Investigation On The Synergistic Inhibition Of SiO₂,ZnO And MMT In PE On Electrical Treeing And Partial Discharges

In recent years,with the development of ultra-high voltage and ultra-high voltage transmission technology,higher requirements have been placed on the performance of insulation materials for power equipment mainly made of polyethylene（PE）.Under the long-term action of high field strength,the emergence and development of electric tree has seriously affected the service life and operational reliability of power equipment.Therefore,it is of great significance to study the electrical tree and partial discharge characteristics of polymer insulating materials to improve the safety and reliability of power system operation.In this thesis,MMT/PE composite,Si O₂/MMT/PE composite and Zn O/MMT/PE composite were prepared by melt blending method with polyethylene as the matrix and organically treated montmorillonite（MMT）,silica（Si O₂）and zinc oxide（Zn O）particles as fillers.The microscopic properties of the polyethylene composite were characterized by SEM,DSC and other testing methods.The combined test experiment of electrical tree and partial discharge was carried out on the composite material by pulse current method and ultra-high frequency method.The variation law of partial discharge parameters in different growth stages of electrical tree was analyzed,and the synergistic inhibition mechanism of Si O₂,Zn O particles and MMT particles on the electrical treeing and partial discharge characteristics of the composites was investigated.The results show that:the organically treated micro-and nano-particles are well dispersed in the composites,and the melting peak temperature and crystallization rate of samples MMT/PE,Si O₂/MMT/PE and Zn O/MMT/PE are higher than those of sample PE.And the crystallinity of samples Si O₂/MMT/PE and Zn O/MMT/PE increased by 5.20%and 2.64%,respectively,compared with that of sample PE.The electrical tree suppression effect in Si O₂/MMT/PE sample and Zn O/MMT/PE sample is better than that of MMT/PE sample.Among them,Si O₂/MMT/PE sample has the shortest electrical tree length,with an average branch length of 220μm,and the branches are densely clump-like,with the best electrical tree suppression properties.MMT/PE sample,Si O₂/MMT/PE sample and Zn O/MMT/PE sample have obvious partial discharge inhibition effect.And the discharge amount and the voltage amplitude of UHF signal in Si O₂/MMT/PE sample and Zn O/MMT/PE sample are lower than that in MMT/PE sample.Based on the synergistic effect between the two kinds of inorganic particles,the intrinsic mechanism of Si O₂,Zn O particles and MMT particles to enhance the electrical dendrite and partial discharge suppression properties of the polyethylene matrix was explained from the crystalline properties and trap properties of the composites,respectively.Through data fitting of UHF signal voltage amplitude and discharge amount,it is revealed that there is a quadratic function relationship between the two,and a method for calibrating UHF method parameters using pulse current method parameters is proposed.During the growth stage of the electric tree,the UHF signal has a larger amplitude and a wider frequency band distribution.In the electrical tree stagnation stage,the frequency distribution of the UHF signal becomes narrower,and the maximum discharge pulse moves to the high frequency direction.The spectral distribution of UHF signal of electrical tree discharge has obvious correlation with the growth stage of electrical tree.Therefore,the growth stage of electrical tree can be judged according to the UHF signal of partial discharge,which provides a basis for evaluating the insulation state of power equipment.