FAILURE ANALYSIS OF METAL OXIDE ARRESTERS UNDER HARMONIC DISTORTION

The probability of accelerated degradation or reduced time to failure of metal oxide arresters (MOA), when continuously exposed to distorted ac conduction, is analysed in this study. Metal oxide-based surge arresters of similar size and electrical characteristics are tested using accelerated degradation at elevated temperature and distorted ac voltage stress. The three-parameter Weibull probability method is applied to analyse the obtained time to failure distribution. The Fourier series' expansion is also relied upon in order to evaluate the content of the harmonic resistive components of the measured leakage current. The results obtained indicate that for 6.24% and 5.58% content of the 3rd and the 5th harmonic component, respectively embedded in the applied voltage stress, the probability of reduced time to failure or accelerated degradation is found to be 58.93 %, and the mean life reduction obtained is just above 40%. These results correlate with the pronounced shift of the U - I curve as well as the increase in the magnitude of the respective harmonic resistive current components of the arrester samples.