Zs at db

[brav]

Just been in class we all been arguing with one of our lecturers about Ze suddenly becoming Zs at the consumer unit. We didn't get a full explanation frm him, so could someone explain why Ze, eflz external to the installation and measured across incoming line to disconnected earthing conductor, is now Zs at db?

 

[sparkytim]

May be its a remote DB at the end of a distribution circuit he is talking about.

 

[kerching]

I will prompt you to do a little bit of research in BGB, as just giving an 'off pat' answer sort of defeats the object really. Sorry to be obtuse...

What is the definition of Zs

In the calculation of Zs what othere parameters are there in the equation

Where have these other values come from

I think when you have got answers to the above 3 questions you will also have worked out the answer to your original question

I always think that if you can find the correct 'route' to getting the answer then it creates a far better understanding... :coat

 

[Technician]

What is between the dis board or consumer

unit and the point where you measure Ze?

 

[brav]

R1 and r2 are the other parameters of zs, but we were taught tht the supply authities line conductor isn't classed as r1, it's the supplies line conductor. And if you measure at the end of the supplies line conductor to earth ur measuring ze, the external impedance?

Nah, it's not a remote db, I'm talking about the first cu where the supply is connected?

 

[Stator_Electrical]

As stated above, you need to know the difference between Zs & Ze - then judge when and where you would actually record "Zs at DB".

Also look at the information supplied on the certificate for guidance....

 

[steptoe]

Apart from disconnecting the earthing conductor to perform Ze, what else is connected when you measure Zs?

 

[brav]

Apart from disconnecting the earthing conductor to perform Ze, what else is connected when you measure Zs?

r1? ze+(r1+r2) but as i said, if Ze is the impedence external to the installation, why would Zs suddenly be where Ze used to be?

---------- Post Auto-Merged at 16:02 ---------- Previous post was made at 15:56 ----------

As stated above, you need to know the difference between Zs & Ze - then judge when and where you would actually record "Zs at DB". Also look at the information supplied on the certificate for guidance....

we were looking at the new green regulations, Generic Schedule of test Results, my lecturer is saying where it says Zs at Db, we measure at the incoming supply side line conductor at the main switch across to disconnnected earthing conductor?

Ok where would the Ze be measured?

 

[steptoe]

ok, I'll try again,

you have got your Ze measurement, now what do you do with your earthing conductor?

 

[brav]

Reconnect it.

 

[steptoe]

ok, so what would you be measuring now?

and why would/might it be a different reading?

 

[shed69]

He's gone out on the lash Steptoe, remember them days??? Either that or he's stuck.....! I hope it's the lash!!!

 

[brav]

Tht would be a Zs because all parallel paths r connected and tht makes sense, cheers. But thts not what I was asking or was told by my lecturer, he said disconnect the earthing conductor and measure to get this Zs at db. I'm glad uv explained it tho as he wasn't budging frm what he was saying and we were all sitting the scratching our heads wondering what had we been learning for the last 3 years lol.

It's a bit difficult have to learn things just when they decide to replace the regs too lol

 

[steptoe]

what he is describing brav is, what we (I think most of us will agree) would call Zdb,

its not a proper term, but it is used for measuring the incoming earth at a remote DB.

---------- Post Auto-Merged at 21:54 ---------- Previous post was made at 21:52 ----------

He's gone out on the lash Steptoe, remember them days??? Either that or he's stuck.....! I hope it's the lash!!!

wish I could too,

remember 'em, ?

NO, and I dont know if thats cos it was so long ago or I just had too good a time!!!

saying that, I can barely remember a couple o' days ago... :|