Facts and Artifacts from IEEE 1310-2012

The ability of IEEE 1310–2012 test method to simulate the possible insulation aging mechanisms of a generator working under repetitive start-stops was studied. Real stator bars, previously aged under service by about 10,000 start-stops were characterized in the laboratory and then submitted to a limited number of thermal cycles according to IEEE 1310–2012 for comparison. The results suggest that a small number of lab thermal cycles is sufficient to create defects that did not exist in the bars aged solely under operation conditions. It is also found that the lab cycles tend to propagate the very few existing defects towards areas where such features were not present in the original condition, such as the inner portion of the stator core. Therefore, depending on how exactly the test results generated by IEEE 1310–2012 are interpreted, there is a risk that the final assessment of any set of tested bars/coils is partially influenced by such test artifacts.