scope:

This document describes the recommended procedure for the measurement of insulation resistance of windings of rotating machines rated 1 hp, 1 kW or greater.

It applies to synchronous machines, induction machines, direct-current machines, and synchronous converters.

It applies to armature windings and Þeld windings.

It does not apply to fractional-horsepower machines.

This document describes insulation resistance characteristics of rotating-machine windings, the manner in which these characteristics may serve to indicate the condition of the winding, and the testing procedure for obtaining insulation resistance values. It gives the recommended minimum value of insulation resistance of alternating-current and directcurrent rotating-machine windings. The Appendix gives maintenance information relative to dry-out procedure.

Other IEEE publications which include information on insulation resistance measurement are listed in Section 10.

Purpose

The purpose of this publication is to:

1) Describe and deÞne insulation resistance as applied to the winding of a rotating machine

2) Review the factors which affect or change insulation resistance characteristics and recommend uniform test conditions

3) Outline and recommend uniform methods for measuring insulation resistance together with precautions for avoiding erroneous results

4) Provide a basis for interpreting insulation resistance test results to estimate the suitability of the winding for service or for overpotential test.

5) Present equations, based on machine ratings, for the calculation of recommended minimum insulation resistance values for various types of rotating machines.