Fluke Test of RESIDENTIAL Villa |

How to solve Maximum Impedance ( Actual Value) of a Circuit

Formula:
Zs max = Ze + (R1+R2)

Where:
Zs max : Maximum Impedance
Ze : Utility Impedance or incomer impedance (Fluke setting: PE, L)
R1: Circuit Live (Fluke setting: Continuity Ro)
R2: Circuit earth (Fluke Setting: Continuity Ro)

To solve Zs max or the Impedance maximum for a certain ckt. or any ckt. in the system, we must first get the utility Impedance Ze. the utility impedance is the impedance of the cable coming from a substation or any feeder. Once you get the Ze then proceed to getting R1+R2. in getting R1+R2 this can be done at farthest outlet or any other circuit, in order to get this we have to short the wire at the other end and get the reading at the other end. R1+R2 is simply the continuity resistance value of live and earth. then after getting it, you can now proceed to the formula above.

Sample computation based on actual Fluke test readings
Ze = 0.44 ohms (Fluke setting: PE, L)
R1+R2 = 0.33 ohms (PE, L)

Therefore,
Zs max = Ze + (R1+R2)
Zs Max= 0.44+0.33
Zs Max= 0.77 ohms

it's value is good enough.
Some Utility/project has given a prescribe or threshold not to go beyond higher Impedance than 0.8 Ohms for TN-S earthing system

I hope this helps.

If not please comment for any clarifications.
Lets continue to improve our electrical world.

Thanks for watching man.