I think the Swiss have the best Europlug-based system. Their three-conductor plugs have the same footprint as basic Europlugs, which makes for very dense plug arrangements. Unlike e.g. the German Schuko plug they only fit in one orientation so you get no polarity issues.
It’s pretty neat.
What do you mean by polarity issues? AFAIK alternating currents don’t have a polarity.
That’s not quite how AC outlets work. Line and neutral can intentionally have different potentials relative to ground depending on how the house’s electrical system is designed. This can become relevant in certain situations like very simple devices (think “lamp socket with a power plug”).
A plug that can’t be inverted makes this a non-issue.
(Edit: Added missing “not”.)
polarity issues
Not an issue, you can swap line and neutral freely. It becomes an issue if you want to use three phases and a three phase motor (because the order of phases is important) but that is covered by other sockets. Plain old Schuko is one phase, LNG.
EDIT: thought about it some more, yeah, devices with switches on L may be pose a shock risk in some cases if you swap.
Those 3 way plug outlets are pretty cool
