The Design Of Transformer Protection Based On Wavelet Transform

With the development of economy in our country recently.there has been more and more requirement of power energy.The scale of power system is enlarged continually,so the function of transformer with large capacity in power system is more important. The normal operation of transformer bears great upon the whole power system, especially costly large-size transformer.In the case of malfunctions, economic damage incurred might be unimaginable.The main protection scheme of power transformer is differential protection, but magnetizing inrush current is still the primary reason that causes transformer protection miss-operating, so the discrimination between magnetizing inrush current and inner fault current correctly is the key that ensures transformer differential protection operating credibility.In recent years,the wavelet transform analysis method has been developed rapidly. As the wavelet transform possesses the properties of multi-scale analysis and time-frequency domain localization, it is particularly well adapted to process sharply changing signals, and to extract characteristics of these signals. First the thesis introduced the wavelet basic theory ,including the multi-resolution and singularity theory ,then the thesis researched into the function of wavelet transform in the transformer protection. Finally the thesis established a new method to distinguish between internal faults and inrush currents based on the characterictic of inrush current , and it also suggested a method based on 32-bit MCU, DSP chip to realize the transformer protection.