Research On Power Frequency Overvoltage And Switching Overvoltage Of The 1000kV System

UHV transmission technology has the advantage of large transmission power,low losses,and less line corridor,which is suitable for China's power industry conditions of large electricity demand and uneven resources distribution.Therefore,it is imperative to build UHV transmission system.However,the increase of grid voltage brings not only longer transmission distance and greater capacity,but also higher requirements of equipment insulation.Considering that the 1000kV power equipment is difficult to manufacture and cost too much,it is of great significance to study the characteristics and control measures of the power frequency overvoltage and switching overvoltage of 1000kV system.This thesis took power frequency overvoltage and switching overvoltage of 1000kV single-circuit transmission systems and double-circuit transmission systems as the research object,considering kinds of operation modes in which overvoltage problems may occured and electromagnetic coupling of double-circuit transmission systems,the ATP-EMTP model of 1000kV single-circuit and double-circuit transmission systems is established.This paper analyzes the generation condition and mechanism of power frequency overvoltage and switching overvoltage.Then,the power frequency overvoltage and switching overvoltage was calculated,and some restraining measures of overvoltage was given according to the influence factors of power frequency overvoltage and switching overvoltage.The influence of shunt reactors,ground wires,parallel resistance,arrester and other devices on line overvoltage is studied and verified by simulation.Through the theoretical analysis and simulation calculation of this paper,it is believed that suitable segmenting operation in the line is conducive to limiting overvoltage because of the 1000kV line has a long power supply distance.A 1000kV line which is less than 100km may not be equipped with shunt reactor,because of the power frequency overvoltage energy in this condition can be controlled within 1.4p.u.The maximum power frequency overvoltage is determined by single-phase grounding unload overvoltage,and the maximum switching overvoltage is determined by the switching operate and the fault excitation overvoltage.By installing the shunt reactor,low residual voltage MOA,good conductor ground wire and small parallel resistor,the line operation can be limited under 1.6p.u..Those above conclusions are valuable in the engineering.