Help with 2330 303 Q

[Cirrus]

How would you answer this Q:
A final circuit is installed using single core pvc insulated cables enclosed in steel conduit. The conduit is used as the cpc. An earth fault loop impedance test identifies that the max permissable Zs has been exceeded. describe:
A) 3 possible faults that may cause the high reading
B) One test that could be performed to verify the reading.


Just blown my mind on so many revision Q's today that my brain has gone into melt down and I have been looking at this Q for so long I have gone blank.

 

[Moog]

I'm only on year 2 however A) as Zs=Ze + (R1+R2). A1) R2- cpc has high resistance at conduit junctions (needs tightening up) or not connected to supply earth A2) Ze- too high may be on TT supply A3) R1- Cable run too long or dodgy connections B) look at results from earlier tests of impediance tests of R1,R2 and CPC that you had to do before ELI and if these were fine then test ELI test at origin of supply to get Ze. If there had been dodgy readings in the earlier tests you wouldn't have done a live ELI test anyway so must be Ze. Do I get a prize?

 

[dainjah]

1 wrong size bonding conductors, 2 poor terminations on bonding conductors, 3 continuity not being made via a direct path and so a strange parallel path reading being achieved. should do an eart loop impedance test with an impedance tester who this helps

 

[adam.h]

I had that question in my exam lol

 

[REIBURN]

hi i have my 2330 303 next week and i am just wondering if any1 has any past papers or knows where i can get my hands on sum, it wud be much appriciated my email address is [email protected]

thanks

 

[Colonel Hathi]

Hi
I would just be cautious about the parallel paths suggestion.
I believe that parallel earthing paths would reduce ZS rather than increase it.
Hope this helps

CH

 

[bugsy]

High current low impeadance ohmmeter - wander lead method - I think
might be helpful if you could obtain a copy of the practical guide to inspecting and testing available from NIC at about £20.00