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Old 11-25-2007, 10:18 AM   #1
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Default Earth Fault Loop Impedance Path help

Hey guys new member here, after a little bit of help for my Approved Electrician Project, project has to be handed in on Tuesday and im stuck on one question? was wondering if anyone could help?


Question goes -

Identify, using a clearly labelled diagram, all parts of the Earth Fault Loop Impedance Path (EFLIP) for the furthest away car ramp. Explain the effects on the EFLIP and the consequences of :

1. A loose connection on the phase conductor at the car ramp isolator
2. A build up of corrosion on the earth connection at the distribution board
3. The wrong type of MCB fitted in the distribution board.

So i have done the drawing but dont know what to put for the 3 questions, im in my 3rd year of apprenticeship and havent done anything on EFLIP as of yet, could anyone help?

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Old 11-25-2007, 12:29 PM   #2
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1. Where are you from?
2. Where are your books?
3. Can you scan the drawing and post it?

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Old 11-25-2007, 01:07 PM   #3
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Quote:
Originally Posted by brian john View Post
1. Where are you from?
2. Where are your books?
3. Can you scan the drawing and post it?
im from sw scotland
there isnt anything about EFLIP in my notes as i havent done anything on it yet

will scan drawing ive done and post it up
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Old 11-25-2007, 01:27 PM   #4
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heres a pic of what ive done
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Old 11-25-2007, 03:32 PM   #5
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JasC

The answers are staring you in the face. Your diagram is fine but to answer a.b.c just think a little

a. loose connection to the phase supply can negate the ELF - loop current path.

b Build of corrosion will effect the resistance at that point and increase the overall EFL value. Perhaps even to the point of limiting a fault current. And possibly generating heat.

c. Installing the wrong type of mcb can affect the trip time of the faulty circuit.

ii. Correct mcb rating is needed to ensure safe disconnection time within the limits of circuit conductors.

ii Correct mcb rating is needed to ensure correct trip times within BS7671
circuit parremeters

iii Correct types of mcb are required to ensure correct opperation of downstream devices. ie, Types A.B or C .( motor control etc)

You can add to the above yourself but you get the drift. Look in the On Site Guide and 16th Regs Book

Frank

Last edited by frank; 11-26-2007 at 03:28 PM.
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Old 11-25-2007, 03:50 PM   #6
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Frank/JAS:

The terminology threw me off and the sideways pic is not the easiest to see.....But the question seemed pretty basic.

What is ELF?
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Old 11-25-2007, 04:07 PM   #7
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yes might seem pretty easy but ive not had the best apprenticeship in the whole world and my brain is a bit weary and tired trying to get this project finished, i had a fair idea how to do it just wanted a second opinion really. I havent done anything on the fault loop path as such before
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Old 11-26-2007, 03:30 PM   #8
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Brian

Earth Fault Loop - Impedance. Can't think what the equivalent Us terminology would be,

Frank
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Old 11-26-2007, 05:41 PM   #9
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I printed the drawing out easier to discern when I am not holding my head at an angle.

I did miss what the car ramp isolator is

GFRP- ground fault return path.

1. An open on one pahse conductor of a two wire circuit will result in a loss of a COMPLETE CIRCUIT and a loss of the operational load.

2. Corrsion on the neutral to ground connection can affect the GFRP impedance and thus the instantaneous operation of the OCP (over current protection) device.

3. The improper OCP (oversized) will result in longer operational times exposiing the disctribution suystem to higher than designed fault currents.


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