Research On The Methods Of Fault Detection And Fault Location Of Ransmission Line

With the development of China ’s modern power system, the improvement of transmis-sion power and voltage levels of transmission lines, the EHV transmission line has becamethe backbone of the power system. After transmission line fault, the type and the location ofthe fault should be quickly and accurately determined in order to prevent the expansion of thefault and ensure the safe operation of the whole power system. In this thesis, the most com-mon short-circuit fault of transmission line in power system is studied, and the principle algo-rithm and application conditions of a variety of fault detection and fault location methods aredeeply compared and analysed. According to the fault feature information of the signal, thefault selection of transmission line is realized by means of integratedly applying wavelet en-ergy entropy and the theory of support vector machine. Moreover, making use of wavelettransform and signal singularity detection principle, and combining with line-mode compo-nent’s modulus maxima of traveling wave current signal in transmission line fault, a sin-gle-ended fault location method which is not affected by traveling wave velocity is put for-ward.When a short circuit occurs in transmission line, the transient process contains a largenumber of fault information. While the fault detection process mainly consists of the fault in-formation extraction and feature recognition. For wavelet energy entropy have the statisticalproperties of the unique advantages of wavelet time-frequency analysis and the statisticalproperties of information entropy on the complexity, the fault feature extraction can be effec-tively carried out. SVM which has been the best method to solve the small sample classifica-tion until now, is used for pattern recognition; the data within the law can be drawn and theshort-circuit fault type can be accurately determined. When there is fault in transmission line,electric current and voltage traveling wave will move to the ends of the line from the faultpoint. There is refraction and reflection when traveling wave encounters the wave impedancediscontinuity point in the communication process. The single-ended method measures thefault distance based on the time difference between the first travelling wave head from theshort-circuit fault point to the generatrix and the travelling wave head yielded by reflectionfrom the fault point to the generatrix.EHV transmission lines model is set up by Matlab and the running of the tenshort-circuit fault is simulated. Ultimately, the simulation results show that the methods offault phase selection and fault location are not affected by the operation mode of system, thetransitional resistance，the fault initial angle，and the velocity of traveling wave，with highreliability and accuracy.