Study On Propagation Characteristics And Location Method Of Partial Discharge In XLPE Cable

The detection and positioning of the cable partial discharge signal is of great significance to ensure the safe and stable operation of the power system.The propagation of the partial discharge signal affects the detection result of the signal,which directly affects the accuracy of the partial discharge location,and the partial discharge positioning method is also the key to accurately location the partial discharge.In this paper,based on Simulink,the frequency-dependent simulation model of the cable is established,and the PD defect test platform is built.Four kinds of typical defect cable samples are made,and the PD signal waveform under the typical defect is obtained.The time-domain and frequency-domain characteristics of each PD signal are analyzed,and the PD signal source is built accordingly.The frequency domain dielectric parameters test platform is built to test and study the relationship between different aging states and frequency domain dielectric parameters of the cable,and the frequency-dependent parameters of the cable are fitted based on the vector fitting method.The experimental results show that the semi conducting particle defect is not easy to cause the phenomenon of partial discharge,and the initial partial discharge voltage of other defects is between 15 k V and 20 k V,the pulse width of time-domain waveform is between 600 ns and 1200 ns,and the signal energy is mainly concentrated in 10 MHz or so;under the same frequency,the greater the aging degree of the cable,the greater the value of the real part and the virtual part of the complex permittivity.Based on the cable simulation model,the propagation characteristics of PD based on Debye and Cole-Cole semiconducting layer model are simulated.Through the comparison of Debye model and subsequent simulation,the propagation characteristics of different PD sources and the propagation characteristics of PD with different aging degree are simulated.The simulation results show that the maximum amplitude of PD signal decreases with the increase of propagation distance,and the pulse width increases;after different PD sources are propagated by cable,the amplitude attenuation of signal shows different attenuation changes and the signal wave speed changes;the larger the aging degree of cable is,the more serious the attenuation of PD signal is,and the wave velocity slightly increases,and the environmental temperature has little effect on the propagation of PD signal.The whole process of PD location is designed.The narrow-band interference in the signal is suppressed by Fourier series method,and the white noise in the signal is suppressed by wavelet de-noising method.According to the characteristics of PD signal in the location of Oscillating wave method,the first arrival wave and the second arrival wave are identified in time domain,and the time delay estimation effects of threshold method,energy accumulation curve method,AIC information criterion method and cross-correlation method are studied.The disadvantages of AIC method are improved,and the AIC location method based on cross-correlation function in strong noise is proposed,and the simulation results of different partial discharge sources and different aging states are located.Finally,the location method is verified by field test.The results show that the location results obtained by the proposed method are basically consistent with the measured results.