- Prospective fault current test 2391

[Diver233]

Hello all,

I’m now overthinking the - Prospective fault current test for the 2391 practical, the exam boards will be a 3 phase and a single phase board.

Do I test the three phase board and double the highest and use that for both DB’s or do I do one for 3 phase db1 and sep one for single phase db2

 

[H]

Calculate ipf as you would per three phase and single phase for each board

 

[Diver233]

Sorry I am now flapping gggrrr

 

[H]

The three phase board will be the origin, for the office just remember to record the Zdb and ipf information, top left on the schedule of test results

 

[H]

 

[H]

Do not flap, just chill out and concentrate

 

[Strima]

Test as close to the source as possible with parallel paths in place.

Test all three phases to earth then all three to neutral.

If your test meter is capable then test across all phases, L1 to L2, L2 to L3 then L2 to L3.

If you can’t test phase to phase then double the highest single phase measurement.

Do you know the difference between PSSC & PEFC?

 

[Diver233]

Test as close to the source as possible with parallel paths in place.

Test all three phases to earth then all three to neutral.

If your test meter is capable then test across all phases, L1 to L2, L2 to L3 then L2 to L3.

If you can’t test phase to phase then double the highest single phase measurement.

Do you know the difference between PSSC & PEFC?

Yes I’m ok with that, Thank you

 

[Richard Burns]

Prospective fault current at origin is the highest current, further into the installation the current will drop due to circuit resistances.
If the protective devices in the next DB are able to withstand the fault current at origin there is no need to measure again at the next DB because you already know they are OK.

 

[Diver233]

Do not flap, just chill out and concentrate

H,
I seam to remember you listed the three faults you had somewhere on here?.
Don’t suppose you can remember can you ?

 

[H]

Of course...

1) High reading on Main protective bonding conductor.

2) Low insulation resistance on the sub board / office board between neutral and earth.

3) No cpc continuity on the switch wire on one of the lights on a lighting circuit.

Also had a couple of high Zs readings due to poor connections and contact resistances.

 

[westward10]

Isn't this tantamount to cheating

 

[H]

Isn't this tantamount to cheating

Of course not, it’s not exam conditions...

Plus there are a few switches to create different faults

 

[Deleted member 26818]

Looking at that test rig, there are 10 possible faults.

 

[westward10]

That switch by the starter is fitted to a non compatible back box.

 

[Diver233]

Of course...

1) High reading on Main protective bonding conductor.

2) Low insulation resistance on the sub board / office board between neutral and earth.

3) No cpc continuity on the switch wire on one of the lights on a lighting circuit.

Also had a couple of high Zs readings due to poor connections and contact resistances.

Thank you,

Wish me luck my test is tomorrow

 

[Richard Burns]

No worries, take it calmly and logically and all will work well.
Use the knowledge you have and think, good luck.

 

[Deleted member 26818]

Good luck.

 

[HappyHippyDad]

Good luck chap!

 

[H]

Best of luck with it. Get it done

 

[Baddegg]

Good luck mate,take ya time think it through it’s not as hard as you are thinking, you’ll look back in a years time with test experience under ya belt and wonder what you were stressing about....

 

[ruston]

Good luck from me too.

 

[The Ghost]

We had a potential of 35 fault injections and the cards were numbered and each candidate was given several random fault numbers which they injected. There is no way to know what faults you will be given. Except that there are only so many faults possible like short, no continuity, high resistance, low resistance and wrong polarity and maybe a few others all of which will be within your meters ability to spot so long as your brain is ok. Thing is to keep calm and work methodically with all fault finding.

 

[H]

How did it go today?

 

[Diver233]

I passed . Thank you for your help

 

[H]

Onwards and upwards

 

[H]

What faults did you have?

 

[Diver233]

What faults did you have?

A massively high continuity cpc reading on a final ring circuit,
Missing L1 connection at the socket of my 3phase motor circuit (think that’s done to make sure you test all 3 phases from the switch to the socket,
Bonding conductors not labelled.

 

[Diver233]

I am so pleased you guys pointed me in the right direction.

Big big thank you guys

 

[ruston]

Well done mate. A load off your mind.