A field assessment of PD and EMI methodology applied to large utility generators

Results and assessment are provided from a nearly 10 year study of the application of a variety of diagnostic methods applied to the condition monitoring of generator stator insulation. The methods studied included various forms of Partial Discharge (PD) techniques and Electromagnetic Interference (EMI) in the frequency domain. The condition of a number of operating machines was tracked by the various techniques and, in most cases, the findings compared with the actual condition determined by subsequent inspection after the rotors had been removed. This has permitted the effectiveness of the various methods to be gauged and allowed an appraisal of the attendant best practices and pitfalls.