Research On Fault Location For Cables-overhead Circuit Transmission Lines

With the cable-overhead hybrid transmission lines more and more applicated in the power transmission system,studying the fault location method to improve the accuracy of fault location is an important premise to guarantee the safe and stable operation of power system.In this paper,the problem of fault location for hybrid lines is studied:ATP-EMTP software is used to simulate and analyze the hybrid transmission lines,and combined with the theory of traveling wave transmission,the paper analyzes the characteristics of the wave reflection when a fault occurs in overhead and cable lines of the hybrid transmission lines.Because of the complexity of the calculation process and the adaptability of the original fault interval estimation method,this paper uses the double terminal principle to determine the time difference between the initial fault traveling wave and the bus at the two ends of the line.The results show that the method is simple,reliable and universal.Based on the full consideration of the relationship between the wave velocity and the frequency,this paper uses autocorrelation analysis to extracted the principal component of the natural frequency of the fault traveling wave.Then combined with the electrical parameters of the line,the velocity can be obtained accurately.In addition,according to the time of the traveling wave propagation between the fault point and the end point of the line,the formula of the fault location is derived,so the fault location method considering frequency dependent characteristics is realized.Finally,according to the fault location results of different fault distance,different grounding resistance,different fault inception angle and range of different faults' types,this paper concludes that compared with the traditional method,the traveling wave ranging method based on the frequency dependent characteristics is superior to the ranging accuracy,stability and anti-jamming ability.