Analysis of High-Frequency Current for Comprehensive Winding Insulation Degradation Detection of Railway Propulsion Motors

In variable-speed drives, a substantial number of voltage harmonics are parasitically injected by the switching of the power devices. Driven by the capacitance change that winding insulation aging implies, the high-frequency currents resulting from inverter-based voltage excitations can show the health state of motor winding insulation. In this paper, differential and phase current are studied for winding insulation monitoring based on current sensing after the application of either DM or CM voltage step excitations. The goal is to experimentally test and analyse a wide variety of common winding insulation aging scenarios, which comprises TT and GW insulation degradation at different winding positions and using different harmonic components. A test railway traction motor is used for validation.