Studies On The Preparation And Properties Of Cellulose Insulation Paper Modified By Nano-TiO₂

Because of the development of ultra-UHV power transmission insulation level ofpower transmission equipment is asked to rise. Especially for HVDC convertertransformers，oil-paper insulation not only has a high AC breakdown strength, but alsostrong DC breakdown strength when the voltage polarity is reversed in AC, DC, pulseand DC reverse polarity complex operating conditions. That converter transformeroil-paper insulation material is studied becomes necessary for the development of theindustry. Meanwhile, oil-paper insulation capability is improved from materialproperties of nature, difficult problem of electrical and field theory and the preparationof the material cross that is faced. Thus, nanoparticles are used to modified theperformance of oil-paper insulation has important theoretical and practical value.The main purpose of this paper is to prepare a new type of insulation paper whichhas high insulation propertiesin the AC and DC fields. First the preparation of insulationpapermodified by nano-TiO2is studied. Then the best match is given by studying thetensile strength, dielectric properties and power frequency breakdown strength. Then thevariety of ACbreakdown strength, DC breakdown strength are studied, the accumulationand dissipation characteristics of space charge under DC field strength are studied.Mechanism thatthe insulation properties of cellulose insulation paper are affected bynano-TiO2is analyzed at last. This paper achieves following results:①The preparation process and ratio of nano-TiO2were obtained. After theinsulation paper modified by nano-TiO2was prepared.Tensile strength, dielectricproperties, as well as breakdown strength of insulation paper modified by nano-TiO2were analyzed. The best ratio of nano-TiO2in insulation paper was3%, tensile strengthof insulation paper modified by nano-TiO2did not decrease, the breakdown fieldstrength of power frequency, the partial discharge inception voltage, the breakdownvoltage, the partial discharge inception discharge voltage underDC of insulation papermodified by nano-TiO2have increased significantlycompared with the unmodifiedinsulation paper;②Insulation paper modified by3%nano-TiO2compared to the unmodifiedinsulation paper, Dc breakdown voltage of positive polarity is significantly improvedafter Pre-pressurized positive and negative polarity voltage, high breakdown voltage ismaintained when the voltage polarity is reversed, that helps to reduce the occurrence accidents of breakdown.③For the first time the insulation paper that can suppress the space chargeinjected to insulation paper, reduce electric field distortion, accelerates the dissipation ofspace charge is prepared with nano-TiO2. PEA space charge tests show that insulationpaper modified by3%nano-TiO2can suppress the space charge injected to insulationpaper, reduce electric field distortion, accelerates the dissipation of space charge underlow and high field strength. Space charge dissipation rate of insulation paper modifiedby3%nano-TiO2is greatly improved.④For the first time mechanism that insulation paper breakdown performance andspace charge accumulation, dissipation performance are improved is studied. Thecontact surface structure between cellulose and nano-TiO2is changed because of thestrong interaction between the nano-TiO2nanoparticles and cellulose. Multi-core modelsimilar interface structure is formed, more traps are formed. TSC tests show that thenumber of shallow traps is greatly increased because of the nano-TiO2contact interfacewith cellulose, the number of deep traps is reduced. Breakdown strength performanceand space charge performance are improved because of changes in the number and levelof the trap.