Redsy,
I don't think they even start looking at the arc waveform until it has over 50 amps flowing in the arc.
From Brenden Foley's post of 12/17 at 2:30 pm in the Arc Fault Breaker thread on the NEC & code issue forum.
The AFCI continually monitors the voltage. We monitor the voltage trace waveform across the resistive element in the breaker. We monitor the voltage drop and convert to current. We are looking for the spikes in this waveform that are indicative of arcing faults. When we see that there is evidence of an arcing fault of 50A RMS or greater, we analyze the current waveform for the signature of an arcing fault. If we see this, the breaker is "armed". We then look for 8 arcing half cycles over the next 1/2 second, (these do not have to be consecutive half-cycles, and they can be positive or negative. If we see 8 half cycles of arcing, we trip the breaker. If the electronics does not see 8 arcing half cycles in that time, the breaker is no longer armed, and goes through the process again. All of this is done with a custom analog integrated circuit. Additionally, we monitor arcs to ground for the parallel arcs in NM-B cable at a 30-mA level. There are MOV's on the board to protect from surges.
Don(resqcapt19)
[This message has been edited by resqcapt19 (edited 02-28-2002).]
