3 phase supply

[Jacko444444]

Next month i will be working on a farm putting a new 3phase board in to supply welders, plasma cutters etc. 3 phase comes into electric shed (Tnc-s) and then supply into barn comes from 80A 3ph MCB with a 300 ma trip upfront. Supply enters barn and goes into an existing board with the earth path separated and spiked down, i will be putting a 63A 3ph supply to new board clipped direct internally in SWA, do i need to protect this supply cable with a 100ma rcd or can i just feed it with an MCB?
Cheers in advance

 

[Toneyz]

You need to read section 705.