Earth fault loop impedance

[Simonslimline]

In my book, that's the tabulated value it gives me

What book is that?

 

[Risteard]

In the byb they have reduced the maximum zs values now so a b32 amp mcb was 1.44 is now 1.37 sorry i forgot the reason why , might be to do with Europe it normally is

The Cmin factor is taken from CLC/TR50480:2011

 

[gazdkw82]

What book is that?

its just one of the questions in my learning material. Its not a book.

Iv checked the official values online and none of them are the same as the tabulated values they have listed.

strange

 

[Andy78]

What book is that?

its just one of the questions in my learning material. Its not a book.

Iv checked the official values online and none of them are the same as the tabulated values they have listed.

strange

They changed with the last edition of BS7671 which was published January 2015 and came into force last July. This introduced the new Cmin factor which dropped the maximum values to 95% of their previous value.

Your course material is out of date in that respect.

 

[gazdkw82]

this is what I'm given

http://i125.photobucket.com/albums/p64/gazdkw82/DAA937C2-599F-45C9-97B9-F5C4C329875C.png

 

[Andy78]

this is what I'm given

http://i125.photobucket.com/albums/p64/gazdkw82/DAA937C2-599F-45C9-97B9-F5C4C329875C.png

Yes those are out of date as of last July. You can still answer the question perfectly well though, just don't learn your tabulated values from those sheets. Refer to your BYB for clarification.

 

[gazdkw82]

Yes those are out of date as of last July. You can still answer the question perfectly well though, just don't learn your tabulated values from those sheets. Refer to your BYB for clarification.

feel shy to ask.....what is BYB?

 

[Andy78]

feel shy to ask.....what is BYB?

The Big Yellow Book, BS7671:2008 amendment 3:2015. Previous editions are knowns on this site as BRB, BGB, (red, green) etc

 

[gazdkw82]

thanks

so working with the tabulated values I'm given in my material would the formula I posted be the right way to go about it?

 

[Andy78]

thanks

so working with the tabulated values I'm given in my material would the formula I posted be the right way to go about it?

I am of the opinion that the course material is out of date as the Cmin factor of 0.95 is already worked into the new maximum values.
The question is simply asking for you to apply the temperature correction factor to the maximum values and compare those values with the given measured values and state whether compliant or not.

You could point out in your answer that the Cmin factor of 0.95 should be applied if you would like to illustrate you have been given out of date material.

 

[gazdkw82]

I am of the opinion that the course material is out of date as the Cmin factor of 0.95 is already worked into the new maximum values.
The question is simply asking for you to apply the temperature correction factor to the maximum values and compare those values with the given measured values and state whether compliant or not.

You could point out in your answer that the Cmin factor of 0.95 should be applied if you would like to illustrate you have been given out of date material.

Yes I would like to do that

seems negative learning material that is out of date