IEEE C57.147-2018 pdf free download – IEEE Guide for Acceptance and Maintenance of Natural Ester Insulating Liquid in Transformers.
1.1 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.
1.2 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.
1.3 System design
The reliable performance of natural ester liquids in an insulation system depends upon certain basic liquid characteristics that can affect overall apparatus characteristics. Such liquid characteristics are integral to equipment design for which the manufacturer should have final responsibility. The reliable operation of the equipment in service, for which the transformer operator should have final responsibility, also depends on maintaining certain basic liquid characteristics. Adherence to the recommended liquid characteristics can assist in obtaining the desired equipment characteristics. Other tests or verification of the integrity of the insulation system may be necessary. The essential properties of insulating liquids used in transformers should be maintained if the liquid is to perform its multiple roles as electrical insulation and heat transfer agent. It should have adequate dielectric strength to withstand the normal range of electric stresses imposed in service. It should have a certain combination of thermal conductivity, specific heat, and viscosity so that its ability to transfer heat is sufficient for the particular equipment. It should have a sufficiently high flash point and fire point to meet safety requirements. The natural ester liquid should not be allowed to become so deteriorated or contaminated that it adversely affects other materials in the apparatus.IEEE C57.147 pdf download.