Introduction
Mineral oil performs two important
functions in transformers. It cools the
transformer and provides electrical
insulation, as well. Th erefore any
deterioration in the oil can lead to
premature failure of the equipment.
When the mineral oil is subjected
to high thermal and electrical stresses,
it decomposes and, as a result, gases are
generated.
Diff erent types of faults will generate
diff erent gases, and the chemical analysis
of these gases, performed through a
procedure called DGA (Dissolved Gas
Analysis), will provide useful information
about the condition of the oil, and
help to identify the type of fault in the
transformer.
DGA requires the removal of an oil
sample from the transformer, and this can
be done without de-energising it. Th e oil
sample is analysed in the laboratory using
gas chromatography.