Abstract: The invention relates to a lead-in structure for coupling of a turbo generator in a circulating process of a circulating medium. The turbo generator includes a turbine and a generator as well as possibly also a feed pump enclosed in a common casing structure. The casing structure also includes at least a first duct for hot, steam-like circulating medium entering the turbine, a second duct for circulating medium exiting the turbine, and a third duct for cooled liquid circulating medium, which, for example, enters the feed pump. The third duct includes an annular channel that is placed, preferably concentrically, around the second duct, which includes an annular channel. The first duct includes an annular channel that is placed, preferably concentrically, between the second duct and the annular channel of the third duct.