Simulation And Protection Plan Research On The Over-voltages Of 500kV Substation

As the hubs of power systems,substations play the key role in the high-efficient and safe operation of the whole power systems.The damages by incident of the equipment in the substation will direct affect the safe operation of power systems and cause great economic losses.From the actual opertation experiences,the conclusion can be drawn that the main causes of overvlotages accidents in substations are the lightning overvoltage and operating overvoltage.According to statistics,there is about 40-70 percent power system faults caused by lightning strikes every year.Hence it is necessary to obtain the performance of substations under lightning strikes.At the same time,the operating overvoltage become more and more prominent as the lifting of the voltage levels.At present,operating voltage has become an important criterion to decide the insulation level in power systems.Based on Hua'neng Weijiamao Plant 500 k V substation project,this thesis mainly deals with the overvoltage problems including the lightning overvoltages and operating overvoltages.The electrical models of main equipment in substation are built by ATP-EMTP software including the Lightning currents,transmission lines,power towers,arresters,etc.In the lighning invasion overvoltage calculation,four different operation modes are studied.In terms of operating overvoltage calculation,overvoltages under three cases are considered including opening transmission lines,opening no-load transformer and operating the disconnector.The influencing factors are analysed to propose the corrsponding measures to reduce the overvoltages.Finally,the co-ordination of insulation in Weijiamao plant 500 k V substation can be optimized based on above calcualtion results.Some effective suggestions are given to the overvoltage protection in the substation.