Thermal Impact of Under-Line Fires on MVDC Overhead Conductors and Clearance Distance Analysis

Abstract

As MVDC systems expand along roadways, overhead conductors face fire hazards from under-line vehicles and containers. Using FDS 6.9.1, this study evaluates thermal responses of an ACSR-OC 160 mm² XLPE-insulated conductor for seven scenarios — passenger car, two cars, van, bus, standard and large containers, and electric vehicle — at heights of 5–10 m, load factors of 50–70 %, and ambient temperatures of 20–40 °C. Failure thresholds are 299 °C for XLPE insulation and 538 °C for structural steel. Passenger-car fires remain safe at 5–6 m, whereas van and large-container fires exceed the threshold even at 10 m. A 70 % load factor shortens time-to-failure, but a 1–2 m height increase restores safety margins. Steel surfaces do not exceed 102 °C across all scenarios. A minimum clearance of 10 m is suggested for logistics and congestion-prone zones, with fire-protective conduits for container areas. Future work should address wind-induced flame tilt and EV re-ignition.