Influence of Increase of Neutral Line Resistance in Current Transformer on Line Differential Protection

被引：0
|
作者：
Huang S. [1 ]
Chen B. [1 ]
Wu Y. [2 ]
机构：
[1] School of Electrical and Electronic Engineering, North China Electric Power University, Beijing
[2] Beijing Sifang Automation Co. Ltd., Beijing
来源：
Dianli Xitong Zidonghua/Automation of Electric Power Systems | 2017年 / 41卷 / 23期
关键词：
Differential equation of current; Neutral line; Ratio of second harmonic and fundamental wave; Three phase maximum current restraint;
D O I：
10.7500/AEPS20170419004
中图分类号：
学科分类号：
摘要：
The increase of neutral line resistance in current transformer may induce misoperation of line differential protections. On the basis of previous research, this paper further analyzes its mechanism: when neutral line resistance in current transformer is greater than a certain value, if a fault happens, the voltage on neutral line generated by fault phase current will produce false current on non-fault phase by the excitation effect, resulting in the asymmetrical waveform of false current. The root cause of the false current is the accumulation of flux linkage. By changing the parameters of the secondary circuit equation, the effect of different neutral line resistance, non-periodic current, remnant level, and volume of current transformer on the value of false current is analyzed. Finally, the characteristics of this kind of misoperation are concluded. The ratio of second harmonic to first harmonic and the ratio of phase differential current to the three phase maximum current is chosen to be criteria. If both criteria are satisfied, the differential protection shall be locked for a short time to avoid this kind of misoperation. The correctness and effectiveness of the proposed scheme are verified by simulation and recorded diagrams. © 2017 Automation of Electric Power Systems Press.
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页码：77 / 82
页数：5
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