I've been reading through your NEC code on line and its a lot easier to get on with than the sh!t we use !!!
Problem with the British Standards is that they are open to interpretation and are ONLY a guide,we don't have any mandatory sections in there !
Don't mix 17th edition with 16th edition
It would help if all the replies stick with 16th edition.
413-02-07 One or
more of the following types of protective device shall be used
(i) an overcurrent device
(ii) a residual current device
Both apply to socket outlets (receptacles) you need an overcurrent device (Mcb ) and Rcd (GFCI)this being no greater than 30mA for
Circuits feeding socket outlets ( this originally was brought in for power outlets outside the protected zone,outlets that fed equipment outside ) and was soon adopted for all power outlets.
These Rcds should trip with 40 milliseconds at a current 5x 30mA =150mA
Or 200 milliseconds at 1x 30mA
If they DO NOT trip within these times then they should be replaced ASAP
You can only test 100 and 300 mA rcds at 1x trip current.
Below is a 16th edition split load consumer unit ( Crabtree Brand )
The service cable comes from the cut out ( service fuse ) into the top of the RED SWITCH on the right hand side,out the bottom of the same switch in a bus-bar connection and a wander lead from the neutral and the hot to the top of the Rcd 30mA the device in the middle of the distribution board.
The Service fuse provides overcurrent protection for the cable feeding the red switch (Main switch) and the Rcd (GFCI)
The Red Main Switch sometimes is not fitted and an RCD is used in its place,Usually 30mA or 100mA ( Not so often a 300mA ) If a 100mA one is used then a 30mA rcd is fitted to control the socket outlets ( receptacles)
See also below
A likely combination would be in a distribution board would be
Red MAIN SWITCH or 100mA Rcd
Lounge heater circuit
water heater circuit
Cooker without socket outlet
30mA RCD (GFCI)
General socket outlets
power to outbuildings etc
cooker with a socket outlet