The content of dissolved decay products in insulating oils is made up of a variety of compounds, such as peroxides, aldehydes, ketones, and organic acids. Each of them is partially adsorbed on the large surface of paper insulation leading to the premature aging of power transformers. The relative assessment of byproduct formation, therefore, can be used as an indicator of the aging of the mineral oil.

1.1 This test method characterizes by spectrophotometry the relative level of dissolved decay products in mineral insulating oils of petroleum origin. While new oil is almost transparent to a monochromatic beam of light in the visible spectrum, the increasing concentration of dissolved decay products shift the absorbance curve to longer wavelengths.

1.2 This test method is applicable to compare the extent of dissolved decay products for oils in service. It can assess the effectiveness of used or stored oil purification during the reclamation process, as well.

1.3 The values stated in SI units are to be regarded as standard. The values stated in parentheses are provided for information only.

1.4 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 to determine the applicability of regulatory limitations prior to use.