Air cooled turbogenerators superseding hydrogen cooling domain

Air cooled turbogenerators have been keeping pace with the evolution in gas turbine unit rating. The latest developments are described which have led to a unit rating of 500 MVA, so far exclusively the domain of hydrogen-cooled turbogenerators. The advantages of both technologies are compared and listed in a cost comparison, resulting in a considerable cost benefit for air-cooling. It is shown that there is still potential for further increase in unit rating of air-cooled turbogenerators.