Abstract
Our company uses a part of 22kV, and 66kV and 154kV XLPE cables with a waterproof layer in the purpose of preventing water penetration to the insulation. We modeled the water volume of a XLPE cable insulation with waterproof layer as RC series circuit, and we calculated a certain 66kV XLPE cable by using this model. The result was that the time was 35.0 years when relative humidity reaches 50%, and P (Permeation coefficient) equaled 4.4×10-10 [g•cm/(cm2•day•mmHg)].
Precision of permeation coefficient of present water penetration test is about 10-8 [g•cm/(cm2•day•mmHg)]. At first, we improved the test by reducing the initial water volume and so on. The result was that P equaled 3.8 × 10-10 [g•cm/(cm2•day•mmHg)]. At second, we improved it by using a dew-point hygrometer. The result was that P equaled 1.4 × 10-10 [g•cm/(cm2•day•mmHg)]. We can estimate precisely a performance of waterproof layer by using second improved test and the calculation model.
