特高压交流系统合闸过电压特点研究

Study on characteristic of switching surge due to closing lines in UHVAC system

由于特高压交流系统采用高阻抗电源、长距离线路和大功率输电的方式,其合闸过电压出现了一些与其他电压等级合闸过电压不同的特性,在系统研究特高压合闸过电压的基础上,对这些新特点进行了深入研究。研究表明,单回线路的合空线过电压一般高于单相重合闸过电压,但在长距离、大功率输电时,后者可能更为严重,应引起重视;在电源容量较小时,双回线路一回运行情况下另一回线路进行合空线操作时,其过电压往往较高,应重点限制;双回线路的单相重合闸过电压与小电抗的取值密切相关,故小电抗取值应在各种运行方式下进行综合选择。此外,特高压交流系统通常应采用合闸电阻限制合闸过电压,且较长线路宜采用较低阻值,较短线路宜采用较高阻值。

Because of the application of high-impedance power supply,long-distance transmission lines and large-capacity power transmission in UHVAC system,the closing overvoltage of UHV has its own features compared with that in other voltage grade.In this paper,based on the systematical study of the UHV overvoltage,the research on those new features is done furtherly.The results show that switching surge due to closing no load lines is generally higher than single-phase reclosing overvoltage in single-circuit lines.But when it comes to long distance and large-capacity transmission,the latter maybe more serious,so it should be paid more attention.When the power supply capacity is smaller and one circuit is still in running in double-circuit lines,the overvoltage of closing another no load lines tends to be high,it ought to be also focused to restrict.For the amplitude of the single-phase reclosing overvoltage in double-circuit lines is closely related with the value of small reactor,the selection of small reactance must consider all kinds of operation modes.In addition,as for UHVAC power system,generally closing resistors is configured to limit overvoltage,and it is better to adopt closing resistors with low resistance values for longer transmission lines and that with high resistance values for shorter transmission line.