The Most Correct Interpretation of Dissolved Gas Analysis

Reliability-based Dissolved Gas Analysis is a new interpretation method that identifies and assesses at-risk power transformers by correlating fault gas production with transformer failure. Unlike conventional DGA that uses a simple limits or thresholds-based approach to identify at-risk transformers without consideration of any real-world transformer failure data, Reliability-based DGA correlates real-world gassing behavior and transformer failure, to more deeply relate gassing behavior with reliability.

With a community of supporting users providing transformer reliability data, Delta-X Research has applied advanced statistics to model the reliability of power transformers as a function of fault energy indices.  The model illustrates fault energy just prior to failure as demonstrated from a statistically significant population of transformers.


Reliability-based DGA model: Probability Density Function for Failure-Related NEI


The new model provides valuable new insights:

  • Cumulative Severity (CSEV) of gassing history – this is a measure of the seriousness of a transformer’s entire gassing history. In simple terms, it indicates how fortunate the transformer is to have survived to this point.
  • Severity (SEV) of a single gassing event – this is a measure of the seriousness of a single gassing event.
  • Hazard Factor (HF) –indicates the rate, in percent per year, at which risk of failure is increasing.

Reliability-based DGA provides both: a rear-view look of how lucky the transformer has been to survive its gassing activity so far; and a forward-looking risk assessment of a transformer’s current gassing event, illustrated by how quickly a transformer is moving to the right on the Reliability-based DGA model.


And although an operator cannot know for certain if or when a particular transformer will fail, the Hazard Factor calculated for each transformer in a fleet can be used to effectively rank the transformers’ risk of continuing operations.  This information can be used to guide operations, maintenance planning and asset replacement decisions.


Reliability-based DGA is a major development in dissolved gas analysis and transformer monitoring software – and will help customers increase reliability, optimize maintenance and maximize ROI, while reducing the risks of an unforeseen catastrophic transformer failure.


Find out how a major US utility is already using Reliability-based DGA to help identify and focus on at-risk transformers so they can implement an effective strategy to maintain and replace them as needed.

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