IEEE Recommended Practice for Testing Insulation Resistance of Rotating Machinery

This document describes the recommended procedure for measuring insulation resis-tance of armature and field windings in rotating machines rated 1 hp, 750 W or greater. It applies to synchronous machines, induction machines, dc machines, and synchronous condensers. Con-tained within this document is the general theory of insulation resistance (IR) and polarization index (P.I.), as well as factors affecting the results, test procedures, methods of interpretation, test limita-tions, and recommended minimum values.