Why are we using unpolarized plugs here in Europe?

Question

The whole world is using polarized plugs and only Europe is using unpolarized ones. Why is that the case? Isn’t it better to use polarized plugs? Why aren’t fires starting when you plug in the plug the other way around?

Answer 1

Why aren’t fires starting when you plug in the plug the other way around?

There are no fires caused when you plug in an AC device in reverse. The terminals in AC are always swapping positive and negative polarity relative to each other so it is symmetrical as far as functionality the device is concerned. It is not like DC where one terminal is always higher potential than the other terminal.

Polarization for AC is a contingency for safety. One current carrying terminal, the neutral, is connected to the earth while the other, the hot terminal, is not.

The reason one of the two current carrying terminals is anchored somewhere to the earth is to prevent the two terminals from both rising to potentials dangerously high above earth (while still maintaing their relative potential between themselves at 120V, 220V, etc). The potential can rise because the power grid covers a vast area which intercepts the vast amount of charge moving between the earth and the atmosphere. Earthing one of the two current carrying terminals drains the charge and prevents this from happening. Otherwise you might get lightning bolts jumping out at you when you reach for the light switch.

Since you are standing on the earth, you are probably near the potential of the neutral terminal which tends to make it safer (but not necessarily safe) to touch than the hot terminal. That said, you don't want the metallic case of your object to be connected to the neutral either.

That's what the ground line is for. The reason the neutral is safer, but not safe compared to the hot line is because even though the neutral is connected to ground somewhere which may or may not be near you and the neutral carries current. The current flow in the neutral causes a voltage drop between neutral between where you touch it and where it is actually connected to the earth. This can move the potential of where you touch it dangerously away from earth potential. The ground line is also connected to earth but never carries current during normal operation so the potential does not move away from earth.

Answer 2

I don't know the history so these are my opinions.

Why are we using unpolarized plugs here in Europe?

1. Earth Leakage Circuit Breakers (ELCB) or RCD's are cheaper to install than rewiring ancient houses and stone castles which are rare in North America or Africa or other countries that were influenced by American power technology with polarized 2 pin plugs for double insulated items and 3 wire receptacles for PE grounded items on wire plugs.

For EU , it seems the standard 2 wire product must be double-insulated, just as it is in North America (NA), but EU chose it to be independent of the position of the Line wire. Consider that the insulation withstanding rating is 10x to 15x the line voltage and insulation is normally tested with both L&N shorted together for 3 wire products as lightning tends to be common mode. Considering that and the cost of rewiring many old stone homes in EU and using ELCB or RCD's (or the more sensitive GFCI's in NA) I think it was a reasonable choice.

Isn’t it better to use polarized plugs?

• Better how? Cost increase vs little or no safety difference using ELCB's on every outlet?

• What is the cost of rewiring every house in EU with polarized outlets vs adding ELCB's? just to improve insulation only for products with asymmetric biased insulation on some products? That does not include toasters as there is always some filament position that has a hot voltage. (hot in the electrical sense ;))

Why aren’t fires starting when you plug in the plug the other way around?

It's double insulated and only cares about the differential voltage not the relative voltage to Protective earth, yet 3 pin plugs ARE polarized , but I don't know if 3 pin receptacles are, I would assume so but you can verify.

NA changed wiring in the '60s from non-polarized 2 pin receptacles to polarized 3 pin receptacles and the appliances followed suit many years later. Yet some double insulated products, especially from China are still not polarized plugs, with smaller blades. That depends on the Class of the products.

Answer 3

I think polarized sockets are not reliable. There is a chance that someone wires them wrongly and someone dies because of this..So even if polarized sockets were everywhere, devices have to assume that line and neutral could be swapped and take according safety measures.

But then, why even bother about polarized sockets?!