College Question

[New2Game]

Can some1 please help with this question. Explain the method used to verify that the 30mA RCD provides supplementary protection against direct contact, and protection against nusinance tripping.

 

[Spark123]

General purpose RCDs are tested at I/\n and should open within 300ms for a bsen61008/9 or 200ms for a BS 4293.
The additional requirement for an RCD used for supplementary protection against direct contact is it needs to be tested at 5I/\n and must trip within 40ms.
To help avoid nuisance tripping the RCD is tested at 0.5I/\n and must not trip.

 

[New2Game]

Tutor says - consider that if appropriate an RCD is tested 3 times. what is the purpose of each of these tests?

 

[Spark123]

1) To ensure correct operation of the RCD at I/\n on +ve and -ve cycles.
2) To ensure doesn't trip at 0.5I/\n on +ve & -ve
3) To ensure it trips at 5I/\n within the prescribed time limit on +ve & -ve
4) To check the correct operation of the test button

 

[JohnD]

Ha,ha, that's 4.

If he says 3, I reckon he probably means:

1) To check that it trips when it should
2) But not when it shouldn't
3) that the test button works.

 

[Spark123]

Ha,ha, that's 4.

I went for the distinction

 

[JohnD]

No, you have failed to answer the question as set.

That's a fail, then

 

[Spark123]

They can set some pretty ambiguous questions can't they?

 

[nozspark]

Ha,ha, that's 4.

If he says 3, I reckon he probably means:

1) To check that it trips when it should
2) But not when it shouldn't
3) that the test button works.

Shouldn't this all be in the past tense....you don't know what's going to happen next time -- it could fail