Analysis and modification of a 500kV transmission line overvoltage problem

The power frequency resonance overvoltage problem of a 500kV transmission line under non-full phase operation after installation of high voltage shunt reactor is analyzed. It is pointed out that the overvoltage problem is the result of the simultaneous action of higher compensation degree of high voltage shunt reactor, untransposition of the transmission line and improper neutral reactor value of high voltage shunt reactor. Technical measure that the transmission line should be transposed and the neutral reactor value should be rechosen is proposed. An equivalent model of tower is used to ensure the accuracy of simulation. Test results after the accomplishment of the modification project show that the proposed technical measure is effective.