Impact of Underground Obstructions in Double-Circuit Underground Power Lines: Ampacity and Induced Effect

This study presents a detailed analysis of the electrical and thermal interactions of underground power transmission lines, considering ampacity, induced voltages, and induced currents in the sheaths. Mathematical models estimate induced currents in different duct bank configurations (triangular, inverted triangular, flat, and vertical), accounting for geometric variations caused by underground obstructions such as pipelines and gas ducts. Two scenarios are investigated: a realistic case that incorporates the effects of obstructions on cable spacing and depth, and an idealized case that assumes uniform geometry. The study also examines the impact of sectionalized and continuous cross-bonding methods on system performance. The results, applied to a 220 kV double-circuit underground transmission line, demonstrate how real-world conditions directly influence the electrical and thermal characteristics of the system. Finally, engineering recommendations are provided, taking into account the induced currents associated with core temperature rise.