Recommendations are made to aid in the selection of metric units, so as to promote uniformity in the use of metric units and to limit the number of different metric units that will be used in electrical and electronics science and technology. The recommendations can cover units for space and time, periodic and related phenomena, mechanics, heat, electricity and magnetism, light and related electromagnetic radiations, and acoustics. This document does not cover how metric units are to be used nor does it offer guidance concerning correct metric practice.

This recommended practice presents uniform methods for testing insulation with direct voltages higher than 5000 V. It applies to large ac rotating machines rated at 10000 kVA or greater and rated at 6000 V or higher. It covers acceptance testing of new equipment in the factory or in the field after erection, and routine maintenance testing of machines that have been in service.

The purpose of this recommended practice is: 1) To provide uniform procedures for performing high direct voltage acceptance tests and routine maintenance tests on the main ground insulation of windings of large ac machines; 2) To provide uniform procedures for analyzing the variations in measured current so that any possible relationship of the components of these variations to the condition of the insulation can be more effectively studied; 3) To define terms which have a specific meaning as used in this document