Simulation Analysis of Three Phase Unbalanced Current and Over Compensation of High Voltage Reactor in Transmission Line

  Introduction  The safe and stable operation of UHV transmission lines is essential to the safety of power grids. When the new substation deconstructs the original long line in the power grid planning and construction， the following problems， such as the three-phase unbalanced current line does not meet the setting requirements， line high impedance over-compensation generates overvoltage， may occur. These problems may seriously threaten the safe and stable operation of the power grid and should be solved.

  Method  In order to solve the above problems， the electromagnetic transient software ATP-EMTP was used to simulate the unbalanced current and overvoltage in 500 kV transmission lines on the same tower， so as to explore the influencing factors and change mechanism of these parameters， and then put forward countermeasures.

  Results  The simulation results show that the main factors affecting the double circuit line's unbalanced current on the same tower include transposition and phase sequence arrangement. Increasing the number of transpositions can effectively reduce the unbalanced current level. By adopting a reverse phase sequence arrangement is also efficient. The main reason that affects the power frequency resonance over-voltage is whether the compensation degree is close to full compensation. During over-compensation， increasing the compensation degree can reduce the recovery voltage， but the potential supply current will increase relatively.

  Conclusion  The above conclusions have guiding and reference significance for power grid planning， construction， and safe operation. Furthermore， it can effectively solve related problems in actual projects.