INSULATION DEGRADATION DIAGNOSIS APPARATUS

摘要

An insulation degradation diagnosis apparatus (1a) comprises a current transformer (7a), a first amplifier (15), a first high pass filter (17), a low pass filter (19), a second amplifier (20), a second high pass filter (21) and a discharge determining part (30). The current transformer (7a) has a filter function, which has an attenuation amount of -60 dB or less and a slope characteristic of -5 dB/oct or less for commercial frequencies, and detects a current flowing through a grounding wire (5). The first amplifier (15) amplifies a current signal from the current transformer (7a). The first high pass filter (17) eliminates low frequency components from the amplified current signal. The low pass filter (19) eliminates high frequency components from the current signal from which the low frequency components have been eliminated. The second amplifier (20) amplifies the current signal from the low pass filter (19) up to a predetermined level. The second high pass filter (21) extracts, from the current signal as amplified by the second amplifier (20), a signal corresponding to a discharge current caused by a partial discharge. The discharge determining part (30) determines, based on the signal as extracted by the second high pass filter (21), whether the partial discharge has occurred in a cable (2).