Laboratory services for transformer oils: What you need to consider

Regular sampling and testing of transformer insulating oil is a valuable procedure in a preventive maintenance program. To find the best laboratory service provider for your needs, request quotes from different laboratories. But what should you look for? Make sure that the laboratory has the necessary certifications and that the price for the laboratory's services is reasonable. But what else is important? Find out more in this blog article.

Why laboratory services are crucial for transformer oils

Laboratory analysis of insulating oils makes it possible to detect signs of aging, contamination, or harmful gases at an early stage. Having transformer oils analyzed is therefore one of the essential inspection and maintenance measures in connection with transformers.

Transformers use oil to insulate, stop discharge and corona discharge, and at the same time dissipate the heat from the transformer. Another important property of insulating oil is that it prevents the oxidation of cellulose paper insulation. Depending on the condition of the transformer oil, the service life of the transformer can be extended. Having transformer oils analyzed is therefore one of the essential inspection and maintenance measures in connection with transformers.

Standards and test groups for laboratory services for transformer oils

Important standards for transformer oil analysis:

• DIN EN IEC 60296 VDE 0370-1:2022-12 This standard specifies the requirements and test methods for new and reprocessed mineral insulating oils used in transformers and switchgear.
• DIN EN IEC 60599 VDE 0370-7:2023-08 This standard provides guidelines for interpreting the analysis of dissolved and free gases (Dissolved Gas Analysis, DGA) in mineral oil-filled electrical equipment. 

• IEC 60422, This standard is used for monitoring and maintaining mineral oil-based insulating oils in electrical equipment and

• IEC 61203 This standard deals with the maintenance of transformer esters in equipment.

The condition of the insulating fluid in transformers influences its performance and makes regular inspection necessary.

A distinction is made between three test groups:

Test group 1: Routine tests

They represent the minimum scope of transformer oil monitoring and regularly examine the progressive ageing of the oil. As a rule, chemical, physical and electrical properties of the transformer oil are examined in this test group.

Test group 2: Supplementary tests 

This is where further information about the quality of the transformer oil is determined. For example, if anomalies such as a changed breakdown voltage or acidity were detected during a routine test. 

Test group 3: Investigative tests

After malfunction of the transformers or abnormalities with regard to temperature behaviour or noise level, conclusions on faults can be drawn with extended laboratory tests without having to shut down or disassemble the transformers immediately. Examples of these laboratory tests are the gas-in-oil analysis (DGA) or the furan analysis.

Connection between laboratory services and long-term transformer operation 

• In addition to regular routine tests, long-term monitoring of transformer operation also plays a crucial role. Inspection and maintenance measures related to transformers can be optimally planned through targeted trend analyses of insulating oil data. Continuous insulating oil analysis in the laboratory helps to identify potential risks at an early stage and extend the service life of your equipment.  

• EOS^® Transformer Database: Optimally documenting insulating oil samples

Transformer oil analysis: How to choose the right laboratory service provider

Important goals for all analyses are to ensure the quality of the analysis results and thus to guarantee the operational safety of the transformers and avoid operational disruptions. This is not possible without the experience of certified companies and laboratories.

1. Ensure that the supplier performs the analyses in accordance with the relevant standards, such as DIN EN IEC 60296, DIN EN 60422, and DIN EN IEC 60599. 
2. A complete analysis package should include physical-chemical tests (e.g., breakdown voltage, water content, neutralization number) and dielectric tests (e.g., loss factor).
3. Choose a provider with proven experience in the analysis of transformer oils and in-depth knowledge in the field of electrical insulating fluids. 
4. A good service provider not only provides measurement results, but also an understandable interpretation of the data and clear recommendations for the maintenance and overhaul of your transformers. 
5. Look for short analysis times, transparent communication, and the option of taking samples on site or using additional services if necessary.  

Or are you one step ahead and already know that a change of transformer oil is due? Then we recommend this article:

• Valuable tips when you have to replace the oil in your transformer

Conclusion: Laboratory services for transformer oils support reliable and long-lasting transformer operation

Regular laboratory services help to ensure the reliable operation of your transformers. By combining different test groups – from routine tests to investigative analyses – you receive reliable data for the optimal planning of your maintenance measures. In addition, detailed laboratory analyses such as gas-in-oil analysis or trend evaluations help to detect aging processes at an early stage and avoid costly failures. 

In order to be able to make well-founded decisions on inspection and maintenance measures to be carried out in connection with transformers, we at Electrical Oil Services are happy to make our many years of experience available to you. Take advantage of this information - it's worth it!

Good to know!

If you have a sample from another service provider but no recommendation for action, you are welcome to contact EOS^® . We will evaluate this analysis for you and make well-founded recommendations directly from practice.

Read more in this article:

• EOS^® Interview: 5 tips for sustainable transformer oil management.
• Information page on the laboratory services offered by Electrical Oil Services 

If you have any questions, we look forward to receiving your request: