Determination of R1 and R2: Theoretically

[Pete999]

out yer coffin early, pete?

Well thank you for that early greeting, yep noisy Son waking me up going to work at Sparrows furt oclock, how are you doing?

 

[puffy]

Guys my post is going off topic. But since we all are in here, what's teh standard/common cpc size for: 25mm, 35mm and 55mm?

 

[telectrix]

can you be more specific? cpc's for those sizes of cable are either same as the line or calculated in accordance with adiabatic equation.

 

[telectrix]

Well thank you for that early greeting, yep noisy Son waking me up going to work at Sparrows furt oclock, how are you doing?

not bad, pete.

 

[Pete999]

Guys my post is going off topic. But since we all are in here, what's teh standard/common cpc size for: 25mm, 35mm and 55mm?

never seen a 55mm2 cable but Chapter 54 BYB

 

[puffy]

can you be more specific? cpc's for those sizes of cable are either same as the line or calculated in accordance with adiabatic equation.

Example:

2.5mm T&E has a cpc size of 1.5mm.

What is the size cpc for a standard or commonly used conductor or 25mm and 55mm? Just the commonly used.

 

[telectrix]

still fail to see what you're driving at. 25mm cable would not be T/E. it would be SWA , singles, etc.

 

[ImpededLoop]

Example:

2.5mm T&E has a cpc size of 1.5mm.

What is the size cpc for a standard or commonly used conductor or 25mm and 55mm? Just the commonly used.

It varies upon application, Ze etc. T&E is primarily a domestic cable which suits a "paint by numbers" set of standard installation methods.

Bigger cables need to be designed properly.

 

[puffy]

Now it makes much sense! So above 16mm is considered SWA? Ahhh ok I'll ask more question in the trainee section. Thanks guys!

 

[telectrix]

not always SWA . ( steel wire armoured). just not made in T/E above 16mm. the size of cpc's is calculated so as to be able to withstand a fault current without thermal damage.

 

[GB.Kayak]

edited.

just looked in osg.

that table gives you the resistance per metre. in milli ohms.

so a 1.0mm line conductor on it's own has a R/m of 18.2 ( i.e. R1 for a 1m length)

a 1.0mm line conductor in series with a 1.0mm cpc has a R/m of twice that ( i.e. R1+R2 per metre.)

r1 is the resistance of the Live conductor end to end
rn res of Neutral conductor ^^^^^^^^^^^^^^^^
r2 res of cpc ^^^^^^^^^^^^^^^^^^^^^^^^^
For final Ring circuit continuity only

Hi,

Every cable has a certain amount of resistance per metre. If you multiply this resistance value by the length of the cable it will give you one of the R values.

For instance, the example that you chose in you post for a 1mm line conductor would give you your R1 value if you multiply it by the length of the cable.

Your second value is for two 1mm cables (line & cpc) so it is exactly double the value of a single cable. If you multiply this value by the cable length you'll get the value of R1+R2.

There's a trainee section of the forum which you should join if you haven't already.

So, is it R1 or r1 in this case? I have just gone to BGB and GN3:

R1 + R2 = (r1 + r2) / 4 ... my money is on Pete!

In design, use the mOhm / m value for the conductors in use eg 2.5 mm2 Line and Neutral and 1.5 mm2 Circuit Protective Conductor. Multiply the Resistance per Metre by the cable length in Metres to give the resistance per conductor in mOhm and divide by 1000 to get Ohms for r1, r2 and rn. Then apply the equation above to get R1, R2 and Rn if required.

 

[puffy]

Well my question was targeted at, say, a lighting circuit. A ring circuit MAYBE different with little r1 and little r2. My brain hurts. But I do remember in class something about r1+r2/4

 

[Engineer54]

My question is, ....Why is this causing so much confusion, these are very basic issues and equations that EVERY electrician should know inside out and backwards!!

 

[Pete999]

https://www.youtube.com/watch?v=xQgDd2mysu0&list=PLjUoQKko1J3rnFn4S6A1XowfJJ6-8kAt6&index=2
Have a look at this vid

 

[Simonslimline]

My question is, ....Why is this causing so much confusion, these are very basic issues and equations that EVERY electrician should know inside out and backwards!!

He's a trainee I believe