This guide recommends a procedure to be used to perform and document a failure analysis and the reporting and statistical analysis of reliability of power transformers and shunt reactors used on electric power systems. Purpose This document is intended to provide a methodology by which the most probable cause of any particular transformer failure may be determined by applying the scientific method to investigations; provide sufficient guidelines@ examples@ and case histories to promote uniformity in the analysis of transformer failures; encourage the establishment of routine and uniform data collection so that valuable facts are not lost or destroyed; encourage consistency of nomenclature and compatibility with similar efforts by other organizations (Examples include but not limited to CIGRE@ EEI@ IEC@ NEMA@ NERC@ and AEIC); and encourage cooperative efforts by users and manufacturers during the failure analysis.