An approach to identify magnettizing inrush currents and its simulation

Power transformer is one of the main electrical equipments. It is the important for the system to run safely and economically. When the short circuit takes place between the internal coils, power transformer different protection works correctly; while the external short circuit fault and over excitation appear, it does not process trip. The distinguishing internal fault current from magnetizing inrush current of power transformer is still the key issues of differential protection of power transformer. The wavelet analysis has the characteristic of multi resolution analysis and good time and frequency domain localization, fits to extract sudden change signals in transient processes, and detects irregularity of signals very well. This paper describes a method for discrimination between internal faults and magnetizing inrush currents in power transformers using the wavelet transform. The experiment simulation shows that the proposed method is more reliable and simpler, and is suitable for different power transformer systems.