Influence of Electrical Discharges in Oil and Combinations of Oil and Paper

Charge or RIV techniques for corona (partial discharge)have been used in factory tests of high-voltage oil-filled equipment.Such tests have also been used in the field. More recently, measurementsof evolved gas have been made as well.In the laboratory, the effect of corona in oil has been determinedlargely by measuring gas evolution using the Pirelli test, in whichdischarges take place in oil vapor. A new technique¿the floating-electrodecell¿has been developed to obtain controlled discharges in oil. Tomonitor the discharges, histograms of the number of pulses versusthe pulse magnitude are obtained periodically. Provision is made todetermine the amount and nature of evolved gas with both the"floating-electrode" and Pirelli cells. When paper or pressboard as wellas oil is used, the development of x wax has been observed with scanningelectron microscopy (SEM).Results are reported for conventional transforner oil and dodecylbenzeneand a naphthenic white oil from which all aromatic componentshave been removed.