What is DGA?
DGA or Dissolved Gas Analysis is a diagnostic test used to detect and determine defects in transformers. It involves studying the gases dissolved or present in transformer oils. DGA is accepted worldwide and has become an industry standard in the prevention of transformer failure.
Through Dissolved Gas Analysis, engineers are able to get reliable results and make informed decisions regarding the overall health or status of a particular transformer. Dissolved Gas Analysis can be done in a variety of ways, but there are only three methods that adhere to the accepted standards. All three methods involve an oil sample for the testing. The DGA procedure starts with extracting the gases from the oil sample. After which, the gases go through a gas chromatograph to be separated. After separation, the gases will be quantified and measured.
What makes DGA stand out is the method of gas extraction from the oil. This is also the part where it is prone to make errors. Traditionally, extraction involved some sort of high vacuum power to suck the gas from the oil. The gas is then collected and measured by using mercury pistons. Another method involves stripping the gases from the oil. This is called direct injection technique. Today, a new method called “headspace method” is being used by engineers mainly because it eliminates errors through automation.
The reliability of DGA will depend so much on the sample itself. Though getting oil samples from a transformer may be an easy task, one must make sure that “stagnant” oil is not present. The presence of this extra oil may be due to un-flushed drain valves and could mean sedimentation at the bottom of the transformer. Another important thing to improve DGA reliability is to use sampling containers that are rinsed very well. Whatever method or technique is used, one must follow proper procedures and adhere to known standards to get reliable results.