Abstract
We analyzed the statics of dielectric breakdown failures caused by water tree degradation in 6 kV XLPE cables using the Hazard Analysis. The data used in this report are actual situation of XLPE cables. The data are classified by conductor size. The failure rates were calculated, and are different according to the conductor size. Furthermore, the failure rates were calculated based on the information of conductor size, cable length and cable age in this report, resulting that the order of the priority of degradation diagnosis can be made quantitatively.