Study on the degradation law of insulation structure and performance of XLPE cables in service with different laying methods
In this paper,the 110 kV XLPE power cable is taken as the research object,and the service of the cable for 13 years under different laying methods is compared.In order to characterize the deterioration of XLPE insulating materials,this paper used a variety of research methods,such as Fourier transform infrared spectroscopy(FTIR),differential scanning calorimetry(DSC),scanning electron microscopy(SEM),thermogravimetric analysis(TG),broadband dielectric spectroscopy and power frequency breakdown test.The results show that the microstructure and macroscopic properties of XLPE cable insulation in service for 13 years are significantly degraded compared with those in non-service cables,as follows:XLPE molecular chains are broken,polar groups such as C=O,C=C and—OH are increased,the melting temperature and crystallinity are lower in direct burial and drain laying,and the melting temperature and crystallinity are higher in cable trench laying.The dielectric constant and dielectric loss have increased,and the frequency breakdown field strength has decreased.Among them,the structure and performance of the cable insulation laid in the row pipe has a faster rate of deterioration,the direct burial laying is the second,and the cable trench laying has the slowest rate of deterioration.The reason for this difference is that the trench laid cable has the best heat dissipation conditions and the lowest cable operating temperature with the same applied current,while the duct laid cable has the worst heat dissipation conditions and the highest cable operating temperature.
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