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A recent EPRI survey on practices associated with the use of AC and DC hipot testing for maintenance purposes on rotating machines indicated that some in the utility industry were concerned that the hipot, or repeated applications thereof, may cause ageing of the stator insulation. Consequently, a study of this issue was performed using a failed hydraulic generator stator winding. AC and DC hipots were systematically applied to several bar groups followed by breakdown testing using AC potential. The results of the test program including their implications will be discussed in the proposed contribution.