A Critical Region in Dielectric Liquids Under High Electric Stress

Using several specially designed discharge chambers embodying point-point, point-plane and point-sphere electrode systems, and filled with dielectric liquid, a zone of low luminescent intensity was detected between the electrode corona and the point in the liquid at which the discharge channel originated. This dark zone is evidently the location of the mechanisms which are the critical precursors of breakdown in the liquid, and is referred to as the critical region. It is of a general ellipsoidal shape, and for the gap lengths of 3 to 7 mm employed, has major and minor axes of about 100 and 50 pm respectively.