Wavelet-fractal characteristics of leakage current on HV insulators

With the increase of voltage grade in power transmission system and the aggravation of industrial pollution, flashover of contaminated insulators is getting more and more serious in high-voltage (HV) and ultra-high-voltage (UHV) systems, threatening the security of power transmission severely. The key to improve the security of power system is to explore methods of monitoring states of insulator´s surface by some eigenvalues. A new idea, using wavelet as the ruler to define fractal dimension, is proposed in this paper, based on self- similarity of knowing essence of things from collectivity to part, from macroscopy to microcosm, in fractal theory and wavelet transform. Wavelet-fractal dimension is defined as the sum of high-frequency values of decomposed signals. The fractal characteristics of leakage current (LC) are gotten from this dimension. The results show that the wavelet-fractal dimension efficiently describes the information of arcs discharge in LC, and it is also a good eigenvalue for flashover discrimination and risk prediction.