| Overhead lines are an important channel for power transmission,because of their wide distribution,long distance,harsh working environment,so they are highly vulnerable to lightning.Over the years,in the overhead line tripping accident of 110 k V and above voltage level,the proportion of lightning tripping accidents has remained high,which seriously threatens the safe transmission of electric energy.With the development of the economy and the power grid,the requirements for the reliability of power supply are getting higher and higher,so,it is urgent to establish an electromagnetic transient model of the key components of the line,build a test platform for the transient voltage and current distribution of the transmission line,study the lightning overvoltage characteristics of the line under different working conditions through the combination of simulation and test,and propose the corresponding lightning protection optimization scheme.In this paper,a 1:1 3D tower model is first established based on finite element software ANSYS,and the wave impedance of each segment of the pole tower is indirectly calculated by calculating the electric field and magnetic field energy by sub-region,and verified by establishing a single vertical cylinder model,with an error of less than 3.16%.Then,based on the electromagnetic transient simulation software ATP-EMTP,the electromagnetic transient model and the integrated EMTP model of key components such as transmission lines,pole towers,lightning arresters,and insulators are established.The scale tower and the actual tower test were carried out separately to test and verify the built model,among which the field measurement result of the overvoltage amplitude at the top of the proportional pole tower differed from the simulation result by 0.27 V,and the relative error was 3.23%,the difference between the actual tower top voltage amplitude and the measured value was only 6.2%,and the difference between the amplitude of the inground current and the measured value was only3.7%.Then,based on the established electromagnetic transient model and integrated EMTP model of the key components of the transmission line,the overvoltage characteristics of the transmission line when it suffered counterattack and shielding failure were studied,and the lightning tripping rate calculation method based on Monte Carlo and EMTP was proposed,and combined with the overvoltage characteristics and lightning tripping rate calculation methods,respectively,the line lightning protection optimization scheme was carried out from the three aspects of pole tower attributes,line attributes,and grounding system attributes,and complete the lightning protection optimization design of transmission lines under three common working conditions: high soil resistivity areas,large span high pole towers,and urban narrow base pole towers.Finally,the shock transient voltage and current distribution test platform were established,and the field test of the actual line impact transient voltage and current distribution were carried out in Huizhou and Foshan respectively,and the field application of some lightning protection optimization schemes such as magnetic ring,inductive lightning rod and current limit coil was carried out. |
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