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The Research of Transformer Differential Protection Based on Wavelet Transforms

Author: LiuJianHui
Tutor: DuanYuBo
School: Daqing Petroleum Institute
Course: Power Electronics and Power Drives
Keywords: Wavelet Transform Singularity Transformer differential protection Magnetizing inrush
CLC: TM772
Type: Master's thesis
Year: 2008
Downloads: 94
Quote: 2
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Abstract


With a growing number of ultra-high pressure long-distance transmission lines in China 's built and running , large-capacity transformer applications are increasing. Power transformers are widely used in the transmission and distribution of electric power system in every aspect , therefore, a higher demand for transformer protection reliability and speed off . Differential protection is the primary protection of the transformer , the transformer when power is restored after excision of the load closing or external fault , the differential circuit magnetizing inrush current will flow differential protection does not recognize and survive the current malfunction occurs . Therefore , the correct identification of magnetizing inrush is to ensure that the key transformer differential protection and reliable operation . Wavelet transform in recent years, the rapid development of a data processing and analysis methods , it has a multi-resolution analysis and time - frequency localization characteristics , especially suitable for the characteristics used to extract the signal edge and peak mutations could measure the signal singularity sex . Transformer inrush current has the singularity, Therefore, the wavelet transform is applied to the recognition of the transformer inrush current . This paper first described the basic principles of the transformer differential protection , and then analyze the magnetizing inrush mechanism and features several magnetizing inrush current identification of principles and methods , and compare its analysis . Subsequently, on the basis of simulation using MATLAB software , select the appropriate db wavelet wavelet transform and analysis of the inrush current and internal fault current . Identification of magnetizing inrush on the basis of the previous intermittent angle principle , the method of the traditional precise measurement excitation inrush intermittent angle to do a little improvement , and direct analysis of the waveform signal wavelet transform , establish criterion , simulation , simulation results show that the method can effectively extract the inrush current distortion characteristics , brake module can be used as a transformer differential protection .

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CLC: > Industrial Technology > Electrotechnical > Transmission and distribution engineering, power network and power system > Power system protection > Protection of components
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