Press- and shrink-fit connections with cylindrical aluminum conductors for high-current applications — Contact- and long-term behavior depending on mechanical parameters

In Gas Insulated Switchgears and Gas Insulated Lines, cylindrical aluminum conductors are used for transportation of energy. To connect the conductors with other parts of the system, separable connections with contact elements are the common and most used solution. In many cases, the separable connections can be replaced with permanent connections in order to reduce costs, operating power losses and increase the reliability, especially if short circuit currents occur. To set up these permanent connections, technologies like the press- and shrink-fit are investigated. Based on the preliminary investigations presented in 2015 a broad variety of connections were established with different interferences, grooved and knurled as well as silver-plated contact surfaces to allow for statistic evaluations. The contact and long-term behavior of the connections are investigated with oven-experiments as well as under current load for a period of more than 10,000 h. Mechanical finite element models of the press- and shrink-fit connections are set up to investigate the resulting contact force as well as the mechanical stress distribution in the contact area. Findings are compared to other common connections, e.g. joints with busbars. As a result, specific recommendations for construction are described and the joining technologies are compared with conventional plug-in connections.