Abstract:Through the comparison of several kinds of main electric conncetion lines in actual use in power plants,designing theory and project experience both prove the feasibility of the various kinds of connection lines.However,the application of GIS gives rise to some problems to the various main connection lines,especially the possible failure of non-separation bundle bus bar to meet the requirement of being economical when the number of units and the out-lines is small,which leads to its limitation in actual use.In consideration of economy and safety,it is one of the approaches suitable for the actual status of the project to adopt bridge connection lining at the initial stage and then convert to half-switch connection lining when the number of system return-ways is small.