IEC 60034-27-4:2018

FOREWORD
INTRODUCTION
1 Scope
2 Normative references
3 Terms and definitions
4 Insulation resistance - components and influence
  factors
5 Polarization index
6 Measurement
7 Interpretation of measurement results
8 Recommended limits of insulation resistance and
  polarization index
9 Test report
Annex A (informative) - Components of the direct current
Annex B (informative) - Graphical estimation of the slope
        parameter X for temperature correction from
        measurement data
Annex C (informative) - Examples of test results of synthetic
        resin based high voltage windings
Annex D (informative) - Measurement of leakage current to
        assess interphase insulation resistance
Annex E (informative) - Other DC tests
Bibliography

IEC 60034-27-4:2018 provides recommended test procedures for the measurement of insulation resistance and polarization index of stator and rotor winding insulation of rotating electrical machines. This document recommends minimum acceptable values of insulation resistance and polarization index of winding insulation valid for fully processed low and high voltage AC and DC rotating electrical machines with a rated power of 750 W or higher.