Do hipot tests damage rotating machine insulation?

Over-potential or hipot tests have been applied for many decades to rotating machine windings to assure that the electrical insulation in windings is fit for service. Hipot tests are used universally as acceptance tests for new windings. However, a rotating machine maintenance engineer often faces plant managers reluctant to approve hipot tests. The managers ask, `Do hipot tests damage rotating machine insulation?' This paper tries to answer this specific question. The authors discuss experience of industry experts from an extensive literature review carried out under an EPRI project. Some quasi-theoretical arguments are used to quantify possible damage to the insulation system by a hipot test. Results from recent hipot test experiments on a large number of stator coils performed under another EPRI project are analyzed. There emerges a compelling conclusion that hipot tests do not appear to cause any significant damage to the insulation system of a rotating machine stator in a serviceable condition.