Theoretical, Simulation and Experimental Research on a Capacitive Sensor Used for Detecting the High-speed Railway Contact Line

The contact wire of high-speed railway has large mechanical wear due to long-term friction with the pantograph contact strip, which decreases the mechanical and electrical properties of the contact wire. Therefore, regular inspection of the contact wire is of great significance to ensure the normal operation of the high-speed rail line. In this paper, a measurement method based on the capacitive sensor is proposed to detect the wear amount of the contact line and a mathematical model of the relationship between capacitance value and wear amount is established. The theoretical capacitance value, considering the edge effect, is calculated based on the model using the Schwarz-Christoffel transform, and the corresponding simulated value is obtained based on simulation analysis with COMSOL. The simulation results are compared with theoretical results, which show good consistency. Subsequently, a testing platform is built and several test pieces under different wear levels are detected. The experimental results show that the measured value and the simulated value have good consistency, which further verifies the feasibility of wear amount detection of high-speed rail contact wire with a capacitive sensor.