Research on power frequency transient overvoltage in 1000kV UHV AC transmission line

Against the background of a single circuit UHV power transmission project in one million voltage from Jincheng to Jingzhou via Nanyang that is reasoned by State Power Grid Corp. of China, its power frequency overvoltages in three operating conditions, i.e., capacity effect of unloaded line, unsymmetrical faults and load shedding, are researched, and the measures to eliminate power frequency voltage rising such as using high voltage reactor to compensate reactive power are put forward. Simulation results show that the maximum power frequency voltage rising caused by capacity effect in unloaded line, single-phase earth fault and load shedding are 1.04 per unit, 1.31 per unit and 1.20 per unit respectively. Under load shedding and unsymmetrical earth fault, the effect of eliminating power frequency voltage rising is better when parallel high voltage reactor is installed at the receiving end of transmission line but not at the sending end or at both ends.