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Abstract
Discrete Wavelet Transform (DWT) is introduced as a signal-processing tool that
109 decomposes a time-domain signal into several time components; every component is
I I 5 covering a band of frequencies. So, the WT can detect the frequency contents of the signal and localize them in time. Starting from 1995, DWT was widely used in power system for
129 power quality analysis and protection applications. Fault identification, localization,
135 classification, and fault location are typical examples of DW1’ protection applications. Also, DWT is used as an alternative or supplementary algorithm with distance and differential
139 relays. Application of DWT to line differential protection will be emphasized in this thesis.
In this thesis, performance of DWT is investigated in the scope of power system protection and transient detection requirements.. Impact of’ the type of mother waveict, sampling frequency, and the signal waveform on the resulted DWT levels is evaluated, A novel DWT computation algorithm is introduced in order to eliminate the complexity encountered in real-time implementation. Efficacy of the proposed algorithm is verified via Digital Signal Processing (DSP) experimental test set-up. The results corroborate the proposed algorithm effectiveness for real-time implementation even with higher sampling rates. Shortcomings of DWT application to power system electromagnetic transient and protection are outlined and corrective recommendations are included.
Further, the wavelet applications to differential pilot relay for tranmission line protection is examined. Features of DWT are exploited to efficiently discriminate internal faults. Performance of’ published differential protection techniques based on DWT is experimentally implemented and intensivelS’ investigated in the real—time considering different operating and fault conditions. Impact ol line model on the DWT-based scheme is outlined. Also, shortcoming of the reported DWT-based protection algorithms are addressed and corrective recommendations are given. A novel approach based on DW’l’ for line differential protection is introduced. This approach is evaluated via simulatIon and results
- are corroborated via the experimental set-up. The proposed scheme sensitivity for internal fault and stability for external fault are examined for di fli.rent operating conditions and fiult resistances at di liereni load and fault inception angles. Thus, the approach superiority to other reported DWI’-htscd schemes is confirmed.