Design of Large Superconducting Turbine Generators for Electric Utility Application

This report represents the results of a detailed conceptual design study of 300 and 1200 MVA turbine generators utilizing superconducting field windings. Design concepts utilized for the rotor involve a NbTi superconductor, a double-shield system, a flexible-disc thermal contraction concept, a convection- dominated helium circuit and an automatic helium level control. The armature designs are based on a new spiral winding concept which is applied at low-voltage and at high-voltage (grid level). Designs are reported that cover a range of reactances. The critical fault clearing time for the lower reactance superconducting generators are appreciably longer than for conventional machines. Increased efficiency of the superconducting machines by about 0.5% plus elimination of the unit transformers with the high-voltage armature yields a life cycle savings for a utility that is equivalent to the original price of the generator.