Study On On-Line Monitoring Technology For Contaminated Insulators

All kinds of insulators in the transmission lines were located in air for long time, on which gathered a bed of contamination because of pollution of the surroundings. When the contamination and humidity state reaches a certain degree, contamination flashover occurs. To guarding against contamination flashover, electrical department set down a scheme to overhaul insulators. However, the scheme spend significant amounts of money on insulator washing and cleaning. Performing the real-time monitor of insulator is a crucial task to solve the safety of transmit electricity wires. It could heighten the level of preventing contamination flashover, and enable the overhaul of insulators to changing from scheme to state overhaul.The change of insulators leakage current has close relation with insulators state and generally reflects the course of contamination flashover. Firstly the mechanism of contamination flashover is researched in the paper and the characteristic of leakage current is analyzed. In this paper, we analyze the spectrum character of leakage current by spectrum analyze method, and the probability character by maximum method. Spectrum analyse make clear low frequency harmonic, especially third harmonic could predict contamination flashover . And following a extreme-value risk function is introduced to predict contamination flashover .And we have confirmed the ratio of leakage current third to fundamental harmonic ,and the value of extreme-value risk function of signal envelop as a criterion to predict contamination flashover. In addition, we write a set of program of simulating arcing model, which provide a measure for studying insulator arcing by computer.On the basis of front study, we develop a set of monitoring system based on leakage current. The system integrate with the amplitude character, frequency character and probability character to predict contamination flashover. It adopts host- extension computer mode.AT89C51 single chip serve as CPU in the extension computer which perform data collecting and beforehand data process. The host computer in monitoring room communicate with the extension computer through relaying of wireless wave. The extension computer start transmitting data when it has found that the amplitude of leakage current exceed a setting value. And the host computer process the data using spectrum analyse method and maximum analyse method after having received the data. On the basis of analytic results, the host computer process correspondingly. It realize real-time monitor of insulator performing state.