Abstract—This paper proposes a new S-Transform (ST) based method for protection of power transformers by considering internal incipient faults. S-transform is a powerful analytical tool that has the property of Fourier and wavelet transforms. The Hyperbolic S-Transform (HST) is used to extract features of inrush current, internal and internal incipient faults, from the differential currents. A decision has been made using extracted features to discriminate internal incipient faults, magnetizing inrush currents and internal faults. In order to study the efficiency of the proposed method, it is implemented in MATLAB environment and tested with simulated faults and inrush cases under EMTP software. In order to simulate internal turn to turn, turn to earth and internal incipient faults, the transformer is modeled using 8×8 RL matrices obtained from the subroutine BCTRAN of EMTP software. The signals are infected with noise and the performance of the algorithm in noisy environments is studied.

Index Terms—Incipient 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 TechAnology, Tehran, Iran (e-mail: grptian@aut.ac.ir).
S. S. Shafiee Bahnamiri is with the Department of Engineering, Shahed University, Tehran, Iran And Islamic Azad University, Joubar Branch, Joubar, Iran (e-mail: Shafiee@shahed.ac.ir).

Cite: A. Ashrafian, M. Rostami, G. B. Gharehpetian, and S. S. Shafiee Bahnamiri, "Improving Transformer Protection by Detecting Internal Incipient Faults," International Journal of Computer and Electrical Engineering vol. 4, no. 2, pp. 196-201, 2012.