Fault Location Based On Voltage Sag Characterization For Distribution Networks

With the development of science and technology and the national economy, China’s distribution network has been expanded yearly, and the demands of power consumers for power quality and distribution automation level is getting higher and higher. Due to more complicated structure, short and heterogeneous lines and presence of laterals and load taps, distribution network occurs faults easily, so fault location quickly and precisely is required, which not only shortens the outage time, reduce the outage area, but also improve the reliability of power supply and ensure the safe and stable operation of the whole power system. Meanwhile, with wide application of power quality monitor devices, how to use the data collected from device such as voltage sag to solve problems in other areas is a new research trend, like fault diagnosis and fault location.The paper introduces the concept of voltage sag characterization and compares different analytical methods of voltage sag. In view of the complex distribution network, based on the analysis method of voltage sag, the fault distance function for each line can be deduced under different fault types, which can calculate the magnitude and phase angle jump of the voltage sag, and provide a theoretical basis for the following contents.Based on the single-end bus voltage sag characterization, the paper studies on the fault location for distribution network. When a fault occurs on the different sections, the bus voltage sags present different characteristics. Using the fault analysis theory of power system, databases for voltage sag and coefficient of fault distance function can be established. Comparing the measured and calculated voltage sag, the possible fault sections can be picked out. Using ranking analysis the fault section can be determined, and the fault distance can be calculated with the fault distance function. The effectiveness of proposed algorithm is verified by cases study about overhead network and cable.For the large scale network with multiple laterals and branches, there are some problems which is that voltage sag is unobservable for a fault occurring far away and multiple estimation. In order to solve these problems, this paper presents an approach for fault location based on multiple-end voltage sag characterization. A0-1linear programming model is built to solve the problem of optimization allocation, whose object function is to minimize the number of the monitoring buses and the key constraint is to guarantee the observability of the whole system considering faults. Based on the optimal monitor plan and multiple-end voltage sag characterization, fault section and fault distance can be calculated using the improved method. The performance of the proposed method is illustrated in the34buses case, and the validity of such a method is testified.Combining with the fault location algorithm, the paper develops a device which can monitor the online voltage sag and locate faults. The hardware design is introduced including configuration and function of each part, and the software of the device based on the Lab VIEW is developed which contains the main processes such as data acquisition, data processing and fault location.