Optimal Design and Synergism Arrangement Methodology of Convex-Shaped Traps for Ultra High Voltage AC GIS/GIL Applications

AC gas insulated switchgear and transmission lines faces critical insulation failure challenges caused by metal particles inside, and the probability of insulation failure caused by metal particles under UHV increases. However, the particle traps in practical engineering, the key devices available to inhibit the movement of particles, lack the ability to proactively capture particles. Firstly, this paper analyzes the mechanism of active particle capture by convex-shaped trap based on the dynamic model of metal particles in GIS/GIL. By analyzing the force of particles and the axial electric field distribution of the convex-shaped trap, this paper considers that the axial electric field distribution near the convex-shaped traps is an important factor leading to the active trapping of metal particles. The external voltage is applied to the starting voltage. Considering the applied voltage is AC voltage, the initial time should be set. Due to the electrostatic induction, the metal particles are negatively charged, and the metal particles on both sides of the trap move towards the trap direction. At the same time, the maximum moving height of the trapped particles under AC voltage is 2～8 cm, so the particles in the trap cannot escape from the trap. Based on the force analysis of particles, it can not only analyze the active capture mechanism of the convex-shaped trap, but also provide a theoretical basis for the subsequent establishment of the capture range calculation model of the convex-shaped trap. On this basis, this paper realizes the performance test and optimization design of the convex-shaped trap. According to the charged motion and collision dynamics characteristics of metal particles, the model for calculating the capture probability of the convex-shaped trap is established, and the structural parameters of the convex-shaped trap should be optimized considering the capture ability of trap. The results illustrate when the diameter of trap is 60 cm and the depth of trap is 30 cm in the UHV GIS/GIL of Sutong GIL Comprehensive Pipe Corridor, the particle suppression effect of the convex-shaped trap is optimal. Further, the area near the convex-shaped trap with capture rate over 90% is defined as the effective capture range considering the randomness of particle collision reflection angle, and the effective capture range of the convex-shaped trap reaches 32 cm. In this paper, a general optimization design method for convex-shaped traps is proposed, which is also applicable to the optimization of other voltage levels for convex-shaped traps. Finally, by analyzing the axial electric field distribution of the grid trap and the convex-shaped trap, it is shown that the grid trap can enhance the effective capture range of the convex-shaped trap. To improve the particle suppression effect near the insulator, a synergism arrangement methodology of the grid trap and the convex-shaped trap near the convex surface of basin insulator is proposed. The grid trap can effectively suppress the metal particles below the insulator. Since the grid trap can increase the capture range of the convex-shaped trap, the convex-shaped trap can be arranged far from the insulator. The optimal arrangement is determined by optimizing the synergism arrangement of two traps. Length of the grid trap arranged near the insulator cannot be less than 40 cm, and the effective capture range of the convex-shaped trap matched with it reaches up to 65 cm. The protection range of the trap combination for insulators can reach up to 225 cm. Based on the theoretical analysis, the trap combination can not only effectively protect the basin insulator, but also improve the insulation level of the three-pillar insulator. In this paper, the theoretical analysis about the active capture mechanism of the convex-shaped traps, the design scheme of the convex-shaped traps for UHV GIS/GIL and the synergism arrangement methodology of the grid and convex-shaped traps are proposed. This methodology provides a reliable technical mean for capturing the metal particles in UHV GIS / GIL. © 2023 Chinese Machine Press. All rights reserved.