Analysis Of Lightning Overvoltage And Lightning Withstand Performance Of Mixed Voltage Transmission Line

Mixed-voltage transmission on the same tower has great advantages and development prospects in terms of increasing transmission capacity,saving line corridor resources and reducing construction costs.A preliminary study on UHV and UHV hybrid transmission on the same tower found that due to the electromagnetic coupling between the multi-circuit transmission lines,which affects the overvoltage level of the transmission line,direct lightning overvoltage is one of the main causes of line faults.Therefore,it is necessary to re-evaluate the lightning resistance level of EHV and UHV mixed voltage transmission lines,and to strengthen the lightning protection measures of the lines.The paper discusses the principle of lightning overvoltage and the calculation method of lightning protection.Taking the single-circuit±800kV and double-circuit 500kV AC/DC transmission towers on the same tower as the research object,the electromagnetic distributed simulation software ATP-EMTP was used to build the distributed parameter model of the line.Lightning current,tower,wave impedance,grounding resistance,insulator,etc.have established simulation models.The improved electrical geometric model is applied,the mutual shielding effect of the lightning protection line on the transmission line and the multi-circuit line is considered,and the line deflection conditions at different lightning incidence angles are calculated;when the lightning line pole is used,the lightning strike channel and the tower are analyzed The distribution of lightning current in the system;calculation and analysis of the propagation of lightning current in the tower,the effect of lightning current waveform on the current distribution of the tower and the influence of the tower on the surge response.The effects of different grounding resistance and lightning protection angle on transmission line counterattack,lightning protection characteristics and lightning overvoltage are obtained,and effective measures to improve the line counterattack and lightning protection performance are proposed.The thesis studies the characteristics of induced overvoltages on overhead lines during lightning strikes and windings,and reveals that the overvoltage on the A phase of the AC line is the largest when the lightning strikes the tower.The phase A overvoltage is the largest in the line.By strengthening the insulation of the line,reducing the grounding resistance of the tower,rationally arranging the lightning conductor,installing the lightning rod,increasing the length of the lightning conductor,and reducing the protection angle,it can effectively reduce the line overvoltage level and prevent the insulation flashover caused by lightning strikes.Effectively improve the lightning resistance of mixed voltage transmission lines.