METHOD FOR OPERATING A GAS TURBINE AND METHOD FOR RETROFITTING A GAS TURBINE

The method for retrofitting a gas turbine (1) comprises providing a supply (25) of a fuel being hydrogen or a mixture containing hydrogen for a first combustion area (8) and for a second combustion area (13) downstream of the first combustion area (8), providing a supply of water for the second combustion area (13) if not present, providing a controller arranged for regulating the amount of water supplied to the second combustion area (13) based on residual oxygen content in the flue gas or a value indicative thereof.