Risk failure calculation
Research has consistently shown that the magnitude of leakage current is a reliable predictor of insulator surface discharge and the ultimate insulator failure. Therefore, the probability distribution of leakage current can be used to assess the risk of insulator failure.
Based on the probability density distribution, the cumulative probability of the leakage current can be produced.
A critical magnitude of leakage current may be set by the electricity utility as that, beyond which insulator failure is eminent. The cumulative probability function then indicates the chances for that set leakage current value to be exceeded, and hence, it also indicates the chances for insulator failure to occur. Fig. 6b displays the final result of the present case study. For the given insulator, placed in the presently defined environment, and under the given power line voltage (220 kV), the figure gives – for any arbitrarily set value of critical leakage current – the risk of having an insulator failure under desert pollution conditions. For example, a set critical leakage current magnitude of 100 mA reflects a 60% chance of insulator failure.