Optimization of the Steam Turbine Protection System as Part of an Electrohydraulic Control System

In traditional hydrodynamic automatic control systems (ACSs) of power steam turbines (STs), the protection scheme (PS) of the turbine unit is used according to the rotation frequency “1 of 2.” In modern electrohydraulic ACS (EhACS), a “2 of 3” PS or an “ n – 1 of n ” PS with a large number of channels is used, enabling the implementation of channel-by-channel testing of the PS and identifying the failure of one of the channels without stopping the ST. In EhACS, the PS is implemented in an electrohydraulic device-a protection unit (PU). Valve PU is preferable over spool PU in terms of cost and complexity of production. In valve PU, in case of the failure of one of the channels during an emergency stop, the residual pressure remains in the protection line the fewer the valves (and, accordingly, channels) in the PU. In the case of ST of the Ural Turbo Engine Plant, the residual pressure of the three-channel PU was unacceptably high (because of the characteristics of the automatic lock of the stop valve [ALSV]). During the reconstruction of the ST ACS of the Ural Turbo Engine Plant, five-channel PUs were used. ALSV reconstruction is thus proposed, which allows the use of three-channel PU on the ST of the Ural Turbo Engine Plant. This leads to an increase in the reliability of the PS operation by reducing the number of channels (and valves) of protection from five to three without increasing the cost of reconstruction of the ACS as a whole.