scope:

This guide deals with the techniques for sampling free gases from gas-collecting relays and for sampling oil from oil-filled equipment such as power and instrument transformers, reactors, bushings, oil-filled cables and oil-filled tank-type capacitors. Three methods of sampling free gases and three methods of sampling oil are described; the choice between the methods often depends on the apparatus available and on the quantity of oil needed for analysis. Before analysing the gases dissolved in oil, they must first be extracted from the oil. Two basic methods are described, one using extraction by vacuum and the other by stripping (displacing) the dissolved gases by bubbling the carrier gas through the oil sample. The gases are analysed quantitatively after extraction by gas chromatography; a method of analysis is described. Free gases from gas-collecting relays are analysed without preliminary treatment.