A method to estimate the insulation condition of high voltage stator windings

The authors present a step-by-step approach to determining the insulation condition of high-voltage stator windings. The approach takes advantage of background information, a wide variety of online and offline tests, and visual inspections that experts often use. Therefore, this procedure can be used as a guide for nonexpert maintenance engineers. The approach is primarily concerned with aging processes that take months or years to result in failure. As one progresses through the procedure, the required information becomes increasingly more difficult to obtain. The accuracy of the prediction of insulation condition is determined by the care and thoroughness of the examiner and the expertise and experience of the maintenance engineer. Unfortunately, although the insulation condition can be assessed, reliable prediction of the remaining life of a stator winding is presently not possible. The authors outline this procedure for stator insulation systems rated 4.0 kV or above