Research On Fault Location Method Of All-Parallel At Traction Network Based On The Three Dimensional Magnetic Field Measurement

At present, the passenger dedicated lines and intercity railways in our country are most designed according to the all-parallel AT power supply system, which are in line with the development trend of high speed and heavy load operated on high-speed railways. All-parallel AT traction network is an important part of the traction power supply system of high-speed railway, and it guarantees the accepted stream operation of electric locomotive traction line. However, the traction lines often occur short-circuit fault for it erects and runs in open but different environments, and so far. the traditional traction line fault location methods can not overcome the problem of low metering accuracy. With the development of measurement technology for magnetic field in recent years, the operation status of the traction line can be reflected by the variety of the space magnetic environment of the traction network. Therefore, on the basis of this, the paper focuses on an All-parallel AT traction network fault location method based on the three-dimensional magnetic field measurement. The method can not only achieve the fault span location, fault type identification and location within the span fast and accurately, but has vast importance to shorten the outage time and improve reliability.In view of the problem, according to the fundamental theorem of electromagnetic field in physics, the magnetic theoretical formula of finite long straight wire at any point in space under the Cartesian coordinates is derived. Fully considering the exclusive wire material of traction network and the characteristics of anharmonic circular cross section, and on the basis of the traction system model established by using the finite element analysis software Ansoft/Maxwell, the magnetic field distribution surrounded with traction lines can be simulated and analyzed. In the paper, the concept of the Wire characteristic spatial distance is explained in detail, on the foundation of this, the paper respectively researches the characteristic spatial distance of the contact line, rail and stranded lines. The analysis results indicate that, in the premise of the fixed precision, the exclusive wire of traction network can be seen as the solid round wires to calculate the magnetic field when the field point achieving the characteristic spatial distance.The changes of traction line current distribution are closely linked to the magnetic field distribution. According to the existing literature work and the actual line parameters, the short-circuit simulation model of all-parallel AT traction network is established in Matlab/Simulink environment. The simulation studies on current distribution under the short-circuit fault of contact wire-rail, contact wire-feeder line, feeder line-rail and the influence by different AT fault section, fault distance, transition resistance has been done.The short-circuit fault location method of traction network based on the magnetic measurement is proposed. According to the operation characteristics of all-parallel AT traction network line, the optimal placement of magnetic field measurement point is selected. Based on the thesis discussed above, the short-circuit fault span location method of traction network is investigated, and the steps to judge the fault span is provided based on the magnetic field signal measurement of both two sides of the fault point. The thesis has conducted research on the distribution of magnetic induction intensity amplitude and phase angle at both two sides of the fault point. By using the mutation of the magnetic induction intensity phase angle, the thesis proposed a new approach to realize the fault type recognition in traction network, and it is a method fully considering the effect brought by AT section, locomotive traction mode and external noise level. Based on the known fault span and fault type, this thesis derives the theoretical formula to achieve the accuracy fault location within the fault span, and the calculation result of examples verify the efficiency and accuracy of the theoretical formula. The advantages and disadvantages of proposed method are analyzed and compared with the existing fault location scheme.In order to apply the method to practical engineering, a design of new-type fault location system of traction network is presented in this thesis. The magnetic sensor installed on the tower along the traction lines can real-time sense the current change of traction network, the intelligent fault indication box should be able to give a preliminary judgment on magnetic signal and send the fault warning signal, and finally, the terminal computer installed in the substations could easily achieve the analysis of fault span location, fault type identification, location within the fault span. The devices and function of magnetic sensor have been preliminarily designed. Meanwhile, the relationship and work flow between each device have been concretely described in this thesis. Cost analysis of the proposed system proved that the project cost has been/could be lessened, and it is effective to be applied widely.According to three aspects including the basic theory, the method analysis, as well as the realization and application, this thesis has made a close study of the short-circuit fault location method based on the three-dimensional magnetic field measurement. The thesis forms a complete system, and provides a new idea to research fault location of the all-parallel AT traction system.