Parameter-Free Fault Location Algorithm For Overhead Transmission Line Of Distribution Network Based On μPMU

With the strategic transformation of the national energy structure,a large number of distributed power sources have been connected to the distribution network,which has led to the continuous expansion of the distribution network scale.The branch overhead transmission line has been widely used in distribution network due to its economical and flexible power supply.However,the fault of multi-branch lines will affect the reliability of power supply and the operation of distributed power sources.The structure complexity of branch line also makes fault location more challenging.Thus,it is urgent to research the fault location algorithm for multi-branch lines in distribution network.In recent years,μPMU(Micro Phasor Measurement Unit)has been gradually popularized,and the synchronous,high-precision voltage and current measurement data obtained by it provides new ideas for fault location technology.The line parameters in the distribution network are commonly inaccurate or unknown due to factors such as management,weather,and aging,which has a significant impact on fault location algorithms based on measured impedance.In addition,the inevitable measurement error also makes the location result further biased.Therefore,in this dissertation,to suppress the influence of line parameters and measurement errors on fault location,with the advantages of micro PMU,the following studies were carried out:Taking the T-type overhead transmission line of the distribution network as an example,a parameter-independent fault location algorithm is first proposed.This algorithm is suitable for lumped parameter line models.The pre-fault and post-fault voltage and current at the three terminals of the line together with the line length are utilized.The location equations are built according to the voltage equality of the fault point and tapping point derived by the adjacent node electrical quantities.The trust region algorithm is used to simultaneously solve the fault distance and line impedance parameters in the equations,so no known line parameters are required.Finally,the equations corresponding to various hypothetical fault sections are traversed,and the reasonable solution is used as the location result.The influence of various fault positions,fault types,and fault resistances on the algorithm is tested by PSCAD in the case of unknown line impedance parameters,which proves its effectiveness and high accuracy.Based on above method,the fault location algorithm is improved and suitable for the N-branch overhead transmission line of the distribution network.The algorithm numbers the nodes of main line and branch line according to a certain rule,summarizes the adaptive location equations,and comprehensively judges the fault point according to the reasonability of the equation solution under various hypothetical fault sections.The simulation results in MATLAB/Simulink show that the algorithm is basically unaffected by line parameters,fault position,fault type,and fault resistance.Finally,the above-mentioned fault location algorithms are improved by sliding data windows to form redundant ranging equations,and the influence of measurement errors on the location results is reduced.The algorithm uses redundant sampling data windows before and after the fault recorded by the micro PMU,extracts multiple sets of voltage and current fundamental component according to different data windows,substitutes them to form multiple ranging equations and uses the trust region algorithm to solve together.Thus,it reduces the effects of measurement errors based on the data redundancy.The simulation results in MATLAB/Simulink show that compared with the method using only one set of data windows,the method of forming ranging equations using multiple sets of data windows can significantly improve the location accuracy and effectively resist the influence of measurement errors.