VCB Vs LBS
VCB Vs LBS
(OP)
What is the difference of a Vacuum Circuit Breaker and a Load Break Switch in terms of its usage?
When was the last time you drove down the highway without seeing a commercial truck hauling goods?
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RE: VCB Vs LBS
"An 'expert' is someone who has made every possible mistake in a very narrow field of study." -- Edward Teller
RE: VCB Vs LBS
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If it is broken, fix it. If it isn't broken, I'll soon fix that.
RE: VCB Vs LBS
RE: VCB Vs LBS
But there is an argument to be made for safety as well. A vacuum bottle, while very good at interrupting current, is considered by many people to not be suitable for isolation of a circuit after a fault has occurred. After a fault, small amounts of conductive material can deposit on the inside of the vacuum bottle and track measurable potential across the very small gap that exists. If someone sees that the VCB is open, they may mistakenly believe that they are isolated from the line source when in fact the leakage may be substantial, and lethal. A Load break Switch, with all of it's faults, is at least a very large air gap when it comes to circuit isolation.
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RE: VCB Vs LBS
Absolutely....We use VCB's all of the time, but always include a visible means of disconnect ahead of the unit for safety.
Alan
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RE: VCB Vs LBS
RE: VCB Vs LBS
LBS can kill the load current within its rating and may close on to a fault within its withstand rating.
VCB can kill the fault current within its interrupting rating.
Be careful don't be confused by the kA rating of a LBS, it is just a pass through withstand.
RE: VCB Vs LBS
I had never thought about that until I saw video of a witness test at KEMA for a 5kV controller I worked on that used an LBS as the disconnect / isolator ahead of a vacuum contactor. The final test was of the withstand capability and they replaced the fuses with bus bars, then bolted them together to ground. They then create the fault but they weren't supposed to try to open the switch. The test technician didn't read that and did it anyway (from a distance with a motorized operator they had attached for the test); the fireworks display was spectacular.
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RE: VCB Vs LBS
RE: VCB Vs LBS
Video - Open 500kV switches
RE: VCB Vs LBS
Alan
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"It's always fun to do the impossible." - Walt Disney
RE: VCB Vs LBS