1373 Figure 3 – Anchoring diagram with a description of the main system components 4. SINGLE WIRE ENERGY SYSTEM (SWET) In the scientific literature and in several SWET patents, Nikola Tesla’s patent (Tesla, 1897) is widely regarded as the prototype of single-wire electric power transfer. Single-wire electric power transmission has been in use since 1925. The theoretical foundations of this approach were developed by Lloyd Mandeno (Mandeno, 1947), who was the first to implement the system in New Zealand, where it became known as SWER (Single Wire Earth Return). Since then, more than 200.000 km of such lines have been constructed worldwide. The theoretical background of 50/60 Hz SWER systems is well established in the literature, with the main challenges being grounding resistance, electromagnetic field distribution, and overall efficiency (Bolshev et al., 2023; Jin et al., 2023). The primary motivation for deploying SWER lines is economic, as their investment cost is approximately three times lower than that of conventional three-phase lines. However, SWER systems also exhibit several disadvantages, including high transmission losses (up to 50%), relatively high line voltages (typically 12-19 kV), significant voltage drops at the customer end, stringent grounding quality requirements (ground resistance below 5 Ω), and other grounding-related issues. Recent advances in transistor-based resonant power converters enable the generation of highfrequency AC currents and voltages. This allows a single transmission line to be supplied with high-voltage (HV) and high-frequency (HF) excitation, typically in the range of 5-30 kHz, compared to the conventional 50/60 Hz operation (Kasprzak et al., 2022). In the project, the solution was proposed, in which a highfrequency SWET line operating in resonant mode connects the ESS to a three-phase 400 V AC grid. This approach results in significant improvements in the operating parameters of the SWET line. Furthermore, within the POSTEN project, the use of a SWET line also offers an economic advantage over transmission via a conventional three-phase low-voltage overhead line (3 × 400 V). Energy transfer is achieved via a thin, single conductor with a small cross-section, enabled by the relatively high operating voltage of approximately 5 kV. Figure 4 – SWET converter system schematic with key electrical parameters The SWET system consists of three power electronic converters, a single-wire transmission line
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