Zs reading

[nicsin02]

Hi guys, I was measuring the Zs on a small office ring circuit (9 sockets) using a Megger MFT, the results I got on every socket was <0.01ohms & when I set it to no trip it came out as 0.13ohms, is this normal? The Zdb is 0.06ohms and no RCD's are used, r1+r2 is 0.180hms, thanks guys

 

[telectrix]

r!+r2 = 0.18 ????? either an extremely short rfc, or superconductors used.

 

[Octopus]

He did say small office ring!

 

[telectrix]

at 0.18, i make the e/e of the rfc at around 9meters.

 

[nicsin02]

It is a very small run, d/b is in office and its wired in just 8metres of dado, any advice on low Zs reading never had it as low before?

 

[telectrix]

you have 2 issues here. a very low Ze and a low R1+R2. MFTs struggle at this level. the best solution is to use a wander lead of around 0.3 ohms to take your readings, then deduct the 0.3 from your result.

 

[Edd]

Sorry I should read before posting