What is the acidity test for transformer oil?

The acidity test for transformer oil is used to determine the level of acidity in the oil, which can indicate the overall condition and aging of the oil. The test is typically performed using the ASTM D974 or IEC 62021-1 standard methods.

The acidity test measures the total acid number (TAN) or the neutralization number of the transformer oil. The TAN is the amount of potassium hydroxide (KOH) in milligrams required to neutralize the acidic constituents in one gram of the oil sample.

The test procedure involves the following steps:

1. Weigh the oil sample and dissolve it in a mixture of toluene and isopropyl alcohol.
2. Titrate the solution with a standardized solution of potassium hydroxide in isopropyl alcohol until the endpoint is reached, indicated by a color change.
3. Calculate the TAN by determining the volume of the KOH solution required to neutralize the acids in the oil sample.

The TAN value is typically expressed in milligrams of KOH per gram of oil (mg KOH/g). A higher TAN value indicates increased acidity in the oil, transformer oil tester which can be caused by oxidation, contamination, or the breakdown of additive packages. The acceptable TAN limit for transformer oil is often specified by the manufacturer or industry standards, typically ranging from 0.1 to 0.5 mg KOH/g.

Monitoring the acidity of transformer oil is important for maintaining the integrity of the insulation system and ensuring the reliable operation of the transformer. Increased acidity can lead to the formation of sludge, varnish, and other deposits, which can impair the dielectric properties of the oil and accelerate the aging of the transformer.