scope:

This standard specifies oil-sampling procedures, analysis requirements and procedures and recommends sensitivity and precision criteria for the application of dissolved gas analysis (DGA) to factory testing of power transformers, reactors and instrument transformers when DGA testing has been specified. DGA is a technique for detecting certain types of faults in oil-filled electrical equipment which may not be detected by conventional methods. The most effective and useful application of DGA techniques to factory testing is during the performance of long-term tests, typically temperature-rise and overloading tests on power transformers and reactors, also chopped lightning-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 and accurate than electrical methods for detecting dielectric failures. However, DGA may sometimes be a valuable source of relevant information of abnormal equipment behaviour.