Volume 4 Number 2 (Apr. 2012)
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IJCEE 2012 Vol.4(2): 186-190 ISSN: 1793-8163 DOI: 10.7763/IJCEE.2012.V4.476

Application of Discrete S-Transform for Differential Protection of Power Transformers

A. Ashrafian, M. Rostami, G. B. Gharehpetian, and M. Gholamghasemi
Abstract—In this paper, a novel scheme based on Hyperbolic S-Transform (HST) is proposed for digital differential protection of power transformers. Hyperbolic S-transform is a powerful tool for non-stationary signal analysis in noisy conditions. Decision logic has been devised using extracted feature from differential currents due to transient phenomena in transformers. The HST of the differential current is calculated. Then, a Decision Index (DI) is calculated according to the spectral energy and standard deviation of the S-matrix. It is seen that DI values are different in the cases of internal faults and inrush currents. The scheme has been implemented in MATLAB environment and the inputs are differential currents derived from EMTP software. In order to simulate the internal turn to turn and turn to earth faults, the power transformer is modeled using 8×8 RL matrices obtained from the subroutine BCTRAN of EMTP software. The differential current signals are infected by noise and the robustness of the algorithm under noisy conditions is investigated.

Index Terms—Fault, inrush current, protection, s-transform, transformer.

A. Ashrafian is with the Department of Engineering, Shahed University Tehran, Iran and Department of Engineering, Shahre-rey branch, Islamic Azad University, Tehran, Iran. (e-mail: a.ashrafian@ieee.org).
M. Rostami is with the Department of Engineering, Shahed University, Tehran, Iran (e-mail: rostami@shahed.ac.ir).
G. B. Gharehpetian is with the Electrical Engineering Department, Amirkabir University of Technology, Tehran, Iran (e-mail: grptian@aut.ac.ir).
M. Gholamghasemi is with the Department of Electrical Engineering Noshirvani University, Babol, Iran (e-mail: ghasemi_maede69@yahoo.com ).

Cite: A. Ashrafian, M. Rostami, G. B. Gharehpetian, and M. Gholamghasemi, "Application of Discrete S-Transform for Differential Protection of Power Transformers," International Journal of Computer and Electrical Engineering vol. 4, no. 2, pp. 186-190, 2012.

General Information

ISSN: 1793-8163 (Print)
Abbreviated Title: Int. J. Comput. Electr. Eng.
Frequency: Quarterly
Editor-in-Chief: Prof. Yucong Duan
Abstracting/ Indexing: EI (INSPEC, IET), Ulrich's Periodicals Directory, Google Scholar, EBSCO, ProQuest, and Electronic Journals Library
E-mail: ijcee@iap.org

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