to respective phases 11, 12, 13 of a bus or power transmission line and the ground sides thereof are commonly grounded via a zero phase current rectifier 44 as a piece of current detector. The ground side conductors of the respective phases of the lightning arresters 21, 22, 23 are collectively grounded through the iron core of a current transformer 44 and the secondary output of the transformer 44 is inputted to an amplifier 6, by which said output is amplified. The transformer 44 outputs the slight current of the specific phase on the primary side with good accuracy to the secondary side. The iron core thereof is saturated to prohibit outputting of the overcurrent to the secondary side at the time of large current. The currents passing the respective phases 11, 12, 13 are subjected to 3-phase vector analysis to erase the capacity- component currents contained in the currents of the respective phases and to determine the composite waveform of only the resistance-component currents. Whether the lightning having the deteriorated nonlinear resistance element exist in the 3-phase lightning arresters or not is diagnosed from this composite waveform.
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