Time-sensitive networking (TSN) provides reliable and deterministic real-time communication for control operations in cars, aeroplanes or industrial processes, and further promises benefits for the operation of power systems. In the letter context, however, communication distances become comparable large and dedicated real-time networks are hardly feasible, which leads to the situation that real-time traffic needs to share communication resources with non-real-time traffic. We follow two goals: First, we explore the question how to use TSN to manage real-time traffic of a mission critical application coexisting with other non-critical traffic in case of network overload and over long distance links; second, we derive what effects the use of TSN has onto global system reliability in the given scenario. Methodologically, we first created a model of a differential protection scenario typical for distribution power grids. We evaluated the behaviour of TSN in this scenario analytically and by simulation before we drew qualitative conclusions about the robustness of the overall system from the results. Our results show that TSN can well meet the performance criteria for critical traffic in the given scenario and also has a promising impact on the robustness of the overall system. The results encourage us in our efforts to further investigate the potential of TSN-based real-time communication in the power grid environment.