Multi-Physics (Electromagnetic–Thermal–CFD) and Techno-Economic Analysis of Double-Neutral and Increased Cross-Section Scenarios in Harmonically Loaded Busbar Trunking Systems

In this study, the double-neutral (3P + 2N) configuration, considered a traditional solution for busbar systems subjected to overcurrent and thermal stresses under harmonic loads, and alternative cross-sectional expansion (from 6 mm × 55 mm to 6 mm × 65 mm) scenarios are investigated using a multidisciplinary approach. In this context, the electrical, electromagnetic, current density distributions, and magnetic flux densities (Bmax) of the systems are modeled in the COMSOL Multiphysics® (AC/DC Module 6.2 version) environment; the obtained q″ (W/m3) loss maps were transferred to FLOEFD convective airflow (CFD) simulations as volumetric heat sources, and steady-state electro-thermal analyses were performed. Convergence tests were conducted with the BiCGStab solver to ensure numerical stability, solver convergence, and spatial grid independence, and high accuracy was obtained at a margin of error of 3.5222 × 10−4. The findings showed that the proximity effect, due to the close placement of the pair of neutral conductors at the 150 Hz harmonic frequency, increased the current density to 4.68 A/mm2 and turned the neutral line into an additional heat source. In contrast, in the 4-conductor scheme where all conductor cross-sections were increased by 18.18%, the magnetic flux density at 150 Hz was suppressed from 27.21 mT to 23.50 mT, and the current density was distributed more homogeneously, optimizing the temperature rise limits (ΔT). Furthermore, the techno-economic cost analysis conducted revealed that, under premium scenarios for LME raw copper and processed bar copper, the application of increased cross-sectional area offered an optimization that was approximately 5.77% more economical per meter (approximately $36 USD for a standard 3 m length) compared to the double-neutral configuration. Consequently, it has been proven that in BTS designs, not only total harmonic distortion (THD) but also the triplen harmonic ratio, frequency-dependent AC resistance (Rac) variations, and material mass–cost balance should be considered together.