Research On Fault Location And Longitudinal Differential Protection Principles Of Four-parallel Transmission Lines On Same Tower

With the rapid development of the electrical industry, it becomes the main trend for power construction in china because of four-circuit transmission line on the same tower have the effectively conserve land area, increasing the transmission capacity of the unit corridor area, greatly reducing the advantages of investment in the construction sector, and so on. Considering the complexity of the structures of four-circuit transmission lines, it has a complex coupling impact on between the back line and the phases, and it has many fault types. As a result, it has much difficult to study on fault analysis, fault lines selection, fault lines location and longitudinal differential protection. In this paper, it has main study on fault lines location and longitudinal differential protection of four-circuit transmission line and non-full four-circuit transmission lines. The main results are as follows:1. These methods of the parameter decoupling of the double circuit transmission lines and four-parallel lines are detail Introduction, for this study of lines relay protection laid a certain foundation. A new decoupling matrix is proposed based on the same idea of decoupling, and according to the feature of mixed lines consisting of four parallel lines and double circuit lines, the corresponding fault Sequence Network is put forward.2. Research and Analysis of the negative sequence current features when occurs asymmetry fault of single circuit line in parameter asymmetry four-parallel lines on the same tower, and considering the unity of the negative sequence networks and negative sequence current ratio characteristics, A fault location method is put forward. Simulation results of PSCAD/EMTDC proof that the new algorithm is correctness and accuracy.3. Considering the actual power grid construction, the T-type transmission lines consisting of four parallel lines and other circuit lines is very popular, so the paper analysis their characteristics of lines consisting of four-parallel lines,double circuit lines and single circuit, it analysis and study the lines based on 12 sequence component method and 6 sequence component method. As a result, the corresponding fault Sequence Net and sequence components are proposed. on this basis, according to these characteristics of negative sequence components to detected fault side, and combines the relationship of positive sequence voltage at fault point to derive the location equation. The solution of the equation is fault location. In addition, drawing the idea of the above analysis, this paper analysis the another line consisting of four-parallel lines and double circuit lines. And another fault location method is proposed based on the corresponding fault Sequence Network.4. Considering the impact of zero sequence mutual and other factors,the traditional longitudinal differential protection can not be directly applied to four-pole circuit transmission line on the same tower. This paper research and analysis the feature of four-pole circuit transmission line by 12 sequence component method, these negative sequence component nets are put forward, and according to these feature of negative sequence component to building new program about Longitudinal differential protection. It proof the reliability and stability of the program by a large number of simulation experiments, but also the program can good solution to the problems of traditional differential protection.