Papers by Author: Ali Hui

Abstract: A new method for image edge detection based on envelope curve of histogram is proposed, aimed at the characteristics of high voltage transmission line. In order to inhibit noise influence on infrared image, envelop curve of histogram, got from Savitzky-Golay(S-G) filter, is used to smooth the image, and the edge of infrared image can be detected based on the extreme points of the envelop curve. Experimental results show that this new algorithm is simple and effective to detect whole contour and detail information, and is better than other traditional operators.

Abstract: A new idea, using chirplet as the staff to define fractal dimension, is proposed in this paper, based on self- similitude of knowing essence of things from collectivity to part, from macroscopy to microcosm, in fractal theory and chirplet transformation. Chirplet fractal dimension is defined as the sum of high-frequency values of decomposed signals. The edge of infrared image is detected through chirplet fractal dimension, experimental results show that this new algorithm is simple and effective to detect whole contour and detail information, and is better than other traditional operators.

Abstract: As the improve of voltage class in power system and the aggravation of industrial pollution, flashover of contaminated insulators in HV and UHV system is growing, imperiling the security of power system severely. The linchpin of enhancing the security of system is excavating ways of monitoring status of insulator’s surface by some eigenvalues. In this paper, distinctive spectrum features of leakage current(LC) are computed, including power spectrum and bispectrum. The results show that bispectrum depicts the information of arc discharge in LC more valid than power spectrum, which is a good eigenvalue for flashover identification and risk predictions.

Abstract: With the increase of voltage grade in power transmission system and the aggravation of industrial pollution, flashover of contaminated insulators in HV and UHV system is more and more serious, threatening the security of power transmission severely. The key of improving the security of system is exploring the methods of monitoring and recognizing states of insulator’s surface by some character values. In this paper, multi-characteristic Hidden Markov Model is founded with wavelet and chirplet fractal characteristics of leakage current(LC), through which the flashover patterns are recognized during the developing stages. The results show that fractal characteristics HMM recognized flashover pattern efficiently and successfully, and that is useful to help related stuff to make correct decision and ensure the security of power delivery.