Process for producing pressurized gaseous nitrogen by cryogenic separation of air in a distillation column system comprising a high pressure column, a medium pressure column, a main condenser and a medium pressure column top condenser both in the form of condenser-evaporators, whereby - the total feed air is compressed in a main air compressor to a first pressure which is higher than the operating pressure at the top of the high pressure column, - the compressed air stream is purified, - the compressed and purified feed air stream is introduced into a main heat exchanger under a first pressure and cooled in the main heat exchanger, - at least a portion of the cooled air is introduced into the distillation column system, - a first gaseous nitrogen stream from the top the high pressure column is condensed in the liquefaction space of the main condenser, - bottom liquid (10, 13) of the high pressure column is sent to an intermediate section of the medium pressure column, - bottom liquid (16, 19, 21, 25) of the medium pressure column is sent to the evaporation space of the medium pressure column top condenser, - gaseous nitrogen from the top the medium pressure column is condensed in the liquefaction space of the medium pressure column top condenser, - liquid nitrogen from the medium pressure column or from the liquefaction space of the medium pressure column top condenser is pressurized to a pressure which is at least equal to the high pressure column pressure, - at least a portion of the pressurized liquid nitrogen is introduced into the high pressure column, - a second gaseous nitrogen stream from the top the high pressure column is warmed in the main heat exchanger, - the warmed second gaseous nitrogen stream is recovered as pressurized gaseous nitrogen product, - the compressed and purified feed air stream is split into a turbine stream and a non-turbine stream, - the non-turbine stream is further cooled in the main heat exchanger and finally introduced into the distillation column system and - the turbine stream is work-expanded in an expansion machine, characterised in that - the compressed and purified feed air stream is split at an intermediate temperature of the main heat exchanger into a turbine stream and a non-turbine stream, - the turbine stream is work-expanded in the expansion machine from the first pressure to a second pressure and - the work-expanded turbine stream is warmed in the main heat exchanger. - the total feed air is compressed in a main air compressor to a first pressure which is higher than the operating pressure at the top of the high pressure column, - the compressed air stream is purified, - the compressed and purified feed air stream is introduced into a main heat exchanger under a first pressure and cooled in the main heat exchanger, - at least a portion of the cooled air is introduced into the distillation column system, - a first gaseous nitrogen stream from the top the high pressure column is condensed in the liquefaction space of the main condenser, - bottom liquid (10, 13) of the high pressure column is sent to an intermediate section of the medium pressure column, - bottom liquid (16, 19, 21, 25) of the medium pressure column is sent to the evaporation space of the medium pressure column top condenser, - gaseous nitrogen from the top the medium pressure column is condensed in the liquefaction space of the medium pressure column top condenser, - liquid nitrogen from the medium pressure column or from the liquefaction space of the medium pressure column top condenser is pressurized to a pressure which is at least equal to the high pressure column pressure, - at least a portion of the pressurized liquid nitrogen is introduced into the high pressure column, - a second gaseous nitrogen stream from the top the high pressure column is warmed in the main heat exchanger, - the warmed second gaseous nitrogen stream is recovered as pressurized gaseous nitrogen product, - the compressed and purified feed air stream is split into a turbine stream and a non-turbine stream, - the non-turbine stream is further cooled in the main heat exchanger and finally introduced into the distillation column system and - the turbine stream is work-expanded in an expansion machine, characterised in that - the compressed and purified feed air stream is split at an intermediate temperature of the main heat exchanger into a turbine stream and a non-turbine stream, - the turbine stream is work-expanded in the expansion machine from the first pressure to a second pressure and - the work-expanded turbine stream is warmed in the main heat exchanger.