Detailed Discussion on Dissolved Gas Analysis of Power Transformer Oil

Introduction
Transformer is one of the most important and complex component in any electrical establishment, therefore much attention is needed on maintenance of the transformers in order to have a fault free service and to maximize the efficiency and lifetime of the transformer.


Dissolved Gas Analysis (DGA) is the study of the dissolved gases in transformer oil and is the most accepted preventive and maintenance tool for the electrical power industry for over three decades. Even though DGA continues to be the most important component in assessing the condition of the transformer, but the demands imposed by the increasing loading of transformers and the aging of the transformer population require new tools and diagnostic approaches. It has been suggested that the 70% of the transformers condition is contained within the insulating oil and periodic checking of these conditions could provide us with the exact condition of the transformer.

Why DGA is important?

DGA is the most effective means of oil sampling and monitoring the condition of oil-filled electrical equipment such as transformers, etc. The analysis gives us detailed description of the types of dissolved gases in the oil, the amount, generation, relative proportion and the changes over time gives us information about, what is happening in the transformer?.

Every possible fault generates one or more gases arising from the subsequent increased degradation of adjacent oil or cellulosic insulation, hence DGA is considered to be comprehensive in responding to many faults. Moreover, since in the early stages these fault gases dissolve in the oil and can then be detected at later point in time when an oil sample is taken, DGA can detect intermittent faults. Also, because fault gases can be detected at very low levels, the DGA technique is very sensitive and extremely suitable for detecting faults at an early stage. Most guides for interpreting DGA results include, and concentrate on, schemes for diagnosing faults, usually by analyzing the relative concentrations of the various fault gases, so the technique can also be described as discerning and contributing to diagnosis as well as the detection of faults.

The main difficulty in making use of DGA results, which arises from its very good sensitivity, is that it is not easy to draw the line between normal and abnormal results, i.e. to be sure that a fault really exists. Most, but not all, interpretation schemes include a normal condition as one of the diagnostic outcomes, but have not been particularly effective in reliably identifying a normal condition.

Dissolved gases

For details please refer previous pages of the blog.