Arc Flash Detection
Arc Flash Detection
(OP)
I'm considering installing arc flash detection equipment to trip upstream breakers instantaneously in the case of an arc flash event. My question is whether this equipment can be of any use in instances where the arcing fault current is already expected to be high enough to trip the breaker on instantaneous.
For example, I've got a 1000A breaker which will trip on intantaneous at 10kA or less, and the calculated arcing fault current is 15kA. Will the arc flash detection trip the breaker sooner due to the time it takes for the fault current to build up? Or will the system be completely useless for all types of faults in this case?
For example, I've got a 1000A breaker which will trip on intantaneous at 10kA or less, and the calculated arcing fault current is 15kA. Will the arc flash detection trip the breaker sooner due to the time it takes for the fault current to build up? Or will the system be completely useless for all types of faults in this case?





RE: Arc Flash Detection
If your arc was 'only' 7kA or 8kA would you want to initiate a breaker trip immediately or wait for the thermal trip to clear it?
RE: Arc Flash Detection
However, I do not know if there could be situations where the arcing current could be lower than the theoretical calculated value. Also, I do not know if it could take a significant amount of time for the arcing current to build up to 15kA.
Also, if any mods are reading, this thread should probably be moved to Electric Power & T&D.
RE: Arc Flash Detection
"Will work for (the memory of) salami"
RE: Arc Flash Detection
RE: Arc Flash Detection
david, From what you're saying, there would be not be much of an advantage to having the detection system, since the breakers will have internal magnetic trips which should be as fast as the optical relays.
RE: Arc Flash Detection
RE: Arc Flash Detection
RE: Arc Flash Detection
RE: Arc Flash Detection
RE: Arc Flash Detection
RE: Arc Flash Detection
thoughts?
RE: Arc Flash Detection
RE: Arc Flash Detection
Arc Maint switches are also useful and extremely cheap.
Bus differential is fast, but I disagree it does a "far better job". Its also typically more expensive. Bus diff used to be the end all be all. It all depends on the Plant preference. Also, there is no reason to assume everything is the sole item protecting the bus.
Its all just a box of tools, choose based on Plant, or more importantly in the arc cases anymore, or insurance requirements/preferences.
There are a couple of white papers out that compare times of different protection elements/philosophies. It has been a few days since I found them but a decent google search should turn them up.
RE: Arc Flash Detection
RE: Arc Flash Detection
I have never seen a light detection scheme were the detection isn't easily routed through the compartments.
Also, I do not diagree there is a bunch of empirically derived factors. However, the "reliance" is typically strictly dictated by Plant safety requirements, insurance requirements and contractrual details.
These typically specify levels and values specifically, making the "reliance" fairly strong.
You only have so many tools at your disposal. As for "complete" protection... again, I would not assume that its strictly one vs. the other. Typically there is more than just one or the other on the bus.
RE: Arc Flash Detection