Method of starting a steam turbine

Abstract

The present invention has the technical effect of reducing the start-up time associated with starting a steam turbine. Embodiments of the present invention provide a new methodology for reducing the steam-to-metal temperature mismatch present during the start-up of a steam turbine. Essentially, embodiments of the invention may raise the pressure of the steam upstream of an admission valve associated with a High Pressure (HP) section of a steam turbine. The initial high pressure of the steam may reduce the enthalpy of steam, reducing temperature of the steam admitted to the HP section.

1 . A method of starting a powerplant machine, the method comprising:
 providing a steam turbine configured for converting steam to a mechanical torque; wherein the steam turbine comprises an HP section; and   increasing a pressure of steam upstream of an admission valve to a pressure matching range, wherein the admission valve is located upstream of the HP section;   wherein the step of increasing the pressure of the steam decreases a temperature of the steam prior to admission into the HP section.   
     
     
         2 . The method of  claim 1  further comprising the step of initiating a start-up of the steam turbine if a start-up permissive is satisfied. 
     
     
         3 . The method of claim further comprising the step of opening the admission valve to allow the steam to enter the HP section. 
     
     
         4 . The method of  claim 2  further comprising the step of determining whether a rotor stress is within an acceptable range. 
     
     
         5 . The method of  claim 4  further comprising the step of maintaining a current load on the steam turbine until the rotor stress is within the acceptable range. 
     
     
         6 . The method of  claim 5  further comprising the step of decreasing the pressure of the steam upstream of the admission valve. 
     
     
         7 . The method of  claim 6  further comprising the step of increasing a temperature of the steam in an HP bowl region of the HP section. 
     
     
         8 . The method of  claim 5  further comprising the step of increasing a temperature of the steam in an HP bowl region of the HP section. 
     
     
         9 . The method of  claim 8  further comprising the step of decreasing the pressure of the steam upstream of the admission valve. 
     
     
         10 . A method of starting a powerplant comprising a steam turbine, the method comprising:
 providing a steam turbine configured for converting steam to a mechanical torque; wherein the steam turbine comprises an HP section and a bypass system;   determining whether a cold start of the steam turbine is requested;   increasing a pressure the steam upstream of an admission valve to a pressure matching range, wherein the admission valve is located upstream of the HP section;   determining whether the steam upstream of the admission valve is within the pressure matching range;   initiating a start-up of the steam turbine if a start-up permissive is satisfied; and   modulating the admission valve such that allow the steam flows into the HP section;   wherein the step of increasing the pressure of the steam decreases a temperature of the steam before steams flows into the HP section.   
     
     
         11 . The method of  claim 10 , wherein the step of increasing the pressure of the steam upstream of the admission valve to a pressure matching range, further comprises the step of modulating a bypass valve of the bypass system. 
     
     
         12 . The method of  claim 11  further comprising the step of determining whether a rotor stress is within an acceptable range. 
     
     
         13 . The method of  claim 12  further comprising the step of adjusting a loading rate of the steam turbine until the rotor stress is within the acceptable range. 
     
     
         14 . The method of  claim 13  further comprising the step of modulating the bypass valve to decrease the pressure of the steam upstream of the admission valve. 
     
     
         15 . The method of  claim 14  further comprising the step of increasing a temperature of the steam in an HP bowl region of the HP section. 
     
     
         16 . The method of  claim 13  further comprising the step of increasing a temperature of the steam in an HP bowl region of the HP section. 
     
     
         17 . The method of  claim 16  further comprising the step of modulating the bypass valve to decrease the pressure of the steam upstream of the admission valve. 
     
     
         18 . A system configured for starting a steam turbine, the system comprising:
 a steam turbine configured for converting steam to a mechanical torque;   wherein the steam turbine comprises an HP section; and   a control system configured for starting the steam turbine, wherein the control system performs the steps of:
 determining whether a cold start of the steam turbine is requested; 
 increasing a pressure the steam upstream of an admission valve to a pressure matching range, before the steam flows into the HP section, wherein an admission valve is located upstream of the HP section; 
 determining whether the steam upstream of the admission valve is within the pressure matching range; 
 initiating a start-up of the steam turbine if a start-up permissive is satisfied; and 
 opening the admission valve to allow the steam to flow into the HP section; 
   wherein the step of increasing the pressure of the steam decreases a temperature of the steam prior to admission into the HP section.   
     
     
         19 . The system of  claim 18 , wherein the control system performs the step of modulating a bypass valve of the bypass system to increase the pressure of the steam upstream of the admission valve. 
     
     
         20 . The system of  claim 19 , wherein the control system further performs the steps of:
 modulating the bypass valve to decrease the pressure of the steam upstream of the admission valve in order to increase a temperature of the steam in an HP bowl region of the HP section.