Research On WAMS Based Fault Location For High Voltage Transmission Network

Fault location algorithm for High voltage transmission lines can promptly and accurately detect the fault point. It not only can greatly decrease the restoring work and outage time, bus also can detect the defective insulation. Fault location plays an important role in the security, stabilization and economic operation of power system. With the development of automation and information transfer techniques, WAMS (Wide Area Measurement System) comes into being which brings new opportunities for the Fault Location research. As a result, there is a great practical significance and engineering value in the Fault Location research based on WAMS. Under such engineering background, this thesis conducts research on this research interests and obtains some innovative research results.Firstly, the new opportunities for the research on fault location based on WAMS are analyzed. After the basic principle of WAMS is briefly introduced, the various existing algorithms based on synchronization technologyis are concluded. These different methods are classified and analysed by the amount of data used, while their characteristics and application performance are evaluated. At last, the current research interests in this area is presented, and the existing problem on the fault locagtion theory is pointed out, which leads to the research content of this thesis.Secondly, in order to obtain the accurate topology information for fault location research and improve the ability of perceiving the power network topology change based on WAMS, a new index, the relative variation of bus load, is proposed to identify the change of load structure. On the basis of this new index, a novel real time topology processing method is proposed. Most of the topology change perturbations can be identified by measurement change detection and power flow analysis. But for the special case that the power flow change is within the reasonable range after the perturbation, the hypothesis-verification method is used to distinguish topology change from large load change. The simulation results show that by using this algorithm we can effectively locate the topology change.Thirdly, the particular power structure in transmission network is studied in this chapter, and two kinds of practical PMU-based fault algorithm are proposed. In algorithm one, the branch lines are assumed as the long-distance lines, and then an efficient PMU-based fault location technique for the multi-terminal transmission lines is presentd. It is assumed that all the terminals are placed with PMU. This technique is based on a fault location index, which is defined as nodal current unbalance. By analyzing the special features of the index, through fault section identification and exact fault location, the fault point can be accurately and effectively achieved. In algorithm two, the branch lines are assumed as the short-distance lines, and then an adaptive PMU-based fault location technique for transmission line with tapped lines is presented. It is assumed that only two terminals are placed with PMU. Through multi fault region estimation, the fault line section can be located. Then the two-terminal fault location algorithm can be applied to implement high accurate fault location. This method solves the problem with the minimum of PMU, which also give a generic algorithm for the two-terminal transmission line.Fourthly, in order to achieve practical application of the fault location algorithm in power grid, two kinds of fault location algorithm suitable for transmission network with any construction are presented in this chapter. In algorithm one, basing on symmetrical component method and linear superposition principle, the additional positive sequence network is established. Then the fault location factor is defined and matching during-fault recorded factors with the during-fault simulated factors is used to determine the fault location. In algorithm two, a fault location optimization model is derived. Using the objective function, the line-based search method is applied to search all lines in the suspicious fault regions and find the exact fault point where the matching degree index is minimal. Numerical studies verify that the two proposed fault location method can accurately and quickly locate a fault under the conditions of different fault types, fault positions, and fault resistances. The proposed approach is especially promising for large-scale power system, and only requires sparse PMU placment.Finally, the researches in this thesis are summarized, and the innovation points and inadequacies are analyzed and evaluated. Then the further work is prospected.