Water Content Determination in Insulating Oil with ASTM D6304-20

The water content of transformer oil is determined using Karl Fischer titration. ASTM D6304-20 method was used for extracting the water from the sample. The method uses an automated InMotion KF Oven, which does not allow the sample to come in contact with the titration cell.

In this application, a coulometric Karl Fischer titrator connected to an automated Karl Fischer oven was used to first perform a temperature scan of the different transformer oil samples in order to identify their ideal gas-phase extraction temperature, and then subsequently to measure their water content. 

Transformer oil or insulating oil is quite stable at high temperatures and has excellent electrical insulating properties.

A limit of 30 to 35 ppm of water in transformer oil is generally referenced, as water affects the dielectric properties of the insulation and the aging rate of the insulating materials. Low water content in transformer oil is, therefore, a very important parameter for safe operation, transformer reliability, and transformer longevity. In extreme cases, transformers can fail because of excessive water in the insulating oil.

As air contains oxygen, which could react with organic samples, an inert gas (nitrogen) was used for the analysis of the transformer oil samples.

Karl Fischer titration coupled with an oven sample changer is a well-established and accurate technique for the determination of water in transformer oils.

This Application Note Includes

• An introduction to the method
• Sample preparation and procedures
• Solutions and chemicals
• Chemistry
• Instruments and accessories
• Results and remarks

Method files (.lmt and .xml) are also included for direct import and implementation of the instrument.

Download our free application note and benefit from our experience in determining the water content in insulating oil.