Tg¦Ä Line Monitoring Of Insulation Online Monitoring System

In this paper, on-line monitoring of dielectric loss angle's tangent (dielectric loss factor) was discussed mainly, in order to improve the accuracy and stability of monitoring data of dielectric loss. It is outlined that the concerned knowledge about insulation online monitoring including the history, necessity and content. Object-orient collective Scheme of online monitoring system of substation is designed. Then this paper introduces the characteristic of down computer in this system and the function of management software in upper computer. Based on detailed analysis about dielectric loss measuring methods, the Spectrum Analysis Method is selected. According as factors that affect accuracy and stability of online monitoring data of dielectric loss, online monitoring system scheme on dielectric loss is developed and key tache in this system is ascertained. The key tache include the Precious Processing Circuit of Analog Signal, the Signal Sample Circuit, Digital Filter, Spectrum Analysis Method. Under the research of the characteristic of three classical analog filter with simulation software-MATLAB, this paper devised lowpass circuit that not only can keep the useful signal out of distortion but also benefits the following sample tache and filter tache. Phase lock and multiple frequency circuit diminishes the influence from frequency fluctuation of electric net; in addition, multiple channels simultaneous sampling, high-precision circuit decreases the error caused from the sampling tache. In digiltal filter, IIR and FIR are researched in detail. For IIR, after researching Pulse Response Method, Step Response Method, Bilinear Transform Method, Direct Design Method, it is found that IIR is unsatisfactory. For FIR, after researching Window Function Method and Frequcy Sampling Method, it is suggested that the filter designed from Blackman Window Function is satisfactory, afterward the filter is programmed with reasonable operational structure. The output of filter is transformed and then dielectric loss angle's tangent is computed by three method-FFT, FAFT or CZT, later the three method's advantage and disadvantage on computing compute dielectric loss angle's tangent is contrasted, At last FAFT is selected in this system. Through running insulation online monitoring system, the skeme which is designed in this paper satistfied the accuracy and stability of monitoring data of dielectric loss angle'stangent...