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As shown in Figure 1, the positive impulse breakdown voltage of SF6 in non-uniform fields can be lower than the positive direct voltage breakdown over a pressure region. Also, in this pressure region, the positive direct voltage required for breakdown goes through a maximum. It is believed that these two characteristics (impulse ratio <1; a maximum in the direct voltage vs. pressure curve) are...
Several investigators (1)(2)(3) have attempted to correlate the breakdown strength of liquid hydrocarbons with their molecular structure. These attempts have been based on a mechanism in which the field accelerated electrons lose energy by excitation of the vibrational modes of the molecule.
A corona discharge can be detected electrically with a resistor or inductor in series with the test gap. The corona current pulse causes an electric oscillation in an inductance or a single sharp voltage pulse across the resistor. The disadvantage of this means of detection is in the interference from a signal which may be created across the inductance or resistance by corona or contact sparking outside...
Saxe and Meek (1) have studied the initiation mechanism of long sparks in positive point to plane gaps. They investigated the optical and electrical characteristics of the corona discharges and leader strokes preceding the impulse breakdown in air at atmospheric pressure. Results show that initially a corona discharge forms around the point; the corona gives rise to a 0.4 micro-second pulse of light...
The negative corona extinction voltage or breakdown extinction voltage has been determined in air and SF6 at atmospheric pressure for the sphere to plane configuration. Spheres or points ranging in size from a 0.250″ radius sphere to a 0.0024″ radius phonograph needle were used with gaps of the order of 1–10 millimeters. The negative corona extinction voltage was also determined for the coaxial cylinder...
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