Application Of Magnetically Controlled Reactors In UHV AC Transmission Lines

Because of large capacitive charging of UHV AC transmission line, capacitance reaction of no loaded line will cause severe overvoltage, and on this condition it will cause higher switching overvoltage. In order to limit overvoltage and compensate charging powers, it is required to install high-compensation-degree parallel reactor. Now UHV Shunt Reactor is not controllable, it not only makes voltage of transmission lines too much lower, but also creates additional power losses in the power grids resulting form its reactive currents.MCR can change its compensation power smoothly. When a transient process is happened on the line, MCR can sharply increase its output to reduce switching overvoltage effectively. So it can solve the contradictions between the limiting overvoltage and reactive power compensation. In the future, MCR will be widely used in UHV AC transmission system. It is thus necessary to research its effect in the practical application.This paper first briefly analyzed economic and necessity of using UHV AC transmission system, expounded the situation of UHV AC transmission system at home and abroad, the situation of MCR researching and applicating in the domestic and international. In accordance with the actual needs of electric power industry development, the author put forword that it is necessary to applicate MCR into UHV AC transmission system, to solve contradictions between the limiting of overvoltage and reactive power compensation.Based on the analysis of MCR's structure, principle, working state, conversion process and dynamic characteristic, a mathematical model of MCR and its control law in real application in UHV transmission lines are analyzed. The UHV AC transmission project from Jincheng to Jingmen via Nanyang that is reasoned owned by China State Power Grid Grop is investigated. The simulation structure illustration of UHV AC transmission line containing MCR is established by Matlab/SPS.The application case of MCR in UHV AC transmission system is simulated and analyzed using the proposed model. Simulation results show that: MCR can regulate the output of reactive power in real-time when the load changes largely; MCR can limit switching overvoltage of energized transmission line to 1.37p.u. when MCR working at its rated power before operating; MCR can limit switching overvoltage of heavy load shedding to 1.35p.u..