Investigation of bearing current in a gas turbine generator due to static excitation system

Shaft voltage and bearing current have become a serious problem in large power plants, the investigation of shaft voltage and bearing current in rotating machines have generated much attention in the field of electrical engineering. In this paper we present an investigation of bearing current phenomena through the use of a simulation model of excitation winding and shaft-bearing system for a 96.3 MW gas turbine generator at a power plant. Simulation results obtained shows that bearing current is produced at the exciter end and turbine end of the generator due to the static excitation voltage. A solution to mitigate the bearing current by using grounding brushes is proposed.