This specification describes a high fire-point mineral oil based electrical insulating fluid, for use as a dielectric and cooling medium in new and existing power and distribution electrical apparatuses, such as transformers and switchgear. The material discussed here is miscible with other petroleum based insulating oils, and may not be miscible with electrical insulating liquids of non-petroleum origin. The insulating oils shall be compatible with typical material of construction of existing apparatus and will satisfactorily maintain its functional characteristic in its application. This specification applies only to new insulating material oil as received prior to any processing. Sampled specimens shall undergo appropriate tests, and shall conform correspondingly to specified physical (appearance upon visual examination, color in ASTM units, fire point, flash point, aniline point, interfacial tension, pour point, relative density, and kinematic viscosity), electrical (dielectric breakdown voltage, gassing tendency, and dissipation factor), and chemical (corrosion behavior against sulfur, inorganic chlorides and sulfates content, acid number, water content, oxidation stability, oxidation inhibitor content, and PCB content) property requirements.

1.1 This specification describes a less flammable mineral electrical insulating liquid, for use as a dielectric and cooling medium in new and existing power and distribution electrical apparatus, such as transformers and switchgear.

1.2 Less flammable insulating liquid differs from conventional mineral insulating liquid by possessing a fire-point of at least 300 °C. This property is necessary in order to comply with certain application requirements of the National Electrical Code (Article 450-23) or other agencies. The material discussed in this specification is miscible with other petroleum based insulating liquids. Mixing less flammable liquids with lower fire point hydrocarbon insulating liquids (for example, Specification D3487 mineral liquid) may result in fire points of less than 300 °C.

1.3 This specification is intended to define a less flammable electrical mineral insulating liquid that is compatible with typical material of construction of existing apparatus and will satisfactorily maintain its functional characteristic in this application. The material described in this specification may not be miscible with electrical insulating liquids of non-petroleum origin. The user should contact the manufacturer of the less flammable insulating liquid for guidance in this respect.

1.4 This specification applies only to new electrical insulating liquid as received prior to any processing. Information on in-service maintenance testing is available in appropriate guides.2 The user should contact the manufacturers of the equipment or liquid if questions of recommended characteristics or maintenance procedures arise.

1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.