In vapour-dominated geothermal sources a large amount of non-condensable gas is mixed with the steam and requires extraction from the condenser, generally by means of a compressor. A plant has been studied in which this compressor is directly coupled, via gearboxes, to the steam turbine shaft. When a ‘trip’ occurs (and this may often happen when considerable load variations cause a small plant to get out of synchronism), very high torque readings have been measured at the turbine–compressor coupling. This paper presents a computer simulation which has been developed for the system to explore ways of reducing these high torques.
