thermal constraints

[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.

 

[Pete999]

Homework question?

 

[westward10]

Homework question?

Yeah he had another one going on Saturday.

 

[hightower]

We'll not just answer homework questions straight. Start by telling us what you think the answers are etc

 

[telectrix]

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.

 

[Deleted member 72666]

the answeer to a,b,c,and d is the bits inside.

Excluding b and d of course.

 

[westward10]

Excluding b and d of course.

Why's that then.

 

[Deleted member 72666]

Why is it not?

 

[westward10]

Tis all the bits inside.

 

[Phil Griffiths]

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.

 

[Deleted member 72666]

Tis all the bits inside.

.....But the 'bits inside' a RCD will not cause it to operate for conditions b & d, RCBO's however....

 

[westward10]

.....But the 'bits inside' a RCD will not cause it to operate for conditions b & d, RCBO's however....

I see where you are coming from now just reread post.

 

[DPG]

Yes, i think he has written the question down wrong. It should say RCBO as far as I can see. Daz.

 

[Phil Griffiths]

Yes, i think he has written the question down wrong. It should say RCBO as far as I can see. Daz.

RCD/RCBO sorry.

 

[Lucien Nunes]

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...

 

[westward10]

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?

 

[Phil Griffiths]

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?

 

[westward10]

I have misworded that, I would say only one relates to the rcd sensing parts.