The development of a d-q axis WPT-based digital protection for power transformers

S. A. Saleh*, A. Aktaibi, R. Ahshan, M. A. Rahman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

35 Citations (Scopus)


This paper presents the analysis and development of a new digital differential protection for three phase (3\phi ) power transformers. The proposed digital protection is based on extracting high frequency sub-band contents present in the d-q axis components of the differential currents in order to identify internal faults. The desired high frequency sub-band contents are extracted using a single-stage wavelet packet transform (WPT), which offers parameterizing the energy in the high frequency sub-band contents using a finite number of coefficients. The WPT coefficients contain information that offer accurate, fast, and reliable detection and classification of transient disturbances, including magnetizing inrush and internal fault currents that may be experienced by 3\phi power transformers. The d-q WPT-based digital differential protection is implemented for off-line performance evaluation using differential currents collected from a 5 kVA, 3\phi, laboratory power transformer. Off-line test results demonstrate accurate, fast, and reliable detection, classification, and response to different types of fault and non-fault currents. These encouraging performances of the d-q WPT-based digital differential protection are obtained with simple implementation, reduced computational burdens, and small memory requirements.

Original languageEnglish
Article number6231705
Pages (from-to)2255-2269
Number of pages15
JournalIEEE Transactions on Power Delivery
Issue number4
Publication statusPublished - 2012
Externally publishedYes


  • Digital differential protection
  • digital filters
  • internal fault currents
  • magnetizing inrush current
  • synchronous rotating reference frame (d-q axis)
  • three phase power transformers
  • wavelet analysis

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering


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