Development of a hot-line diagnostic method for XLPE cables and the measurement results

Hot-line diagnosis is needed to avoid breakdowns of XLPE (cross-linked polyethylene) cables due to water trees. The authors superposed a low DC voltage on an AC commercial voltage, measured the DC component of the current which passed through the insulation, and discovered that the DC component had a close relationship with the degradation caused by water trees. A hot-line diagnostic measurement system based on this DC superposition method was developed. The old cables that were removed and cables now in use were measured with the system; the results are reported.<
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