The ongoing re-equipment of electric power systems is based on the use of smart grid technologies. Among the key tasks that are solved on this basis are increasing the capacity of power transmission lines, reducing losses, and improving power quality. To address these issues, one can use compact power transmission lines. Such lines are notable for their complex split-phase designs and close together placement of current-conducting parts, so as to keep the distance to a permissible minimum, which is achieved by the use of insulating spacers. This article reports the results of computer-aided simulations performed for a standard railroad power supply system, the traction substations of which were connected to 220 kV networks through compact overhead lines (COHLs). The purpose of the study was to calculate the values of quantitative metrics that measure power quality and energy efficiency as well as electromagnetic safety. Modeling was performed in the three-phase reference frame with the use of techniques and algorithms implemented in the Fazonord software package. We considered a power supply system with 25 kV overhead contact systems. It was assumed that the external network used three different designs of COHLs: with coaxial, linear, and sector-shaped arrangements of conductors. Based on the results obtained, we concluded that (1) when using COHLs, the voltages on bow collectors of electric rolling stock were stabilized and did not exceed permissible limits; (2) losses in the traction network were reduced; and (3) the parameters of power quality and electromagnetic safety conditions in external power supply systems of railroads were improved, if judged in terms of electric and magnetic field strengths. Out of the eight types of COHLs considered, compact lines with the three-segment and concentric arrangement of conductors had the best performance, and the use of COHLs with the vertical arrangement of conductors made it possible to reduce electric field strengths. However, the designs of such transmission lines are quite complex and entail higher construction costs.

The paper addresses the issues of electromagnetic safety in traction networks of 25 kV AC railways. The purpose of the research is to develop digital models to determine the strengths of electromagnetic fields (EMFs) created by traction networks near portal-type metal structures. Such a structure in this study is represented by an overpass located above the tracks. The presence of a conductive structure significantly complicates the picture of EMF distribution in space. In contrast to the plane-parallel EMF of the traction network on interstation tracks in the spans between the supports of the catenary system, the field in this situation becomes three-dimensional. The technology for detecting strength relies on the concept of segments of limited length conductors, some of which may be buried. In order to apply the quasi-stationary zone equations to frequencies of up to 2000 Hz, it is essential to ensure that the size of the set of objects composed of these conductors does not exceed several hundred meters. Based on the modeling results, the dependences of the amplitudes and components of EMF strengths on the z-coordinate passing along the axis of the railway were obtained. In addition, three-dimensional diagrams were constructed to analyze the distribution of EMF in space. The findings of the studies show that the presented technique allows considering the influence of metal structures when modeling the electromagnetic fields of traction networks. It can be used in practice to develop effective measures to enhance electromagnetic safety conditions.

Power supply for traction substations (TSs) of AC railways has traditionally been provided by 110–220 kV overhead transmission lines (OHL). These OHLs can be damaged during strong winds and ice formation. Furthermore, these lines generate significant electromagnetic fields (EMFs), which adversely affect maintenance personnel, the public, and the environment. Mitigating the resulting damages requires the establishment of protection zones, necessitating significant land allocation. Enhancing the reliability of power supply to traction substations and reducing EMF levels can be achieved through the use of gas-insulated lines (GIL), whose application in the power industry of many countries is continuously increasing. The aim of the research presented in this article was to develop computer models for determining the EMF of a GIL supplying a group of traction substations, taking into account actual traction loads characterized by non-sinusoidal waveforms and asymmetry. To solve this problem, an approach implemented in the Fazonord AC-DC software package, based on the use of phase coordinates, was applied. This allowed for the correct accounting of the skin effect and proximity effect in the massive current-carrying parts of the GIL, as well as the influence of asymmetry and harmonic distortions. The simulation results showed that the use of GIL brings the voltage unbalance factors at the 110 kV busbars of the traction substations within the permissible range, with the maximum values of these coefficients not exceeding 2%. The results of the harmonic distortion assessment demonstrated a significant reduction in harmonic distortion factors in the 110 kV network for the GIL compared to the OHL. The performed electromagnetic field calculations confirmed that the GIL generates magnetic field strengths one order of magnitude lower than those of the OHL. The obtained results lead to the conclusion that the use of gas-insulated lines for powering traction substations is highly effective, ensuring increased reliability, improved power quality, and a reduced negative impact of EMF on personnel, the public, the environment, and electronic equipment.

This study aims to develop models for defining harmonic distortions in electromagnetic modeling of artificial railroad structures, taking into account high harmonic generation of electric locomotives. The research objects included tunnels and galleries, as well as through-type and deck-type truss bridges. Calculations of sites having a flat relief were carried out for comparison. When developing digital models, an approach representing power supply systems in phase coordinates in the Fazonord software package (5.3.7.0-2024 version) was used. Sets of conductors grounded on both sides were used for constructions. Electromagnetic fields were defined by simulation of five down trains weighing 3192 tons and moving at intervals of 22 minutes. For several constructions, the maximum working values of electric field intensity at the studied sites exceeded the permissible value of 5 kV/m, i.e., 9.8 kV/m for the deck-type truss bridge and 5.9 kV/m for that of the tunnel type. Due to extended train intervals, magnetic field intensity had never exceeded the specified limit of 80 A/m. Our study revealed that high harmonics of electric locomotives provoke severe distortions in the hodographs of magnetic fields, while artificial structures significantly change field distribution in the section of the electric traction network. Thus, digital models of traction-energy systems were developed. These models make it possible to accurately define the dynamics of changes in electromagnetic field intensity in a space surrounding the electric traction network of 25 kV inside artificial structures consisting of many metal parts. The computer technology developed by the authors can be effectively used in the development of measures to ensure electromagnetic safety in artificial structures of electrified railway transport.

Аннотация. Представлены результаты моделирования несинусоидальных режимов тяговых сетей. Получены формы кривых токов, напряжений и мощностей на токоприемниках электроподвижного состава. Ключевые слова: тяговые сети 25 кВ, несинусоидальные режимы, формы кривых токов, напряжений и мгновенных мощностей, моделирование.