Study on Insulation Degradation Characteristics and Health State Evaluation of Onboard Cables for EMUs

The inter-car jumper cable is a key component for power transmission between carriages in high-speed trains. During long-term service, it is exposed to overvoltage impulses, electromagnetic interference, and carriage displacement, forming a coupled environment of strong electric fields and repeated mechanical bending. These stresses accelerate insulation degradation and may pose significant risks to the safe operation of high-speed trains. To address this issue, this study establishes a multiphysics simulation model to investigate the distribution of the electric field and the concentration of mechanical stress under various loading conditions, identifying the regions most susceptible to insulation deterioration. Subsequently, based on degradation-influencing factors and experimental measurements, degradation-sensitive characteristic parameters are extracted, and a degradation equation is established to describe their variation with service mileage. Lastly, a multidimensional feature-based insulation evaluation model is constructed using the fuzzy analytic hierarchy process (FAHP), achieving a prediction error of only 0.861%. Combined with the microstructural evolution of the main insulation layer, the study further clarifies the coupled electrical-mechanical degradation mechanism. This work reveals the key factors governing insulation degradation, proposes a quantitative evaluation method, and offers practical guidance for the operation and maintenance of inter-car jumper cables.