Study on DC component caused by water treeing in XLPE cable

In this paper, based on the possible mechanism of DC component production, a set for measurement of the DC component in a piece of aging XLPE cable insulation has been designed in the laboratory. The AC component of the current in the insulation is much larger than the DC component, and the main problem is therefore to filter the AC component or to strengthen the DC component in order to obtain a sensitive DC component measuring system. During experiment, a bypass capacitor is used to filter the AC component and an additional direct voltage source is used to strengthen the DC component. The results of experiment indicate that the DC component is correlated with the ageing degree of XLPE insulation. They also show that the value of the DC component varies with the amount of high AC voltage applied. The experimental results are helpful to realize a hot line diagnosis system about water treeing in XLPE insulation cable.