0.00ohms,looptest at board.

[mazo]

hi,folks
can anyone tell me why i get a loop value of 0.00 ohms at the supply to a sub dist board (incommer)but when i loop test at the sockets off the board i get what's expected 0.34 and so on.
appreciate your knowlege guy's
thanks
mazo.

 

[mrloy99]

hi,folks
can anyone tell me why i get a loop value of 0.00 ohms at the supply to a sub dist board (incommer)but when i loop test at the sockets off the board i get what's expected 0.34 and so on.
appreciate your knowlege guy's
thanks
mazo.

Maybe a very good earth?Maybe very close to supply transformer?
Any other ideas?

 

[mazo]

thanks mrloy99
the board is connected to a rising busbar,fed in about,150mm swa,but i thought i should still get the value of ZE +R1ANDR2 of the supply cable.of at least 0.01
mazo

 

[Guest123]

Hey.

Big chunks of copper in them there bus risers and fat armoured too, a Zs's dream.

 

[Archie]

Had something similar once, it turned out the meter was faulty. I never found out why sometimes it seemed OK and other times read 0.00?? Didn't like the low readings.
The meter got worse and then read 0.00 for every test, cost £70 to fix + calibration extra, they never told me what they fixed, I guess they just changed a circuit board. Like most equipment nowadays, there are no user serviceable parts.
Hope this helps.

 

[Had8Lives]

I've seen a Zs reading of 0.00 ohms at the incomer of a sub board before. The bonding to the steel framework of the building which had footings buried deep in the ground was the reason. Not a problem, just it leads to high Prospective Fault Currents. Such is life!