Design and Fabrication of A 72 kV Bushing for the TESLA Breaker

Present day gas insulated switchgear (GIS) technology commonly uses SF
6
as its insulation and arc extinguishing mechanism, due to favorable dielectric and arc quenching properties. However, SF
6
is a known greenhouse gas, with a global warming potential (GWP) of 23,500, compared to a GWP of 1 for CO
2
. As a result, significant efforts are being made to find suitable replacements. Previous research has shown promising dielectric properties for supercritical fluid (SCF) CO
2
and the mixtures, which may serve as a replacement to SF
6
. Rather than relying on fluorinated gases with high electronegativity, the high-pressure SCF CO
2
achieves the superior dielectric properties through its high density and thus short mean free path. SCF CO
2
is contained at much higher pressures (approximately 10 MPa, compared to less than 1 MPa for a SF
6
-insulated circuit breaker), resulting in significant challenges in designing the bushing of the SCF CO
2
insulated circuit breaker. In this paper, we presented the design and fabrication process of a 72kV class bushing for SCF CO
2
circuit breakers, named TESLA – "Tough and Ecological Supercritical Line Breaker for AC". Finite element simulations have been conducted to examine the electric field distribution, mechanical stress and thermal performance of the proposed bushing geometries. In addition, a custom-designed reusable mold has been developed to facilitate the bushing’s fabrication process that is promising for scaling up. The process of vacuum-assisted high-pressure resin transfer molding is adopted for the fabrication of the bushing.