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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.
 
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.
 
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
 

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