Compressed gas-insulated switchgear (GIS), normally using SF6 gas as an insulating medium, is now widely established all over the world and represents the leading technique in the construction of high-voltage switching electric power stations in urban areas. It offers distinct advantages to power supply utilities. Due to low space requirements, GIS is adaptable to all types of buildings. GIS also provides environmental protection by shielding humans and animals in its vicinity from emanating electromagnetic fields. It is itself protected from environmental hazard, such as lightning and pollution. The advantages of GIS are compromised by the phenomenon of contaminating conducting particles which are inevitably present inside the enclosure. Metallic particles are known to drastically impair the insulation integrity of compressed gas insulated sub-station (GIS) equipment. Such particles present a special hazard when present in close proximity of support insulators. Most GIS equipment manufacturers employ a variety of techniques and devices, such as electrostatic particle traps, to control metallic particle contamination. Further research is vitally needed to detect the presence of these particles and mitigate their effects, and thus minimize unplanned outages. Reliability of electric supply is important and its economic impact is recognized by all users and suppliers. The efficiency and effectiveness of dielectric coatings on high voltage electrodes in gaseous insulation systems have been studied over the past several years. Data indicate that the dielectric coatings are beneficial and improve the breakdown voltage in gaseous insulation systems. Moreover, results of some preliminary studies show that such coatings reduce the adverse impact of metallic particles in GIS equipment, thus increasing the reliability of the system. The objective of this project is to use modeling and computational methods to investigate the effectiveness of conductor coating in mitigating adverse effec ts of particle contamination in a horizontal section of a coaxial GIS system. The probability of insulation failure in the presence of metallic particles can be calculated by combining the particle position density function with the breakdown voltage profile of a given GIS system. The numerical model also will be used to study the effect of parameters such as particle size, gap dimensions, and voltage waveshape on particle trapping. Theoretical results will be verified experimentally. The principal investigator, has studied the dynamics of metallic particle movement in GIS equipment. His research has included the use of a comprehensive computational program to analyze the effect of various parameters on the particle movement in coaxial electrode systems under 60 Hz voltage. International collaboration between Kansas State University, USA, Chalmers University of Technology, Sweden, and the University of British Columbia, Canada, will be accomplished in this project. At Kansas State University the principal investigator will elaborate the particle dynamics model in a coaxial electrode system with one electrode coated and predict improvement in the breakdown voltage profile and the breakdown probability of the compressed gas insulated transmission line (GITL) system in general. Experimental work will be needed to verify the results of the modeling. Experimental data will be obtained at the high voltage laboratory at Chalmers University of Technology, under the direction of Professor Stanislaw Gubariski. The proposed collaboration will enable verification of modeling outputs by conducting appropriate experiments. The impact of the proposed study will be in the broad area of energy infrastructure in urban USA by making compressed GIS/GITL technology more efficient, environmentally friendly, and easier to operate and maintain. The proposed project should be of interest to both utilities and manufacturers.
