基于故障特征提取及最严苛工况寻找的换流器直流差动保护快速整定

Research on Rapid Setting of Converter DC Differential Protection Based on Fault Feature Extracting and Harshest Condition Searching

现有换流器直流差动保护定值多来源于厂家推荐,一旦不合理需要修改并重新EMTDC仿真验证,工作量成倍增加。提出了一种基于故障特征提取及最严苛工况寻找的直流差动保护快速整定方法。该方法不再反复地EMTDC仿真验证,而是基于一次仿真结果,从提取波形故障特征以及寻找最严苛工况的角度获取保护定值,整定速度大大提升。首先分析了保护特征量的影响因素,提出了一种换流器区内接地故障分析模型;然后采用变化时间窗提取了保护特征量的故障特征;最后给出了保护定值的指标,用于确定最严苛的工况。以糯扎渡特高压直流工程为例,算例结果表明了所提整定方法的可行性。此外,结合故障特征的分布规律,还给出了直流差动保护分段的原则。

Mostly, existing setting of converter DC differential protection is obtained from manufacturer＇s recommendation, while the value has to be modified and verified with EMTDC simulation if it is considered unreasonable, always causing multiplied workload. In this paper, a rapid setting method is proposed for converter DC differential protection based on fault feature extracting and the harshest condition searching. In this method no repeated EMTDC simulation validationis required, and protection settingis got with several approaches such as extracting fault feature from waveform and searching the harshest condition, based on resultsof only one simulation, so setting speed is improved greatly. Firstly, factorsinfluencing on protection characteristic parameters are analyzed, and an analytical converter model with inner ground faults is proposed. Secondly, fault features of protection characteristic parameters are extracted with changed time window. Finally, indications of protection settings used to search the harshest conditionare given. Taking Nuozhadu UHVDC project as example, feasibility of this method is verified. In addition, combined with distribution of fault feature, principle for dividingstages of DC differential protection is given.