Study On The Characteristics Of XLPE Cable Based On Accelerated Electrical-heating Aging Test

Cross-linked polyethylene(XLPE)cable is widely used in distribution and transmission grid for it has the the advantages of light weight,simple manufacturing process,easy installation and maintenance.Meanwhile,its mechanical properties and dielectric properties are also outstanding.The cables will be aging during the operating process because of the electric field and temperature factors.Aging can cause accidents,which will bring security hidden trouble.Therefore,study on electro-thermal aging of XLPE cable insulation and assess the degree of aging has important theoretical and practical value.Electrical and thermal accelerated aging test was implemented to XLPE cable.Apply alternating voltage 26.1kV and select 103 ?,114 ? and 135 ? three temperatures to sampling and testing in various stages of aging.Test measurements include Elongation at break and tensile strength which reflecting the mechanical properties,gel content which reflecting crosslinking degree,X-ray diffraction and infrared spectroscopy which reflecting material structure,differential scanning calorimetry and thermal gravimetric analysis which reflecting thermal stability,breakdown voltage,dielectric spectrum and space charge which reflecting dielectric properties of the materials.The results show that,the gel content has presented a downward trend after the first rising with aging stage changing at different aging temperatures.The higher the gel content,the greater the degree of crosslinking,the greater the mechanical strength of the material.The specimen was less oxidation in the electric aging process and the initial decomposition temperature changed little.During the aging process,part of the crystal has formed internal of the sample which make the melting temperature rising,while the degradation makes the material structure uneven,the layer of crystallization increasing,the improvement of crystalline phase deterioration,melting range widening.Besides,the type and number of polar groups will increase during the aging process.Dielectric loss factor has a peak value varying with frequency curve,which is larger than the aging peak.Finally,Space charge tests show that the more severe insulation aging the more easily for charge to inject,the trend of breakdown field strength presented a decreasing wth the deepening of aging.The research of this paper can provide an important reference for the insulation characteristic of the XLPE cables.