三调谐直流滤波器高压电容故障分析与保护

云—广特高压直流输电工程直流侧采用的三调谐滤波器只有一个处于高电位的电容器,该高压电容器承受几乎全部直流电压和大部分谐波电压降,导致容易在运行中发生电压击穿损坏。因此有必要对它的故障原因和故障特征进行深入分析和探讨。笔者讨论了直流高压电容器的内部结构和工作条件,接着分析了电容器单元故障时不平衡电流的大小和特征,并基于PSCAD/EMTDC工具建立详细的三调谐直流滤波器高压电容的模型,证明了其故障时不平衡电流大小与两桥臂电流之和成固定比例的关系,最后对高压电容器应配置的保护方式提出了建议。

Failure Analysis and Protection of High Voltage Capacitor in Three Tuned DC Filter

In Yun nan-Guang dong UHVDC transmission project there is only one capacitor with the high potential in the three tuned filter,which undertakes almost all DC high voltage and most of the harmonic voltage drop,easily leading to occurrence of failure because of voltage breakdown.The internal structure and operating condition of the capacitor are discussed first.The unbalanced current value and characteristics under the units fault,are deduced.which produced by the two bridge arms.Based on PSCAD / EMTDC the units model is established the simulation demonstrates that the unbalanced current has the fixed proportion relations with the sum of two branches current.Finally,the units protection modes which should depose to HV capacitor are put forward.