Forensic analysis of multiple medium voltage 3MW self-excited generators following field testing

Multiple medium voltage 3MW self-excited generators failed at startup following field testing. Initially it was reported that only insulation resistance and polarization index testing was performed. However, forensic evidence showed tunneling in the insulation system that could only come from high energy testing. In this paper we will discuss the steps in performing forensic investigations of electric machinery failure using Root-Cause-Failure-Analysis (RCFA) practices commonly applied in reliability engineering and the tests performed to provide evidence of the causes and hypotheses. The ability to determine the depth of an analysis based upon information provided will also be discussed.