2391 help

[kenny5522]

a) the effect on earth fault protection provided by a BS EN 60898 circuit breaker if it is connected in the neutral conducter only

b) why the effect in a) above occurs.

 

[tony mc]

In affect the neutral conductor is not part of the earth fault loop.

It goes like this

Fault
CPC
Earthing conductor and MET
The return path via earth TT general Mass of earth TNS TNC S Metalic return.
The earth neutral of supply transformer
The transformer winding
The line conductor back to the point of the fault.

So if the protective device was in the neutral conductor the chances are it will not operate.

Hope this makes sense

 

[kenny5522]

thats great wasn't 100% sure it might come up tommorow night i have got my 2391 exam. thanks once again

 

[solo2771]

yeah what he said lol

 

[tony mc]

Draw the earth fault path and get it in your head as its 15 easy marks.

Make sure you put the right system on the drawing that your are asked so note TT TNS or TNC-S.

If you are asked for a TNS and put in a ROD for a TT you will be deducted alot of marks.


This question along with testing continuity ring final ccts conductors often comes up.

 

[kenny5522]

will do got the drawings all sorted in my head hope it comes up.

 

[tony mc]

Good luck know how you feel.

 

[kenny5522]

I need more thank luck i think i need a mircale or another couple of months but i will give it my best shot, thanks will let you know.

 

[Paul.M]

Good luck Kenny and try and remember a couple if questions and post them up to help others (like me) that are studying for it. Keep calm and I'm sure you'll be fine.

 

[kenny5522]

will do i will try to remeber as many as i can and will try to help others as i have had so much help off here i think i would of be in a lot worse state than i am now.

 

[mattmoo1974]

a) the effect on earth fault protection provided by a BS EN 60898 circuit breaker if it is connected in the neutral conducter only

b) why the effect in a) above occurs.

Surely the answer is you have no protection if there is a fault between line and cpc?
The CPC will be the fault path and the current will keep flowing until you pop the main incoming fuse, As there is No protective device in the line conductor.
Thats what id go for mate, I mite be wrong. Hope this helps.
Oh and by the sounds of it, Its a short answer question.
So you d get away with putting A) If the Protective device is connected in the netural conductor if would not operate under fault conditions(line to CPC)