Study On Fault Location Of Transmission Line Based On Transient Traveling Waves

In modern power system, the high-voltage transmission lines undertake the task of power transport. When the line gets a failure, to find out the trouble spot in time and restore power quickly is very important. There are various fault location methods, of which the traveling wave method with its high accuracy and merits of being free from transition resistance and fault types has been widely studied and applied.The fault location methods are divided into two modes:single-terminal and double-terminal. They use wavelet transform method to determine the time the traveling-wave head reaches the bus bar, and calculate the fault distance using the wave speed. Affected by atmospheric and geographic factors, the value of the wave speed is unstable, so the fault location method using the wave speed will cause principle errors.In this paper a new fault location method free from the wave speed is derived using information of both terminals.The traveling waves disperse during the online propagating, which may cause the wave head distortion, affect its singularity and affect the accuracy of single-terminal fault location method in principle. In this paper, high-pass filter is adopted to extract high-frequency wave components and filter out low-frequency components to reduce the affects of dispersion and improve the accuracy of the single-terminal fault location method.Affected by terrain and other factors, some lines are hybrid transmission lines. In this paper, the fault section is determined by double-terminal information first, and then the fault distance is calculated using single-terminal fault location method, which supplements the existing double-terminal fault location method of the hybrid transmission lines and improves its stability.Generally, fault location devices have the function of fault type identification. Detecting zero-modulus and line-modulus accurately is needed by using the current grounding fault criteria, and the zero-modulus is a loop formed between the earth and three-phase conducting lines which can be easily affected by earth resistively and other factors. Some papers propose that using the zero-modulus criteria may cause misjudgments. In this paper, criteria based on the polarity and amplitude of modulus maxima are proposed by using wavelet transform method to deal with each phase of traveling waves signals produced in the grounding fault and comparing the polarity and amplitude of wavelet transform modulus maxima corresponding to the singularity of each phase wave head, which supplements the existing criteria and improves the accuracy of the fault type identification. To verify the feasibility of the methods discussed in this paper, the simulation models of actual transmission lines parameters has been established, and plenty of simulation experiments has been done. The simulation results verify its validity and correctness.