Comparative analysis of stator iron core damage using nominal and reduced flux

Good quality of insulation between stator iron laminations is one of the major preconditions for proper operation and top performance of generating units. Local hot spots and overheating as a result of insufficient insulation between stator iron laminations, beside the other problems, will cause premature aging of high voltage insulation in stator bars. This type of test can be done with generator in regular operation or during an outage. The most reliable results are achieved during an outage, when the rotor is removed. Two methods for testing stator lamination insulation were compared on an 125 MVA turbogenerator. The purpose was to compare the results of the tests using methods with full and reduced flux