Saturation Detection-Based Blocking Scheme for Transformer Differential Protection
- Authors
- Lee, Byung Eun; Lee, Jinsik; Won, Sung Ho; Lee, Byongjun; Crossley, Peter A.; Kang, Yong Cheol
- Issue Date
- 7월-2014
- Publisher
- MDPI AG
- Keywords
- saturation detection based blocking; harmonic blocking; current differential relay; transformer protection; operating time delay
- Citation
- ENERGIES, v.7, no.7, pp.4571 - 4587
- Indexed
- SCIE
SCOPUS
- Journal Title
- ENERGIES
- Volume
- 7
- Number
- 7
- Start Page
- 4571
- End Page
- 4587
- URI
- https://scholar.korea.ac.kr/handle/2021.sw.korea/98146
- DOI
- 10.3390/en7074571
- ISSN
- 1996-1073
- Abstract
- 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.
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