Revision Standard - Inactive-Withdrawn. The purpose of this IEEE guide is to present information necessary to permit an effective evaluation of the insulation systems of large alternating-current rotating electrical machines. Such an evaluation can serve as a guide to the degree of maintenance or replacement which might be deemed necessary, and also offer some indication of the future service reliability of the equipment under consideration. The guide is intended to apply in general to large alternating-current rotating electrical machines rated at 10000 kVA or more, and operating at voltages of 6000 V and above.