Three-dimensional modeling and Optimization of a Fully-covered Interdigital Capacitive Sensor for Power Cable Insulation Detection

Due to the advantages of XLPE cable, it is frequently used in power transmission and distribution systems. For long-term use, there are inevitable insulation defects. To detect the status of cable insulation, an improved capacitive sensor that fully covers the cable is proposed, which can be used for nondestructive monitoring of cable insulation, especially for cable joints. In this paper, the geometric structure of the fully-covered interdigital capacitance sensor is designed, and a 3D model of the sensor is built with COMSOL Multiphysics. Three parameters i.e. signal strength, sensitivity and penetration depth are defined for sensor optimization. The influences of electrode length, width, and thickness on interdigital capacitance sensors are discussed. When the length exceeds 5 cm, the length of the electrode does not affect the sensitivity. Electrodes with larger width lead to better signal strength and sensitivity, but the penetration depth decreases. With the increase in the electrode number, the signal strength increases while the sensitivity and penetration depth decrease. Taking YJV1*185 cable as an example, the electrodes of equal width and with a thickness of 0.02-0.12 mm could achieve better measurement results.