基于等效瞬时电感判别变压器励磁涌流的新算法

基于变压器铁心磁导率在励磁涌流与内部故障时变化情况的不同,应用瞬时励磁电感和等效瞬时电感的概念,可有效判别变压器励磁涌流.但是,现有的等效瞬时电感计算方法存在较大的误差,对准确判别变压器励磁涌流构成了威胁.为此,提出了改进型的等效瞬时电感计算方法,有效考虑了等效电阻的影响,极大地改善了计算精度.以此为基础,给出了2种判别励磁涌流方案,即时域法和频域法.通过动模实验,对改进型算法和现有的近似算法进行了对比研究.结果表明,应用改进型算法求取的等效瞬时电感更为准确,使时域法和频域法的判别精度得到了极大的改善,有力证实了文中所提出的新算法正确、可行、有效.

A NOVEL EQUIVALENT INSTANTANEOUS INDUCTANCE BASED ALGORITHM USED TO DISTINGUISH INRUSH CURRENTS FOR TRANSFORMERS

Distinguishing magnetizing inrush currents from internal faults can be effectively fulfilled by using the criterion of an instantaneous excitation inductance and an equivalent instantaneous inductance, which is based on the difference of the magnetic permeability in iron core of transformer between inrush currents and internal fault. However, existing methods cannot accurately obtain the equivalent instantaneous inductance because the large computational error greatly influences the accuracy of the criterion above. Therefore, an advanced computational method considering the equivalent resistance is proposed in this paper to calculate the equivalent instantaneous inductance. It greatly improves the computation accuracy. Two methods in time and frequency domains are further presented in the paper to distinguish inrush currents from internal faults based on the proposed method. Discussions to compare the proposed novel method and existing ones through experimental tests are given. The results show that the proposed method can provide more accurate calculation results and enhance the accuracy of the criteria in time and frequency domains.