| The development of the society has driven the constant development of the power industry and transmission line of electricity Electric load is increasing constantly, the development of the modern power system require transmitting the large capacity to the load centre, the enlargement of living line scale will take up more transmission corridors, which is uneconomical. In order to save the transmission line corridor, the double transmission line on the same tower is used by line system more and more. There are many merits in the double transmission line on the same tower, such as the transmission corridors are narrow, the transmission ability is strong, and the investment is saved etc. Further more, due to the effect of the line faults for the stability and reliability of power system is not neglected, the fault location had become a problem that got more attention from the department of power network management and experts. The structure of the double line on the same tower is very complex, the fault analysis and the fault location are more difficult.The development and general situation of the research in this field in China and in other countries is reviewed in this paper. All the existing algorithms can be classified into three main methods: traveling wave location, single terminal location and two terminal location, the principle and application condition of each algorithm are presented and discussed. Firstly, the fault analysis, of the double transmission line on the same tower was introduced. Many fault types only appear in the double-circuit line rather than single circuit line, symmetrical component method cannot be applied in double-circuit line directly due to phase to phase and line to line couplings and the asymmetrical impedance matrixes corresponding to it. As to this, A new method of the mode transformation for the double-circuit line is presented in this article. Moreover, the transformation matrix with goodfeatures can be used for the novel fault location and fault analysis.we analyze the fault by this method, at first, six phase transmit system was switched two separate three-phase systems and eliminated the line to line mutual inductance ; Then, these two groups of three-phase systems adopt the method of the asymmetric fault to analyze separately and set up the positive, negative, zero sequence network, thus compose the six sequence network; Finally , we utilize the border terms of the fault to make up the composite sequence network of the six sequence network, and then calculate the asymmetric fault to the composite sequence network. The article provided thirteen figures of fault composite sequence network in the double-circuit line, this method is suitable for all fault types in the double-circuit line system.Because there is the coupling in line to line, the operation and the fault location are influenced. The paper deduced the induced formulation of the coupling voltage and current, and analysed the influence of the coupling to the measuring impedance and the overhauling circuit.The accurate fault location for high voltage transmission line plays increasingly important role in power system. Several kinds of the fault location method were introduced in the article and were classified. We analysed in depth the advantage and the problem of various kinds of the fault location method and pointed out the applicable scope of every fault location method. The paper describes an accurate fault location technique for the double transmission line, which uses post-fault voltage and current derived at one line terminal. Several kinds of typical fault location formulae were deduced. The method of the fault location doesn't influenced by the source impedance, the load current and the transition resistance. Finally, the paper enumerated an instance, The Pscad software was utilized to carry on the artificial test to the fault of double-circuit line. The artificial result verified the exactness of the method of the fault location in this text. |
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