Gas Formation in Transient Cavities Undergoing PD Pulse Burst Discharges in Transformer Oils

Partial discharges in mineral oils take place in the form of pulse bursts within minute microcavities, which are formed at high-electric field charge injection sites. The lifetime of these transient microcavities is determined by the interval between their creation and their ultimate collapse due to dynamic instability. The vapor pressure within these microcavities has been estimated to be as high as 10 MPa and lately there has been considerable speculation as to the nature and type of gases within these microcavities. Currently, carried out experiments indicate that these gases consist principally of hydrogen, CH₄ (methane), and C₂H₆ (ethane) with smaller traces of other lower molecular weight hydrocarbons.