That's very interesting but would I be wrong in thinking it really doesn't make much sense? - the basic principle, that is; not your post.
Which part?
He was adamant that the brief for the study group was to develop the best domestic wiring system in the world.
Then no one else (apart from some colonies) uses it.
Among the problems they tried to overcome were: the inflexibility of the then common system of radials to each socket-outlet (usually one per room), the conductor being sized for the single socket; the voltage drop on sockets furthest from the fuseboard in the meter cupboard;
That was the inadequacies of the then methods; they could have been addressed without inventing the ring.
the unavailability that could result from a single conductor breakage;
That results in danger of cable overload.
the dependence of the ADS on a single cpc;
Is that a valid reason considering the other circuits and the rest of the world.
the number of fuses required for a system using a separate fuse for each socket;
Again, that's not because it is not a ring. One large capacity radial will achieve the same.
The solution to these problems was the ring final, that had two sources of current at each accessory, as well as a duplicated cpc.
You can connect another cable if you want without the restrictions of our ring circuits.
A little later it was realised that the conductors being effectively in parallel, their CSA could be reduced somewhat.
Not really - only with unnecessary restrictions.
I shall use metric sizes:
A 30A ring with BS3036 fuse and no restrictions (to achieve the above with no hazard) would require 41A cable - 6mm².
To achieve a ring with 30A fuse and 2.5mm² (total CCC of 54A), reduced to 39A because of the fuse was further reduced Half of 39 - near enough the 20A minimum.
The only valid reason for rings seems to be the oft-quoted saving in copper - not even that with MCBs
the Ministry of Works requested the installations committee of the IEE to look at reducing the amount of copper required by a further CSA reduction of the conductors, to about 2/3 of the CSA that would seem at first sight to be necessary.
That has also been the case with radials so not a reason for a ring.
The risk of an open-circuit allowing the CCC of the conductors to be exceeded was considered to be acceptable, given the relatively small loads that were common at the time, and the considerable safety margin built in to the CCC tables for conductors.
That could also have been done with radials.
