Wavelet packet transform and direct-quadrature axis-based hybrid technique for differential protection of power transformers

Aktaibi, Adel (2015) Wavelet packet transform and direct-quadrature axis-based hybrid technique for differential protection of power transformers. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Detecting and identifying the disturbances in power transformers have always been challenging tasks for accurate and reliable protection of power transformers. Several approaches have been tested for designing protective devices such as DFT, ANN, fuzzy logic and wavelets etc. The modern power system is highly polluted with harmonics, and the transient disturbances usually are non-stationary and non-periodic. Thus, these techniques may not be adequate for protection of newer power transformers. Current research indicates that the wavelet packet transform (WPT) provides fast and accurate distinguishing criteria for this purpose, because WPT do not suffer from such problem. However, such wavelet based relay requires a certain sampling frequency for its analysis, which may have some impact on the new trend of interconnected protection system. According to IEEE standards (C57.116) and (1547), the requirement of 6 cycles of fault duration is valid for conventional and newer interconnected power transformer protection system. This research introduces a new dqWPT-based hybrid technique for the protection of power transformers to be integrated with the operation and control circuits without affecting their performance. The

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