Investigation of the Gassing Properties of Dielectric Liquids

The gassing properties of some dielectric liquids in the presence of different gases (H2, CO, CO2, N2, O2, CH4, and H2O vapor) have been investigated by means of the experimental apparatus described in IEC 628 specification which measures the oil tendency to emit or absorb gases when it is sub jected to an ionizing electric field. Such tests have been carried out at different temperatures and for different durations. At the end of each test the volume variation of the gas phase has been measured and its composition has been analyzed. Such analyses provided a relevant contribution to the interpretation of the different test results. Further investigation using mass spectroscopy has been started in order to clarify the nature of the products which are found in the oil phase after the test completion; although such a research is still in a preliminary stage, some very stimulating results have already been obtained.