NOVELTY - The turbine has a nozzle diaphragm outer ring (17) fixed to a turbine casing (11), and nozzle diaphragm inner ring (18) located inside the outer ring. Nozzles (19) are placed between the outer and inner rings that form a steam passage, and rotor blades (36) are mounted on a turbine rotor shaft (26). The inner ring has sealing fins (41) protruding from an inner surface of the inner ring towards the shaft. An overhang (38) is attached to the outer ring, and has an inner surface (38a) overlay welded or coated with a protective material having durability greater than a material of the overhang.    USE - Used in a geothermal turbine plant.    ADVANTAGE - The inner surface of the overhang is overlay welded or coated with the protective material having a durability greater than the material of the overhang, thus preventing damage to the turbine against aging, severe degradation of each component in the turbine, and improving corrosion resistance and erosion resistance of each component of the turbine, and hence sustaining turbine efficiency at a high level over a long period of time. The structure of the turbine promotes more effective use of energy resources for stable electric power supplies, improves maintainability of turbine components of the turbine operated under severe conditions, thus decreasing occasions of shut down for maintenance, inspection and repair of the turbine components and emergency shut down due to troubles, raising operational availability of the turbine plant, and improving reliability at cycling load operation of the turbine. The structure of the turbine increases operational flexibility of the turbine plant, and efficiently operates the plant, thus realizing saving and effective use of geothermal resources.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of a turbine stage of a geothermal turbine.    Geothermal turbine (10)    Turbine casing (11)    Turbine stages (12)    Nozzle diaphragm outer ring (17)    Nozzle diaphragm inner ring (18)    Nozzles (19)    Inner peripheral slot (20)    Turbine rotor shaft (26)    Rotor blades (36)    Overhang (38)    Inner surface (38a)    Sealing fins (41)