Transmission-line theory based study on voltage distribution along the line and the disposition scheme of series capacitors of UHV transmission lines with series capacitors

In this paper, the transmission-line theory based fast algorithm for voltage distribution along the UHV transmission line with series capacitors is proposed. Firstly, the two-port transmission parameter matrix of UHV transmission lines is transformed to the two-port node admittance matrix, therefore, the lumped parameters of strict equivalent π model for UHV transmission line is obtained. Secondly, the parameters are filled into the commercial power flow software to calculate the power flow of the target grid which includes the UHV transmission lines with series capacitors. Thirdly, the power flow calculation results are regarded as the terminal conditions of the UHV lines with series capacitor, and the transmission parameter matrix is used to calculate the voltage distribution along the line rapidly. In the algorithm, the voltage distribution along the line is obtained accurately; moreover, the reactive power supply capacities of both sides of the UHV lines with series capacitors can be taken into account, which implies that the engineering applicability of the proposed algorithm is very strong. At last, the relative disposition scheme of UHV series capacitors and UHV line shunt reactors as well as the centralized/distribution layout scheme of UHV series capacitors are investigated, and some useful conclusions are drawn. According to the proposed algorithm and the conclusions, the guidance suggestion is given for the UHV series capacitors schemes of `Wandian Dongsong' UHV transmission project and `Ximeng Waisong' UHV transmission project.