Theoretical analysis of particle-initiated corona activities in hybrid gas-insulated transmission lines

This paper theoretically addresses the factors affecting the partial discharge activities due to metallic particles in hybrid gas-insulated transmission lines (HGITL) using the charge simulation method. There are two main reasons for using flexible HGITL. They are: (1) to overcome the technical problems and the huge cost associated with the on-site welding of large number of coaxial cylinders; and (2) to improve the utilization of the internal insulation system. The results are interpreted in terms of the basic principles of the streamer criterion in compressed gases, and also their trends are compared with those for other experimental works. The results reveal that HGITL have superior mitigation of the particle-initiated corona activities over the normal GITL, where the bundled HGITL have less improvement. The corona inception voltage decreases with the increase in the wire length, the surface charge density on the conductor insulation/spacers and the close proximity to charged or uncharged spacers, and with the decrease in pressure. On contrary, the number of occurrence of streamers and the integration of the effective ionization coefficient have opposite trends. Ribbed spacers are less sensitive to particle length and show a considerable improvement in the insulation reliability, especially when the rib becomes closer to the conductor insulation.