Why Perform DGA Tests Before and After a Temperature Rise Test for Transformers

When it comes to ensuring the reliability and longevity of transformers, certain tests are essential. One such critical test is the temperature rise test, which helps determine the heat dissipation and insulation performance of a transformer. However, to fully assess the transformer's condition, it's important to perform dissolved gas analysis (DGA) tests both before and after the temperature rise test. This article will delve into the importance of these DGA tests and highlight why they are so crucial in the context of transformer maintenance and diagnostics.

Understanding the Temperature Rise Test

The temperature rise test, as described in IEEE and IEC standards, is a standard procedure that manufacturers use to determine the thermal performance of transformers during factory testing. The test is critical because it provides information on the transformer's ability to dissipate heat effectively under various loading conditions. Typically, the manufacturer will specify the heat rise limit, which should be indicated on the nameplate or within the supplied documents. Adherence to these standards is important to ensure that the transformer operates safely and efficiently during its lifetime.

The Key Role of Dissolved Gas Analysis (DGA)

Dissolved gas analysis (DGA) is a diagnostic tool used to analyze gases dissolved in the transformer's oil. It helps in detecting potential issues such as overheating, arcing, and partial discharges, which can lead to insulation degradation and eventually, transformer failure. This test is particularly useful for early detection of faults before they become severe.

Why Perform DGA Before the Temperature Rise Test?

Baseline Measurement and Trends: Performing a DGA test before the temperature rise test establishes a baseline for the transformer’s current state. This allows for the comparison of future test results to identify any emerging trends or new issues. By establishing a baseline, the test results can indicate whether the transformer is operating within expected parameters.

Preventative Maintenance: Early detection of potential issues can help in implementing preventative maintenance measures, thus extending the transformer's operational lifespan and reducing the risk of unexpected failures.

Why Perform DGA After the Temperature Rise Test?

Post-Test Evaluation: After the temperature rise test, performing a DGA test is crucial for several reasons. It helps in evaluating the transformer’s condition under the stress of the test, identifying any new gases that may have been released due to thermal stress, and ensuring that no significant damage has occurred during the test.

Acceptable Level of Gases: The C57.130-2015 standard provides guidelines for acceptable levels of gases generated in conventional mineral oil-filled transformers and reactors during factory temperature rise tests. By performing a DGA test after the test, it is possible to determine whether the levels of gases produced are within acceptable limits. Any deviations may indicate underlying issues that need to be addressed.

Guidance for Application of DGA Techniques

IEE Standard C57.130-2015: The IEE standard C57.130-2015 is a guide that offers detailed procedures for applying DGA techniques to oil-immersed transformers and reactors. This standard contains several key components, including recommended procedures for sampling, recommended actions based on the interpretation of results, and a bibliography of related literature. By following these guidelines, professionals can ensure that they are applying DGA effectively and obtaining reliable results.

Evaluation Procedures: The document provides evaluation procedures that help in analyzing the gases produced during the temperature rise test. These procedures are designed to help operators interpret the results accurately and make informed decisions regarding the transformer's maintenance and operational status.

Guidelines for Acceptable Levels of Gases: Additionally, the document includes guidelines for acceptable levels of gases. These guidelines help operators ensure that the transformer is operating within safe parameters and can help in identifying potential issues early on.

Conclusion

In conclusion, performing DGA tests both before and after the temperature rise test is essential for the proper maintenance and monitoring of transformers. It provides valuable insights into the transformer's performance and condition, helps in identifying potential issues early, and ensures that the transformer operates safely and efficiently. Adhering to standards like IEEE C57.130-2015 and following the recommended procedures can help professionals achieve the best results from their DGA tests, ultimately contributing to the longevity and reliability of the transformer.

Keywords: Dissolved Gas Analysis, Transformer Temperature Rise Test, IEEE Standard