ASTM D6786-15

5.1 Particles in insulating oil can have a detrimental effect on the dielectric properties of the fluid, depending on the size, concentration, and nature of the particles. The source of these particles can be external contaminants, oil degradation by-products, or internal materials such as metals, carbon, or cellulose fibers.

5.2 Particle counts provide a general degree of contamination level and may be useful in assessing the condition of specific types of electrical equipment. Particle counts can also be used to determine filtering effectiveness when processing oil.

5.3 If more specific knowledge of the nature of the particles is needed, other tests such as metals analysis or fiber identification and counting must be performed.

1.1 This test method covers the determination of particle concentration and particle size distribution in mineral insulating oil. It is suitable for testing oils having a viscosity of 6 to 20 mm²/s at 40°C. The test method is specific to liquid automatic particle analyzers that use the light extinction principle.

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

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.