Design and Electric Field Calculation of a Wall Bushing Made from Nonlinear Materials

Abstract

The capacitor bushing is the most commonly used bushing in power systems. However, the use of the capacitor bushing is limited by the complexity of the insulation and grading electric field structure. At the same time, as the voltage grade of the power system increases, the bushing needs to be made larger and its manufacture is more complicated, limiting the use of the capacitor bushing for such power systems. In light of present high-voltage bushing problems, the present paper proposes a new type of high-voltage bushing structure that adopts a three-layer structure with nonlinear composites for internal insulation to replace the original bushing condenser in a capacitor bushing. From the inside to outside, the three layers are a uniform-voltage layer, leakage-current-limiting layer, and electrode extended layer. The uniform-voltage layer and electrode extended layer made from materials having nonlinear conductivity are used to make the electric stress uniform in the main insulation and at the edge of the flange, avoiding breakdown of the main insulation and flashover of the flange. The design of the new bushing is applicable to a variety of voltage levels of DC power systems. At the same time, the new bushing is smaller, the production of the bushing is simpler, and the risk of a bushing fault is reduced, marking a technical innovation for high-voltage bushings in power systems.