It is important to have reliable field techniques for assessing the insulation quaility of large rotating machine stators in order to reveal any defects which could lead to a winding failure in service. Toward this objective, a variety of nondestructive measurements of internal discharges (corona) have been applied and compared on an old mica-asphalt insulated generator. Extensive field measurements of RIV corona and integrated corona charge per cycle (related to power factor tip-up) are reported and interpreted, and verified by tests on coils returned to the laboratory.
No takes yet. Share an insight, caveat, or question.
Harrold et al. (1973) studied this question.