Fault Location Method For Power System With Finite Node Information Based On PMU

With the rapidly development of power grid,locating faults quickly and accurately in large-scale and complex power grid is an important guarantee for the stable operation of power system.At the same time,it puts forward higher requirements for the measurement and monitoring of the whole system.Traditional fault location and detection is mainly realized by various fault recording devices,lacking accurate common time markers,and recording data is only locally valid,so it is difficult to analyze the dynamic behavior of the whole system.Phasor Measurement Unit(PMU)can obtain the measurement information of nodes,and use the high-precision unified time scale of Global Positioning System(GPS)to realize the real-time synchronous and high-speed acquisition of node phase angle and electrical quantity.It has the advantages of high time synchronization,high accuracy and short update cycle.Therefore,fault location based on PMU limited node information can effectively improve the rapidity and accuracy of output results.Considering the installation cost and usage rate of the equipment,PMU has only achieved full coverage at 500 KV and above,but at 220 KV and below nodes,the whole network has not been installed and applied,and nodes without PMU have been installed.so it is impossible to judge whether the fault occurs by measuring the changes of voltage and current in the data.In order to solve this problem,this paper proposes an optimized PMU configuration method to reduce the number of PMUs installed in the power grid,and proposes an accurate fault location method using limited PMU information.For the power network with incomplete PMU,an improved objective function is constructed on the basis of guaranteeing the observability of the system,and the improved scheme is used to optimize the configuration of PMU,so that the optimized configuration scheme meets the requirements of fault location calculation.According to the topological structure of the whole network and the configuration of PMU,the constraints of fault location are optimized,and a method to construct a predicted fault zone is proposed,which can divide the whole network into regions while reducing the number of PMUs required.When a fault occurs,the system can first locate the area where the fault may occur,improve the rapidity of the fault location process and effectively save the cost of equipment.On the basis of dividing the system into predicted fault zone,a two-stage unbalanced current fault location algorithm is proposed,and three types of predicted fault zone are analyzed and calculated respectively.Firstly,using the idea of differential current,the sum of regional currents is calculated,and the suspicious fault zone is determined by comparison,and the type of fault region is judged.After locating and classifying the suspicious fault zone,the unbalanced current value is calculated,and the fault location is finally determined according to the unbalanced current value calculated.When the system is not observable after the fault occurs,the virtual fault nodes are set up to locate the fault correctly according to the number and location of the virtual nodes.In this paper,the proposed method is simulated by using IEEE14-bus system and IEEE39-bus system.The results show that the proposed method has good adaptability and reliability under different fault conditions.