CPC and fault currents

[Emmadas]

Hi All, I was looking at the 'Learn Electrics' video on youtube about Zs and I was confused about the fault currents that flow down the earth wire to disconnect the circuit breaker. The video says that in a fault 700amps flows down the earth wire, but how is that possible when the csa of the earth wire allows only a certain amount of current to flow through it, can someone help me to understand?

 

[kerching]

Any size of wire can carry any amount of current. But if the cable is too small then it will be thermally damaged or destroyed
Adiabatic equation determines if the csa of the cable is sufficient to allow a large enough fault current to flow and trip the OCPD BEFORE the cable is damaged