433-1974 - IEEE Recommended Practice for Insulation Testing of Large AC Rotating Machinery with High Voltage at Very Low Frequency
Description: This document provides a uniform method of VLF testing in order to obtain consistent results, accumulate meaningful experience, and lead to establishment of standards of test level. The purposes of this recommended practice are: (1) to define terms that have a specific meaning in VLF testing; (2) to describe VLF-test equipment and wave shape; (3) to provide a uniform procedure for testing the armature insulation of large AC machines with VLF voltage; (4) to recommend constants for relating VLF tests to power-frequency and direct-voltage tests to obtain equally effective test levels. The document applies to large AC rotating machines rated at 10000 kVA or greater and rated 6000 V or higher. It covers acceptance testing of new equipment in the factory or onsite after erection. This recommended practice also covers routine maintenance testing of machines that have been in service.