A study on DC component method of on-line diagnosis for XLPE cables

Many research papers show that water treeing is one of main causes of insulation degradation of XLPE cables. A DC component will be produced through the insulation of the cable containing water trees, when the cable is stressed with AC voltage. The component is considered to appear due to the rectifying effect of water trees in insulation. Therefore, by measuring the DC component, it is possible to diagnose insulation aging as a result of water trees for XLPE cable in service. In this paper, the relations between the DC component and the density of water trees, and between the DC component and the length of water trees are investigated using 10 kV class XLPE cables in the laboratory. It is found that the DC component will grow with the rise in length or density of water trees.<<ETX>>