特高压交流输电系统短路电流零点漂移影响因素分析及防治措施

在特高压输电系统中,当线路发生故障时,断路器动作会产生较高的瞬态过电压,其中直流分量部分可能会使故障电流出现零点漂移现象,使断路器灭弧室内燃弧时间延长,影响断路器的开断能力。为此,首先结合特高压示范工程,对影响零点漂移的因素进行了理论分析,并根据浙江北—上海西特高压输电线路,考虑断路器断开时的电弧模型,利用ATP/EMTP进行了仿真计算,得出:影响特高压零点漂移的因素有故障发生时刻、故障点的接地电阻大小、故障点的位置,以及负载电流的大小,其中负载电流的变化可能会引起长达2个周波以上较严重的零点漂移。最后总结出断路器串联50Ω的合闸电阻可有效减小短路电流首次过零时间。

Analysis on Characteristic and Influencing Factors of Current-zero Offset in UHVAC Systems

In an ultra-high transmission system,circuit breakers will have a higher transient over-voltage when failure occurs on the transmission line,the DC component may cause the current-zero offset,it will make the arcing time extension in the arc chute and affect the breaking capacity of circuit breaker.Consequently,we theoretically analyzed the influential factors of the current-zero offset on the UHV demonstration project.Moreover,considering the arc model of the disconnected circuit breaker,we utilized ATP/EMTP to simulate the Zhejiang North-Shanghai West ultra-high voltage transmission lines.The conclusion can be drawn that,the failure time,the size of the grounding fault resistance,the location of the failure point,and the value of the load current are influential factors of the current-zero offset.Changes in load current may cause the current-zero offset to be more serious for more than two cycles.A 50 Ω closing resistor in series at the port of the circuit breaker can effectively reduce the first zero-crossing time of the short circuit current.