Research On Fault Detection And Location Of Transmission Line Based On Wavelet Theory

Transmission line is an important part of power supply system,which is in the complex environment.Transmission line is also the fault-proneness part of power supply system,the location of which is difficult to find.Therefore,fault quick locatingis importantfor troubleshooting and the stable operation of power system after the failure.Firstly,this thesis briefly introduces the background and research purpose and meaning of fault location,expounds the present situation at home and abroad,puts forward the main research content.Then the thesis illustrates the wavelet multi-resolution analysis and Mallat algorithm,and uses the singularity detection theory of wavelet transform in fault transient line potter character analysis.Then the thesis analyzes equivalent circuits of transmission line fault,and decomposes the fault network into the network of fault state and fault state,which makes the analysis of the transmission line fault network into analysis of additional network failure.On this basis,the three phase short circuit transient process is analyzed.This thesis expounds the basic transmission wave theory and wave equation.According to principle of line twists and turns reflection of fault traveling wave,the thesis analyzes it by grid method.Then,the thesis changes electromagnetic coupling phase domain transformation in a three-phase system to form a contact electromagnetic mold domain of three-phase system by Karen Boolean transformation,gets zero current and line mode current and makes the wavelet processing to it to avoid the effects of alternate with electromagnetic coupling.Then,in view of the wave speed uncertainty problems,the thesis studies the distance measuring algorithm which is not affected by wave velocity and improves the precision of fault location.In actual working condition,there are a series of noise signal,which affects the accuracy of the fault point extraction and reduces the precision of fault location.In order to solve this problem,the thesis proposes a coefficient estimates threshold algorithm based on wavelet transform,which makes fault traveling wave signal with noise after each layer of wavelet transform coefficient square,so as to highlight the characteristics of the fault signal in the singular point.Finally,the thesis sets up transmission line model by using MATLAB,simulates respectively for transmission line fault location in quiet and noisy,proves the validity and accuracy of de-noising algorithm through the theoretical analysis and simulation analysis.The Ranging algorithm and de-noising algorithm proposed in the thesis has good theory value and application value in the field of power transmission line fault accurate positioning.