Research On Method Of One-terminal Traveling Wave High Precise Fault Location For Transmission Lines

Along with the rapid development of electrical industry, power grid is becoming larger increasingly in scale and operation and management for it are becoming complex as well. As a result, the problems of safety and stabilization in power system are standing out increasingly. High voltage transmission lines are vital in power sytem, and shoulder important missions of electric energy transmitation. Rapid and exact estimation for the position of faulty transimission lines not only saves a large amount of manpower, restores faulty transimission lines in time and guarantees power supply reliably, but also plays an increasingly important role in safety, stabilization, economy of power system. Thus, it brings electric power department social and economical benefit inestimably.Fault location is a sort of technique for estimating fault position of faulty transimission lines. According to different fault characteristic, it can estimate fault position rapidly and exactly. One-terminal traveling wave fault location just installs fault location device on one terminal of transmission lines, and doesn’t have to use communication and synchronization. Besides better real-time estimation and economy, it isn’t affected by communication device reliabitlity, and hardly have influences caused by fault resistance, line asymmetry and so on. Hence, correlative research on one-terminal traveling wave fault location has very important academic sense and project applied value.However, one-terminal traveling wave fault location exists the problem in identifying reflected traveling wave, and also have region in which reflected traveling wave cannot be identified. Up to now, its method is manual through observing traveling wave waveform and dragging staff. As a result, accuracy of fault location is affected by man-made factor in a certain extent.Aiming at the problems above, this dissertation dissertates and summarizes main innovational and distinctive work made by author in transmission network fault location field as following:(1) Voltage traveling wave Peterson’s Rule and current traveling wave Peterson’s Rule are derived by virtue of voltage and current refraction coefficient, and they have duality. Because Bus’s capacitance has smooth effect for voltage, but smart effect for current, they offer theoretical basis in order to implement fault location with current traveling wave in view of CT’s better high frequency transform characteristic.(2) In order to show rule of traveling wave generation, refraction and reflection at fault point, a universal method to analysing fault traveling wave is proposed. It decomposes additional fault state network into normal system transmission lines and fault point new fault branch. Its contents include that current traveling waves how to generate, refract and reflect at the fault point. They are all determined by current in new additional fault branch at the fault point. If fault point new fault branch is asymmetrical and grounded, zero mode component and aerial mode component are transformed each other.(3) On the foundation of realization for one-terminal traveling wave high precise fault location, corresponding design scheme for fault location system is proposed. Adopting hardware start-up mode based on the phase fault current and measuring the duration of start-up signal, it can record high speed sampling data for realizing data storage and analysis through upper application in industrial computer.(4) One-terminal traveling wave high precise fault location algorithm is proposed. It includes one-terminal traveling wave fault location algorithm and improved subtractive clustering singularity measurement method. In order to distinguish reflected traveling wave, the fomer uses different subalgorithm through magnitude of zero mode component. While two-phase short-circuit or three-phase short-circuit occuring, fault location is implemented using reflected wave of fault point in aerial mode component. While single phase-to-grounded fault and two phase-to-grounded fault occuring, pre-location is implemented using initial traveling waves in zero mode component and aerial mode component at first, then precise location is implemented through distinguishing reflected wave of fault point and that of opposite bus. In order to increase the precision of fault location, the latter considers wavelet wavelet transform modular maximum to be data sets, and precisely confirms clustering centers as the time of singularity point using both magnitude and density of data sets.(5) A massive data processing method for one-terminal traveling wave high precise fault location is proposed. It implements one-terminal traveling wave high precise fault location through interfering recognition, recovery for high speed sampling data, traveling wave signal extraction and digital filtering, fault type recognition, mode selection, valid data segment interception and confirmation the time of singularity point based on improved subtractive clustering singularity measurement method, and corrects traveling wave velocity and line length as well.(6) This dissertation provides the physical experiment for one-terminal traveling wave high precise fault location key technique. After confirming traveling wave velocity through measuring trial line parameters, simulation of short circuit is carried out. The traveling wave generated during fault can be detected by use of high data sampling. Even though fault distance is short to 49m, one-terminal traveling wave fault location still can be implemented. The results and analysis prove that the fault location has high precision, and can effectively solve the problem in the large-scale of "death earea". The waves of digital simulation and that of physical experiment have the same changing orderliness, so digital simulation and physical experiment verify for each other.The results of physical experiment and digital simulation prove that the method proposed in this dissertation is correct and feasible.The method proposed in this dissertation has advantages, such as high accuracy in fault location, independence of opposite terminal’s information, no communication of two terminals, concentrative management of substation, and convenience in usage. It isn’t suited in fault locaion for distribution lines with net and tree structures, but for transmission lines of voltage grade 220kV or above.