What is DGA? Dissolved Gas Analysis.
This is just a VERY basic explanation of DGA.
Power transformers use oil as both an insulator and for cooling. Under normal conditions the oil will contain assorted gasses such as C0, C02 and Hydrogen. As the oil ages or under fault conditions the oil can, over time, break down releaseing gasses. By measuring the gasses and the speed in which they are increasing we can work out what, if any, fault is going on in the transformer. A healthy transformer will have relatively steady gas levels. If one or more gasses start to rise then we can determine what's going on inside the tank and deal with it. Different faults produce different gasses. For example, a while ago I took an oil sample from a TX, analysed it and found higher than previous levels of acetylene. This is a big red flag. Resampled a week later and risen once again. Acetylene is produced during arcing in oil so we knew it was serious. The power station took the transformer out of service. We drained off enough oil to look inside and found a connection was black. It had worked loose and was arcing. So DGA can save the life of a transformer.
How is DGA performed? Either by manual sampling and analysis or by online DGA where an analyser is bolted to the transformer and the oil continuously monitored. More about that tomorrow.
This is just a VERY basic explanation of DGA.
Power transformers use oil as both an insulator and for cooling. Under normal conditions the oil will contain assorted gasses such as C0, C02 and Hydrogen. As the oil ages or under fault conditions the oil can, over time, break down releaseing gasses. By measuring the gasses and the speed in which they are increasing we can work out what, if any, fault is going on in the transformer. A healthy transformer will have relatively steady gas levels. If one or more gasses start to rise then we can determine what's going on inside the tank and deal with it. Different faults produce different gasses. For example, a while ago I took an oil sample from a TX, analysed it and found higher than previous levels of acetylene. This is a big red flag. Resampled a week later and risen once again. Acetylene is produced during arcing in oil so we knew it was serious. The power station took the transformer out of service. We drained off enough oil to look inside and found a connection was black. It had worked loose and was arcing. So DGA can save the life of a transformer.
How is DGA performed? Either by manual sampling and analysis or by online DGA where an analyser is bolted to the transformer and the oil continuously monitored. More about that tomorrow.
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