Research on power frequency overvoltage of UHV double-circuit transmission system with series compensation

By using EMTP, this paper analyzes effect of various factors on power frequency overvoltage during rejecting load in UHV double-circuit transmission system with serious compensation. They include system structure, source capability, scale of power flow, line´s operation mode (double-circuit and single-circuit), and compensation degree of series compensation device and its bypassing situation. Based on results from calculation, followings can be concluded: serious compensation has inhibition to power frequency overvolatge causing by rejecting load with both no fault and single-phase grounding fault. And the higher compensation degree is, the lower voltage is. On same conditions, the voltage is higher when power plant sending system than power grid sending system. Overvoltage level increasing change with transmitting trend is obvious when line operates single circuit. Bypassing situations of series compensation have influence to line-side voltage causing by rejecting load with single-phase grounding fault. And on the series compensation linkage measure ( that is, only faulty-phase series compensation is bypassed), voltage level is lower than others.