Analysis of Dielectric Breakdown of Hot SF₆Gas in a Gas Circuit Breaker

Abstract

-This paper presents the analysis of the dielectric characteristics of a hot SF 6 gas in a gas circuit breaker. Hot gas flow is analyzed using the FVFLIC method considering the moving boundary, material properties of real SF 6 gas, and arc plasma. In the arc model, the re-absorption of the emitted radiation is approximated with the boundary source layer where the re-absorbed radiation energy is input as an energy source term in the energy conservation equation. The breakdown criterion of a hot gas is predicted using the critical electric field as a function of temperature and pressure. To validate the simulation method, breakdown voltage for a 145kV 40kA circuit breaker was measured for various conditions. Consistent results between the simulation and experiment were confirmed.

Prediction of Insulation Capability for Ground Fault to Consider Asymmetry in SF6 Circuit Breaker

“…The radiation loss can be calculated by using empirical arc model as function of both arc temperature and arc radius. In this model, the emitted energy from arc is 90% of the total arc energy and 80% of the emitted energy is reabsorbed in the arc edge [1]. This simplified model can save the computational time significantly.…”

“…The physical phenomena in a gas CB, which are the radiative heat transfer, turbulence effects, electromagnetic field, metal vapor, nozzle ablation, and so on, are mainly focused on the arc physics [1]. However, the 3-D analysis has difficulty simulating these arc phenomena because of the significant computational time compared to a 2-D analysis.…”

“…Thus, the insulation capability for a ground fault must be considered in the dielectric design of a high-voltage CB [1], [2]. A 3-D analysis should be performed to estimate the dielectric characteristic after current interruption if the CB has an asymmetric region such as a shield, a tank, a hot-gas exhaust, or the connection parts of a bushing, as shown in Fig.…”

Improvement of dielectric performance of solid/gas composite insulation with YSZ/ZTA coatings

“…Apart from the outstanding electrical and thermal properties, the boiling point of SF 6 is relatively low in comparison with other electronegative gases. Moreover, SF 6 is not ozone depleting and toxic 3 . Nevertheless, the Global Warming Potential (GWP) of SF 6 gas is very high.…”

Analysis of SLF Interruption Performance of Self-Blast Circuit Breaker by Means of CFD Calculation

“…The ablated nozzle material by (1) was treated as a mass source term in the mass conservation equation. The arc was treated as an energy source term and the flow equations were solved by the Finite Volume Fluid in Cell method as a computational fluid dynamics (CFD) scheme [2]. The calculated and measured pressure rise in the HC was compared to validate the CFD computation, as shown in Fig.…”