Measurement of autocorrelation function and power spectral density of pre-breakdown conduction current pulses in liquid dielectrics

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Abstract
A technique for the study of the pre-breakdown conduction current pulses in insulating liquids has been developed. It consisted of recording these pulses during the experiments on a magnetic tape and subsequently subjecting them to a number of statistical analyses. The analyses included the determination of the autocorrelation function and computation of the power spectrum. Typical examples showing the effects of applied electric stress, temperature and additives to the liquid on the autocorrelation function and power spectrum of the current pulses are given. The autocorrelation function showed that such fluctuations of the current were random and did not contain hidden periodic components. From the corresponding power spectra it was found that the fluctuations lay in the low audio frequency range.