IEC 60296 Unused Mineral Insulating Oils for Transformers and Switchgear
IEC 60296 Fluids for Electrotechnical Applications - Unused Mineral Insulating Oils for Transformers and Switchgear
4 Properties of oil
NOTE - Oil characteristics are listed in Tables 1 and 2 and in Clause 6.

4.1 Functional properties
Properties of oil that have an impact on its function as an insulating and cooling liquid.

NOTE - Functional properties include viscosity, density, pour point, water content, breakdown voltage and dielectric dissipation factor.

4.2 Refining and stability
Properties of oil that are influenced by quality and type of refining and additives.

NOTE - These can include appearance, interfacial tension, sulphur content, acidity, corrosive sulphur, 2-furfural and related compounds content and stray gassing.

4.3 Performance
Properties that are related to the long-term behaviour of oil in service and/or its reaction to high electric stress and temperature.

NOTE - Examples include oxidation stability, gassing tendency and electrostatic charging tendency (ECT).

4.4 Health, safety and environment (HSE) properties
Oil properties related to safe handling and environment protection.

NOTE - Examples can include flash point, density, PCA (polycyclic aromatics) and PCB/PCT (polychlorinated biphenyls/ terphenyls).

5 Classification, identification, general delivery requirements and sampling
5.1 Classification
5.1.1 Classes
For the purposes of this standard, mineral insulating oils are classified into two classes:
- transformer oils;
- low temperature switchgear oils.

5.1.2 Antioxidant additive (inhibitor) content
Transformer oils are classified into three groups, according to their content of antioxidant additive:
- uninhibited transformer oils: marked with U;
- trace inhibited transformer oils: marked with T;
- inhibited transformer oils: marked with I.

5.1.3 Lowest cold start energizing temperature (LCSET)
After the inhibitor marking, the LCSET shall be indicated.

Standard LCSET in this standard is -30 °C; optionally, other LCSET can be selected according to Table 1.

5.2 Requirements
General requirements of this standard are given in Table 2.

Specific requirements are defined under Clause 7.

5.3 Miscibility
Unused mineral insulating oils of the same class (5.1.1), the same group (5.1.2), same LCSET (5.1.3) and containing the same types of additives are considered to be miscible and compatible with each other (see IEC 60422).

5.4 Identification and general delivery requirements
Identification and general delivery requirements are as follows:
a) Oil is normally delivered in bulk, rail tank cars, tank containers or packed in drums or IBC (intermediate bulk containers). These shall be clean and suitable for this purpose to avoid any contamination.
b) Oil drums and sample containers shall carry at least the following markings:
- supplier's designation;
- classification (see 5.1);
- oil quantity.
c) As agreed between the supplier and purchaser each oil delivery may be accompanied by a document specifying the supplier's designation, oil classification and compliance certificate.

NOTE - This standard may be traceable to a specific batch of oil processed.

d) The supplier shall declare the generic type of all additives, and their concentrations in the cases of inhibitors and passivators.

5.5 Sampling
Sampling shall be carried out in accordance with the procedure described in IEC 60475.