Local Characteristic—scale Decomposition Method Based On Traveling Wave Fault Location Of Transmission Lines

With the constructing of strong smart grid and the expanding of power networks, UHV, long-distance and high-capacity transmission lines are widely used increasingly in recent years. And the transmission line fault location is becoming a heated issue both in China and abroad. It is difficult to extract traveling wave signal because of the rapid change. Local characteristic—scale decomposition(LCD) is used for traveling wave signal analysis in this paper. A fault location method is proposed combining Teager energy operator. Lots of fault simulation analysis proved its effectiveness in power systems.Firstly, this paper analyzes the transfer characteristics of traveling wave in transmission lines. Then traveling wave transfer characteristics of single line is analyzed. A new time-frequency signal analysis method, namely the local characteristic—scale decomposition(LCD) is proposed. Basic theory and simulations are analyzed. Traveling wave fault location method based on LCD-TEO in transmission lines is proposed. First, fault current traveling wave signals can be decomposed into some intrinsic scale components(ISC) and remnant. Then Teager energy operator is applied to gain the instantaneous energy spectrum of ISC1 component.Extract the first energy change points of the spectrogram as the initial fault traveling wave arrival time. Theoretically, LCD is not necessary to select parameters comparing with Wavelet Transform, and the phenomenon of unexplained negative frequencies is not existed compared with HHT relatively. By using EMTP-ATP, a 500 kV transmission line model is simulated, and data analysis and processing has been accomplished under MATLAB. Fault location distance got from LCD-TEO method is compared with wavelet transform, and HHT transform. Simulation results show that traveling wave arrival time is accurate by LCD, and fault location results are more accurate than other methods. The error is less than 200 meters. Finally, this paper conduct plentiful simulations among single-phase earth faults, two-phase short-circuit faults, two-phase earth faults and three-phase short circuit faults. Different fault distances are set up during simulation process. Results show the effectiveness of this method.The LCD decomposition method in this paper can extract the high-frequency component of fault traveling wave accurately. Fault initial traveling wave head can be extracted precisely combining the Teager energy operator. Thus, it can locate fault accurately,reduce recovery time of fault and enhance the operation reliability of power systems.