The Research Of Voltage Sag Source Location In Distribution Network

With the development of modern power electronics technology,sensitive electric power loads are developing rapidly. However, sensitive electric power loads put forward higher requirement for power quality then traditional loads. This may cause customers complaints of power quality events more frequently, of which 80% of the complaints involved in the voltage sags.Voltage sag has become the most serious dynamic power quality problem. Voltage sag source location is to determine the disturbance origins’ relative position to monitoring device. Only after information about a disturbance location is available, can diagnosis and mitigation strategy be carried out. Moreover, any disputes can be resolved fairly.First of all, this paper takes Liang Ying substation power supply area in Xuyi County as an example, researchs spread domain and intensity of the voltage sags impact at 20 kV distribution network in a variety of short circuit faults and large motor starting, etc. and provides advice on the harm of distribution network to effectively reduce voltage sag.Secondly, based on the detailed introduction of the existing sag source location methods, Through modeling and simulation analysis of the 5 kinds of existing locating methods, it points out the advantages and disadvantages of those methods including disturbance power and disturbance energy(DEP), current real component polarity(RCC), investigating slope of the system trajectory(SST), distance relay(DR), resistance sign(RS).The method proposed in this paper is based on the analysis of power system faults by applying superposition principle of linear circuits. The direction of disturbance power under the stimulus of disturbance voltage has been found to be a good indicator of the sag source location. taking the voltage and current transformer polarity direction as in the reference direction in monitor devices, if the polarity of disturbance power is positive, a disturbance is located at upstream, while the negative polarity indicates downstream. In the simulation test kinds of disturbance types,including various failures such as single phase ground fault and two-phase short circuit ground fault, two-phase short circuit fault, three-phase short circuit fault,and large motor starting, capacitor switching,etc, in two terminal power supply system, radial grid, and IEEE 9 nodes standard model,were verified the accuracy of the method.Finally, the paper designs the voltage sag online locating and monitoring device. through experimentations, the method proposed in this paper is effective to be used to any grid structure(radial type, ring type, one-source, multiple-source, etc.).