Patent ID: 9631521
Date: 2017-04-25
CPC Classifications: F01K,F02C,F05D,Y02E

Claim:
1. A method for operating a combined-cycle power plant, the plant comprising at least a gas turbine and at least a steam power generation system, the plant activating at least one electric generator connectable to an electric grid, wherein the gas turbine comprises a compressor and wherein the steam power generation system comprises a steam turbine, a heat recovery steam generator and a bypass line, wherein the gas turbine de-loads to a condition, where the compressor operates at its nominal speed, the method comprising: de-loading the steam turbine in coordination with the de-loading of the gas turbine to a condition where the total load exported by the plant to the grid is substantially equal to zero, wherein the gas turbine and the steam power generation system are connected; and with the de-loading of the steam turbine, opening the bypass line to reduce the steam pressure to a fixed value relative to the nominal pressure, wherein the de-loading of the steam turbine and the reduction of the steam pressure by acting on the bypass are such that the minimum steam turbine load and the minimum steam pressure are reached prior to the reduction of the steam temperature caused by the reduction of the gas turbine exhaust temperature during the de-loading of the gas turbine.