Research And Application Of MOA Online Monitoring System Based On Improved Harmonic Analysis

Zinc oxide arrester(MOA),as an important device to avoid electrical equipment from overvoltage in the power system,protects the safe and stable operation of electrical equipment in the power system under extremely short conditions.MOA will be affected by the aging of its internal zinc oxide valve disc,moisture,and the contamination of the surface of the porcelain sleeve during operation,which will cause the resistive current which accounts for 10-20% of the total leakage current to increase greatly,but the total leakage current will not change much.Therefore,on-line monitoring of MOA requires a clear grasp of the change in resistive current.The valve plate of the zinc oxide arrester meets the nonlinear volt-ampere characteristics.The resistive current flowing in the zinc oxide arrester is composed of the fundamental wave,the third harmonic and the noise.There are three forms of resistive current flowing in the zinc oxide arrester.The medium fundamental current component has strong anti-interference to the higher harmonics of the power grid.Therefore,the fundamental component of the resistive current flowing through the zinc oxide arrester valve plate can be used as a response of the aging degree of the zinc oxide arrester.Based on the investigation of existing online monitoring methods at home and abroad,this paper conducts a detailed study of the characteristics and equivalent models of MOA,explores various conditions that affect the accuracy of MOA resistive current monitoring,and uses improved harmonics in conjunction with the actual situation of the project.The analytical method designed the MOA online monitoring system.This algorithm uses db N wavelet denoising and fast Fourier transform(FFT)to reduce the spectrum leakage and the fence effect of the original FFT.The algorithm is compared with multiple simulations in Matlab.The simulation results prove theeffectiveness and feasibility of the algorithm.On this basis,the hardware platform of the MOA online monitoring system is further developed.The hardware development is based on TMS320F28335.The communication module uses E52-TTL-50 wireless communication.The scheme design has completed the schematic diagram of the hardware circuit,and designed the PCB layout.At the same time,anti-interference improvement has been adopted for the complex working conditions on the site.Finally,the software of the online monitoring system is designed.The software of the MOA online monitoring system was written by Delphin2010.The signals collected on-site were sampled by the local unit and then wirelessly transmitted to the database of the background host computer.Through the host computer,the status of the MOA could be monitored online in real time and the previous data analyzed and compared.To achieve the purpose of effectively monitoring the operating status of MOA.