三相变压器等效瞬时电感的计算分析及CT配置新方案

葛宝明等人以单相变压器模型为基础,提出一种利用等效瞬时电感变化特性判别变压器励磁涌流的算法,具有较好的识别效果。但对于三相变压器不同接线方式,尤其是YΔ/接线方式下等效瞬时电感的计算问题,目前还未见相关文献研究,该文对此问题进行了深入的分析和探讨,研究结果对利用等效瞬时电感变化特性判别变压器励磁涌流算法在工程中的应用,具有一定的指导意义和参考价值。针对变压器Δ侧绕组内部环流对等效瞬时电感计算结果影响大,而又难以通过线电流计算得到的特点,提出了一种新型的变压器差动保护CT配置方案。该方案保证了等效瞬时电感的正确计算,同时又不会使差动保护存在保护死区。

Analysis of the calculation of equivalent instantaneous inductance in three-phase transformer and a new CT's configuration

An algorithm based on the variable characteristic of the equivalent instantaneous inductance to distinguish inrush currents from fault currents in transformer protection was put forward by GE Bo-ming et al,which is validated by transformer with current transformer(CT) connected in each winding.Current transformer is hard to be connected in transformer winding,which could affect the calculation of the equivalent instantaneous inductance in three phase transformer,especially that connected in wye-delta mode.This paper analyses the calculation of the equivalent instantaneous inductance in wye-delta connected three phase transformer,which has directive meaning and reference value to the research on the discrimination between inrush currents and fault currents based on the equivalent instantaneous inductance.The circulating current in the winding of delta side of transformer is hard to be calculated from line currents and affects the accurate calculation of the equivalent instantaneous inductance greatly.In that case,a novel configuration of current transformer(CT) in transformer differential protection is proposed,which ensures the accurate calculation of the equivalent instantaneous inductance as well as no dead zone in transformer differential protection.This project is supported by National Natural Science Foundation of China(No.50277012).