WHen doing the continuity of a ring main and the cpc is 1.0mm should the reading be 1.25 times the R1 or Rn value. And 1.75 if its 1.5mm?
right. look at the ratios. 2.5:1. that would give a value for R2 at 2.5 x R1. SSSSiimmmmppplleeessssi would say little more for 1mm
R2 = (RTXA1)/(A1+A2)
Where A= The CSA of the conductor.
Whats RT refering to? and is A1 say the size of cpc csa? and A2 the csa of the line conductor?
RT represents the total, in this case, the R1&R2.
A1 is the CSA of R1, and A2 is the CSA of R2.
For example... say you have an R1&R2 of 0.85ohms and you want to determine R1, Rn and R2. In theory we can determine Rn from obtaining R1's value.
So..
R1&R2 = 0.85 ohms..
R2 = (RTXA1)/(A1+A2) = (0.85x2.5)/(2.5+1.5) = 0.53 ohms
R1 = (RTXA2)/(A1+A2) = (0.85x1.5)/(2.5+1.5) = 0.32 ohms
So we have (R1) 0.32 ohms + (R2) 0.53 ohms = 0.85 ohms (R1&R2)
Rn will allways be the same as R1 because they are the same CSA if you have a difference of more than 0.02 ohms you have to investigate this. That is providing the Neutral is the same legnth as the Line conductor, which in a ring it will be.
should be same as r1what about rn