@Ash The polarized plug and E26:

The thing is, the E26 thread is only possible to touch when the lamp is not fully in, which by itself (touching thread  on a partially out lamp) is considered a single fault.
Broken Neutral is considered as another fault.
Reversed socket is yet another independent fault.
These two are not dependent on each other (loose bulb does not cause open Neutral nor vice versa)

So you can not have just one single independent fault leading to any exposed metal having dangerous voltage on it.

To have the voltage accessible, the lamp has to be partially unscrewed AND the Neutral has to be broken at the same time.
That would be TWO faults.

Indeed, this concept requires the connection polarity to be guaranteed, which is the case in the US (with the polarized plug, you are not allowed to use nonpolarized with standard E26 sockets), but it is not the case over most 230V area (with the exception of practically only the GB Commonwealth).
Then the sockets must be designed so the thread is either inaccessible (lamp in) or internally disconnected (lamp not fully in, the upper section of the thread when lamp is out completely), aka E27. There the lamp must be partially unscrewed AND the internal connection bridged (so still conductive), so again two faults.
By the way not that much independent as the case of E26 and a polarized plug anymore: If the insulating socket sleeve is cracked (just a one single fault), the thread that could be connected to a phase, becomes accessible. So a single, although less likely, fault leads to a dangerous condition.
Not so in the E26, where the thread is completely metallic and connected to Neutral. There even when the shell becomes accessible, there is still no dangerous voltage on it.


No low voltage in normal environments safety concepts anywhere on the world, even when they differ from each other, anticipate two independent faults at the same time and require the system to be safe with two independent faults. All is based on only one single independent failure being considered at a time. The word "independent" means there is no cascading possible, so an overheat leading to isolation fault are two failures, but one could be consequence of the other one, so the consequent isolation fault is not independent (so does not count as another fault), and its effects then belong to the first fault (so "overheat" causes the "current can flow where it should not").

Same way you may argue the PE wire becoming open AND internal appliance short circuit at the same time, could lead to the exposed metal having live voltage on it, so lead to a dangerous situation. But only because it needs TWO independent faults to happen at the same time, it is not considered a problem.

What about the requirement of a polarized plug on Fluorescent lamps, Xmas light sets, .... (For Fluorescent, i mean in the context of safety, not in the context of lamp starting reliability)

What about the requirement of a polarized plug on Fluorescent lamps, Xmas light sets, .... (For Fluorescent, i mean in the context of safety, not in the context of lamp starting reliability)

The fusing position for the Xmass set is the most likely reason. Or just to not "look suspicious".

The way how ballasts may energize fluorescents when inserted just by one end (assume RS ballast, not a preheat):
If you insert just one end, the lamp is rectifying.
If that is the hot end, the lead ballasts have the capacitor in series. Because the lamp can carry only one current direction and the capacitor has to carry both to be conductive, the setup is in fact not conductive, so the pins sticking out are safe. Or the ballast should have a provision to prevent its operation when the cold end is not inserted.
If you insert just the cold end and that end is at Neutral, you have no voltage there.
But if that end is at Phase, the lamp may ignite, start to conduct (in one direction) and so carry the current to the exposed pins.
This does not have to e the case for all ballasts, but some may be designed along these lines to ensure safety. And you don't really know exactly, the only thing you know is the ballast UL certification applies only for the prescribed connection and that has clearly marked what is the Neutral and what is the Phase. If you reverse that, the UL signature becomes invalid. So to guarantee that, you have to use the polarized plug.

Plus I would guess these days the polarized plugs are the main standard, so making anything else would make it more expensive. So saving of the extra cents looks to me as the most plausible reason behind fluorescent lanterns and the Xmass sets to have their plug polarized. It is just the cheapest plug form.

@funkybulb: @wide-lite 1000: Wait, modern sets of minilights are supposed to have polarized plugs? Because none of the sets I or my parents bought in the last 5 or 10 years have had polarized plugs (except C7 & C9 strings), even sets I have that were made this year don't have polarized plugs .

I've never cared. I used whatever cord fits in the plug and that is long enough to suite my need.

I have a cloth cord from the 30s powering an emergency light.

中国人表示，我也会用美标极性插头的电源线来防止我不小心将100-127V的灯具误插到220V插座上，其实中国的插座也是分极性的，左零右火上接地。

实中国的插座也是分极性的，左零右火上接地。

But is the code really mandating the exact polarity of the connection?
Because although the European type C/E sockets are polarized, the codes mandates only the PE connection (obviously). The working conductor could then be connected in either way, with just the condition of being the same among the single building (older standards in some states required certain polarity, but at the same time you could buy socket splitters having on opposite sides opposite polarity connection, so violating even the "common connection in one building" rule). In fact many distribution systems even do not have working Neutral (these have the 230V across two phases), so any device should be constructed so the polarity does not make any difference in working, nor safety.

确实是分极性的，因为中国的三极插头是和澳大利亚相同的标准，排列呈三角形。但是两极插座兼容欧洲和日本的，所以使用日本电器时就有点提心吊胆的，生怕哪天忘了用变压器就直接烧毁了。

@funkybulb: @wide-lite 1000: Wait, modern sets of minilights are supposed to have polarized plugs? Because none of the sets I or my parents bought in the last 5 or 10 years have had polarized plugs

No. Standard mini sets all have non-polarized plugs. The 'heavy-duty' or 'commercial grade' mini sets all have polarized plugs (to prevent plugging them into standard mini sets).

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As for me, yep I'll use cords with non-polarized plugs on homebuilt stuff (or polarized, all depends on what the light is, and what cords I have laying around.)
I've also taken a good number of plugs on extension cords to the grinder .LOL. to make them non-polarized, for plugging into strings of Christmas lights...