Apologies in advance for the dumb question on current...

[Spark2be]

If you take the domestic 230V and the standard Ze for a TNS of 0.8 ohms and using ohms law;
I = V / R you get a current of 287.5A
Where does the standard main 100A or 150A breaker fit into this?

Please excuse my naivety, I can't get my head around this and I probably need it spelt out to me be gentle, again I am a rookie!!

 

[plugsandsparks]

its the upstream breaker thats needs to be concerned. The job of the isolater is for downstream

 

[Spark2be]

Sorry mate I am still no clearer....... :-(

 

[Spark2be]

Ah I follow you now. Thanks for answering the question, sometimes it just clicks lol.

 

[Geoffsd]

If you take the domestic 230V and the standard Ze for a TNS of 0.8 ohms

Not a standard, a maximum - normally <0.2.

and using ohms law;
I = V / R you get a current of 287.5A

That will be the earth fault current, but as above - liable to be a lot higher.

Where does the standard main 100A or 150A breaker fit into this?

They're not breakers, just switches and rated CCC.

 

[Deleted member 26818]

If you take the domestic 230V and the standard Ze for a TNS of 0.8 ohms and using ohms law;
I = V / R you get a current of 287.5A
Where does the standard main 100A or 150A breaker fit into this?

Please excuse my naivety, I can't get my head around this and I probably need it spelt out to me be gentle, again I am a rookie!!

They don't. You'd be lucky to get a 100A supply for anything where the Ze is 0.4ohms or above.