Elimination of particle effects in SF/sub 6/ insulated transmission systems. Second quarterly report, January 1--March 31, 1979

Abstract

The purpose of this program is to develop methods and equipment to eliminate the adverse effect of particle contamination in SF/sub 6/-insulated transmission systems, CGIT, so that the excellent dielectric properties of SF/sub 6/ can be fully exploited. The program consists of three major parts: theoretical and experimental evaluation of concepts; optimization and verification studies in CGIT systems; reliability analysis, documentation of designs and economic analysis. The mode of particle trapping with an elevated particle trap is shown to be dependent on particle size. Tests with dc voltages show that particles can escape from the trap area. Closing the end openings of the trap can prevent this, but interfere with the trapping of small particles. The use on an adhesive material contained particles in the trap and allowed trapping of small particles. Three candidate adhesive materials were selected for further extensive aging studies. Tests on the adhesive materials showed that wire particles lying flat on the surface can not be pulled off the adhesive at fields of 145 kV/cm which is some 2 x 10/sup 3/ larger than the field normally inside the particle trap. Traps mounted around the insulators can prevent particles from initiating flashover of the insulator. Insulators more » without traps can cause large particles to be trapped under the insulator. The concept of using conical barriers mounted around the solid insulators to prevent particles from contaminating the insulator looks promising if used together with an elevated particle trap. A method of usinga tunable oscillating diaphragm was tested for evaluating the static electric adhesion properties of candidate insulating materials. Preliminary tests indicate that the charge required for adhesion of a particle is not a simple function of the dielectric constant of the materials. « less