Arc Fault Detection going global ...

[Cookie]

Could you expand on that statement a little?

See the attached PDF:

 

[Cookie]

Could you expand on that statement a little?

Where the above PDF lead to the 3 PDFs I've attached below.


Lowering the magnetic trip value on single pole US breakers worked well, until it was theorized that in long circuit runs with a high Ze short circuit currents in US home wiring could be as low as 75 amps at the furthest point in the run.

A concept breaker was designed with a 75 amp pick-up, but was soon realized this would cause nuisance tripping on high inrush loads like vacuum cleaners, tools, ballasts, window AC units and light bulbs burning out.

As such an electronic AFCI was created in an effort to discriminate between inrush and sputtering short circuit aka arcing faults.


Easy solution would have been to restrict the length of 2.08, 3.31 and 5.261mm2 circuits. But nope, never happened.

Here is the whole concept being demonstrated:

When current is just below the magnetic trip level on a EU breakers it takes 7 seconds to trip. When set above the magnetic trip level that opening is instant.

The theory is that 7 seconds vs 1.5 cycles is the difference between a house fire.

The theory also stretches to cords, in the UK plug top fuses blow much faster than a breaker when the cord is damaged.

 

[DPG]

Earth fault loop impedance, solenoid coils in MCBs, RCDs and fused plugs.

I'm not convinced that a 13A fuse in a UK plug would detect an arc fault. The point at where the arc was occurring would heat up, but the fuse would not necessarily blow.

 

[Cookie]

I'm not convinced that a 13A fuse in a UK plug would detect an arc fault. The point at where the arc was occurring would heat up, but the fuse would not necessarily blow.

Parallel arc faults involve very high currents, limited only by Zs in domestic installations.

 

[7029 dave]

 

[Cookie]

Serial arcing is the end stage of joule heating, that is assuming combustion has not already ensued.

 

[DPG]

Parallel arc faults involve very high currents, limited only by Zs in domestic installations.

Sorry, I was referring to series arcing. I wasnt very clear there.

 

[Cookie]

Sorry, I was referring to series arcing. I wasnt very clear there.

Its alright

Sadly AFCIs stop looking for serial currents below 5 amps. Not sure about UK AFDDs.

 

[DPG]

Its alright

Sadly AFCIs stop looking for serial currents below 5 amps. Not sure about UK AFDDs.

I must admit I don't know the lower cut off point for UK AFDD devices either.

 

[pc1966]

Recently i saw for the USA market they are selling testers for AFCI (AFDD) such as mentioned here:

AFCI Testers

AFCI testers or indicators for arc-fault circuit interrupters

www.nachi.org

But for now I have no idea if any MFT offer AFDD testing, or even if the EU/UK market has an agreed standard for that (i.e. like the 15-30mA limit for RCD, etc).

Finally it seems those testers are to verify the AFDD, not sure if anything is available to test a circuit suspected of triggering it. For RCD we have low current clamp ammeters that can measure the leakage to know if we are close to tripping, not sure when 9or if) that will also appear on MFT.

Oddly though that article says the testers are less meaningful than the self-test button. Hmm...

 

[Cookie]

Recently i saw for the USA market they are selling testers for AFCI (AFDD) such as mentioned here:

AFCI Testers

AFCI testers or indicators for arc-fault circuit interrupters

www.nachi.org

But for now I have no idea if any MFT offer AFDD testing, or even if the EU/UK market has an agreed standard for that (i.e. like the 15-30mA limit for RCD, etc).

Finally it seems those testers are to verify the AFDD, not sure if anything is available to test a circuit suspected of triggering it. For RCD we have low current clamp ammeters that can measure the leakage to know if we are close to tripping, not sure when 9or if) that will also appear on MFT.

Oddly though that article says the testers are less meaningful than the self-test button. Hmm...

That a whole other story altogether...

 

[Vortigern]

Speaking of arcs, I have a problem in my computer/printer area related no doubt to arcing. I switch on my multiple socket switch and the MCB pops sometimes. So there is a printer, computer, speakers, a couple of lights probably adding up to about 500w max. All equipment is in good condition. I think it is the switch arcing when switched on, so a fairly minor arc is being detected by an older wylex MCB. What need then for AFDD?

 

[DPG]

Speaking of arcs, I have a problem in my computer/printer area related no doubt to arcing. I switch on my multiple socket switch and the MCB pops sometimes. So there is a printer, computer, speakers, a couple of lights probably adding up to about 500w max. All equipment is in good condition. I think it is the switch arcing when switched on, so a fairly minor arc is being detected by an older wylex MCB. What need then for AFDD?

But I'm sure we've all seen evidence of bad connections/arcing which haven't tripped an OCPD. The arcing in your example would most likely be worse due to the amount of switch mode power supplies present after the switch.

Just playing devil's advocate - I'm not convinced either way about AFDDs yet!

 

[pc1966]

Speaking of arcs, I have a problem in my computer/printer area related no doubt to arcing. I switch on my multiple socket switch and the MCB pops sometimes. So there is a printer, computer, speakers, a couple of lights probably adding up to about 500w max. All equipment is in good condition. I think it is the switch arcing when switched on, so a fairly minor arc is being detected by an older wylex MCB. What need then for AFDD?

Electronics has high in-rush, so a bouncing switch is going to hammer home a few high current peaks.

We used to have 10 monitors off a 20A rotary switch (actual load probably no more than 500W) and it burned out the switch contacts after a year or two of daily use. Ended up having a zero-crossing SSR and NTC termistor arranged after the switch so it reduced the peak current to 20A or so and then connected after the first half-cycle on the next zero crossing. Was still working about 10 years later.

 

[DPG]

Electronics has high in-rush, so a bouncing switch is going to hammer home a few high current peaks.

We used to have 10 monitors off a 20A rotary switch (actual load probably no more than 500W) and it burned out the switch contacts after a year or two of daily use. Ended up having a zero-crossing SSR and NTC termistor arranged after the switch so it reduced the peak current to 20A or so and then connected after the first half-cycle on the next zero crossing. Was still working about 10 years later.

Theres a lot to be said for zero crossing switching. I'm surprised it's not used more often.