IEEE C57.121-1998

This guide recommends tests and evaluation procedures, as well as criteria and methods of maintenance for less Flammable hydrocarbon transformer insulating fluids. Revision Standard - Inactive-Reserved. The evaluation and handling procedures for less flammable hydrocarbon transformer insulating fluids are covered. The guide's purpose is to assist the transformer operator in receiving new fluids, filling transformers, and maintaining the fluids in serviceable condition.