The determination of failure mechanisms of insulation in rotating equipment by photomicrographic techniques

Organic polymeric insulation failures can occur in two main directions: One is a break in film continuity which may be caused by embrittlement due to thermal aging, hydrolysis, oxidation, electrolysis, and manufacturing defects; the other failure mechanism can be due to the change in resistivity, which can also be brought about by the chemical changes listed under embrittlement. The field of organic polymeric semiconductors illustrates this latter point of resistivity. Here, the emphasis is on the deliberate production of organic semiconductors. In the insulation field one strives to avoid the conductive state. Embrittlement, the first mechanism of failure, reduces to the point of lack of continuity of the organic insulation film. This type of failure can be illustrated by photomicrographic techniques used by metallurgists and resinographers. The technique is not new, but its application to embrittlement failures of insulation is new.