IEEE 286-2024

This recommended practice applies to stator coils or bars (half coils) of electric machinery operating at any voltage level. It usually applies to machines with a voltage rating of 6 kV and higher. Individual stator coils outside a core (uninstalled), individual stator coils installed in a core, and completely wound stators are covered in this recommended practice. The tests apply to all coil insulation systems: pre-impregnated coils, post impregnated coils (global vacuum pressure impregnation), and fully-loaded (resin-rich) taped coils. This recommended practice is not applicable to non-impregnated individual coils. The coil insulation under test is the major groundwall insulation that is external to the conductor structure. Only that part of the strand and turn insulation that is dielectrically in series with the groundwall insulation enters into the measurements. When testing individual coils and utilizing guard electrodes, only that part of the groundwall insulation under the low voltage electrode (outer electrode) enters into the measurement.