The barring gear assembly is designed to drive in rotation a shaft of a turbo-alternator group having an axis of rotation A. The barring gear assembly includes a main wheel fixed on said shaft and defining lateral sides located on either side of the axis of rotation A, a barring gear module having a support piece on which is mounted a clutch system for coupling and uncoupling a secondary shaft to and from the main wheel, the secondary shaft being driven by an auxiliary motor, and the barring gear module being positioned on one of said lateral sides (C1) of the axis of rotation A.