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Posted By Topic: earth fault loop impedance test

woodz
Aug 19 2012 14:53

One of the requirements for testing an installation is earth fault loop impedance but what if i am not allowed to liven until inspected..Also if a worker doesnt have loop impedance tester is there a cheaper way to test (not live)
   

devils advocate
Aug 19 2012 19:12

start by actually reading the section on testing in the wiring rules that will answer your question

its actually about the shortest and easiest going section of the lot and it is rather important
   

Dave.I.
Aug 19 2012 20:42

disconnect the cable at the switchboard end, twist together the earth and phase conductors.
go to the furtherest socket outlet in the circuit, and measure the resistance between phase and earth.
Compare this value to table 8.2.
   

woodz
Aug 19 2012 22:07

Thats dave and to the otha bloke you sound like a typicalt work colleague i wouldnt get along with ;)
   

Dave.I.
Aug 19 2012 22:10

No worries - it tells you all about it in section 8.3.9


   

woodz
Aug 19 2012 22:11

im looking for the loop impedance going back to the street transformer supply.Anyway ill find the answer.cheers anyway
   

devils advocate
Aug 20 2012 07:35

suspect that that sentiment might be reciprocated here 'mate' - your colleagues probably got fed up with the dumb questions...

why dont you put the head on that contains some brains and using your electrical knowledge think about the question you are asking before asking it?

are you asking 'can you measure FLI on a live cable by using an ohm-meter'?

or 'can I use R values recorded on the mains cable when disconnected for FLI records'?

either which way be afraid


   

AC Guy
Aug 20 2012 07:49

Couple of places on the Interweb that might be useful to those that seem to be struggling with this stuff, i.e. mr woodz.

http://www.elek.com.au/Files/Understanding%20Earth%20Fault%20Loop%20Impedance.pdf

and

http://www.elek.com.au/cablecalc.htm

The last one might be the best hundred and forty-nine bucks some could spend.
   

CW
Aug 20 2012 09:01

linky below to an older post, maybe of use. there is a answer there from pluto that is no doubt on the button, didn't read it all.

only dumb question is the one you don't ask then let the smoke out.
http://www.electricalforum.co.nz/index.php?action=more_details&id=1325079549&PHPSESSID=f07bf21f53a4ce90fcd4c7fdf2304bbc
   

CW
Aug 20 2012 09:04

But i did like this bit

"here is NO stated external EFLI requirements in AS/NZS 3000:2007 + amendments 1 and A, the only use is to ensure that all switchgear is able to clear an earth fault condition occurs, which does not occur very often"
   

Dave.I.
Aug 20 2012 09:29

@CW - only dumb question is the one you don't ask then let the smoke out

I agree.

@devils advocate - must be hard being perfect.
   

devils advocate
Aug 20 2012 10:58

who said anything about being perfect?

i just find it extremely frustrating and very sad that anyone can hold a practising license and not have a rudimentary understanding of testing... thats it... whats wrong with that?


   

CW
Aug 20 2012 11:07

Because some asks a question i might consider fundamental to putting on a tool belt, doesn't give me the right to belittle that question or treat them with any less respect than an apprentice 1 week into his time. The OP is just a name to me, for all i know he might well have spent 50 years working in another aspect of the trade.
   

Dave.I.
Aug 20 2012 11:14

@devils advocate
Different people operate in different parts of the industry. To someone hardly ever using certain standards, they can be confusing.
For example (this is a true story!), I am an instrument tech, with electrical registration as well. I am quite entitled to do PEW, but had not referred to the regs or AS/NZS 3000/2007 for the 20 years since I was registered (mostly ELV work, with a bit of 230/400v faultfinding / maintenance thrown in).
I personally went and sat the inspectors exam, as I got a new job requiring electrical as well.

However to someone not using the standard on a regular basis it can be daunting.

So don't assume that everyone needs to be intimate with AS/NZS 3000:2007. That was my point.
   

Dave.I.
Aug 20 2012 11:16

@CW - we were typing at the same time! I do agree also with your point about belittling people who ask questins.

A bit of respect goes a long way.
   

AC Guy
Aug 20 2012 12:41

So it's worse than we thought... now we have an inspector who doesnt understand how to test for ELFI.... something seriously wrong with this industry me thinks...
   

Tommo
Aug 20 2012 13:01

Bam ! this is guuna have some hurt on it... meh sits back and waits.......
   

devils advocate
Aug 20 2012 13:11

Sorry for being a total plonker guys will try and do better.
   

Dave.I.
Aug 20 2012 13:23

@ ac guy

If you read my story a bit more carefully.......

1 / I did my inspectors exam 'after' I started working in PEW again after 20 years of being REGISTERED.

2 / I am not an inspector, I merely did the course and sat the exam to re-learn the regs / standards BEFORE I started doing PEW again. (pretty pro-active I would have thought)

3 / if you notice, I actually answered the original question (I believe correctly, pointing to the correct part of the standard)

Please adjust your reading glasses and check what I have written before commenting on my skills.
   

Dave.I.
Aug 20 2012 13:26

Just after I adjust my writing glasses - point 1 should read :

1 / I did my inspectors exam 'BEFORE' I started working in PEW again after 20 years of being REGISTERED

See - even I'm not perfect devils advocate!!
   

Dave.I.
Aug 20 2012 13:37

@ AC Guy

As I obviously didn't make my story very easy to understand,
Could you please point out the bit in any of my posts in this topic that leads you to believe that I do not understand how to test for ELFI.
then I will be able to set the record straight.
I look forward to hearing from you again.
   

devils advocate
Aug 20 2012 19:04

i didnt post the guff about being a plonker - i stand by my other posts...

dave I - fair dos to you for taking the time to answer the orignial question

cw - i dont believe any of my comments were belittling - i was always taught to look for an answer and think about a question before i asked it... and hey we dont always get that bit right do we..

i do however find it totally unacceptable that someone who has passed an EWRB regulations exam has no apparent understanding of EFLI

doesnt matter what area of the industry you are in how hard is it to get the book and read it... like i said the testing section isnt exactly the longest section is it!

if you think i'm a prick for thinking that that is piss flipping poor whatever really

hell we all make mistakes its the striving to be better thats important and the trying to learn that counts... in that respect fair dos to the original poster for posting... just a shame they couldnt be bothered to open the book first and help themselves
   

CW
Aug 20 2012 20:50

shame i preferred it when you were a sorry plonker.

   

charlie
Aug 21 2012 20:07

Main earth lead and main nuetral Megger between them you should get 000> Meg Ohmms or close to it , means the main nuetral is connected as well as the main earth.

a handy way of fault finding sometimes too for broken nuetrals.
   

AlecK
Aug 22 2012 14:06

For us old farts, EFLI hadn't been invented when we sat our exams.
Well actually it had, but we weren't taught about it, and never did the test.

It only became something relevant to sparkies' daily lives with 3000: 2000, that was in 2003 for NZ... and even then it was optional.
Became mandatory only in 2010.

Hardly surprising that some haven't yet got their heads around it
   

Dave.I.
Sep 02 2012 22:23

@AC Guy
since you think you are not a tosser, still waiting to hear why you thought I did not know what I was talking about here.....