Method Of Adjusting The Terminal Voltage Of High Voltage No-load Line By Using Series Adjustable Capacitive Impedance

China's power industry is booming.In order to improve the transmission capacity and economic performance of the line,China's power grid is vigorously building EHV and UHV transmission lines,but the EHV and UHV grids have long lines and high voltage levels.Therefore,the EHV and UHV transmission lines will generate very large capacitive reactive power,and the excessive capacitive reactive power in long lines will produce unacceptable power-frequency over-voltage.Over-voltage operation of EHV and UHV transmission lines not only damages related electrical equipment and line insulation,but also reduces the static and dynamic stability of the power system.In order to ensure the stable operation of EHV and UHV transmission lines,corresponding measures must be taken to suppress the EHV and UHV transmission lines of the capacitance effects.Aiming at the problem of the voltage increase at the end of the high voltage no-load transmission line caused by transmission line grounding capacitance,new voltage regulation device is proposed in this paper.The device is composed of a variable iron core coincident cross-sectional area type adjustable capacitive impedance parameter circuit.The adjustable capacitive impedance is connected to the head end of the high-voltage transmission line,theoretically analyzing the voltage regulation principle of the series capacitive impedance on the terminal voltage of the line,and then analyzing the working principle of the device and the adjustment range of the equivalent capacitive impedance parameters.When the capacitance of the secondary side is adjusted to a fixed value,changing the coincident cross-sectional area of the iron core can adjust the equivalent capacitive impedance,and verified the parameters of its equivalent capacitive impedance,the experimental results show that reducing the cross-sectional area of the iron core can achieve a large capacitive impedance modulus.And then taking a 500 kV transmission line as an example,the voltage regulation effect of the device with that of the line terminal parallel reactor were compared and analyzed.The theoretical analysis and experimental results showed that the voltage regulating device of the series capacitive impedance can reduce the terminal voltage of the high voltage no-load line,and a smaller capacitive impedance can reduce the higher terminal voltage.Finally,according to the capacitive impedance value is connected to the head end of the no-load line,the specific capacitive design of the adjustable capacitive impedance device is carried out,including the core cross section,the number of turns of the coil,the diameter of the wire,the capacity of the device,etc.For the subsequent variable section type adjustable capacitive impedance device of the manufacture provides a theoretical basis and reference basis.