The thermal system of double-reheat unit will change a lot after using echelon cycle(EC)

so the reheat pressure optimization rules of conventional thermal cycle are no longer suitable. By using the self-developed thermal calculation software in Shanghai Turbine Plant(STP)

thermodynamic calculations of various pressure configurations(main steam pressure

primary reheat pressure

secondary reheat pressure) were performed in typical double-reheat EC system

within actual engineering application range. The results show that

after using the EC

increasing the first reheat pressure and reducing the second reheat pressure will reduce the unit heat rate and improve the cycle efficiency. Under different boundary conditions

the recommended values of first reheat pressure and second reheat pressure can be concluded. This research could provide reference for practical engineering design.