My understanding (which may well be incomplete or wrong) is that the standard's tests for AFDDs work on the assumption that once there is a break in a cable which causes intermittent arcing, the arcing chars some of the insulation over time, and the carbon makes future arcing easier. So the tests are with carbon rods. A lot of the youtube tests try to create arcs with small copper to copper gaps, which tend not to last more than a second or two, and may be seen by the AFDD as a motor-type spark and not trigger a disconnect.

So when a youtuber shows an AFDD failing to disconnect, it may be that the AFDD is actually working correctly. Or it may be being completely useless. Or the standard isn't up to scratch. We can't tell from the video.

Indeed - actually the type test for AFDDs is quite odd.  A section of PVC twin cable without CPC is pre-damaged with high voltage, to create a local decomposition.

The standard is too expensive for causual readers, but luckily you can read a pretty good description of the process  on page 16 here.

You are quite right passing the test does not guarantee real world operation  - copper copper arcs tend to either burn clear or weld shut and stop arcing, carbon electrodes or brass can usually be persuaded to maintain an arc for a while.

  Cables with a CPC like we use in the UK are likely to trip an RCD once the PVC carbonises to the point of conducting, if arcing  or not, and LSF type cables do not respond in the same way as the PVC, and tend to produce rather less conductive char.

The doc above is a Swedish chap doing a rather more lab based check on AFDDs with other scenarios, that  may or may not be more realistic.
He too find situations where the varuious makers offerings are not the same.

As I said above, the devices and the standard, appear very immature, and the absence of testgear and diagnostics to allow any kind of fault tracking is a serious obstacle.

Mike.

I have reached out to Kevin at Chauvin Arnoux UK to see if they are working on an AFDD tester or are working on bringing anything to market to test AFDDs with the prospective of an installer/tester. 

Indeed, and another point made in the video but glossed over here, is who is going to pay for the time spent by an installer going round all of the sites where he has installed AFDDs to do a firmware update every time one is issued?

There are some Klien AFDD testers around in the USA but they don't test to the standards here.

Indeed, and another point made in the video but glossed over here, is who is going to pay for the time spent by an installer going round all of the sites where he has installed AFDDs to do a firmware update every time one is issued?

There are some Klien AFDD testers around in the USA but they don't test to the standards here.

Are you thinking of these testers ?

The Klein Patent of 2008 gives away how they do it. I suspect something similar could be done for the 220V equivalent.

It only really does one sort of arc waveform, but it would at least trigger that part of the AFDD.

There is a Siemens patent that achieves the same ends with a differnt circuit and generates a slightly different waveform though that style is not out in the wild in any actual test gear to my knowledge.

Note that apart from the wait 20secs between retests, for the Klein uint, there are no special energy related precautions. The Siemens patent mentions a small fan to cool the resistor bank- which could probably be ommitted with a similar time limitation

It may become more common once the 20 years is up and patents have expired.

Mike.

Personally I say to Hagar if it needs a firmware update then you better send your Hagar electrician to site to get the job done or Hagar can pay me to attend site to do the firmware upgrade.  Unfortunately my time is not free.  Lets say my call out charge and first hour of labour are £75 plus vat.  Additional charges may apply if it is outside my local area of lets says 10 miles. 

On a side note I have upgraded many routers back in the day via telnet and FTP and TFTP.  Every so often a firmware update would fail and render the unit useless.  This meant when I went to site to do the firmware upgrade I would take a spare, do a backup of config and then apply the firmware upgrade.  I wonder what happens if the AFDD firmware upgarde breaks the AFDD what is the electrician espected to do?  Do the Hagar AFDDs have 2 firmware partitions so it can fail safe or allow recovery.  Do Hagar exspect the engineer to carry a spare b16 c16 D16, C16, C20, C32, D6, D16, D20, D32 with them. 

firmware update every time one is issued?

Depends on the nature of the change - it it's just adding yet another few waveforms to the list of "acceptable - don't trip" ones, then you could take the attitude that unless the customer is complaining of unwanted tripping (and has the kind of equipment that generates that particular waveform) then there's no need to upgrade.

If you wanted to take a precautionary approach (e.g. to cover customers buying in some new equipment and plugging it in themselves in the future) I guess a firmware check/upgrade could be done as part of an EICR.

   - Andy.

What if the firmware was not for the AFDD waveform/signature  but for the Bluetooth itself.  Lets say to address a security vurability in the Bluetooth itself. 

well that alone is a good reasoin not to use such a brand - it is a massive exposure of a potential vulnerability.

Mike.

Mr Savoury has posted a update video on his previous AFDD episode.

www.youtube.com/watch

I have watched it and the others he has done on AFDD and I find it quite interesting.  Several AFDD tested in what seems to be real world potential fault situations.  Several things come to mind

1)  No real way to test and verify that the AFDD is functioning correctly.  Test button is for the RCBO side of the unit.  POST (Power on SELF Test) may or may not work as intended

2)  Different propriatory software and hardware across different manufacturers.  Fault or status indicators of differing colours and sequence could lead to confusion for the electrician or the person operating the CU eg Home owner

3)  Differing trip characterists on the AFDD tripping side, some are more sensative than others.  However they all to claim they conform to the same standard. 

I'm sure they all do meet the standard - but as said many times, and also demonstrated with a bit of theatre by DES and others, the acceptance tests as written in the standard are not especially realistic of faults as they occur in the real world.

Very few of us when tracking down a fault find pairs of carbon rods, spacing adjustable by a micrometer, to be the cause of the problem - people just do not fit that sort of thing to a UK installation ! To be fair even if someone wanted to, I've never even seen it as a standard part in the catalogues.

Nor do folk go around applying many KV to twin flex to trigger partial decomposition between cores.

And yet those are the series and parallel arc tests that an AFDD  has to identify to earn its badge of compliance.

In that sense Dave's rat bite or abrsaion plus some saline to represent rat wee is perhaps more realistic of the sort of damage that might start a fire in a real property - and by not connecting the CPC it overlooks that in the UK at least, an RCD trips for that sort of fault anyway.

Mike.

mapj1 said:

the acceptance tests as written in the standard are not especially realistic of faults as they occur in the real world.

Maybe the people who write the UK standard need to revisit the standard?

It is not a UK specific standard, it is a European one, and it in turn it is heavily based on the US one. But yes, I would strongly support a bit more transparency about what AFFDs must detect by design to pass type approval, then what else they may detect as a bonus,  and what they  must not trip on,  to avoid false alarms, as well as how well or badly they reject arc like interference coming from the supply side.

The technology is not especially complex by electronic digital signal processing standards - essentially sampling, then Fourier transforms and some spectral pattern recognition, but it is very, very  different to the one condition-one trip operation we associate with existing protective devices.

And I think it really should be testable in the field.

Mike.