XLPE Cable Material Vibration-thermal Ageing Characteristicand Lifetime Assessment

High voltage XLPE cables are widely used becasuse of its outstanding physical and electrical properties in power distribution.Cables lay at tunnel,railway,bridge and other engineering conditions,which causes fatigue damage.With time going on,cable sheath cracking and shield serious corrosion often happen.In the engineering condition,XLPE cable insulation aging is not a single result of electricity,however,it has many factors like electricity,thermal and mechanical.Therefore,it is necessary to clarify XLPE damage mechanism about vibration fatigue.In this thesis,cable ageing test platform is established.One platform is under vibration condition and the other platform is static condtion.Cables are laid on the vibration platform and the current generator is used to maintain the temperature stability.In this condition,we can experiment about vibrationthermal ageing and thermal ageing respectively.Temperature sensors are used to measure cable core temperature and surface under vibration-thermal combined ageing.Test data from temperature sensor are compared with ANSYS software simulation about XLPE cable insulation under different ageing time and stress.From this,temperature diffusion from internal to external can be analyzed resonablely.Secondly,samples under vibration-thermal combined ageing from different ageing period are tested with Oxidation Induction Time(OIT),Scanning Electron Microscope(SEM),Fourier Transform Infrared Spectroscopy(FTIR).From these tests,XLPE material molecule construction structure and morphology structure variation under different ageing period can be conducted.We can analyze XLPE ageing characteristic from different view.This thesis mainly assesses lifetime about under vibration-thermal ageing condition.Combined with Arrhenius equation,inverse power function and the maximum likelihood function,assess related parameters about Wiener model.The probability density curve and reliability curve of XLPE were calculated by theoretical.And the life distribution of XLPE insulation material under different condition is carried out.This method has advantage of easy operation and short time test.It has guiding sinificance for designing laying method at strong vibration area and operation maintenance strategy.