Thermodynamic and Short-Circuit Performance of Rigid Overhead Contact Systems in Ho Chi Minh City Line 1 Metro Tunnels

This paper presents a rigorous electro-thermal evaluation and safety margin analysis comparing the Advanced Rigid Overhead Contact System (ROCS, 2100 mm2) and conventional Flexible OCS (170 mm2) in Ho Chi Minh City Metro Line 1. Utilizing interconnected mathematical frameworks, the study models both dynamic transient load profiles and worst-case short-circuit scenarios. Simulation results reveal that under a 25.78 kA fault lasting 1 s, the OCS suffers severe thermal shock, violently surging to 155.0 °C and breaching its mechanical annealing threshold. Conversely, the massive aluminum ROCS acts as an effective heat sink, restricting fault temperatures to a safe 36.6 °C. Under continuous cyclic operational loading with a 2.1 min headway, the ROCS demonstrates high thermal inertia, constraining transient spikes to 21.5 °C and stabilizing its long-term temperature rise within a bounded stability band (35 °C to 65 °C) below the 79 °C cyclic saturation limit. These findings mathematically prove the superior climate resilience and structural safety margins of ROCS for high-capacity tropical underground transit networks.