2391 practical help - Zs at DB reading

[itigeezer]

Hi,

I've got my 2391 practical next week and currently getting myself a bit confused over where I get the "Zs at DB" figure for the GSTR,from. I remember my lecturer saying something about the wording/meaning of these new forms being backwards, and that this mens "away from the board", as usual my notes make now sense 4 weeks after I've wrote them. headbang

Anyway, simply, is this reading just completed with my lowest ZS reading? Or am I well and truly short of the mark?

Cheers

 

[Zeespark]

Zs is taken at the remote point of the circuit.

AndyGuinness

 

[NozSpark]

Zs @ DB is exactly what it says,, you take a Zs at the incomming supply to the DB. In a 3ph DB then it will be the highest of each Line - Earth

 

[itigeezer]

Yep, now my notes make sense again. Time for bed I think, knock revision on head for one day!

Thanks chaps!

---------- Post Auto-Merged at 00:42 ---------- Previous post was made at 00:37 ----------

Zs @ DB is exactly what it says,, you take a Zs at the incomming supply to the DB. In a 3ph DB then it will be the highest of each Line - Earth

So for my practical I only have do the Zs at DB for the 3 phase board as the single is fed by this??

 

[electrician786]

You will still have to do Zs at single phase board.

 

[itigeezer]

Next question/s in relation to my practical exam next week. Help much appreciated.

Protecting the RCD when doing the IR test at 500v DC

Is it possible to test the whole single phase installation from the load side of the RCD without damage (with functional earth leads removed)? And/will disconnecting the neutral and having the RCD open protect it sufficiently?

 

[OnOff]

Zs @ DB is exactly what it says,, you take a Zs at the incomming supply to the DB. In a 3ph DB then it will be the highest of each Line - Earth

Is this sometimes known as Zd as in one and the same? I couldn't find reference to "Zs @ DB" or indeed Zd in the (red) regs where it has all the symbols. Not got the green so I don't know if it's in there.........

 

[NozSpark]

If you look at the standard forms in BS7671 then it is asked for as Zdb in the schedule of tests