The Study On Extraction And Processing Technology Of High Frequency Signal Of Partial Discharge In Cable

High frequency partial discharge detection is the important means of detecting the state of the cable,it has a more effective test capability for the defects in the cable insulation that endangering the safe operation,especially the early tiny defects,However,the environmental interference signals,such as periodic narrow-band interference and white noise,will seriously affect the correctness of the detection results,Therefore,obtaining accurate partial discharge high frequency signal is the key to diagnosis and evaluation the real insulation state of the cable.In this paper,the extraction and processing technology of high frequency signal for partial discharge of cable is studied,It mainly includes the research and development of high frequency signal detection platform for cable partial discharge,the optimization of interference suppression algorithm in the detection platform,and Partial discharge test and result analysis of 4 typical defects based on this platform.The research and development of the high frequency signal detection platform for cable partial discharge start from the research and performance test of the sensor,then the signal is amplified and filtered by the signal conditioning module,at last,the detected partial discharge signal is processed,the spectrum is displayed and create an installable file for the inspector to use.The optimization part of the interference suppression algorithm in the detection platform is mainly aimed at the current environmental interference problem,selecting the best selection algorithm for the detection platform from the existing interference suppression algorithm,the Fast ICA,wavelet analysis and threshold de-noising are used as a systematic interference suppression method for the partial discharge detection platform finally.The random pulse interference is suppressed by K-means clustering based on the time domain variance and the standard difference parameters in the frequency domain.In addition,an off-line data processing method based on EEMD decomposition of frequency slice wavelet to suppress white noise interference is given.The partial discharge test and result analysis of 4 typical defect samples based on this platform mainly include the making of 4 kinds of conventional defect samples,partial discharge test and result analysis,the process of making the sample,the size of the sample and the steps of the partial discharge test are introduced in detail,the partial discharge measurements of 4 kinds of defects were carried out in the discharge quantities of20pC,30pC and 50pC,the test results are compared in 3 aspects,namely,the time domain waveform,the discharge feature spectrum and the statistical feature,from the comparison of statistical features indicate the negative half cycle skewness of 2#rough edge defect cable q_ave-?spectrum is minimum and the kurtosis of n-q spectrum is maximum,the asymmetrical degree of the q_ave-?spectrum of the 3#pore defect cable is the smallest.The 4#main insulation damage defect cable is the minimum skewness and kurtosis,whether it is the q_ave-?spectrum or the n-q spectrum,the correlation between the positive and the negative half of q_ave-?spectrum is the largest of 5#outer shield burr tip defect cable.Through the experimental verification above,the developed high frequency signal detection platform for the partial discharge of the cable can obtain the partial discharge signal accurately and display it clearly and install it easily,which is suitable for the partial discharge test in the laboratory.