On the use of dielectric coatings in particle-contaminated gas insulated switchgear

Electrical insulation performance of GIS/GITL systems is adversely affected by metallic particle contaminants. These particles may be free to move in the electric field, or may be fixed on the conductors, thus enhancing local electric fields. Dielectric coatings applied to the inside surface of the outer enclosure of a coaxial GIS/GITL system improve the insulation performance. Coating reduces the degree of surface roughness on conductors, thus decreasing the high local electric fields. The electric field necessary to lift a particle resting on the bottom of a GIS/GITL enclosure is much increased due to the coating. In a horizontal coaxial system with particles resting on the inside surface of the enclosure, the motion of such particles is random in nature. Particles in practical systems can exist in a wide variety of shapes and sizes, and of materials of different densities. In this paper, only aluminum wire particles of 0.27 mm diameter in a 110 mm/304 mm diameter coaxial electrode system under 50 Hz AC applied voltage are considered. In the theoretical calculation, wire particles were represented by a cylinder hemispherically terminated at both ends