Abstract:The protection action during typical dead zone fault of bus coupler and section switch in 220 kV bus protection system at present is described,and the logic problems of typical dead zone protection are analyzed. The CT differential current criterion of both sides are put forward to judge dead zone fault ahead of time,thus the protection can effectively avoid trip pingnormal bus segment when the dead zone failure happens in closed position,so it can effectively reduce the influence scope ofthe accident. At the same time,in all kinds of bus faults,the improved logic selection accuracy and export action time are compared with the current protection logic,and the advantages and disadvantages of the improvement measures are also discussed,which can provide a useful reference for the future protection designing and commissioning.