Calculation Of Lightning Overvoltage And Research On Lightning Protection Measures Considering Surge Corona Of500kV Substation

In recent years, power industry of our country is developed rapidly, and the operatingvoltage of transmission lines is increasing at the same time, correspondingly, the height oftower is also increasing, which increases the possibility of transmission lines suffer fromlightning. It is necessary to study the lightning overvoltage to which the transmission linesand the substations withstand for the lightning overvoltage is one of the main reasons forlightning accident of transmission lines and substations.Surge corona has significant effect on the lightning overvoltage when thetransmission lines occurring the surge corona, so the accuracy of surge corona equivalentmodel is particularly important. In allusion to the shortage of surge corona equivalentmodel in the existing numerical simulation, the single-phase surge corona model has beenestablished according to the q-u characteristics curve of surge corona and the analysis ofthe electric field distribution around transmission lines when the lines suffer from lightning.Three-phase double-circuit line surge corona model has also been established based on thesingle-phase surge corona for the change of coupling coefficient of conductors. The modelnot only considers the coupling between phases but also takes the coupling between thedouble circuit lines into account. The comparison between the simulation and experimentalresult in reference proves the accuracy of surge corona model proposed in the paper.After that, the effects of surge corona, grounding resistance of tower and the decreaseof wave velocity on the lightning overvoltage propagating on the transmission lines of500kV GIS substation have been studied. The results show that once the surge coronaoccurring on the lines, overvoltage wave propagating on them will occurs significantattenuation; with the increase of grounding resistance of tower, the lightning overvoltageon the transmission lines has a trend to increase; the decrease of wave velocity will lead theovervoltage to rise. Finally, the influence of operation mode on the lightning overvoltage which is theequipments (transformer) in substation suffered has been studied, and the influence thatadopting Gas Insulated Line (GIL) to connect the main transformer and GIS on lightningprotection has been researched. The paper checks the arrest initial allocated program in theworst operation mode, and a reasonable protection program has been proposed for the lakeof the initial program.