Study On Electrical Treeing Propagation And Partial Discharge Characteristics In Ultrasonic MMT/PE Nanocomposite

Polymer/layered silicate nanocomposites(PLS) are widely used in power field, which own excellent electrical properties. Due to the characteristic of layered structure of the inorganic nanometer phase, the stripping degree and dispersed form in polymer matrix will affect the performance of nanocomposites directly. Therefore, a large number of scholars began to investigate the method to control structure of PLS nanocomposite. The ultrasound technology can promote the nanometer layer of silicate stripped or dispersed, in order to further improve the electrical properties of nanocomposites.In this paper, nanometer montmorillonite(MMT) are stripped process by using ultrasonic technology and mixed with low density polyethylene(PE) in the melt intercalation method, and montmorillonite/polyethylene nanocomposites(SO-MMT/PE) are prepared. The crystal morphology of the materials were characterized by DSC and PLM etc technologies; then the influence of ultrasonic technology on breakdown stress and the dielectric spectrum of nanometer composite material are comparative studied; Finally, focuses on the electrical tree branch form and the partial discharge phenomena of composites in the process of electrical tree growing.DSC and PLM experimental results show that MMT are stripped process by using ultrasonic technology and mixed with PE, which can improve the crystallinity of PE and make PE molecular chain arrangement more closely.Breakdown strength and dielectric spectrum experiment results showed that ultrasonic technology makes the breakdown stress of nano composite material increased by 12.96%, and the relative dielectric constant is higher than PE matrixbut lower than that of the nanocomposites without ultrasound treatment. Visiblely ultrasonic processing technology can make montmorillonite layer structure stripped, thus effectively improve the electrical properties of polyethylene matrix.The analysis method combined statistical method and time-frequency analysis method is proposed on the basis of the ?-q-n graph, namely ?-f graph. By using the graph, the discharge characteristics are analyzed under different aging stages and different forms of electrical treeing, the results showed that the discharge in branch channel behavior of S-O-MMT/PE nanocomposite changes with the branch form. At the beginning of the development of electrical branch, the discharge signals is small, mainly distributed under 10 MHz, but with the development of electrical branches, the discharge signals will increase constantly and the frequency of discharge signals distributed in 10~15MHz. Accordingly,the frequency of the discharge signals can be used to analyze the electric branch growth stage, thus to judge the polyethylene insulation status.