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Energies 2014, 7(7), 4571-4587; https://doi.org/10.3390/en7074571

Saturation Detection-Based Blocking Scheme for Transformer Differential Protection

1
Wind Energy Grid-Adaptive Technology Research Centre, Chonbuk National University, Chonju 561-756, Korea
2
Department of Electrical Engineering and Wind Energy Grid-Adaptive Technology Research Centre, Chonbuk National University, Chonju 561-756, Korea
3
Korea Electrical Contractors Association, #533-2, Deungchon-2Dong, Gangseo-Ku, Seoul 157-718, Korea
4
Department of Electrical Engineering, Korea University, Seoul 136-701, Korea
5
The School of Electrical & Electronic Engineering, the University of Manchester, Manchester M13 9PL, UK
6
Department of Electrical Engineering, Wind Energy Grid-Adaptive Technology Research Centre and Smart Grid Research Centre, Chonbuk National University, Chonju 561-756, Korea
*
Author to whom correspondence should be addressed.
Received: 26 February 2014 / Revised: 27 June 2014 / Accepted: 10 July 2014 / Published: 18 July 2014
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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. View Full-Text
Keywords: saturation detection based blocking; harmonic blocking; current differential relay; transformer protection; operating time delay saturation detection based blocking; harmonic blocking; current differential relay; transformer protection; operating time delay
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This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).
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MDPI and ACS Style

Lee, B.E.; Lee, J.; Won, S.H.; Lee, B.; Crossley, P.A.; Kang, Y.C. Saturation Detection-Based Blocking Scheme for Transformer Differential Protection. Energies 2014, 7, 4571-4587.

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