This International Standard specifies oil-sampling procedures, analysis requirements and
procedures, and recommends sensitivity, repeatability and accuracy criteria for the application
of dissolved gas analysis (DGA) to factory testing of new power transformers, reactors and
instrument transformers filled with mineral insulating oil when DGA testing has been specified.
The most effective and useful application of DGA techniques to factory testing is during the
performance of long-term tests, typically temperature-rise (heat run) and overloading tests on
power transformers and reactors, also impulse tests on instrument transformers. DGA may
also be valuable for over-excitation tests run over an extended period of time.
Experience with DGA results, before and after short-time dielectric tests, indicates that DGA
is normally less sensitive than electrical and acoustic methods for detecting partial
discharges. However, DGA will indicate when these partial discharges become harmful to the
insulation and may be detected by inspection [2].