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Phil Griffiths

what 2 methods are they to determine the sustainability of a protective conductor for thermal constraints during earth fault conditions??

And might be a long shot but can anyone tell me what component of a RCD will operate for a ..
a. line to earth fault 2.3 ohms
b. line to neutral fault 0.01 ohms
c. neutral to earth fault negligible impedance
d. an overload approx twice the nominal rating of the device

For a 230V single phase circuit Thanks again.
 
what 2 methods are they to determine the sustainability of a protective conductor for thermal constraints during earth fault conditions??

And might be a long shot but can anyone tell me what component of a RCD will operate for a ..
a. line to earth fault 2.3 ohms
b. line to neutral fault 0.01 ohms
c. neutral to earth fault negligible impedance
d. an overload approx twice the nominal rating of the device

For a 230V single phase circuit Thanks again.
the answeer to a,b,c,and d is the bits inside. :(
 
Well the first question i don't have a clue that why i have came on here to ask, as for the second set of questions i have had a go and have got this ..

a. RCD - thermal due to earth leakage from line conducted.
b. MCB - magnetic due to difference between natural and line conductors.
c. RCBO - magnetic - due to current passing threw earth
d. RCBO - thermal due to overload.

more then likely its wrong so can you help.
 
Yes, i think he has written the question down wrong. It should say RCBO as far as I can see. Daz.
 
In real life, if you put in an RCD where you wanted an RCBO you could burn someone's house down - then you would be sorry!

Your answer to D is correct. Points to ponder re your other answers:
A, is the 'leakage sensing' differential mechanism thermal?
B, what difference are you thinking of?
C, can an RCBO sense current passing 'through earth?'

Finally with the protective conductor question, if you haven't got a clue, don't waste time on here, get those books out and start reading...
 
Two are the thermal/magnetic parts of the device, the other two the rcd sensing parts of the device. Op which ones go with which?
 
i take it d and c are the sensor parts of the device, and a and b are magnetic and thermal?Thermal would trip once an overload occurs cause the metal strip to bend, and magnetic for small or moderate overload?
 
I have misworded that, I would say only one relates to the rcd sensing parts.
 

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