Distribution Network Fault Location Algorithm Based On μMPMU And Fault Observability Optimal Configuration

As an important role connecting the transmission network and users in the power system,the distribution network is closely related to users.The reliability of its power supply and the stability of its operation directly affect user experience and satisfaction.However,the management of the distribution network is relatively loose,resulting in a high frequency of faults.Additionally,there are several limitations on the configuration of measurement devices,which pose challenges to fault distance measurement in the distribution network.Currently,fault distance measurement in the distribution network faces the following problems:1.inability to obtain accurate parameters of the lines,2.a large number of untransposed lines,3.limited access to phase voltage values due to the special V/Vconnection form of potential transformers(PT)in the distribution network,and 4.a large number of external loads in the network,which are usually not equipped with measurement devices required for fault detection.Therefore,fault distance measurement in the distribution network has always been a challenging and popular research topic.The multifunctional micro phasor measurement unit(μMPMU),as a device for accurately synchronously measuring current,voltage,and frequency in the distribution network of the power system,provides a new approach to solve the problem of fault location in the distribution network.However,due to the high cost of μMPMU devices,it is still not feasible to extensively deploy them in the distribution network,limiting their assistance in fault location.Therefore,it is crucial to optimize the deployment of μMPMU in the distribution network in a reasonable manner to achieve fault observability with the minimum configuration of μMPMU,which is currently a challenge.To address these issues,the following research has been conducted:Based on the model of N-branch untransposed overhead lines in the distribution network,a fault location algorithm is proposed that simultaneously solves the problems of unknown line parameters,voltage measurements,and untransposed line.This algorithm utilizes voltage and current measurements at both ends of the lines before and after the fault,as well as the line length.It establishes distance measurement equations based on the principle that the calculated voltage values from both ends should be equal at the fault point.The trust region algorithm is used to solve the fault distance in the equation system.Finally,various assumed fault section equations are iteratively solved,and the solutions that meet the conditions are considered as the final location results.Simulation results demonstrate that this method has high accuracy and reliability,overcoming the problems of unknown line parameters,voltage measurements,and untransposed line.Based on the fault location algorithm mentioned above,a specific definition of fault observability in the distribution network is given.Additionally,the problem of fault measurement on external load branches without synchronized measurements in fault location in the distribution network is addressed.The observability of these branches is analyzed based on the defined fault observability criterion.An observability configuration scheme is proposed for external load branches without synchronized measurements,and based on this,the basic configuration unit of the distribution network is defined to describe the minimum configuration interval in the network that satisfies fault observability.Subsequently,a corresponding fault distance measurement algorithm is proposed for the basic configuration unit based on the basic model and algorithm for untransposed lines using voltage measurements.Simulation results show that the configuration scheme and fault location algorithm based on the basic configuration unit can ensure fault observability,and they are not affected by fault types or transition resistances,while achieving high measurement accuracy.The proposed basic configuration unit ensures internal fault observability under specific configuration conditions.By dividing and configuring the topology of the distribution system based on the structure of the basic configuration unit,the entire distribution network topology becomes fault observable since each basic configuration unit is fault observable.Therefore,based on the basic configuration unit,a distribution network μMPMU optimization configuration algorithm based on combinatorial optimization is proposed.This algorithm optimizes different forms of basic configuration units,divides the topology of the distribution network,and enables observation of all nodes and branches in the network with the fewest number of μMPMU.This optimization configuration algorithm,integrated tightly with the proposed fault distance measurement algorithm,accurately locates faults under the background of unknown parameters and line untransposed,providing a new approach to optimize the configuration of μMPMU in distribution networks.