Abstract: To prevent units from being damaged by open phrase operation, a power plant planned to update GIS circuit breakers in phasedivision operation into threephase mechanicallinked mechanism on site.Comparing two updating schemes and the operation situation of the unit, nondisassembling circuit breaker, partial adjustment on the size of material,and direct connection between the transmission part and the shaft of the circuit breaker must be taken in the updating scheme. The scheme has the advantages of low cost, nonstop busbar, arc extinguishing chamber with nondisassembling circuit breakers, convenience, flexible transformation and so on, which fundamentally eliminates the risk in the open phase operation of GIS circuit breakers in generator transformers,and ensures the safe operation.

Key words: GIS, circuit breaker, open phase, threephase mechanical linkage