AFCI question

[walkerj]

http://forums.mikeholt.com/showthread.php?t=104963&page=5



No, I have not seen this happen, and I have not heard of it happening.

I am saying that it is plausible that line side problems could cause a properly functioning AFCI to open, but only if the line side problems cause the appropriate load side current flow. I entirely agree with you that the AFCI is looking at the current flow through the load; but I can draw out a circuit where something on the line side affects the current flow on the load side.

-Jon

Please draw us a picture. We like pictures

 

[ronaldrc]

Your picture

 

[quogueelectric]

Ok real life example of series arc in resi application.

How many times have you gone to a service call where the service drop was not sealed properly and water has been intruding into the meter pan slowly destroying the aluminum stab/buss for the meter.

The aluminum buss will corrode until catostrophic failure and arcing on and off losing a phase and welding itself back together.

This supply voltage (line side) arc will transmit itself downstream to the normal load as a series arc.

The phase effected should trip however just as the basics of locksmithing, No 2 breakers are exactly the same so the one with the most sensitive settings will trip first.

 

[peter d]

Ok real life example of series arc in resi application.

How many times have you gone to a service call where the service drop was not sealed properly and water has been intruding into the meter pan slowly destroying the aluminum stab/buss for the meter.

The aluminum buss will corrode until catostrophic failure and arcing on and off losing a phase and welding itself back together.

This supply voltage (line side) arc will transmit itself downstream to the normal load as a series arc.

The phase effected should trip however just as the basics of locksmithing, No 2 breakers are exactly the same so the one with the most sensitive settings will trip first.

I have no idea what you're trying to say. You lost me with the "arc will transmit itself downstream to the normal load as a series arc."

 

[gar]

081009-2126 EST

peter d:

We believe that the AFCIs are using information from the current flowing thru the breaker to detect a series arc condition. No matter where in the series loop the arc is generated, before or after the breaker, that abnormal current resulting from the arc will be seen by the breaker.

Obviously this breaker must have some load on it or there would be no current signature flowing thru the breaker.

If the arc is in some other series loop that does not include the breaker of interest, then this of interest breaker should not trip.

.

 

[peter d]

081009-2126 EST

peter d:

We believe that the AFCIs are using information from the current flowing thru the breaker to detect a series arc condition. No matter where in the series loop the arc is generated, before or after the breaker, that abnormal current resulting from the arc will be seen by the breaker.
.

Ok, thanks. That makes sense now.

 

[quogueelectric]

I have no idea what you're trying to say. You lost me with the "arc will transmit itself downstream to the normal load as a series arc."

We tend to study electrical theories with perfect power supplies with perfectly held voltage values and no internal impedance.
In real life we have a xformer which has an aluminum wire delivery system to the point of use which is your house.
For the purpose of this thread the statements so far seem to imply that line is the panel at the service back to the xformer and load is from the breaker out to the load and back to the panel neutral.
I there is an arcing bussbar in your meterpan it means that the line power supply is arcing and faulty before it reaches the breaker.

 

[peter d]

I there is an arcing bussbar in your meterpan it means that the line power supply is arcing and faulty before it reaches the breaker.

I just didn't understand how an AFCI would detect an arc on its line side.

 

[ELA]

I wonder if the AFCI could rely both on the current signature and the voltage signature?

It seems reasonable to me that if the AFCI only detected the current signature it might then detect an upstream arc since current is the same in a series circuit.

If they also analyze the voltage signature, that may change in a series circuit, then could it possibly exclude an upstream arc?

 

[quogueelectric]

I wonder if the AFCI could rely both on the current signature and the voltage signature?

It seems reasonable to me that if the AFCI only detected the current signature it might then detect an upstream arc since current is the same in a series circuit.

If they also analyze the voltage signature, that may change in a series circuit, then could it possibly exclude an upstream arc?

Yes I wonder if the circuitry uses a differential voltage sensing circuit to differenciate between line and load events.??