Utilization of Repetitive Surge Oscillograph (RSO) in the detection of rotor shorted-turns in large turbine-driven generators

The use of the RSO technique for the detection of shorted-turns in the field winding of large synchronous generators with cylindrical rotors has become more widely accepted in North America in the last few years. The test procedures have been previously described in a number of publications. However, interpretation of the RSO traces haven not been well defined, and the benefits and limitations of its application are not well understood. Using some recent experience, this paper is intended to provide guidance on signal interpretation and to clarify the main advantages and limitations of the application of the RSO testing.