Guidance on and recommended practices for the installation and maintenance of liquid-immersed power transformers rated 501 kVA and above with secondary voltages of 1000 V and above are provided in this guide. The entire range of power transformers, including extra high-voltage (EHV) transformers are covered in this guide. Special transformers, such as furnace transformers, rectifier transformers, etc., are not covered in this guide. Distinctions are made, as required, for various MVA ratings, voltage ratings, and types of liquid insulation.