Study On-line Monitoring Technology Of Insulator Leakage Current

Pollution flashover is a kind of phenomenon that will cause serious effect on insulator's operation.It is known that the surface of insulators has been covered by some pollutants and such kind of pollutants will form a conductive channel around the surface.That is the reason why the pollution flashover occurs to insulators.To solve the problem of pollution flashover,this thesis designed a set of on-line monitoring system by considering the leakage current of the insulator as the characteristic quantity.Based on the on-line monitoring system,this thesis will dynamically reveal the insulator's pollutant gathering process and it will provide significant evidence and strong guarantee for insulator's stable movement and the safe operation of the distribution line.In this thesis,the pollutants gathering process of insulator will be judged according to the insulator flashover process in the leakage current changes.From the point of view of preventing pollution flashover,the monitoring range of leakage current is determinedand the leakage current on-line monitoring system is designed.The monitoring system obtains the leakage current of the insulator through the zero-flux sensor and the installation of the active compensation device to improve the measurement accuracy.With the differential amplifier to extract and amplify the signal and the application of active second-order filter on the signal filtering,itreduce external interference and op amp noise on the signal,the DSP through the AD data collection,the data after the application of the window FFT on the signal.In order to better determine the state of the insulator,considering the time domain and frequency domain characteristics of the leakage current,the ratio of the third harmonic to the fundamental wave,the ratio of the third harmonic and the fifth harmonic,the amplitude Pulse number of three characteristics to reflect the insulator state.The data has been transmitted by GPRS wireless network and it has been received and stored bythe monitoring computer,which will extract the data with the application of Labview.The characteristic quantity will be drawn in order to intuitively analyzes theoperation trend of the insulator.To prevent the interference of the external electromagnetic field signal,this paper sets the shielding system to eliminate the external interferenc signal.In order to verify that the system designed in this paper meets the outdoor application conditions,the system is experimentally verified,and then the system is tested in a high pressure environment.The experimental results show that the device can accurately detect the leakage current of the insulator surface,which can effectively reflect the operation state of the insulator.The on-line monitoring system designed in this paper not only reflects the pollution condition of the insulator surface in real time but gives some suggestions on the cleaning work of the insulator.