Research on the insulation properties of 10kV XLPE damp cable

With the urbanization thriving in China, electric cables are gradually replacing the overhead line and widely used in urban distribution grid. Meanwhile, fault rate of electric cables has increased in recent years. Owing to the harsh environment the electric cables worked at, most of them experienced high humidity, even immersion in water, which cause lots of practical problems. That is, inner layer of electric cables is easy to be damped, leading to insulation faults eventually. In this paper, a heating cycle voltage test platform was designed and three serious damp 10kV XLPE cables were selected. The heating cycle voltage test was used to heat the damp cables, evaporating moisture gradually. The variation of insulation resistance and dielectric loss tangent, due to the evaporation of moisture, was obtained by measuring these parameters during different periods of the heating cycle voltage test. With the heating cycle voltage test proceeding, the internal moisture of cable seeped from the place around the joint gradually and the insulation state was improved. Finally, an equivalent circuit model of damp cable has been proposed to qualitatively analyze the affects of moisture on the insulation of cable theoretically.