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Why 82 Ω cannot achieve ADSCan any breaker clear an 82 ohm loop?

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Take that 82 Ω and go looking for a protective device that will disconnect in time. Check BS 7671 · Tables 41.2 to 41.4:

DeviceHighest Zs in the table
Fusesaround 44 Ω, dropping as the rating rises
Type B circuit breakersaround 14.5 Ω
Type Caround 3.64 Ω
Why 82 Ω cannot achieve ADS the highest Zₛ each device allows, against the electrode reading 3.64 Ω Type C circuit breaker 14.5 Ω Type B circuit breaker 44.0 Ω fuses, at best your electrode reading, Rₐ = 82 Ω 82 Ω 0 20 40 60 80 ohms
Nothing in BS 7671 Tables 41.2 to 41.4 comes anywhere near 82 Ω, so no fuse and no circuit breaker will disconnect in time. And the electrode reading is only the start — a circuit's own R1+R2 still has to be added on top of it. That is why an installation on an electrode this poor needs an RCD, not a bigger fuse.
Nothing in those tables goes anywhere near 82 Ω

So with an RA that high, no fuse and no circuit breaker will achieve automatic disconnection of supply. And remember your RA is only the start — add a circuit's R1 + R2 and Zs is higher still.

✋Which means the RCD is doing a different job. On a TT system like this the RCD is not there for additional protection — it is there for fault protection, because nothing else can provide it. On an EICR there are separate boxes for the two, and this is the distinction they are asking about.

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