Research On Fault Location Methods In Distribution Network Based On Fault Information

With the rapid development of national economy and improvement of people’s living standards, urban and rural distribution network have made considerable progress. The power loads increase rapidly while the power supply reliability and power quality are getting more demanding from power consumers. As the terminal part of power customer service, the accurate analysis, rapid location and effective isolation of fault after a fault occurs will minimize the loss of customers, improve power supply reliability and ensure system security and stability. In this paper, the fault location methods in distribution network based on fault information are studied deeply.The traditional fault location methods use information from single information source, mainly based on alarm information uploaded by monitoring devices. However, taking into consideration the pretty low level of distribution automation and the insufficiency of monitoring devices in distribution network, enough information are not available in most cases, which is unable to obtain the accurate fault position. At the same time, with the wide application of power quality monitoring devices, how to use voltage sag information for fault location is a new research trend.For the sake of taking the most advantage of these fault information to improve the accuracy and the perfect degree of fault location methods, this paper made in-depth and meticulous research on distribution network fault location methods based on fault information. The main research works are as follows:1、This paper introduces the fault information such as breaker operational information, FTU alarm information, voltage sag and power factor angle information, of which the sources, meanings and usages are analyzed. The general features of distribution network topology and the methods of topology search are also introduced. The adoption of breadth-first search algorithm in topology search overcomes the shortcomings of depth-first search algorithm. All these provide a theoretical basis for the realization of the subsequent fault location methods.2、A fault location method based on fault information is proposed for distribution network without enough monitoring devices. On the basis of the existing monitoring devices, accurate fault location can be realized just by adding a power quality monitoring device near the bus, which can also avoid "pseudo-fault points". In the first place, the method locates fault section based on FTU alarm information, followed by fault distance calculation based on voltage sag and power factor angle information.The method of fault section location is started from the circuit breaker. The distribution network topology search use breadth-first search as search algorithm. Based on FTU alarm information, fault sections are determined by most downstream device which has uploaded alarm information and the installation of downstream monitoring terminals. After the fault sections were determined, voltage sag and power factor angle information are introduced to calculate fault distance. Based on the theory when a fault occurs at different position, the bus voltage sag amplitude and power factor angle will present different characteristics, faults are simulated off-line several times to obtain bus voltage sag amplitude and power factor angle versus fault distance function expression. Then, the fault distance calculating functions establish fault information database. When a failure occurs, the measured bus voltage sag amplitude and power factor angle will be brought into fault distance calculating function in the database to calculate fault distance. So the accurate fault location is obtained. The simulation experiment of a real distribution system verifies the effectiveness and accuracy of the method.3、For multi-branch complex distribution network, in order to solve the problem that distant fault causes unobvious bus voltage sag, with the help of power quality monitoring devices installed in the system, this paper proposes an improved fault location method based on multi-point voltage sag information. Faults were simulated off-line in different sections, voltage sag information uploaded by multiple power quality monitoring devices establish multi-point voltage sag information database. When a fault takes place, correlation analysis is made between the actually measured multi-point voltage sag information and the voltage sag information of each section in the database based on correlation analysis theory. The discretion of the correlation degree determines the accurate fault section. The simulation experiment of IEEE 34 Node radial distribution network verifies the effectiveness of the method.In summary, this paper has made a deep research on the problem of distribution network fault location based on fault information. Fault section is located in use of FTU alarm information, after that bus voltage sags and power factor angle information are used to obtain a precise fault location. At the same time, correlation analysis theory is used for fault location in complex distribution network based on multi-point voltage sag information. The research content has important application value to perform the rapid fault location in distribution network and improve the reliability of power supply.