A wavelet-based method to discriminate internal faults from inrush currents using correlation coefficient

• Published in: International journal of electrical power & energy systems Vol. 32; no. 7; pp. 788 - 793
• Main Authors: Vahidi, B., Ghaffarzadeh, N., Hosseinian, S.H.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.09.2010; Elsevier
• Subjects: Applied sciences; Computation; Connection and protection apparatus; Correlation coefficient; Correlation coefficients; Decomposition; Discrete Wavelet Transform; Electrical engineering. Electrical power engineering; Exact sciences and technology; Faults; Inrush current; Internal fault; On-line systems; Online; Transformer; Transformers and inductors; Correlation coefficient; Transformer; Discrete wavelet transform; Internal fault; Inrush current; Performance evaluation; Electric transformer; Differential protection; On-line systems; Discrete wavelet transforms; Algorithm; Three phase current; Fault currents; Wavelet transformation; Sampling rate; System simulation; Digital protection; Effectiveness factor; Electric fault
• ISSN: 0142-0615; 1879-3517
• DOI: 10.1016/j.ijepes.2010.01.015

In this paper a new method based on discrete wavelet transform and correlation coefficient is presented for digital differential protection. The algorithm includes offline and online operations. In offline operation, discrete wavelet transform is used to decompose typical three-phase differential currents for inrush current. Then an index is defined and computed. The index is based on the sum of the energy of detail coefficients at level 5 of three-phase differential currents at each half cycle. The online operation consists of capturing the three-phase differential currents using 10 kHz sampling rate, decomposing it by db1. Finally, the inrush current and internal fault is detected based on correlation coefficients of the computed index of pre-stored typical inrush current and a recorded indistinct signal. The effectiveness of the approach is tested using numerous inrush and internal fault currents. Simulations are used to confirm the aptness and the capability of the proposed method to discriminate inrush current from internal fault.