Design And Implementation Of On-line Monitoring On The Running State Of Arrester

Currently, zinc oxide arrester is the common arrester in transformer substation. Zinc oxide arrester ensures the electric power equipment at a manageable level when suffering the lightning surge current shock. Due to long time in the outdoor environment and influenced by power frequency voltage, lightning arrester valve plates may be affected by damp and aging, which lead to greatly reduction of the protection performance on the power equipment. It is easy to cause electric power equipment damage, even affecting the operation of the power grid. It is necessary to monitor and evaluate the arrester regularly.This paper discusses the microstructure and equivalent circuit of valve disc of arrester and describes the relationship between characteristics value of leakage current with various fault conditions of arrester. Conclusions have obtained that the arrester currents, resistive current and resistive current fundamental wave and third harmonic generation characteristics of the surge arrester can reflect failed state effectively. The advantages and disadvantages of several common arrester online monitoring methods are analysed, and finally harmonic analysis method is used as a way to extract characteristic data of the monitoring system. In this paper, the effects of interphase interference, power grid harmonic interference, field environment temperature and humidity have been discussed during the online monitoring process of arrester. Aiming at the potential spectrum leakage and fence effect, the sampling error caused by the frequency fluctuation of power network in the case that FFT is introduced for the leakage current signal. The time shifting phase difference method based on Hanning window is also proposed for correcting the amplitude, phase and frequency of the spectrum of the leakage current signal. The improved wavelet threshold denoising method is used to remove white noise and electromagnetic interference in the environment before the data from the lightning arrester is processing. The validations have been performed in MATLAB and the conclusions denote that effective results can be obtained on the basis of the above methods.This paper introduces the working principle of online monitoring system of arrester and designing the communication protocol of the software module. To achieve remote data transmission, the wireless serial port is used to send and receive data. The procedure of data transmission of MCU is written based on the communication protocol. The design of upper monitor is completed based on Labview 2013, which has realized the receiving and accessing of data collection and signal processing. The test and analysis for the software module of online monitoring system show that the software modules designed in this study can run stably and display the data accurately.