Modeling of Electromagnetic Fields of a Gas-Insulated Line Supplying Traction Substations

Traditionally, AC power is supplied to railway traction substations from 110–220 kV overhead power lines, which are susceptible to damage during strong winds and ice formation. Furthermore, these transmission lines generate significant electromagnetic fields, adversely affecting maintenance personnel, the public, and the environment. To mitigate the resulting damage, protective zones requiring significant land allocations are necessary. Improving the reliability of traction substation power supply and reducing electromagnetic field levels can be achieved by using gas- insulated lines (GIL), the use of which in the power industry in many countries is steadily increasing. The objective of the research presented in this article was to develop computer models for determining the electromagnetic fields of a GIL supplying a group of traction substations, taking into account the actual traction load, characterized by non- sinusoidality and asymmetry. To solve this problem, an approach implemented in the Fazonord AC-DC software package and based on the use of phase coordinates was used. This allowed for the accurate consideration of the skin and proximity effects in the massive current- carrying parts of the GIL, as well as the effects of asymmetry and harmonic distortion. Modeling results showed that the use of GILs resulted in voltage asymmetry factors on the 110 kV traction substation busbars being within the permissible range, with maximum negative- sequence asymmetry factors not exceeding 2 %. Harmonic distortion determinations revealed a significant reduction in harmonic distortion factors in the 110 kV network for GILs compared to overhead power lines. Electromagnetic field calculations confirmed that GILs generate magnetic field strengths an order of magnitude lower than those of overhead power lines. These results suggest the high efficiency of using gas- insulated lines for powering traction substations, ensuring increased reliability, improved power quality, and reduced negative impacts of electromagnetic fields on personnel, the public, the environment, and electronic equipment.