INDUCTION NOISE ELIMINATING METHOD IN DEGRADATION DIAGNOSIS ON POWER CABLE AND TESTING DEVICE FOR POWER CABLE

摘要

PROBLEM TO BE SOLVED: To eliminate influence of power frequency noise entering from the outside and its harmonic noise during degradation diagnosis on a power cable.;SOLUTION: A test voltage with a frequency different from a power frequency and neither of an integral multiple and an integral submultiple of the power frequency, for example, with a frequency of 51 Hz is impressed to the power cable 5 and a lossless reference capacitor 6, and using current flowing through both of them, a capacitative current in a leading phase advanced by 90° from the test voltage is equilibrized by means of a lossless current measurement bridge 7 and a loss current of the power cable 5 is extracted. After an obtained waveform is equalized with reference to the frequency of 51 Hz by means of a digital oscilloscope 8, they are incorporated as discrete numerical value data. The data are FFT-analyzed by means of a waveform analysis computer 9, and an amplitude and a superimposed phase value for each harmonic component are obtained. When the amplitude and the superimposed phase for each harmonic component are evaluated, a water-tree degradation state of the power cable can be diagnosed.;COPYRIGHT: (C)2003,JPO