Research On Partial Discharge Detection Technology Of Metal Oxide Arrester Based On UHF Method

Metal Oxide Arrester(MOA)is widely used in power system due to its excellent protection characteristics.The safe and stable operation of MOA is directly related to the quality and reliability of power supply.During the long-term operation,the performance of resistors and insulation materials in MOA will gradually degrade.And partial discharge occurs when the deterioration is serious.Although traditional current detection methods can reflect the early performance deterioration of MOA,they are unable to accurately detect the late development of deterioration.As a new detection technology,Ultra-High-Frequency(UHF)method is extensively applicated in partial discharge detection of various electrical equipments.However,UHF method is less used in insulation performance detection of MOA.Based on UHF detection technology,this article conducts theoretical,simulation and experimental research of partial discharge detection in arresters.In this article,the causes of arrester failure and the types of defects are firstly discussed and analyzed.The typical defects such as internal moisture and insulation deterioration are then simulated so as to analyze the change of electric field both inside and outside the arrester.Combined with the simulation results,the intrinsic mechanism of partial discharge in arrester is elaborated.In order to analyze the propagation characteristics of electromagnetic waves aroused by partial discharge in arrester,the article simulates the MOA model by software CST(Computer Simulation Technology).The simulation results indicate that the electromagnetic signals are affected by the characteristics of the excitation source,the location of the detection monitors and the types of partial discharge.Furthermore,the results provide valuable reference for UHF detection of partial discharge in arrester.In the meantime,the article carries out live detection experiments on 1000 kV,750kV and 500 kV arresters.Various operating conditions such as internal moisture,resistor short circuit and outside short circuit are simulated.The experimental results verify the effectiveness and practicability of UHF methods applied in arrester state detection.In addition,various methods for partial discharge feature extraction are further studied.Based on Wigner-Ville Distribution(WVD)technique,the joint time-frequency analysis of partial discharge signals was made.Based on statistical operators and fractal theory,the characteristics parameters were extracted from partial discharge spectrums.As a result,the partial discharge features of arresters under different defects have been obtained.The research in this article provides a new solution to arrester state detection,and further research will provide theoretical guidance for insulation state assessment and fault type diagnosis of arresters.