Cooling system for a gas turbine, compressor guide blade and method for cooling a gas turbine

The invention proposes a cooling system ( 42 ) for a gas turbine ( 1 ), with an annular duct extending axially in the compressor ( 5 ). In the annular duct, a ring ( 15 ) of compressor guide blades ( 14, 28, 33 ) and a ring ( 17 ) of moving blades ( 16 ) fastened to a rotor disk ( 19 ) of the rotor ( 3 ) are provided, with at least one cooling-air extraction point ( 34 ), arranged on the rotor ( 3 ), for diverting a cooling-air stream into a cooling-duct system arranged in the rotor ( 3 ), and with a turbine unit ( 8 ), in which, when the gas turbine ( 1 ) is in operation, components subjected to thermal stress by a hot gas ( 20 ) can be cooled by the divertible cooling-air stream, and also with a feed line ( 46 ) for feeding a liquid ( 45 ) into the cooling-air stream. In order to make it possible to feed a liquid into the cooling-air stream simply and cost-effectively, the invention proposes that the feed line ( 46 ) extend with a subduct ( 44 ) through at least one of the compressor guide blades ( 28, 33 ) of the ring ( 15 ), and the orifice ( 48, 49 ) for the outlet of the liquid ( 45 ) be connected in the region of the cooling-air extraction point ( 34 ).