IEEE C57.93-2019

The recommendations presented in this guide apply to the inspection, installation, and maintenance of liquid-immersed power transformers rated 501 kVA and above with secondary voltages of 1000 V and above. This guide covers the entire range of power transformers, including extra high-voltage (EHV) transformers. This guide does not cover special transformers such as furnace transformers, rectifier transformers, etc. Distinctions are made as required for various MVA ratings, voltage ratings, and types of liquid insulation. The manufacturer's instruction manual should be the primary reference for transformer inspection, installation, and maintenance, especially while the equipment is under warranty. This guide should be used in conjunction to supplement the manufacturer's instruction manual, or as a substitute when it is not available. Clause 4 contains information for use with transformers rated below 10 MVA with high voltages less than 69 kV. Clause 5 applies to transformers rated 10 MVA and above with high voltages of 69 kV and above, including EHV transformers. For transformers with high voltages that are less than 69 kV and larger than or equal to 10 MVA, users should follow Clause 5.