Particle behavior and trap design for ±320 kV gas-insulated power transmission line (GIL)

Abstract

The movement of metal particles in the electric field of the DC gas-insulated transmission line (GIL) may cause local electric field distortion on the surface of the insulator, which seriously affects the operation stability of GIL. In this paper, based on a ±320 kV GIL platform, the movement characteristics of metal particles (aluminum blocks, aluminum wires, aluminum balls) inside the GIL are studied. The suppression effect of particle activity for particle trapping and surface coating are experimentally studied in DC electric field. The relationship between particle trap porosity and particle suppression effect are discussed and verified with experiments. The research results show that under negative voltage, the minimum take-off voltage of metal particles in ±320 kV GIL is -190 kV, which is far lower than the steady-state operating voltage of GIL. Once the spherical and blocky particles take off, they will continue to reciprocate rapidly between the conductors. When the block particles are close to the insulator, they might be attracted and adsorbed on the surface of the insulator. Metal wires after taking off tends to show “firefly" movement near the high-voltage conductor. The coating has a significant effect on increasing the take-off electric field of metal particles. It is verified that the traditional AC GIL particle trap is not effective in inhibiting particles in DC voltage. The suppression of the DC GIL particle is positively related to the porosity of the particle trap to a certain extent. The conclusions of this paper can be reference for the development of future stable and reliable DC gas-insulated equipment.

Significantly suppressing metal particle-induced surface charge accumulation of spacers in DC gas-insulated power transmission lines

“…The gas ionization near the particle tips introduces hetero-polar surface charge, and the trapped charge in turn polarizes homo-polar charges on the surface nearby, showing a concentrically distributed bipolar pattern [21]. Based on our recent test on an actual ±320 kV DC gasinsulated power transmission line (GIL), linear particles with length ranging from 5 mm to 15 mm have already started to 'jump' at +280 kV, which corresponds to an electric field of less than 1.5 kV mm −1 , much less than the average designed electric field inside the chamber [22].…”