HVDC and FACTS
The bulk power transmission from generators to load centers is one of the main study areas in electric power engineering. Electrical power engineers and researchers have been exploring new ways of power transmission for decades while making efforts to enhance the capability of existing power grids. Multiple-phase transmission was proposed by American researchers in 1972. The transmission capacity can be increased dramatically by utilizing multiple three-phase lines, for example, 6, 9, or 12 phases. The main benefits are lower phase-to-phase voltage than a single three-phase system, and the reduction of line-to-line spacing to save the land usage. Compact transmission was introduced by ex-Soviet researchers in 1980. The surge impedance loading can be improved by optimizing line and tower structures: increasing the number of sub-conductors in each phase to smooth the electric field distribution around conductors, and reducing the phase-to-phase spacing. The concept of fractional frequency transmission system (FFTS), presented by one of the authors in 1995 , is under investigation. It uses low frequency on transmission system, for example, one third of normal frequency, to reduce impedance – so-called electrical distance. Dutch scientists discovered superconductors in 1911. Superconductor technology could also be applied in power transmission. Small capacity generators, transformers, and cables have been manufactured using superconductors. However, there is a long way to go before industrial application. Wireless transmission has the possibility to transport electric power without transmission lines. This concept can be traced back to Tesla's test in 1899. Current study and feasible industrialized application are mainly on microwave, laser, and vacuum tube transmission. Wireless transmission has been studied for over 30 years. There are a lot of technical problems to be solved, and it is far from industrial utilization.
KeywordsReactive Power Power System Stability High Voltage Direct Current Thyristor Control Series Capacitor Reactive Power Compensation
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