Simulation Study on Typical Defects of 110 kV Cable Buffer Layer

In order to analyze the effect of typical defects of cable buffer layer on the operating performance, the simulation modeling of 110 kV cable was carried out in various cases. Several contact states between the aluminum sheath and the buffer layer were simulated, including the ideal contact state, local air gap defect, deposition of water-proofing powder from damp buffer layer, and imperfect grounding. The electric field is evenly distributed in the cable section, and there is no field distortion with ideal state. When the air gap exists at the interface of aluminum sheath and the buffer layer, the electric field in air gap is severely distorted, and the maximum field strength locates at the triple junction of air gap, aluminum sheath and the buffer layer. The electric field of air defects may be higher than that in cable insulation, far exceeding the breakdown field strength of air and then leading to the partial discharge. At the same position, the field distortion caused by the water-proofing powder deposition is lower than air defects. The local imperfect grounding may also produce larger area of electric field distortion, which will lead to large-scale partial discharge and even interfacial breakdown between the buffer layer and the aluminum sheath. This paper can provide theoretical and simulation reference for the operation and maintenance of high voltage cables.