Control structure for preventing overspeed of steam turbine

The invention discloses a control structure for preventing overspeed of a steam turbine, which is characterized in that a single-end fulcrum bolt fixed cantilever semi-arc bracket for radially fixing a speed measurement primary element on a speed measurement gear of the steam turbine is changed into a double-end fulcrum bolt fixed semi-arc bracket, so that the measurement gap of the speed measurement primary element is increased by more than 0.08 mm; a newly-added speed measurement gear is arranged on a front box inspection hole cover plate of the steam turbine, and the newly-added speed measurement gear conducts axial measurement through a speed measurement primary element. Meanwhile, the material formula of the speed measuring gear, the double-end fulcrum bolt fixing semi-arc support and the speed measuring primary element is limited. A set of axial measurement protection assembly is additionally arranged on the basis of an original radial measurement protection primary element, the radial device primary el