The integration of large-scale heavy-duty electric vehicle (HDEV) charging infrastructure presents significant challenges for existing power distribution grids. This paper evaluates the grid impact of megawatt-level HDEV charging using a coupled simulation approach. A detailed mobility model from previous work simulates HDEV arrivals, parking durations, and energy requirements at highway rest areas over a year, generating realistic charging profiles. These profiles, serve as input for quasi-static time series power system simulations. The analysis employs SimBench benchmark distribution grids (Rural, Semi-Urban, Commercial, Urban). Three distinct scenarios for connecting the HDEV charging infrastructure are investigated across 36 combined simulation cases. The paper focuses on the impact on transformer utilization, line utilization, and voltage magnitudes, comparing scenarios with and without HDEV charging. Results indicate that while transformer capacity appears generally sufficient to accommodate the additional load, line utilization emerges as a critical bottleneck. The findings highlight that significant grid reinforcement, primarily upgrading distribution line capacities, will be essential for the widespread deployment of HDEV charging.
