A Novel FEF Method for Insulation Status Monitoring of Underground Power Cables

Monitoring on underground power cables in a close-fitting manner using mobile robot can acquire more actual information about insulation status of cables. Focusing on a water tree detection module in the monitoring system, this paper proposes fringing electric field (FEF) method to detect probably formed water tree in the insulation layer. An arch substrate based interdigital FEF sensor is designed to reduce the disturbance caused by applying traditional interdigital FEF sensor in the water tree detection. The mathematical model of the novel sensor is built by finite element method. Comparison of the electric field distribution that produced by the above two kinds of sensors is carried out by finite element analysis. Effect on novel sensor performance caused by excitation frequency is discussed. Parameters of the proposed sensor are optimized by analyzing the electric field penetrability with varying finger width and electrode separation. Simulation results demonstrate the sensor’s design is reasonable and the electric field penetrability of the novel sensor is remarkably improved compared with traditional interdigital FEF sensor.