2 questions

[joe_berks]

1. in appendix 4 the volt drop tables.. what is the r , x , z ? how do i incorporate that into the volt drop formula?

2. i have always thought that if you are wiring in singles, the cpc has to be the same csa as line conductors. the designer on this job has spec'd for me to wire rings in 4mm for line and 2.5 for cpc. i looked in the regs could'nt find it but im sure its in there . does anyone what reg it is?

 

[acat]

Not sure about question 2 hopefully someone else will answer that.

If you look at BRB page 258 top paragraph explains your z r and x

Z cross sectional area
R resistive component
X reactive component

Hope that helps


Chris

 

[Risteard]

If you apply the adiabatic equation you may find that your cpc does not need to be the same size as live conductors, otherwise twin & earth cable would not comply with the Regulations.

 

[ian.settle1]

It's to do with large cables and inductive load on cable, not used on smaller cables as it is deemed negligble for cable calcs

 

[joe_berks]

oh right. i was almost sure that you had to use the same size cpc, unless the cpc is incorporated in the cable (ie t and e) oh well thanks anyways. with this r x z malarkey... how do you do the formula? on lesser sized cables it just gives you the mV/A/m figure then you just do that multiplied by the design current , multiplied by the length of run, divided by a thousand.