Multi-Physics Calculation and Contact Degradation Mechanism Evolution of GIB Connector Under Daily Cyclic Loading

A 3-D electromagnetic-thermal-mechanical coupling finite element model of a gas-insulated bus plug-in connector is proposed in this paper with a subsequent analysis for the contact fatigue mechanism. Special attention has been paid to the contact degradation mechanism under normal cyclic operation conditions, which is important for the optimal designing and condition monitoring of the equipment. The current constriction effect and the contact resistance are considered through modeling the equivalent contact bridges between contact interfaces, and the current densities derived from the electromagnetic field are applied as load inputs in a electrical-thermal-mechanical analysis where varying of friction coefficient is considered. The validity of the calculation model has been demonstrated by temperature rise and relative motion experiments, and the influence of daily changing current and environmental temperature on the thermal and mechanical characteristics of plug-in connector has been analyzed. Analysis results show that the temperature rise among different contact fingers of plug-in connector is not the same with different contact forces, and the plastic deformation can be induced on contact spots. The insert depth of connector can be changed under the action of alternating thermal loading induced by daily change of current and environmental temperature, leading to contact degradation and overheating fault of plug-in connector.