Why would "a bit of bondage" be locked?

[JohnW2]

The current has to increase to a point where the speed of automatic disconnection of supply is met.

Unless you're quibbling about what happens to the AC waveform within the first cycle (20 msec), the fault current will be at its greatest when the fault first appears, and will decrease thereafter (until disconnection occurs) as heating of the cable increases its impedance. It's not a further increase in current (which doesn't happen) that causes the protective device to operate after a period of time - that's simply the time taken for the device to operate (despite the decreasing current, due to the cable heating up).

Kind Regards, John.

 

[JohnW2]

John, The equation above proves that the more power you use, the more current you must use; and you need to use power to heat the cpc!

What on earth are you talking about? Generation of heat is the consequence of current flowing through a resistance - it's not an 'extra' use of power.

Kind Regards, John.

 

[david911cockburn]

echoes/John,

The loop impedance values given within Chapter 41 are unlikely to be met in a TT system, hence the use of an RCD or local supplementary bonding.

 

[DetlefSchmitz]

Muuum...He's doing it again!

Just ignore him dear.

 

[JohnW2]

echoes/John, The loop impedance values given within Chapter 41 are unlikely to be met in a TT system, hence the use of an RCD or local supplementary bonding.

So what?

Kind Regards, John.

 

[echoes]

John,

The equation above proves that the more power you use, the more current you must use; and you need to use power to heat the cpc!

No, still not getting the point. In the simplest terms I can thinkl of: Of course there will power dissipated in the CPC. And that will heat it up; and that will increase its resistance; and that wiil reduce the current; and that will lower the power dissipation, and that will decrease its temperature; and that will decrease the resistance; and that will increase the current; and that will increase the power dissipation ad infinitum.

No contradiction of Ohm's law, no time machines, simple maths...

 

[echoes]

Muuum...He's doing it again!

Just ignore him dear.

I know, please ignore me. It's perverse light relief.

 

[JohnW2]

Muuum...He's doing it again! Just ignore him dear.

I usually do (ignore him). Against my better judgement, I thought I'd just have another go at trying to determine whether he really is as stupid as his mutterings suggest, or whether he is simply a (knowledgeable) wind-up merchant. It's really hard to tell since, if I were trying to portray the impression of gross ignorance and stupidity, I don't think I could do any better than his posts!

Kind Regards, John.

 

[david911cockburn]

Table 41C offers us an alternative way of meeting our disconnection times only it gives us R2 values as opposed to loop impedance values, this is a part of the discussion over Table 41C.

If you meet the R2 values within Table 41C this will give a disconnection time of 0.4seconds, because you are effectively removing the bottleneck usually caused by the need to heat a cpc that has a higher resistance than the R1 value of for example - twin and earth cable.

OK so far?

 

[DetlefSchmitz]

NP

 

[JohnW2]

If you meet the R2 values within Table 41C this will give a disconnection time of 0.4seconds, because you are effectively removing the bottleneck usually caused by the need to heat a cpc that has a higher resistance than the R1 value of for example - twin and earth cable.
OK so far?

No, definitely not OK. What on earth are you talking about? There is no 'need' to heat a CPC - it's just something which inevitably happens when current flows.

Kind Regards, John.

 

[david911cockburn]

Therefore Chapter 41 is in its' entirety concerned with the speed of automatic disconnection.

If the speed of automatic disconnection cannot be met by over-current protective devices alone, the touch voltage or potential difference between two earthed conductors will rapidly be increasing as the current/power increases forcing the resistance of the cpc down during a fault of negligable impedance to earth!

This is why either 'local' supplementary bonding or an rcd must be used in a TT system.

 

[david911cockburn]

John,

If the cpc is getting hot, it is using power to do it!

 

[holmslaw]

..

 

[JohnW2]

If the speed of automatic disconnection cannot be met by over-current protective devices alone, the touch voltage or potential difference between two earthed conductors will rapidly be increasing as the current/power increases forcing the resistance of the cpc down during a fault of negligable impedance to earth!.

David, you really are an enigma. You clearly have the ability to write coherent English, even if it rarely makes any sense in terms of physics/engineering. I would therefore assume that you must be able to read and comprehend to some extent, but it's very hard to find evidence of this is what you then write.

What, in your difficult-to-understand mind, is meant to be causing this 'increase' in current/power and, even if that increase were to exist, why on earth should that 'force down' the resistance of the CPC. As you've been told more times than I can remember, the effect of current flow, hence power dissipation, will be to increase temperature and hence increase resistance.

Kind Regards, John.