LW8-40.5 Outdoor High Voltage AC Vacuum Circuit Breaker for Power Transmission and Distribution System Control

We've been supplying these since the mid-2000s, and they pretty much set the standerd for 40.5kV outdoor protection. That SF6 system operates at 0.50MPa at 20°C, but what it does is maintain arc extinction without the pressure swings you'd expect with tempearture changes, so you don't end up with nuisance trips. Most buyers go with the 31.5kA short-circuit breaking current for substation duties.

Basically, the CT14 spring mechanism gives you about 3000 operations before you need to think about major mechanicla servicing, which is better than some motor-driven setups we've seen form competitors. It weighs roughly 1400kg with the mechanism included, so you'll need a decent foundation for outdoor pad-mounting. Check the insulating gas presure rating on the COA, because we usually ship at 0.52MPa or so to account for gas loss during transit, but confirm temperature correction factor on site. The arc chamber uses SF6 as the extinguishing medium, and that's what handles the 185kV lightning impulse or 95kV power frequency insulation levels.

Actually, we've found that the 1600A rated current works well for distribution feeders, but if you're switching capacitor banks, the 2000A version handles inrush much more reliably. It's not designed for high-frequency switching environments like steel mills, though, where you'd want a dedicated generator breaker.

21 full-rate interruptions at 40kV without maintenance is what the lab got during type testing. The loss of SF6 will cause it to fail open — there's no backup. Insulation level numbers aside, the arcing contacts are silver-tungsten, which resists pitting better than reagent-grade copper alternatives.