基于零序过滤的变压器励磁电感计算方法及涌流识别

Transformer Excitation Inductance Calculation and Inrush Current Identification Method by Filtering the Zero Sequence Current

目前,以单相变压器T形电路为基础,利用等效瞬时电感的变化特性识别励磁涌流的方法效果较好,但计算励磁电感需使用变压器各侧绕组电流,对于Y,d接线变压器,如果电流互感器按典型方案配置,其三角形(△)侧绕组电流未知,故不能直接利用现有方法计算励磁电感。文中提出一种基于零序过滤的励磁电感计算方法,无需测量△侧绕组电流,只需利用△侧线电流就可计算出代表正、负序分量共同作用结果的励磁电感,且计算结果在变压器正常运行、故障及涌流时都有显著特征,可准确、有效地识别励磁涌流和内部故障状态。PSCAD仿真验证了该算法的准确性。

The conventional inrush current identification method by the variability of equivalent excitation inductance is based on the equivalent T-circuit of single phase transformer, which relies on the measurements of all winding currents. However, the delta winding side current of a Y-d connected transformer is not measurable by typically configured current transformers; therefore the method is not applicable. The paper proposes an algorithm by filtering the zero sequence current to calculate the excitation inductance of a Y-delta connection transformer. The algorithm can calculate the excitation inductance representing the combined effects of both positive and negative components by using the delta side line currents. The calculation results are significantly different in various operating conditions, therefore can identify internal faults or excitation inrushes effectively. PSCAD simulation results validate the method.