Let's say we have a L-N arc fault, RCD's will not detect such a fault as is the nature of there operation in detecting residual leakage to earth and thus an imbalance in current flow in the live wires.
MCB or RCBO and fuses will only operate if the arc fault meets their operating criteria found in their time/current curve so as to operate/trigger the device, it has however been shown that impedances measured in arc faults at our national voltage ratings are shown to diminish current flow in parallel faults thus increasing the likelihood of the device failing to detect the fault.
@Cookie - The youtube vid' posted demonstrating a arc fault and subsequent temperature values was to say the least a laughable video, the conditions were not controlled, the temperature measurement method was flawed and questionable and thus any data gathered was irrelevant, the fact you post stuff like this because it fits your position without scrutinising it and seeing the obvious flaws demonstrates you may have a form of cognitive dissonance in that you are happy to accept anything that supports your mindset with little to no scrutiny yet play the opposite game of auto dismissing any points raised that do not shore up your argument.
I do not know why you wrote the section about the UL as I am very aware of them but you have to accept that other national bodies and standards exist around the world and to assume that the UL standards somehow trump (pardon the pun) all the others is a disillusioned view to take, even when taking into account the history and size of this body, like you have found, it isn't always a good thing. I am also well aware the UL would love to become the worlds recognised safety symbol as would any of the main bodies like CE, regarding the UL achieving this then that can only be good for US business and trade given they would thus have leverage to manipulate world trade from within the standards they must conform to, what you will find though is the rest of the world is not so easy to just hand over this influential power so your claim that we are just going through the same motions that the US did 15/20 yrs ago are simply your unfounded opinion. We have our own trading and safety standards which also go through similar lab testing, computer analysis etc etc
The UK regulations are not governed by UL standards, in part there may be sections are areas that are lifted and repeated but there exists no direct influence hence the implementation of AFDD's in the UK BS 7671 is very different in approach and effect than that of your electrical standards.
Please remember you are the one coming onto a UK based forum telling us AFDD introduction into the BS7671 is fraudulent, this is based on your own experiences in the US, at no point have you posted anything that demonstrates this nor have you provided any irrefutable evidence, regardless of whether of not the UL has done intensive research and modelling into our own grid networks and installations is not in itself proof, it just demonstrates a research facility trying to ensure products made under UL standards could possible be meet the requirements of other nations following different codes... I totally fail to see how this is any kind of rebut to what I have said.
I ask you some simple questions with what I consider to be the correct answers ..firstly forget all that has occurred in the US and all the controversy you suggest AFDD's are having in the US and just think about my questions...
Do the AFDD provide a level of protection that is ill afforded by other devices or variations of devices ?...YES.
Would this protect property and subsequently save lives?.. YES.
Is the overall cost and implementation of using the devices warranted by the fires expected to be avoided?... remains to be seen but in Europe the biggest cause of property fires are electrically related, a device that can reduce this and has been demonstrated to should be worth reviewing.
Are there any other practical alternatives that afford the same level of detection of arc faults and protection from them?... NO
I noted you mentioned heat sensors/detection so I am all ears here on how you expect to monitor every part of an electrical installation including the integrals of faulting appliances with heat detection as an alternative and at what cost ... by the time your average heat detector has gone into alarm you already have a substantial problem, even smoke detectors are too slow in comparison to avoiding the fire altogether.