Does a 32amp distribution circuit wired in SWA to a sub board need RCD protection ?

[WilliamAtkin]

For context i am in my 2nd year in college and my head is going round in circles a question in my project for which i need to select the right protective devices for :
A 32A distribution circuit from the main board to supply summerhouse will have a four-way SP-N distribution board fitted supplied by a 3-core thermoplastic SWA cable clipped direct. In the main board all the other circuits are on RCBOs.
I'm pretty sure I can't have a RCBO feeding another RCBO because of discrimination , and I think because the supply is wired in SWA that the distribution circuit doesn't need RCD protection .If I am correct in thinking this could someone give me the reason to why the circuit being wired in SWA means no rcd protection is needed
What I have done for this question is a 32A MCB in the main board for this distribution circuit feeding the summerhouse board and in the summerhouse I have put RCBOs in that four-way board- Is this correct ?
I also had another thought that I could do a 32A RCBO in the main board for this distribution circuit feeding the summerhouse board and then have just MCBs in the 4 way - board
I am quite confused about this and have been looking through section 5 of the regs but the words and the way the regs describe things don't make things crystal clear to me

 

[Penguin]

It’s obviously frustrating NOT to be issued with enough information for your paperwork test scenario.! But that’s probably as it’s not what their look for from you.
Start thinking about different value types of RCBOs ??? What does that ‘Letter’ before the amp rated number mean. or B32 C32 D32.

 

[mainline]

calculate the Zs for that cable size and the length, and then calculate the volt drop. If all that comes out ok for a given cable size then you won't need RCD protection to achieve fault protection.

That's still going to be dependent on cable type or installation method.

 

[timhoward]

That's still going to be dependent on cable type or installation method.

Agreed, read post #1 !