Calculating Earth Size

[Carl Knowles]

Hello All,

Just a quick one. We look after a factory that has a 250amp busbar running around the factory. We have a machine plugged in with a 70mm 4 core swa and the ZS reading is too high so we are going to run in a separate earth to help, how would we determine the size needed to run in?
Thanks.

 

[Bobster]

Adiabatic equation. What's the Zs you have got?

 

[Pete999]

Adiabatic equation. What's the Zs you have got?

What Rob said.

 

[Carl Knowles]

ZS 0.25, max permitted is 0.18 from the protection device.

 

[Carl Knowles]

The run is 56m

 

[Bobster]

Miss understood your question, thinking the Zs was too high, as in you meant that the fault current was going to be greater than the withstand current of the CPC.

You just need to use the basic Zs = Ze+R1+R2.

 

[Deleted member 26818]

Miss understood your question, thinking the Zs was too high, as in you meant that the fault current was going to be greater than the withstand current of the CPC.

You just need to use the basic Zs = Ze+R1+R2.

???

 

[jackhammerJIM]

What is the Ze ?

 

[Top Cat]

What is the Ze ?

Ze, this is the politically correct way of saying someone is gender-neutral.
Oh sorry, forgot we were talking electrics!

 

[cliffed]

Hello All,

Just a quick one. We look after a factory that has a 250amp busbar running around the factory. We have a machine plugged in with a 70mm 4 core swa and the ZS reading is too high so we are going to run in a separate earth to help, how would we determine the size needed to run in?
Thanks.

Half the csa of the conductors ie 35mm earth required