Gerhard Salge

Effect of Different Dielectric Coatings in Divergent Fields

Dielectric coatings are widely used in electric power equipment to increase the breakdown voltage and to reduce the insulation distance.

Surface discharge along solid dielectrics in atmospheric air

This paper intends to contribute to the understanding of the propagation of surface discharges along an insulating surface under impulse voltage in atmospheric air. A concentric cylinder system has been used that allows to generate surface discharges propagating up to length of 0.6 m. A PE tube is mounted on the cylindrical conductor as an insulating layer. The HV is applied to the inner conductor. The discharge is initiated by a needle that is placed directly on the insulating surface. Impulse voltages and discharge currents are measured. The experimentally measured data serve as a basis for a simplified model to describe the surface discharge.

On the discharge phenomena in the 10%SF/sub 6/-90%N/sub 2/ gas mixture under fast oscillating impulse conditions

The discharge phenomena were investigated in a background uniform field (plate - needle to plate arrangement) varying the needle protrusion (length=3 to 5 mm; tip radius= 200 /spl mu/m), the gas pressure (300 and 500 kPa) as well as the gas mixture composition (100%SF/sub 6/, 10%SF/sub 6/-90%N/sub 2/, 100%N/sub 2/). A positive polarity, low damped, fast oscillating (1.2 MHz), high voltage impulse (up to 450 kV peak) was applied to stress the test gap. The V-t characteristics in the mixture (breakdown voltage vs. time to breakdown) is reported and then compared to both the same curve of pure gases and similar measures available in literature. The discharge mechanism in the mixture is described and compared to the pure gases through voltage (capacitive sensor), discharge current (Rogowski coil), emitted light (photo-multiplier tube) and pictures from an image converter operating in both streak and frame modes.