一起换流变绕组差动电流保护动作的分析及改进

Analysis and Improvement of Differential Current Protection Action of Converter Transformer

换流变压器的差动保护动作是否正确对于直流系统安全稳定运行至关重要,由于部分换流站在换流变绕组差动保护设计时未考虑谐波制动功能,保护装置无法正确区分励磁涌流和内部故障电流,导致换流变充电时因励磁涌流造成保护误动作。对此,结合某换流站在换流变绕组差动保护动作案例进行建模与仿真,分析该换流站换流变压器网侧绕组差动保护动作原因,判断其动作逻辑是否正确。根据空载合闸时的绕组差动电流经滤除直流分量后与标准的正弦电流波形相似性很差的特点,通过仿真分析设定了Hausdorff距离的绕组差动电流保护闭锁判据的整定值,进而避免了换流变充电时因CT饱和特性不一致导致的绕组差动保护误动作。

The correct differential protection action of the converter transformer is crucial for the safe and stable operation of the DC system.Due to some converter stations not considering the harmonic braking function in the differential protection design of the converter winding,the protection device cannot correctly distinguish between excitation inrush current and internal fault current,resulting in protection malfunction during charging of the converter due to excitation inrush current.In response to this issue,this article mainly combines the modeling and simulation of a case study of a certain converter station operating on the differential protection of the converter winding,analyzes the reasons for the differential protection action of the converter transformer grid side winding at the converter station,in this paper,the setting value of the winding differential current protection lock-up criterion for Hausdorff distance is set through simulation analysis,so as to avoid the winding differential protection malfunction caused by the inconsistent CT saturation characteristics during commutation charging.