Investigation Of New Algorithms For Fault Location Of HV Overhead Transmission Line

With the developing of power systems, more and more long distance HV transmission lines have been constructed, as increases the probability and severity of short circuit faults. Therefore, it will do great damage to the industry, agriculture and daily life of the people, once faults occur on the transmission line. To ensure proper operation of the system, it is of great importance to determine the exact fault location when fault happens.For many years, accurate fault location of HV transmission line has been paid much attention to. On the basis of a lot of predecessors' achievements, new algorithms for single-terminal and two-terminal fault location of the power transmission line are systematically discussed in this dissertation. In reference to the fuzziness existing in single-terminal fault location, Fuzzy Logic System (FLS) is introduced to the fault location for the first time, and a new method for single-terminal location with power frequency is put forward based on the FLS. Subsequently, by means of the construction of an approximate formula for fault location and the computation of the corresponding average and minimum grades, a comprehensive criterion is presented to compare different location algorithms and then help to choose the most suitable one. The criterion can be dynamically generated in aid of the system parameters measured before the appearance of faults. Furthermore, the opposite system is calibrated with a set of impedances instead of a certain typical one, which is usually adopted in the traditional fault location. Therefore, the influence of the varying of impedance of the opposite terminal on the locating precision is greatly weakened. Large quantities of emulation show that the precision of fault location excels those of the traditional methods, as confirms the effectiveness of the algorithm.In recent years, fault location without data synchronization between the two or multi terminals has become more attractive in application, along with the development of communication and computer network techniques. Based on a lot of simulations with the parameters approximating to the actual condition, in-depth comparisons between the existing algorithms for two-terminal location are made in the thesis. The robustness of the algorithms for two-terminal location, i.e., the feasibility to different type of faults and the capability to suppress all kinds ofdisturbances, is first explicitly put forward. What is more, two new algorithms for two-terminal location with a form of fraction are brought forward for the first time, which integrate the data synchronization between the two terminals with the robustness of the algorithms. As a result, elimination of phase difference and the robustness of the algorithms are assured, with the support of reasonable theoretic basis. The results of simulation show that the two algorithms are applicable not only to the single or double circuit with one power source at each end, but also to the three-terminal or multi-terminal locations, almost without any alteration. With strong robustness and no necessity for any synchronization, the above algorithms exceed the existing congeneric algorithms for two-terminal location which are based on power frequency phasor by higher precision and stronger robustness, and in some range of the error of the data of voltages and currents measured excel those algorithms needing Global Position System (GPS) to accomplish synchronization at the expense of hardware investment as well, the new algorithms seem to be more economical and technically available.At the same time, being aware of the error due to the variation of the overhead line parameters with the environment, which is a common problem, the technique of on-line self-adaptive estimation for the parameters of the transmission line is first put forward. With the aid of this technique, the precision of fault location could be greatly immune to the external interference, which comes from the variation of line parameters, especially for the variation caused by tough climate or severe chilliness in some areas where the line passes by.The key of the method is that it takes a changing distance of the transmission line as a constant horizontal distance between poles, and all of the influential factors come down to the variation of the parameters of transmission line. In engineering, the parameters estimation could be obtained through the system load variation between maximum and minimum every day. The algorithm and technique proposed is simple in form, easy in process, and need no more new hardware. It is of great value for the two-terminal or multi-terminal location of all kinds of transmission line.