2391 written exam last nite

[bobby101]

did the exam last nite i thought the exam was not to bad still quite tough and the dreaded VD question came up by VD i mean voltage drop i think i managed to work it all out but i made the stupid stupid stupid mistake of saying it was within six percent instead of five dont know how heavily i will get penilised for that but was quite impressed with myself for being one of the very few to work it out dont get me wrong i did make a few more schoolboy errors on the exam too but fingers crossed got my practical on mon at 8am aarrgghh had a few beers last nite though how did the rest of you find it and what questions did you think were nuts cause i think there were a few

 

[GStueyXR]

Think is was not within 6% (nor 5%) mate....

VD was 13.5 V i think

 

[rockcliffe]

What system was the earth fault diagram last night?

 

[GStueyXR]

Tn-c-s

 

[CRAGS]

I got answer wrong but did mention 5% so maybe a mark

 

[bobby101]

The question for volts drop went something like this
Determine the volt drop on this circuit and determine if this complies
With the regulations.

A circuit at 20 meters long
2.5mm cable
40 amp supply
7.41 from GN3

Solution:

mΩ/m x L
1000

= 7.41 X 20
1000

=0.148Ω

Using the VIR calculation

V=IxR

V=40x.0148
=5.92volts

Then 5% of 230 volts is 11.5volts

Therefore 5.92 volts is within the voltdrop of 11.5 volts

i think this is correct please confirm.

 

[brucelee]

i am not sure mate i just started to answer by calculating restance then X that by IB then X L divided by thousand think i completly trashed it came out with about 13.2v
thought it was something to do with V = IXR but wasnt sure only know how to do it by nv/A/M X IB X L divide 1000
hope someone got a test sheet out so i can have another look and learn how to work it out

 

[brucelee]

hi all
the question on how a fuse would be affected if connected in the neutral by

a). Overload
b).earth fault
c).Short circuit current

what was answer to this

 

[bobby101]

i answered that

i the correct dissconection time would not be achived
ii the earth fault protection would not operate correctly
iii the circuit breaker would still operate

dont know if this is corret though

 

[brucelee]

was it a fuse or cb, i answered something like

i) the circuit breaker would operate leaving line at full voltage
ii) the circuit breaker would not operate leaving line-earth at full line voltage
iii) the circuit breaker would operate

 

[bobby101]

your answer to i may be incorrect as the circuit breaker has operated in the event of a fault there would be no voltage present i think

 

[brucelee]

i thought because it was in the neutral it only breaks the neutal so anything upto that point would still be live

i couldnt understand what they where asking in a few questions . The way they word things just confused me there were a lot of sneaky ones

i think if i sat that same exam again i would still struggle i dont feel confident in passing
I flew through then went back over it a few times and there was one that i think i had answered wrong and had to rewrite it at the end the volt drop one just completly boxed me. it was all the two things for this two methods for that they speak complete and utter jargon

do you have exam success and past papers as a lot of this never even came up did it
and a lot out of GN3 didnt come up

 

[GStueyXR]

Question on fuses was...

A. Fuse element breaks.
B. No effect on fuse element
C. Fuse element breaks


To add detail about what would still be live was irrelevant... but, in both cases there would still be a live voltage up to the point of the element.

Regardless, question asked effect of fuse.... no more detail, not worth risking adding detail that could be wrong.

 

[CRAGS]

Question on fuses was...

A. Fuse element breaks.
B. No effect on fuse element
C. Fuse element breaks


To add detail about what would still be live was irrelevant... but, in both cases there would still be a live voltage up to the point of the element.

Regardless, question asked effect of fuse.... no more detail, not worth risking adding detail that could be wrong.

Not sure if I will get marks but I put A breaks B none C breaks

 

[GStueyXR]

Not sure if I will get marks but I put A breaks B none C breaks

Full marks i reckon CRAGS