2391 question

[i=p/u]

have 400/230v supply tn-c-s system with 35mm supply conductors..(ze 0.1 ohms) there is an extension built which is a 30m run of 3 core swa with 25mm conductors, one core is used as circuit protective conductor

Q , state giving reason wheather the copper cpc incorparated in distribution circuit is suitable as part of the main equpotential bonding to gas and water services installed to the new building from public supply

Q, descibe a suitaqble test to confirm the continuity of cpc in distribution cable

 

[i=p/u]

kk spark, i see its not in book as such but you use your noggin and follow suit

 

[spark 68]

things like length of circuits , testing more than 1 ciruit at a time

Tip: read the question, it mentions a conductor, not a circuit

as the length is less, you will have less leakage so a Higher IR reading

 

[Deleted member 26818]

In general, the greater the area of insulation there is, the lower the resistance.
As such all of the answers should be 'increase'.

 

[i=p/u]

weeeeeeeeeeeeee:77:

 

[spark 68]

As such all of the answers should be 'increase'

are you sure spin ?, I did mine in December, and Iam almost sure we were told the Csa had no effect on an IR test.

I will stand to be corrected, and bow to superior knowledge

 

[i=p/u]

but would it not be proportional ahhhh ok i do get what you saying

In general, the greater the area of insulation there is, the lower the resistance.
As such all of the answers should be 'increase'.

 

[i=p/u]

i thought changing csa didnt matter about insulation resistance so who right, me me me

 

[Deleted member 26818]

I think you will have to decide yourselves.
Consider why insulation resistance would decrease, then apply it to the various scenarios in the question.

 

[ringer]

RCD question

b) 200mA
c) 300ms

only 30mA (or less) RCDs used for additional protection are tested @ 5X I delta n

general purpose RCD to BSEN 61008 max = 300ms

general purpose others max = 200ms

Spark, where did you get this information from regarding testing at 5X ?
And the 300ms for BSEN61008, all others at 200ms ?

 

[spark 68]

Hi Ringer,

general purpose RCD to BSEN 61008 max = 300ms

general purpose others max = 200ms

This is in the OSG, but excludes S types and the types which are 30mA or less which trip in the 40ms required @ 5 X I delta n for additional protection.

Spark, where did you get this information from regarding testing at 5X

This is also in the OSG, but I got the info. from elsewhere, which escapes me at the minute.

red OSG (cos I haven't got the green one yet) pages 91 and 92 sections 11.2, 11.3, 11.4 and 11.5

 

[spark 68]

Hi ringer,

Forgot to mention, apart from the RCDs required to trip in 40 ms,, you only test @ 1/2 Idn and 1X Idn on both halfcycles (only 4 tests)