Taking the Ze

[hsharp]

I was shown how to take the Ze from a domestic installation, at collage last week.
I have forgot how to do it, where to connect the probes of the MFT, and weather or not to disconnect the earth.
I need to know before Friday.
Can anybody go through it? would be better with diagrams.

Thanks would appreciate.

 

[accordfire]

I was shown how to take the Ze from a domestic installation, at collage last week.
I have forgot how to do it, where to connect the probes of the MFT, and weather or not to disconnect the earth.
I need to know before Friday.
Can anybody go through it? would be better with diagrams.

Thanks would appreciate.

Broadly..... (and depending on MFT to some extent)....

Ensure that it is safe to remove the main earth from the system - ISOLATE THE SUPPLY FIRST.

Then it's a case of connecting the earth lead to the incoming earth (having made sure all other earths are disconnected)
Live to live, neutral to neutral

MFT to lowest Ohm setting, and hit the button.

Erm.... do you not have a GN3?

 

[BigTom83]

Google 'earth fault loop impedance test' I'm sure somewhere u will find a guide with diagrams.

Do you not have a college book or college notes? U should get some if your serious about learning the subject. For testing, there is a book called part p doctor which goes through testing step by step with clear diagrams.

Think about what it is your trying to measure, the impedance external to the installation (the supply side) so you need to test at the incoming point of the DB.

I could continue to go through it step by step, but I'm not sure it will help you. The best way to learn testing is not to know how to do it, but discover what your actually measuring and for what purpose. Get your head into a book or a website finding out what your measuring and why and what the impact of the result is.

Good luck, it ain't that hard tbh.

Tom

 

[Guest111]

Go on youtube,there are videos by electrical training groups that show how to do all the tests.

 

[applemac]

External earth loop impedance (Ze) test - YouTube

this ones good, explains the test but on a 3 phase install, on single phase obviously you only have one incoming line
where as this chap is testing 3 lines in and doubling the highest of the two.
dont forget to fasten earth back into the bar.

so tnc-s your max stated .35 ohm
tns max .8 ohm
tt 200 ohm

give your croc clip a good squeeze and push the line probe hard onto the incoming line.

- - - Updated - - -

http://www.youtube.com/watch?v=PUTn3t65na4

this ones good, explains the test but on a 3 phase install, on single phase obviously you only have one incoming line
where as this chap is testing 3 lines in and doubling the highest of the two.
dont forget to fasten earth back into the bar.

so tnc-s your max stated .35 ohm
tns max .8 ohm
tt 200 ohm

give your croc clip a good squeeze and push the line probe hard onto the incoming line.

 

[i=p/u]

id reccomend alan lynch part p(book) even tho he does dumb it all down,,,,,,

 

[hsharp]

We used a Metrel MI3125 Eurotest Combo[FONT=Arial, Helvetica, sans-serif].

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[i=p/u]

turn off supply to installation, remove earthing conductor, but you might have to prove isolated before emoving earthing conductor .... and so on..

that book is pretty easy to follow and has pictures...

 

[hsharp]

Thanks

 

[RmBo_0]

The test itself is really easy but remember safe isolation procedure and to re-connect the earthing conductor before switching the power back on

 

[Octopus]

We used a Metrel MI3125 Eurotest Combo.

Are you testing TT, TNCS or TNS - with the Metrel it matters!

 

[hsharp]

I need to know for all

 

[Mfctitch]

Can I just say that it's nice for once to see a fairly simple question answered without anyone being a smart arse
As was becoming quite common on here.

 

[Geordie Spark]

Can I just say that it's nice for once to see a fairly simple question answered without anyone being a smart arse
As was becoming quite common on here.

It's a bit early, so there's still time.

 

[hsharp]

Well said