Electric-Thermal Stresses of Three-Phase Loaded Plug-in Connectors Considering an Uneven Contact Resistance Distribution

High-current connectors used in gas-insulated switchgear must ensure the demanded ampacity at rated and short-circuit currents. Their resilience to short-term currents has been determined through elaborate high-current tests considering single-phase arrangements so far. Recent findings indicate that it is crucial to account for the proximity effect in three-phase applications, as it can result in locally increased current densities. Furthermore, electromagnetic forces during short-circuits or off-center plugging can lead to unevenly distributed mechanical loads on the contact element. Locally reduced contact resistances may result in increased current density and localized heating, which can act as the trigger for welding and potential contact failure. Due to the complex geometries of the arrangements, an electromagnetic-thermal finite element method (FEM) model is developed to calculate the temperature distribution in the contact elements of plug-in connections. To validate the model, a corresponding test arrangement was loaded with three-phase AC current. In the next step, unevenly distributed contact resistances and varying conductor distances were considered. The resulting temperature distribution in the contact elements was measured and evaluated. The validated FEM-model, utilized either in conjunction with or as a potential substitute for elaborate short-circuit tests, is used to identify critical load scenarios for the contact elements in three-phase systems.