What would a clean-sheet set of wiring regulations look like today?

In no particular order..
Assuming all countries got the same reset at the same time, an internationally agreed standard for plugs and sockets indoors and outdoors for a start then we could ditch the plug and socket regs. 
Probably higher voltages than 230, as nowadays really good insulation  (by the standards of the old sweats) is cheaper than copper and energy losses are a bigger consideration, so fewer wider spaced transformers would be good. 
Probably not bother with the bayonet lamp holder.
Compulsory all-pole Isolation immediately after metering points.
Double pole breakers.
Standardised Din rail terminal positions and breaker profiles.
No PME
Training on how to do decent diagrams
Insulation on the (full size?) earth cores of cables.

M.

mapj1 said:

No PME

I've never really understood what the alternatives are and how they are 'better', given that 'Earth' is everywhere, and phenomenally good by the cubic mile.

It feels as if the different factions make different assumptions about the natural spacings between electrical equipments, and the ease (lack of) 'earth' connections (and what they are trying to do/not-do with said connections).

It's all as \clear\ conductive as mud.

Three phase doesn't help .

Philip Oakley said:

I've never really understood what the alternatives are and how they are 'better', given that 'Earth' is everywhere, and phenomenally good by the cubic mile.

Agreed ... potentially with the consideration of 'assume TT but connect TN-S' might actually achieve better safety, but possibly with the downside of lack of selectivity pas a certain point in the distribution?

Philip Oakley said:

mapj1 said:

No PME

I've never really understood what the alternatives are and how they are 'better', given that 'Earth' is everywhere, and phenomenally good by the cubic mile.

Earth is good - the problem is getting a adequate connection to it (a square mile of contact would do nicely, but would be a tad inconvenient).

The main problem with PME is the -C- part of TN-C-S - i.e. they put N current down "earth" conductors, so if there's a problem at all you naturally end up with significant voltage differences between things that should by design be at the same potential.

TN-S is the obvious alternative. Although there have been some supply impedance earthed (IN-S?) suggestions that have the advantage that even during an earth fault event all the exposed-conductive-parts remain close to true earth potential - so ADS becomes a lot less critical.

  - Andy.

In a world where we only need 150mA to 'fast' trip a circuit RCBO, which can be backed up in case of failure by a time delay RCCB at the consumer unit (and possibly even a second one with a longer time delay at the meter!), do we really need the very low earth impedances of TN-S?

I suppose belt-and-braces, but I think a system created today would be essentially all RCBO, and TT might be optimum.
As noted above, install TN-S but assume TT?

EIreland said:

do we really need the very low earth impedances of TN-S?

Earthing isn't just about ADS .. there's a bigger problem of trying to keep equipotentiality that spans into other areas - e.g. IT/comms systems, EMI and where SPDs can dump their unwanted surge currents into (and probably a few others too) - so a solid reliable earth is still good in my mind. Not least when you consider the potential unreliability of consumer's TT electrodes in the increasingly dry ground these days.

I still like the idea of IN-S - everything "earthed" is solidly connected together and to Earth, but earth fault currents are low, so large potential differences are mostly avoided. 

  - Andy.

I've thought a lot about this (obviously since I started the thread!), but I think if we accept a scope limitation to domestic and light commercial, where a lot of the cowboy electrics etc is, we can do something interesting with the cables.

Modern aluminium alloys are much better with regards oxidation or whatnot in large sizes, so we could have a cable with something like: 2x16mm Aluminium phase cores, CPC and a pair of 0.5mm2 Copper 'control' cores. The CPC could either be something like 1mm2 copper (with an emphasis on ADS through RCBO) or 16mm2 aluminium for really solid earthing.

The cable would not be "cheap", but it would probably not be ruinously expensive given how cheap Al cores are in the US and other places. I tried to estimate it at about £2-3/m or so in bulk. Such a cable, using XLPE insulation, would have a current rating of 60 Amps even on Reference Method 'A' (in a conduit in a thermally insulated wall).
Thermal overloads in a domestic setting would be almost impossible.

If we use the cable for everything, we could also use the 'control' cores to implement DALI or a similar protocol for lights and switched appliances, with the cores commoned on busbars in the consumer unit. Then all the switched earths and oversleeved conductors that can get people into trouble in lighting would be replaced with simple tree circuits. Light switches and light fittings need exactly one feed and wiring is achieved by joining all the colours together. Same for things like thermostats or central heating valves, or the remotely switched sockets Americans love so much.

Together with a four phase core version for three phase circuits (or huge single phase circuits with four pole RCBO), we could meet all the domestic cable requirements with a one or two not comically expensive cable types. Since only a single phase conductor size would be in domestic use, we could fit everything with heavily optimised lever connectors that will mitigate the remaining issues with Aluminium.

It's a bit radical, but metal doesn't seem to be a driving cost in the construction of electrical systems any more.

I've thought a lot about this (obviously since I started the thread!), but I think if we accept a scope limitation to domestic and light commercial, where a lot of the cowboy electrics etc is, we can do something interesting with the cables.

Modern aluminium alloys are much better with regards oxidation or whatnot in large sizes, so we could have a cable with something like: 2x16mm Aluminium phase cores, CPC and a pair of 0.5mm2 Copper 'control' cores. The CPC could either be something like 1mm2 copper (with an emphasis on ADS through RCBO) or 16mm2 aluminium for really solid earthing.

The cable would not be "cheap", but it would probably not be ruinously expensive given how cheap Al cores are in the US and other places. I tried to estimate it at about £2-3/m or so in bulk. Such a cable, using XLPE insulation, would have a current rating of 60 Amps even on Reference Method 'A' (in a conduit in a thermally insulated wall).
Thermal overloads in a domestic setting would be almost impossible.

If we use the cable for everything, we could also use the 'control' cores to implement DALI or a similar protocol for lights and switched appliances, with the cores commoned on busbars in the consumer unit. Then all the switched earths and oversleeved conductors that can get people into trouble in lighting would be replaced with simple tree circuits. Light switches and light fittings need exactly one feed and wiring is achieved by joining all the colours together. Same for things like thermostats or central heating valves, or the remotely switched sockets Americans love so much.

Together with a four phase core version for three phase circuits (or huge single phase circuits with four pole RCBO), we could meet all the domestic cable requirements with a one or two not comically expensive cable types. Since only a single phase conductor size would be in domestic use, we could fit everything with heavily optimised lever connectors that will mitigate the remaining issues with Aluminium.

It's a bit radical, but metal doesn't seem to be a driving cost in the construction of electrical systems any more.