Preparation And Research Of Electrospinning PI Porous Fiber Membrane For Oil-paper Insulation

Oil-paper insulation structure is an important insulation part of oil-cooled transformers to ensure normal use.It is required that the insulation paper has excellent aging resistance and electrical insulation performance.However,traditional insulation oil-paper needs to be improved in heat-resistant insulation performance.After forming an insulating structure with transformer oil,the electrical insulation and heat resistance of traditional insulating oil paper can be improved,and the electrical equipment will run more stably.In this study,an electrospinning method was used to spin the Polyimide（PI）porous fiber membrane,which can penetrate the transformer oil and has good heat resistance and insulation.PI porous fiber membrane was prepared by two-step method combined with electrospinning.The membrane was immersed in transformer oil and its properties were tested.Through the breakdown field strength test of pure PI fiber film,the breakdown mechanism of pure PI fiber film is analyzed,and the dielectric and thermal properties of pure PI fiber film are analyzed.The research found that:the pure PI fiber membrane was tested for breakdown field strength,and its breakdown field strength was 50 k V/mm;the dielectric constant and dielectric loss of the pure PI fiber membrane were low,which is 1.725 and0.0067,respectively;the pure PI fiber The initial decomposition temperature of the film is 534℃,which has good thermal performance.Further research found that when the fiber membrane was punctured multiple times to 25 times at the same point,the breakdown field strength of the fiber membrane varied between40-55 k V/mm and the average breakdown field strength was 53 k V/mm.Al₂O₃/PI and Fe₃O₄/PI composite fiber membranes were prepared by electrospinning and thermal imidization.The chemical structure and micro morphology of the two composite fiber membranes were characterized.It was found that two kinds of nanoparticles had been successfully introduced into the fiber respectively.By analyzing the effect of nanoparticle content on the electrical properties of Al₂O₃/PI and Fe₃O₄/PI composite fibers,it is found that the breakdown voltage of Fe₃O₄/PI composite fiber reaches the maximum of89.36 k V/mm when Fe₃O₄ content is 3 wt.%,and the dielectric constant and dielectric loss of composite fiber membrane are 1.61 and 0.0053 respectively.When the amount of Al₂O₃ is 2 wt%,the breakdown voltage of Al₂O₃/PI composite fiber reaches the maximum,which is 74.89 k V/mm.At this time,the dielectric constant and dielectric loss of composite fiber membrane are 1.37 and0.00076 respectively.The addition of nanoparticles can effectively improve the breakdown field strength and reduce the dielectric constant and dielectric loss.