Study on the frequency characteristics of leakage current waveforms of artificially polluted 12t suspension insulators by the clean fog method

In order to establish a method for monitoring contamination on insulators based on leakage current waveforms and their frequency characteristics, the leakage current waveforms and the frequency characteristics of a string of artificially polluted 12t suspension insulators were investigated by the clean fog method. As a result, it was found that leakage current waveforms become similar to the symmetrical wave when strong local arcs occur; hence, the intensity of the odd order of harmonic components, e.g., 50, 150, and 250 Hz, is high. Furthermore, it was clarified that the transition of the leakage current waveforms until flashover occurs is classified into six stages and that a threshold may exist in the magnitude of peak leakage current and prominent odd-order harmonic components by which the occurrence of flashover can be predicted