This paper studied the leakage current of insulator strings applied with operating stress during icing regime and evaluated the insulator string's icing status based on leakage current characteristic. Artificial icing test were conducted on one kind of widely used ceramic insulator. Leakage current waveforms of the insulator string during the icing regime were recorded by leakage current monitoring system. The relationship between the maximum leakage current and the icing duration was studied. Power Spectral of the maximum leakage current series of every 20 minutes were analyzed. It was found that the power spectral of principal frequencies such as 50 Hz, 150 Hz and 250 Hz rise with the icing duration and relate closely to the icing thickness on insulator strings. Fitting curves of the power spectral density with the icing duration were given. It provided a good approach to evaluate the insulator strings' icing status.
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