Optical signatures of the breakdown processes of insulating oil

Photo-emission during the breakdown processes of an insulating oil is recorded and analyzed. A standard oil tester is used to energize the gap at a constant rate of rise of the applied ac voltage of 50 Hz. Standard spherical electrodes of a radius of 25 mm and a spacing of 1.75 mm are used. A laser beam is employed to adjust the inlet iris of a photo-multiplier telescope to the center point of the gap. The photo-multiplier output is monitored by a fast oscilloscope. Very interesting and informative oscillograms, optical signatures, characterizing the breakdown processes are obtained and studied. Obtained breakdown-processes optical-signatures are very distinct in nature and are used to identify the different phases of breakdown. Presented experimental results prove very useful, through theoretical discussion, in understanding the breakdown mechanizms.