Transmission Line Fault Traveling Wave Analysis And Ranging

With the development of China power grid, the transmitted power and voltage of the transmission line are enlarging gradually. EHV lines have long distances, always cross mountains and are hard to find the fault location. It is important for EHV transmission lines to quickly and accurately locate faults with aspects to their safe and economical operation. Compared with conventional fault location based on fundamental components, traveling-wave based fault location is more accurate and not apt to be affected by transition resistor, fault type, distributed capacitance, bus configuration and CT saturation, etc. In recent years, following with the development of the traveling wave, wavelets, mathematical morphology theory and DSP technology, fault location based on traveling wave make great progresses. Some single and double ended approaches based on traveling wave have been presented. Some location devices based on traveling wave have been developed and bring into service.It must be noticed that the reliability and accuracy of the location device based on traveling wave need to increase. In this paper, propagation regularity of traveling wave, phase selection and fault location are studied. According to these, the paper completed the theory of wave propagation and fault location. The main contents and contribution are shown as follows:(1) As the foundation of traveling-wave based fault location, the theory of wavelet and mathematical morphology are introduced and compared in this paper.(2) General rule of traveling wave propagation are generalized in the paper. It researched the refraction and reflection regularity when traveling wave across different type bus. The influence of frequency and corona are discussed in the paper.(3) Phase selection method based on steady-state variable cannot meet the challenge of traveling wave based fault location and protection. The paper calculate the primary, mode wave and present a new fault recognition and phase selection approach which based on mode wave and phase wave. The simulation show the approach is simple and reliable.(4) At present, there are not enough discussions about coupling phenomenon oftransmission line fault modal traveling waves when study application of traveling waveshome and abroad. Modal traveling waves will couple each other when there are asymmetryphase to ground fault in transmission line. The paper analyses the generation of the coupling parts and the characteristics of their propagation. The refraction and reflection coefficient of modal wave are calculated in the paper. According to the characteristics of the ground mode traveling wave and the aerial mode traveling wave, the paper describes the relationship of the ground mode parts of the reflected waves from the fault point and the interception waves from the opposite bus, the aerial mode traveling parts of the reflected waves form the fault point and the interception waves from the opposite bus. The simulation show the result is effective.(5) The characteristic of single and double ended fault location method is generalized and a new single ended location method based on back-direction traveling wave is presented in the paper. According to the coupling rule of modal wave, the polarity of the second back-direction aerial mode and ground mode traveling wave can determine the property of the second back-direction aerial mode and calculate fault distance. The new method combining with the method based on polarity recognition will increase the reliability of conventional single ended fault location method.(6) The developing fault location device based on traveling wave is simply introduced in the paper.