Saturation detection-based blocking scheme for transformer differential protection

Byung Eun Lee, Jinsik Lee, Sung Ho Won, Byongjun Lee, Peter A. Crossley, Yong Cheol Kang

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


This paper describes a current differential relay for transformer protection that operates in conjunction with a core saturation detection-based blocking algorithm. The differential current for the magnetic inrush or over-excitation has a point of inflection at the start and end of each saturation period of the transformer core. At these instants, discontinuities arise in the first-difference function of the differential current. The second- and third-difference functions convert the points of inflection into pulses, the magnitudes of which are large enough to detect core saturation. The blocking signal is activated if the third-difference of the differential current is larger than the threshold and is maintained for one cycle. In addition, a method to discriminate between transformer saturation and current transformer (CT) saturation is included. The performance of the proposed blocking scheme was compared with that of a conventional harmonic blocking method. The test results indicate that the proposed scheme successfully discriminates internal faults even with CT saturation from the magnetic inrush, over-excitation, and external faults with CT saturation, and can significantly reduce the operating time delay of the relay.

Original languageEnglish
Pages (from-to)4571-4587
Number of pages17
Issue number7
Publication statusPublished - 2014


  • Current differential relay
  • Harmonic blockin
  • Operating time delay
  • Saturation detection based blocking
  • Transformer protectio

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Energy Engineering and Power Technology
  • Energy (miscellaneous)
  • Control and Optimization
  • Electrical and Electronic Engineering


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