Evaluation Of Surface Degradation Of Insulation Oil-Paper Based On Image Processing Technology

As an important part of transformer insulation,oil-paper insulation determines the overall insulation of the transformer.Its role is outstanding and significant,but oil-paper insulation is vulnerable to impact damage and difficult to recover.Therefore,studying the degradation mechanism of oil-paper insulation can improve its insulation performance and extend its use.Life is particularly important.At present,scholars mostly observe the microscopic morphology of insulating oil-paper from SEM images,but there is no further in-depth statistical information.This paper mainly uses image processing technology to conduct experimental research and detailed analysis on the aging of insulating oil-paper and the entire process from the initiation of partial discharge to breakdown.At the same time,a model of laminated oil-paper was made to study the surface deterioration of laminated oil paper with different degrees of aging.In this study,insulating pressboard in different aging states were produced.After the breakdown experiment was performed on them by the constant pressure method,the fiber diameter,porosity,surface roughness,and carbon mark area after breakdown were calculated using image processing technology.It is used as a characteristic quantity to study the surface deterioration characteristics of pressboard before and after breakdown under different aging conditions;the discharge stage is divided,and the degradation law of insulating pressboard during the pressurization process is studied;local pressurization experiments are carried out on laminated oil-paper with different aging degrees,and the starting voltage,extinguishing voltage and carbonization traces on each layer of insulating oil-paper during the discharge process were measured for each sample,and the fiber surface morphology was observed.The effect of thermal aging on the deterioration of laminated oil-paper was studied.Studies have shown that:(1)for different aging states of insulating pressboard,the morphology change trend is different;after 16 days of aging,the degree of polymerization of the insulating pressboard is close to 500,the corresponding fiber width is 68.1%-81.8%of the fiber width of the unaged pressboard,the ratio reaches 13.83%,and corresponding to the normalized roughness of 0.191;after 32 days of aging,the degree of polymerization is close to 300,the fiber width is mostly around 30μm,the porosity is 16.74%,and the corresponding normalized roughness is 0.221.(2)During the partial discharge process,the fibers are compacted tightly at the beginning of the discharge,and the surface is smooth.From the discharge development period,there are continuous bubbles in the sample,the internal pressure of the paper(board)is not balanced,the cellulose macromolecules are broken into small molecular chains,and the fibers gradually Sparse,the discharge burst period begins to polymerize,bend,and produce crystalline particles.After breakdown,the fiber breaks and splits,and there are large pieces of fiber bonding at the fracture.According to image processing and calculation analysis,as the pressure time increases,the fiber diameter gradually decreases.After breakdown,the fiber diameter distribution is in the range of 36-42μm,and the proportion of fibers smaller than30μm increases.The porosity gradually rising,it reached 1.3 times that before the pressure test.(3)Through the research of laminated oil-paper,it is found that in the initial stage of discharge,thermal aging has little effect on the partial discharge development of laminated oil-paper in the normal direction.In the later stage of discharge,this effect begins to appear;thermal aging affects the insulation performance of laminated oil-paper.The creepage speed in the horizontal direction is accelerated;the first layer of insulating paper is more strongly impacted by electrons and has a higher carbonization rate.It is affected by the normal direction electric field at the contact point of the electrode and the insulating paper,while the lower layer of insulating paper is affected by free electrons.Under the effect of horizontal and vertical components,the fibers are loose in large areas,displaced and deformed,and the threads are broken.The degree of deterioration is directly proportional to the pressure time and thermal aging time.The degree of insulation paper damage is reduced as the number of layers increases.