Optimization of Geometrical Parameters of ECT Sensor for Power Cable Insulation Detection

Cross-linked polyethylene (XLPE) power cable is widely used in AC/DC transmission and distribution system. The insulation defects of the cable may lead to safety problems and economic losses. Electrical capacitance tomography (ECT) technology can be used to show the distribution of dielectric constants of insulation layer, and thus detecting insulation defects of XLPE cable and its accessories. Because of the `soft field' effect in the sensitivity field of ECT system, it is necessary to optimize the structure and parameters of capacitive sensor for more accurate images. In this paper, the model of 8-electrode ECT sensor is constructed, and its geometrical parameters, including electrode thickness, electrode angle and the ratio between the radius of the shielding and the cable, are optimized by orthogonal experiment design. The signal strength and the uniformity of sensitivity field distribution are taken as the evaluation indicators. The simulation results show that the setting of the shield has a great influence on the indicators. When the shielding layer is too close to the cable, the uniformity of the sensitivity field is influenced. However, the influence of electrode thickness and angle on signal strength and sensitivity field uniformity is relatively small.