IEEE C57.139-2010

This guide discusses and recommends methods of testing and evaluating dissolved gases in mineral based transformer oils found in Load Tap Changers (LTCs). General types of LTC mechanisms, breathing configurations, and electrical design will be included for evaluation criteria in determining when mechanical damage or failure has occurred. Dissolved Gas Analysis (DGA) of the oil in the LTC is required. This guide will not be manufacturer specific, rather category specific.