It is of significance to fully understand the insulation characteristics in order to find or prevent defects in XLPE cable insulation layers

which is helpful to ensuring security of devices and power system operation. For this purpose

we selected test sample cables in operation for different years to assess the remaining life of XLPE cables.Moreover

voltage-endurance test and isothermal relaxation current method were used collaboratively to comprehensively assess samples’ remaining life. Gradual breakdown test at 90 ℃ constant temperature was used firstly

and the same boost parameters for different samples was applied to get the breakdown time of the samples. Testing results were combined with life factors from isothermal relaxation current method to estimate remaining life of the samples. The results show that the cables applied in 1985 and 1987 are in a serious state of deterioration

whose remaining life expectancy is about 10 years; those applied in 1996 are in a very good state

and their remaining life expectancy is about 30 years. It is found that the results from isothermal relaxation current method can be adopted to identify the cables’ aging trend while the voltage-endurance test can be used to draw a specific conclusion about the remaining life. Thus

the use of cable electrical characteristics can be a reasonable estimation of the remaining life of the cable and can guide cable repair or replacement work. It is a reasonable assessment of cross-linked cable aging and life expectancy.