A Wavelet-based Restricted Earth-fault Power Transformer Differential Protection
Proteção de Transformadores de Potência, Faltas à Terra Restrita,Faltas Espira-Terra, Transformada Wavelet.
Power transformer differential protection schemes have been widely studied in recent years to improve their accuracy and speed. Researches have been developed by using the most varied digital signal processing techniques. Internal faults may cause critical damages to the power transformer, and they need special attention for this kind of disturbance, mainly in faults on the winding of the power transformer that is not too sensitive to the principal differential protections. This work aims to present a restricted earth fault protection based on the wavelet transform (REFW) for detecting ground faults close to the transformer neutral point (turn-to-ground faults) and supporting the conventional phase differential protection, which presents limitations in this kind of faults. The proposed REFW protection uses only high-frequency components instead of traditional low-frequency components obtained by means of phasor estimation methods, speeding up the detection of turn-to-ground faults.