Gas turbine with compressor casing protected against cooling and Method to operate a gas turbine

The gas turbine comprises a turbine and a compressor with a compressor casing (14), whereby the compressor for the cooling of the turbine has a tapping line(16) for the bleed of compressed or partially compressed air. The tapping line has a shut-off device, especially a valve (19), and a cavity (17) which lies in front of the shut-off device in the direction of flow of the bleed air. Independent claims are also included for the following: (A) a method for the running of a gas turbine in which the valve is closed or partially closed when the turbine runs down; and (B) a compressor with a tapping line for turbine cooling.