Mechanism Of Influence Of Machine-Heat Combination On Performance Degradation Of Insulating Paper

Aiming at the fact that the core of the converter transformer for UHV DC transmission line is vibrating more severely,this paper studies the change trend and deterioration mechanism of the performance index of cellulose insulation paper under the machine-thermal synergy.The main work includes:Firstly,the aging mechanism of insulating paper is introduced.Based on the degradation mechanism of its main component cellulose,various factors affecting the aging of insulating paper,such as temperature,moisture and oxygen.Secondly,the existing performance indicators and detection methods for characterizing the deterioration degree of insulation paper are described in detail,and a thermal synergistic aging scheme for feasible insulation paper machine is developed.Thirdly,design and build an insulating paper machine-heat aging test platform to realize the machine-thermal synergistic acceleration aging of insulating paper samples.Seven sets of aging experiments were set up,covering aging conditions such as frequency and amplitude of different temperatures and different mechanical vibrations.Finally,the mechanical properties of the aged samples,such as tensile strength,polymerization degree,etc.,were combined with molecular dynamics equations to characterize the aging trend of insulating paper,and then different aging was obtained by X-ray diffraction analysis and scanning electron microscopy.The research in this paper shows that under the combined action of temperature and mechanical vibration,the cracking process of cellulose has the chemical reaction of molecular bond cleavage accompanied by the disintegration of macromolecules,and the cellulose arrangement will be relaxed under the repeated stretching conditions of mechanical vibration.And the phenomenon of creep,and the looser the arrangement,the stronger the acceleration of the tensile force on its aging.Through the microscopic mechanism of X-ray diffraction experiments and scanning electron microscopy experiments,it was found that the crystal type of the insulating paper did not change under the action of mechanical vibration and temperature,and the crystal size became small.And as the amplitude increases or the old exchange time prolongs,the arrangement of cellulose becomes looser and the mechanical strength gradually decreases.