Performance Research Of Frequency Domain Reflection Spectroscopy For The Detection Of Buffer Layer Defects Of High Voltage Cable

As the main artery in the urban power system,high voltage cable lines are crucial to the safe and stable operation of the urban power grid.In recent years,faults caused by defects in the buffer layer of high voltage cables have occurred frequently.The existing cable defect detection methods all have their limitations,making it difficult to detect buffer layer defects in high voltage cables.Scholars at home and abroad have applied the frequency domain reflection spectroscopy technique to the defect detection of distribution cables and achieved certain results,which provide a new idea for the defect detection of the buffer layer of high voltage cables.To this end,this paper investigates the performance of frequency domin reflectance spectroscopy for the detection of buffer layer defects in high voltage cables through theoretical analysis and modeling simulations.Firstly,this paper establishes the theoretical model of high voltage cable transmission line applicable to very high frequency range,establishes the analytical calculation method of electrical parameters of high voltage cable body distribution in very high frequency range,proposes the calculation method of electrical parameters of high voltage cable body distribution considering the frequency-dependent characteristics of semi-conducting layer,and analyzes the influence of electrical parameters of high voltage cable body distribution on frequency domain reflection spectroscopy.Secondly,this paper summarizes the generation mechanism of typical latent defects of buffer layer damage,damp and ablation in high voltage cables,establishes the dielectric impedance characteristics of buffer layer defects in high voltage cerbless proposes the calculation model of frequency domain reflection spectroscopy of non-cross-bonded high voltage cable lines with multiple buffer layer defects,and analyzes the influence of buffer layer defects on the frequency domain reflection spectroscopy of non-cross-bonded high voltage cable lines.The analysis results show that the frequency domain reflection spectroscopy is shifted to the right and the resonant frequency point becomes larger in buffer layer damage defects;the frequency domain reflection spectroscopy is shifted to the left and the resonant frequency point becomes smaller in buffer layer damp and ablation defects,and the greater the severity of the defects,the more serious the shift,in which the phase spectroscopy of the frequency domain reflection spectroscopy is shifted more in damp defects than in ablation defects,and the use of frequency domain reflection spectroscopy can achieve the detection of buffer layer defects in high voltage cables.The influence of different diagnostic functions on the effect of buffer layer defect localization was analyzed by using the integral transformation method,and the best diagnostic function was obtained.Finally,the calculation method of distributed electrical parameters of high voltage cable joints is proposed,and the analysis model of the frequency domain reflection spectroscopy of high voltage cable lines considering cable joints and cross-bonded is established to analyze the influence of buffer layer defects on the frequency domain reflection spectroscopy of cross-bonded high voltage cable lines.The analysis results show that in a cross-bonded section,the offset direction of the frequency domain reflection spectroscopy is opposite to that of the first and third sections when buffer layer defects are generated in the second section.On the other hand,the relative error and recognition sensitivity of the diagnostic function for locating the buffer layer defects in cross-bonded high voltage cable lines are studied.The analysis results show that the relative error of locating the buffer layer defects is within 1.5%,and the recognition sensitivity is low when the severity of the buffer layer defects is very small.The research results of this thesis lay a theoretical foundation for the detection of buffer layer defects in high voltage cables using frequency domain reflection spectroscopy technology,and prove the effectiveness of frequency domain reflection spectroscopy technology in detecting buffer layer defects in high voltage cables,which provides a high reference value for practical engineering applications.