用归一化等效瞬时电感分布特性识别励磁涌流的新算法

针对具有Y/△接线方式的三相变压器,提出了一种新的变压器差动保护TA配置方案：该方案是在传统变压器差动保护接线基础上,在变压器△侧接入一相绕组TA,然后与所测得的线电流结合,利用KCL定律可以容易地求解出△侧各相绕组电流.该方案既保证了等效瞬时电感的准确计算,使其不受△侧绕组内部环流的影响,又不会使差动保护存在＂死区＂.在此基础上,文中提出一种基于归一化等效瞬时电感分布特性的励磁涌流识别新算法：对等效瞬时电感进行归一化处理,使判据定值的选取更具有普遍性,与具体变压器参数、类型无关;利用分布特性更好地反映了等效瞬时电感的变化特征和规律.新算法识别灵敏可靠,HYBRISIM（Hybrid Simulator）实验数据也验证了新算法的准确性和有效性,其在超高压大容量变压器保护方面具有较好的工程应用前景.

A NEW ALGORITHM BASED ON THE DISTRIBUTION OF THE NORMALIZED EQUIVALENT INSTANTANEOUS INDUCTANCE FOR THE DISCRIMINATION OF INRUSH

Oriented to wye-delta connected three phase transformer,a new configuration of current transformer(CT)in transformer differential protection is proposed.In this configuration,only one single phase CT connected in any phase of the delta side is more needed than the traditional scheme.Worked with line currents measured by other current transformers connected in both sides of the transformer,any phase current in the delta side can be calculated based on the Kirchhoff's Current Law.This new scheme ensures the accurate calculation of the equivalent instantaneous inductance,which is immune to the loop current existed in the delta side of transformer,as well as no dead zone in transformer differential protection.A new algorithm based on the distribution of the normalized equivalent instantaneous inductance for the discrimination between inrush current and fault current is proposed.The normalization of equivalent instantaneous inductance makes the setting-value have little relation with the parameter of transformers,which has more universal meaning in the determination of setting values.Utilizing the distributive characteristic of the normalized equivalent instantaneous inductance,the variety of the normalized equivalent instantaneous inductance is effectively revealed.At last,experiment data obtained from HYBRISIM(Hybrid Simulator)validates the reliability and sensitivity of this algorithm.This algorithm has good prospect of engineering application in the EHV transformer protection.