On 25 November 2014 at 21:17, Eric Smith <spacewar at gmail.com> wrote: I don't know the reasoning for Germany, but in my town in Norway it was apparently used in order to reduce costs, actually. Traditionally 3-phase in Norway has been distributed with 3, not 4 wires: If balanced, earth return current is zero. Some years ago the Norwegian system was unified with what's standard in most of EU, I'm not sure if things changed then (but at least in the past there was no 'neutral' and 'live' in a home - both wires were equal in that respect, and the voltage to earth was never 220V (as we used back then, now it's 230V), it could vary but was in practice never more than 160V, normally just 120V. Less of a jolt than if you touched both wires. Wire to earth accidents is a much more common affair than wire-to-wire accidents). Anyway, I'm not an expert on this so as I said I'm not certain if the policy of using only 3 wires has changed - but at least with that system, distributing 3-phase means that you could transport 200% more effect with only one additional wire. Even with four wires it pays off. And that's why it was done AFAIK. [In addition it seems that feeding 3-phase all the way to the consumer is nearly 'free' with TN, see below] (Reading up on this a bit - apparently the traditional Norwegian power distribution system was called 'IT', Isolated Terra, while new and refurbished areas are now using TN, Terra Neutral (400V), the system which is now common in Europe. What impact this has for the jolt when you touch the wire I'm not sure about [update: Ouch, you'll get 230V to earth], but apparently TN is what makes it feasible to distribute 3-phase to every house. With the older IT system the (then) 3-phase 380V system had to be installed separately. With TN you get both 230V and 400V directly available for the consumer. But I think you'll need 4 wires in practice. It still pays off, economically.] Now I slowly retract my steps back to the more familiar lower-voltage DC land where I feel on more solid ground.. :-) -Tor