Failure evaluation of the electrical insulation for high voltage stator windings machines and root cause analysis through visual inspection of dissected coils

This paper will discuss insulation dissection for different insulation systems and different failure mechanisms. The preparation process and inspection tools necessary for dissection will be presented. The key principles for performing insulation dissection on different insulation systems will be presented along with case histories and experiences with previous dissections. Examples of common failure modes for coils are also presented with discussion and photos. This paper should be useful for all those that need to perform visual evaluations of dissected coils samples in high voltage stator windings - both for manufacturers and for owners of electrical equipment who are evaluating test reports and test results.