Transmission Line Sag Measurement Research Based On Electric Field Sensing

With the continuous progress of science and technology and rapid economic development,information technology,digitalization and automation have become the core development trend of society.The new power system realizes the integration of energy entities and modern information technology through multi-sensing,big data,intelligent control and other technologies.The stability of power systems has become a research hotspot for experts and scholars at home and abroad.As a reliable carrier in long-distance power transmission and distribution,the monitoring of the condition of overhead transmission lines is crucial.As one of the important indicators for the operation and maintenance of transmission lines,timely sag measurement is of great significance to maintain the stability and reliability of the power system.Traditional contact measurement may be affected by conductor electromagnetic interference,while non-contact measurement methods have no direct electrical contact with the measured object,and are more portable and flexible.Among them,the transmission line magnetic field is susceptible to interference from the surrounding environment,while the electric field is relatively constant,not easily affected by environmental,meteorological and other factors,easier to conduct sensing monitoring.Considering the basic properties of sag and electromagnetic field,we mainly study the transmission line sag measurement based on non-contact electric field sensing and the related simulation.The main research work of this paper is as follows:1.Overview of the basic theory of transmission line sag and electric field.Firstly,based on the basic concept of sag,the definition of sag,the factors affecting sag and the sag model of the conductor are introduced,and the necessity of sag measurement of transmission lines is explained by analyzing the relevant theory of conductor sag and its hidden dangers;then the basic theory of electric field calculation is introduced,and the numerical calculation theory of electromagnetic field and the numerical calculation method of electric field are considered,and the finite element method is selected as the basic tool for sag measurement research;then the specific finite element analysis is introduced.Then introduces the specific content of the finite element analysis,from the concept,basic principles and mesh convergence of the three dimensions of the analysis of the use of the finite element method.2.Analysis of electric field coupling simulation of transmission lines under typical scenarios.Based on the finite element methodology,the electric field calculation laws of unipolar and bipolar transmission lines are analyzed;at the same time,the basic assumptions and simplified models of electric field simulation are proposed,and the conductors of transmission lines under different arrangement distributions are parametrically modeled into two-dimensional and three-dimensional models,and single conductor,horizontal arrangement,triangular arrangement and double vertical arrangement scenarios are considered;subsequently,the finite element analysis software COMSOL Multiphysics is used to simulate and analyze the electric field coupling under these typical scenarios,and the characteristics and laws of the electric field distribution of the transmission line are obtained from various aspects such as electric field distribution,grid dissection and electric field under the conductor.The relationship between the variation of the sag and the electric field is also considered,which provides the theoretical basis for the sag measurement study of the transmission line.3.Conducting research on transmission line sag measurement based on non-contact electric field sensing.Based on the electric field sensing,analyze the sag measurement principle of single conductor,and get the coupling relationship between sag and electric field by establishing the electrostatic model of transmission line and measurement point;combine with the finite element analysis,propose the sag calculation model through inverse reasoning;then analyze the influence of transmission line parameters on the sag measurement,construct the functional connection between transmission line parameters and sag calculation model coefficients,and verify the feasibility of the measurement method through simulation and theoretical comparison.The feasibility of the measurement method is verified through simulation and theoretical comparison;meanwhile,for multi-conductor lines,the sag measurement schemes for single-and dual-round lines are designed respectively,and the measurement array research is carried out,which can realize the sag measurement of conductors simply and efficiently by only obtaining the vertical electric field components and the basic structure of the line measured by the sensing array.The method is simple,convenient,easy to operate,and takes into account the multi-scene distribution,making the proposed measurement method more extensive and applicable to transmission lines of any structure.