Analysis and experimental work on cavity defects in solid insulation

The repetition rate and magnitude of internal discharges in artificial cavities in samples of XLPE (cross-linked polyethylene) were investigated. The effect of cavity diameter and of filling it with different materials with different conductivities and permittivities was studied. It is shown that, in general, increasing the applied voltage increases both the repetition rate and the magnitude of discharges (conduction current pulses in milliamperes). It is also shown that the foundation of cavities reduces the breakdown voltage. Samples of polyvinyl chloride and polystyrene were also used in these tests. It is concluded that the number of discharges per second increases with decreasing cavity diameter.<
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