昭通—从化直流输电工程孤岛运行时换流站交流过电压水平研究

孤岛运行作为昭通—从化±500 kV同塔双回直流输电工程的设计运行方式之一,能够有效地提高南方电网的稳定水平,但必须以解决换流站交流过电压问题为前提。对该工程孤岛方式下的交流过电压水平进行了计算,结果表明:换流母线最大操作过电压水平为1.68 p.u.,满足规程要求;暂时过电压水平最高达1.49 p.u.,采取措施后其持续时间短,满足设备要求;小组交流滤波器/电容器开关断口暂态恢复电压最大值不超过1 329 kV;考虑发生概率很小的双回直流双极ESOF这一苛刻工况,A型避雷器最大吸收能量为3 617 kJ,裕度39.7%。因此,孤岛运行方式下设备的过电压水平、避雷器能耗以及小组滤波器/电容器开关断口暂态恢复电压均满足要求。

Study on the Converter Station's AC Overvoltage Level as Zhaotong Conghua DC Transmission Project in Islanded Operation Mode

It is the key issue to control the converter station＇ s AC overvoltage of Zhaotong-Conghua±500 kV DC same-tower double circuit transmission project as it is in islanded operation mode, which is one of the normal operation modes designed for the project with benefit to the improvement of CSG＇ s stability level. Calculations on the AC overvoltage level as the project being in islanded operation mode are carried out in this paper, and the results are as following： 1.68 p. u. is the maximum switching overvoltage in various fault conditions, and it meets the demands of regulations; 1.49 p. u. is the highest transient overvoltage level, and it will be in short duration after adopting certain measures as to meet the requirement of equipments; 1 329 kV is the limit of maximum recovery voltage across AC filter/capacitor circuit breakers; 3 617 kJ is the maximum arrester absorption energy in various fault conditions including the little probability case where double circuit simultaneous bipolar ESOF occurred in islanded operation, and thus it has a margin of 39. 7%. Hence, the overvoltage level, arrester absorption energy and transient recovery voltage across AC filter bank circuit breakers are all in control.