IEEE C57.121-1988

This guide recommends tests and evaluation procedures, as well as criteria and methods of maintenance for Less Flammable Hydrocarbon (LFH) transformer insulating fluids. These are also known as High Molecular Weight Hydrocarbon (HMWH) fluids. HMWH dielectric fluids are hereby defined as those fluids having an ASTM D92 fire point of 300 °C or greater, being primarily composed of, but not restricted to, hydrocarbons. These fluids meet the requirements of ANSI/NFPA 70-1990, National Electrical Code [1]1 Article 450-23 as a less flammable dielectric for use in indoor applications when used in properly designed and installed transformers. Ester- and silicone-based fluids are not covered by this guide. Methods of reconditioning LFH fluids are also described. It is not the intent of this guide to address retro-filling transformers with LFH fluids. Any such substitution of fluids should only be performed after consultation with the manufacturers of fluid and equipment. Where instructions given by the transformer or fluid manufacturers differ from those given in this guide, the manufacturer's instructions are to be given preference.

The purpose of this guide is to assist the transformer operator in evaluating and processing LFH fluids received in new transformers, as received from the fluid manufacturer for filling transformers, and as processed into such equipment. It also assists the operator in maintaining the fluid in serviceable condition. This guide, therefore, recommends standard tests and evaluation procedures, methods of reconditioning and reclaiming LFH fluids, and the analysis results at which these processes become necessary. It will also address the routines for restoring resistance to oxidation, where desired, by the addition of inhibitors.

New IEEE Standard - Superseded. IEEE C57.121-1988, IEEE Guide for Acceptance and Maintenance of Less Flammable Hydrocarbon Fluid in Transformers, covers the evaluation and handling procedures for less flammable hydrocarbon transformer insulating fluids. Its purpose is to assist the transformer operator in receiving new fluids, filling transformers, and maintaining the fluids in serviceable condition.