Dissolved gas analysis: Early fault indication and trend analysis

A review of the two approaches of dissolved gas analysis – detailed fault diagnosis and trend analysis with fault indication – is given.

byJürgen Schübel, Alexander Alber (Pollok)


A review of the two approaches of dissolved gas analysis – detailed fault diagnosis and trend analysis with fault indication – is given. The advantages and disadvantages of the two approaches under the aspects of measurement uncertainty, economic efficiency and integration into a condition assessment strategy are outlined. A concept of signal processing enhancing the capabilities of trend analysis and early fault indication is described. It is concluded that trend analysis with early fault indication is sufficient for most cases of an integrated condition monitoring system.

Evaluation of electrical equipment is an essential but complex process for any asset operator to ensure both operational safety and economic efficiency. As described in detail in CIGRÉ TB 761 [1], the condition of the individual components of the transformer system must be assessed with regard to the following aspects:

  • replacement
  • safety
  • maintenance
  • refurbishment / upgrading and
  • oil treatment

This information is condensed, usually in the form of condition indices, and presented for the entire fleet of equipment for decision-making. Over the last 30 years, a very useful method for condition assessment has been the analysis of dissolved gases in insulating oil. This has been used to evaluate the condition of the active part of a transformer, the tap changer, and the bushings.

To read the article, subscribe and choose the option which suits you best. We offer both free and paid options, and the registration takes only a minute.
Subscribe to Transformers Magazine