Saturation Detection-Based Blocking Scheme for Transformer Differential Protection

Energies

Byung Eun Lee³  Jinsik Lee¹  Sung Ho Won⁵  Byongjun Lee²  Peter A. Crossley⁴ 

[1] Department of Electrical Engineering and Wind Energy Grid-Adaptive Technology Research Centre, Chonbuk National University, Chonju 561-756, Korea; E-Mail:;Department of Electrical Engineering, Korea University, Seoul 136-701, Korea; E-Mail:;Wind Energy Grid-Adaptive Technology Research Centre, Chonbuk National University, Chonju 561-756, Korea; E-Mail:;The School of Electrical & Electronic Engineering, the University of Manchester, Manchester M13 9PL, UK; E-Mail:;Korea Electrical Contractors Association, #533-2, Deungchon-2Dong, Gangseo-Ku, Seoul 157-718, Korea; E-Mail:

关键词: saturation detection based blocking;    harmonic blocking;    current differential relay;    transformer protection;    operating time delay;   

DOI  :  10.3390/en7074571

来源: mdpi

【 摘 要 】

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.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland.