Examination of the breakdown site in new and aged polyethylene insulated cables

Discharges have been monitored and located in short lengths of cable tested to breakdown. These tests have been used to detect prebreakdown deterioration. The discharge location system is novel and has enabled limited energy breakdown sites to be located. Not all the breakdowns were initiated at the region of the inner screen boundary. In short-term tests to breakdown on new and dry aged cables at a maximum field of 30 MV/m there was no gradual increase in the discharge level above the detection limit of 1 pC. It appears possible that ageing with applied voltage at ambient temperature can improve the breakdown strength.<
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