Transformer oil is a liquid medium with good insulation performance, which is a mineral oil obtained from natural petroleum through distillation and refining. The selection of transformer oil is generally based on the altitude of the location where the transformer is installed, and transformer oil has good insulation strength. Immersing insulation materials in oil not only improves insulation strength, but also protects them from moisture erosion. The specific heat of transformer oil is also very high and is commonly used as a coolant.
Common testing items and methods for transformer oil include:
1. Acid number: ASTM D664
2. Testing the dielectric breakdown voltage of insulation oil: ASTM D877
3. Liquid power factor/dispersion factor: ASTM D924-08
4. Interface tension: ASTM D971
5. Specific resistance: ASTM D1169
6. Corrosive sulfur: ASTM D1275
7. Visual examination: ASTM D1524
8. Karl Fischer water determination: ASTM D1533
9. Electrical breakdown voltage of filtered and degassed liquids: ASTM D1816
10. Gas evolution tendency under electric field and ionization: ASTM D2300
11. Oxidation stability: ASTM D2440
12. Test Method for Gas Chromatography for Detection of Dissolved Gases in Electrical Insulation Oils (Gas Chromatography): ASTM D3612
13. Antioxidant testing: ASTM D4768 or D2668
14. Particle count: ASTM D6786
The above testing items can confirm the cleanliness of the new transformer oil on one hand, and can also serve as benchmark data. Regular testing should be conducted after the transformer oil is put into use, and the test data can be compared with the data of the new transformer oil to facilitate problem detection.
