2391 practical help

[beaniebag7]

Hi, I am doing my 2391 practical tomorrow. I thought I understood it all but realised I don't! There is a 3-phase distribution board which supplies a single phase distribution board. I am fine with the 3-phase side of things. When measuring R1+R2 of circuit of single phase do I just do it as normal with the main switch off. I'm aware that somewhere along the line I need to be including the resistance of the feeder cables. To do Zs=Ze + (R1+R2) do I use the Ze already found on the 3-phase or measure a new one from the single phase? Please Help!

 

[Denatone]

The Ze is measured at the point of entry to the main distribution board and measures the impedance of everything you can't really change.
for any other distribution boards fed from the main one you would measure a Zdb for each new board (which takes into account Ze plus resistance of cables from the main dist. board) and use that instead of Ze in Zs = Ze + R1 + R2.