The Effect Of The Aggregation Morphology Of Polyethylene On The Relaxation Process And Space Charge Properties

Polyethylene and its nanocomposites are excellent cable materials.The rapid development of ultra-high voltage direct current transmission has put forward higher electrical and mechanical strength requirements for dielectric materials.The injection and dissipation of space charge directly changes the electric field distribution of the insulating material,and plays a role of increasing or decreasing the local electric field strength inside the insulating material.At present,there is a consensus in the world that space charge has a significant influence on the electrical properties of dielectric materials such as electrical conductivity,breakdown field strength,electrical aging,and heat aging due to the distortion of space charge on the internal electric field distribution of insulating materials.The morphology of polyethylene materials has a certain relationship with the space charge characteristics.The crystallization of polyethylene materials and the regularity of the structure will affect the space charge.However,the corresponding relaxation process also changes when the morphology structure is different.In the process of temperature change,the degree of chiplet shift or defect generation is also different.The series of behaviors of space charge inside a dielectric has a lot to do with defects inside the material.In this paper,the aggregation structure,relaxation process and space charge behavior of polyethylene materials were studied,and the effects of aggregate structure on the relaxation process and space charge storage and release were investigated.The low density polyethylene and its nanometer magnesia composites were used as research objects,and the composite materials were prepared by melt blending.The aggregation structure of polyethylene was changed by different annealing methods and introduction of a magnesium oxide nucleating agent.The aggregation structure of polyethylene materials was characterized by polarized light microscopy and differential scanning calorimetry(DSC).Dynamic mechanical analysis(DMA)and thermal stimulation current(TSC)were used to test the relaxation process of materials,and electroacoustic pulse method was used.(PEA)Tests the space charge characteristics of materials.In the test of pulse electroacoustic method,the space charge distribution of polyethylene material was measured by different electric field strength and short circuit time,and the relationship between space charge behavior and morphology of polymer molecules was studied.The results show that the crystallinity of the polyethylene material has an important influence on the space charge characteristics.Increasing the crystallinity of the material contributes to the dissipation of space charge.