scope:

This guide recommends tests and evaluation procedures, as well as criteria and methods of maintenance, for natural ester-based (e.g., vegetable oil) insulating liquids. Methods of reconditioning, field applications, and diagnostics of natural ester-based insulating liquids are also described.

Purpose

This guide recommends standard tests and evaluation procedures of natural ester insulating liquids for application in distribution and power transformers and other liquid-filled electrical equipment. Natural ester insulating liquids are also being applied in retrofilling existing liquid-filled equipment. This guide provides recommendations for new and retrofill field applications including: field testing of equipment filled with natural ester insulating liquids, methods of reconditioning and reclaiming natural ester insulating liquids, and the analysis results at which reprocessing or replacement of the insulating liquid is necessary.