Study On The Mechanism Of Generating Frequency Overvoltage Of UHV Transmission Line And Its Suppression Measures

Nowadays, energy resources and productivity in our country are in inverse distribution, and under such circumstance, the development of long-distance high-capacity UHV transmission technology will become the inevitable choice of China's future electricity. Among various problems in the construction of UHV, the amplitude of the frequency overvoltage is the biggest one. It can determine the insulation of the whole system and it is also a main basis when selecting the electrical equipment. In addition, other types of overvoltage are developed from the frequency overvoltage. Superimposed overvoltage causes serious damage, so the research on frequency of overvoltage is of vital significance.Three mechanisms of the power frequency overvoltage has discussed in this thesis: capacitance effect of long no-load line, normal operation to cut off the load,and the voltage rises due to asymmetrical faults. The causes and influencing factors of each method are deduced by the formula, and the common methods of suppressing overvoltage are summarized.This thesis uses PSCAD/EMTDC simulation software to build two simulation line models of single circuit and double circuit lines, and the simulation parameters of main equipment such as transformer, arrester and transmission line are given. The main simulation is to simulate the voltage change caused by the three generating mechanisms and the influencing factors in the single circuit line structure, and focus on the power frequency overvoltage simulation caused by the single-phase ground load rejection. In the double circuit line structure, the main simulation is the power frequency overvoltage caused by the single-line and double-line rejection load, and the main factors of the parallel reactor are simulated, such as compensation position,compensation degree. Considering all the factors of the power frequency overvoltage,a reasonable suppression scheme is proposed, including the installation position of the parallel reactor, the proportion of the compensation capacity at different positions of the line and the total compensation amount, and this scheme has been simulated and verified.