Influence of the Degree of Freedom in Normative Test Conditions on the Short-Circuit Behavior of Power Plug-In Connectors

High-current connectors used in gas-insulated switchgear consist of plug, socket and spring-loaded contact element which realize the electrical and thermal contact. Proof of their resistance to fault currents is provided by testing with standardized test procedures, which give specific rated current values and boundary conditions. The short-term fault currents that occur in practice do most likely not correspond to the tested current-time shapes exactly. As these standardized parameters cannot always be set precisely with the test equipment, most standards, such as the considered IEC 62271, allow variations of the short-circuit duration within certain limits. Another possible deviation is the separate consideration of peak current and short-time-current testing. To keep the thermal load of the contact system thereby constant, the short-circuit current is adjusted together with the short-circuit duration using the Joule integral. Since recent findings show that this is an unsuitable approach for contact elements, the proposed
$\boldsymbol{I}^{\mathbf{x}}\boldsymbol{t}-\mathbf{criterion}$
is applied instead. Repeated short-circuit loads are applied to new and thermally pre-aged contact elements. In order to map the transferability of the laboratory tests to practice the peak current in the first halve wave is varied. This allows a more precise estimate of the short-circuit behavior in real operation considering pre-loads.