The purpose of this recommended practice is to describe the power-factor tip-up of coil insulation and to establish preferred procedures for its measurement. This recommended practice applies to stator coils of rotating machinery operating at 6600 V or higher. the coil Insulation under consideration is principally the major ground-wall insulation which is external to the conductor structure. Only that part of the strand and turn insulation which dielectrically in series with the ground-wall insulation enters into the measurements.