I. Introduction
Steam Turbine generator is a generator driven by steam turbine. The superheated steam produced by boiler expands into steam turbine to make work, which makes the blades rotate and drives the generator to generate electricity. As an important equipment of power system, the safe and stable operation of large steam turbine generator is very important with the development of the generators, electromagnetic and thermal load increase. This could cause local overheating, which could lead to insulation deterioration, core slackness and sets vibration in generators. All of these could cause abnormal downtime, or threat to-power system security. This brings new opportunities and challenges for the design and operation of turbo-generators [1]–[2].