Voltage Sag Source Location Method Based On Monitoring Point Optimization

Voltage sag is the most common power quality problem in power system nowadays.It is the main cause of misoperation or even damage of sensitive power devices,major safety accidents and economic losses.Power departments and customers are also paying more and more attention to the impact of voltage sags.Accurate positioning of the sag source can effectively reduce the time to restore the power supply,and solve the contradictions and disputes between the suppliers and users.This paper introduces the definition of voltage sag,enumerates the impact of sag on several different power components,describes three measures to weaken the impact of sag,and makes a detailed analysis of the three main causes of sag.Then several classical upstream and downstream positioning methods and their principles are studied,and models are established to verify and analyze these methods.The results show that the positioning effect of classical positioning methods is affected by system structure and fault types,and there are some limitations.For the voltage sag caused by single-phase grounding fault with the highest frequency in power system,this paper adopts the equivalent impedance sequence component method to extract the zero sequence component with the greatest variation when single-phase grounding fault occurs in small current grounding system,so as to locate the sag source accurately.The simulation verifies the validity of this method.In this paper,a fault location method combining voltage sag matching method with impedance method is proposed.Combined with the layout optimization of monitoring points and upstream and downstream location,the possible fault range is reduced,and the calculation amount of fault location is reduced,so as to achieve accurate and rapid fault location in the system network.Firstly,the optimal algorithm is used to optimize the location of monitoring points,and then the upstream and downstream locations are combined to narrow the possible range of faults.The bus nodes in the range are matched by voltage sags using voltage matching method to determine the bus node nearest to the fault point.Finally,the impedance method is used to analyze and calculate the relevant lines on the bus to determine the final fault location.The method is validated by the IEEE 14-node model,and the results show that the method is feasible and effective.