Fluke Test: Loop Impedance, Continuity & RCD |

Описание: 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: Zi No Trip N, PE, L or Zi Hi-Current N, PE,L)
R1: Circuit Live (Fluke setting: Continuity RLo)
R2: Circuit earth (Fluke Setting: Continuity RLo)

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 = 0.47 ohms (Fluke setting: N, PE, L)
R1+R2 = 0.33 ohms (PE, L)

Therefore,
Zs max = Ze + (R1+R2)
Zs Max= 0.44+0.38
Zs Max= 0.82 ohms (This is written in the Load Schedule as Zs actual because it is actual readings)

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.

I hope this helps.

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

Thanks for watching man.