The characteristics of an insulation system can be evaluated in terms of dielectric strength,insulation resistance, dielectric loss, etc. This reportis applicable to a method of measuring dielectric loss properties of the insulationsystem of the slot portions of new coils or bars for rotating electrical machines having rated voltageUNof 5 kV and above. The test is applicable to form wound coils or bars in which the insulation is cured before the winding is inserted in the stator. For tests on post-impregnated machines, see Appendix A.