Features and mechanism of negative-sequence second harmonics of magnetizing inrush current in transformers

Zaibin Jiao, Wu Xing*, Zhao Wang, Jiliang Jin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

32 Citations (Scopus)

Abstract

The no-load switching of transformers is the main influencing factor of malfunction of current differential protection, which will cause power quality problems such as harmonics and voltage dips as well. In the AC/DC hybrid power grid, because of the harmonic coupling property of the converter, the harmonics on the AC side will cause protection malfunction and blocking on the DC side, thereby threatening grid security. Based on the approximation magnetization curve of the transformer core, the analytical expression of magnetizing inrush current and its second harmonic component is deduced. The influence of switching parameters on the negative-sequence second harmonic component is analyzed. It is pointed out that the three-phase balance remanence caused by breaker switching will not result in the phenomenon of the negative-sequence second harmonic current being the main ingredient. Only the three-phase unbalanced remanence will result in obvious negative-sequence characteristics of magnetizing inrush current. The conclusion is verified by simulation using PSCAD software and provides an important theoretical basis for solving problems in practical engineering.

Original languageEnglish
Pages (from-to)146-151
Number of pages6
JournalDianli Xitong Zidonghua/Automation of Electric Power Systems
Volume39
Issue number11
DOIs
Publication statusPublished - 10 Jun 2015
Externally publishedYes

Keywords

  • Direct current protection
  • Magnetizing inrush current
  • Negative-sequence second harmonic
  • Remanence

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