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 .

Putting technical topics to one side, I think a big improvement could come from simply re-writing the document from scratch with an improved structure which groups all of the requirements in a more coherent, logical way and removes the fragmented, rather disjointed structuring of the document. As these types of very long-lived documents get steadily amended over many decades, everything new tends to get tacked and bolted on to existing document as a series of extra paragraphs, extra subparagraphs or extra sub-sub-paragraphs, new sections. It all becomes rather incoherent over-time.

I would also look at the governance arrangements for how the Regs are modified, so that new requirements added to the Regs have clear risk assessments and financial assessments which are publicly available to demonstrate and justify why the new requirements were added, to bring some demonstrable rigor into the process.

Related to this, I'd also add a second companion document, which captures the 'why' details about each requirement. There's a failing common to most standards and regulations, that documents set out what is required, but the reasoning and justification to explain how those requirements have been arrived out is often not documented, or poorly documented but that's actually quite valuable information, particularly for those requirements which are quite obscure, where the 'why' is not readily apparent, or where the 'why' may become invalid over time so call into question if the requirements are still necessary generally.

I might also add a clearer process within the Regs governance, for people/parties to raise topics, issues or modifications to get things changed or improved, or to address contradictions or incompatibilities which emerge.

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.

It is an interesting thought experiment to consider how things might have been done differently if it wasn't for historical accident..

Years ago we weren't that fussed about ADS, just made sure that everything was solidly earthed. If we'd continued down that line we might now have c.p.c.s that a 4x the c.s.a. of the line conductors (so even during earth faults exposed parts remain below 50V) and probably concentric earth cables (perhaps think SWA but with copper armour strands) so far less reliance on RCDs etc.

Part of the idea behind ring circuits was instead of having multiple final circuits, you run the distribution circuit to the socket and have a final circuit for each appliance (far better discrimination, and better use of resources as copper is shared between different uses, making the best use of diversity). Ideal when you want lots of sockets for relatively low power appliances. Had we carried on in that vein, especially with the vast increase in the number of appliances, we might have ended up with domestics based on something more like flush dado bus-bar trunking with sockets just clipped in where ever they're wanted, no lighting circuits, just a FCU in each room for the lights, and possibly high demand appliances like cookers and showers tapping into the same system. So no CU as such, just one or two big fuses (maybe one per floor).

  - 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.

One might end up with something similar to the First Edition.

TurboGen said:

Putting technical topics to one side, I think a big improvement could come from simply re-writing the document from scratch with an improved structure

I think that is a bit harsh. There is a structure, which follows the internationally agreed one - see p. 20 of BOB.

I wouldn't want to write standards, or laws. Sometimes, I find my self thinking that something could have been worded better, but I also find it difficult to come up with something which is.

I think that I would change the Scope. With no real interest in anything with a supply > 100 A per phase, I would be happy with a much simplified document, which would cover domestic and light commercial - e.g. an ordinary shop and a flat above. The rest would be covered by something akin to what we have now.

Things like voltage and type of earthing system are an entirely different matter. Changing the voltage would cause mayhem will all existing appliances.

That said, they seem to cope in Brasil with two different voltages.

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.