Recentry, the neccessity of establishing the way to diagnose the aging of insulation materials and to prediction of insulation breakdown become important.
In this paper, the prediction of breakdown is considered. A cylindlical void which is made of polyethylene is used for experiments. And the distribution of the discharge magnitude in relation to phase angle of applied voltage is measured by a partial discharge measuring system.
The discharge measurements, such as the discharge magnitude Q, number of pulses N, average discharge magnitude QAV, the skweness and the kurtosis are calculated from the distribution to estimate the time to breakdown. In the early stage of aging. life (time to breakdown) can be estimated by regression line which shows the relation between the life and the discharge measurement.
And the new parameters G and C are proposed for the prediction of breakdown and are examined their effectiveness for prevention. G-parameter is the center of gravity and C-parameter is the gradient of the discharge distrbution. They symbolize the portent of the breakdown. It is confirmed that these two parameters are efficient to predict the breakdown just before the breakdown occured.
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