Calculating voltage drop on larger SWA cables

[roukel01]

Hi All

A question I've asked many a lecturer and none of them have come up with the same answer.

When looking at the current carrying capacities for SWA cables, from about 35mm onwards you get an r, x, z value. What are these and which one do you use when carrying out voltage drop calculations. is it as straight forward as the smaller sized cables or is it a little more complicated?

Thanks

 

[malcolmsanford]

R= resistive load
x= inductive reactance
z= impedance

It is when you start to design using cables over 25 /35mm you need to start using all these different co-efficients and of course temperature, grouping etc etc.

To be honest if your just installing a 35mm 40mts for a distribution circuit then you bog standard

m/V/A/m(z) x Ib x L / 1000 would be adequate without those r and x factors needed. It's when you get to 50mm+ the factors are needed for cost saving purposes

 

[roukel01]

ok, so for a 200Amp 3 phase supply, run underground. 135M run, what are we looking at?