Diagnosis of porcelain and glass insulators conditions using phase angle index based on experimental tests

In this paper, an improved method to diagnose the critical conditions in the porcelain and glass insulators has been proposed through investigating leakage current (LC) and applied voltage signals. Hence, Fast Fourier Transform (FFT) analysis has been used to calculate the phase angle values of the applied voltage and LC signals. Analyzing phase angle difference of LC and applied voltage waveforms demonstrate a strong correlation of the phase difference between the applied voltage and LC waveforms with the insulators conditions. So, the phase difference cosine (P.D%) has been offered as a diagnostic index of porcelain and glass insulators conditions. In this case, when the P.D% value is lower than 30%, the insulators are in clean and normal conditions. On the other hand, if the P.D% is more than 30%, the insulators are in extreme conditions. Moreover, by increasing %P.D value more than 85%, the probability of the flashover occurrence in porcelain and glass insulators will be very high. The obtained experimental results validate the veracity of considering P.D% as a criterion for prediction of flashover in porcelain and glass insulators.