The fastest RCBO in the world

[brianmoooore]

On a 50Hz AC circuit, the minimum trip time is dependant on what point in a cycle the fault occurs. If the fault occurs as the AC waveform crosses zero, there is no design of RCD possible that would switch off 'instantly'.

 

[Rockingit]

What is the fastest RCBO you know?
Fastest is meaning it has the lowest trip times.

Right..... so making an assumption that we're talking about a 5x figure (as most faults are in fact likely to be close to ADS levels) then typically in my experience of testing AC types I'm seeing numbers around 8ms - 12ms area for most manufacturers. HOWEVER - in type A RCD devices we are now typically seeing longer disconnect times at 1x than we used to (and we no longer have to test at 5x). So, if you have two RCD's in series it is still a game of chance as to which may trip first and as others have said is also entirely dependant on a heap of other factors and physics at play.

If you're experiencing nuisance tripping, as I suspect is the case, then you need to look at the cause of the fault, not the characteristics of the protecting devices.

 

[Energizer]

There is no such thing as instantaneous cause and effect in the way you are imagining it. Even if the device operated at the speed of light, (around 300,000 Km per second = 186,282 miles per second) it would still take an extremely small amount of time to operate . Albeit, this would be so fast, possibly immeasurable, so for all intent purposes as close to your instantaneous as you could get.

Even at this high speed the sun's light doesn't reach Earth until around 8.3 minutes after it was initially propagated, and the nearest star to ours, just over 4 years!

But things start to get even more mind boggling when you delve into Albert Einstein's relativity which describes the relationship between space, time, speed and measurements.

Extremely small amount of time is the key to my problem.
Logically, to measure any current, leakage current or normal current, we need a time, small amount of time. Now is to manufacturers to build different devices with different sensibility for different applications. I would like to identify the most sensitive RCB.
The electrical wires length in the house comparing to distance to the Sun is nothing, so I assume the speed of current is instantaneous, in my house. The distance between two RCB is too small to have any delay so the waveform is synchronous, I think.

 

[Energizer]

Right..... so making an assumption that we're talking about a 5x figure (as most faults are in fact likely to be close to ADS levels) then typically in my experience of testing AC types I'm seeing numbers around 8ms - 12ms area for most manufacturers. HOWEVER - in type A RCD devices we are now typically seeing longer disconnect times at 1x than we used to (and we no longer have to test at 5x). So, if you have two RCD's in series it is still a game of chance as to which may trip first and as others have said is also entirely dependant on a heap of other factors and physics at play.

If you're experiencing nuisance tripping, as I suspect is the case, then you need to look at the cause of the fault, not the characteristics of the protecting devices.

Yes, you are right. I have two RCD in cascade, first in the main distribution board and second is integrated in the portable power strip.
I had the same thoughts about nuisance tripping. When I touch the phase wire to the earth, this may cause different peaks so this nuisance could trigger both RCD (not confirmed by measure). What about integrate an anti nuisance filter in the power strip?

 

[DPG]

Out of interest, why do you keep experiencing this regular tripping of your RCDs?

 

[brianmoooore]

Out of interest, why do you keep experiencing this regular tripping of your RCDs?

Exactly! You seem to be more intent on shooting the messenger, rather than listening to his warning and acting upon it.

 

[Energizer]

Out of interest, why do you keep experiencing this regular tripping of your RCDs?

I'm searching to have a security device, in this case a power strip with integrated RCD to trigger while the upstream RDC remains ON. Is a question of sensitivity and rapidity. When you buy a fast and sensible RCD that is intended to trigger faster (to protect sensitive devices for example) than other but in real life is useless because I still need to open the main distribution board to reactivate the main RCD. With this portable 10mA RCD or without - is the same thing, the main RCD is triggering. There should be a way to protect small circuits without cutting off all the house.

 

[DPG]

I'm searching to have a security device, in this case a power strip with integrated RCD to trigger while the upstream RDC remains ON. Is a question of sensitivity and rapidity. When you buy a fast and sensible RCD that is intended to trigger faster (to protect sensitive devices for example) than other but in real life is useless because I still need to open the main distribution board to reactivate the main RCD. With this portable 10mA RCD or without - is the same thing, the main RCD is triggering. There should be a way to protect upstream small circuits without cutting off all the house.

But if you are getting repeated tripping of an RCD then you have something wrong somewhere. Are you getting tripping of your RCD?

 

[brianmoooore]

A 10mA RCD trips between 5mA and 10mA. A 30mA RCD trips between 15mA and 30mA. Any differential fault current that exceeds the tripping current of that particular 30mA RCD is equally likely to trip either or both RCDs.
You will only get discrimination if the fault current exceeds the tripping current of the 10mA RCD but is less than that of the 30mA one.
You can, of course, replace the 30mA RCD with a 'S' type delayed version, but then the rest of the circuits supplied by that RCD will not have the required level of protection.

 

[Energizer]

But if you are getting repeated tripping of an RCD then you have something wrong somewhere. Are you getting tripping of your RCD?

No, I don't have repeated tripping. I simulate a fault. Both RCD shuts off when I want only one to shut off, the closest to me and to the fault