In my EE.SE search today, I noticed that high-voltage is a really... bad tag. Not the tag itself, but the fact that it's managed to propagate into so many not-high-voltage questions. I'd say 2 of the 10 most recent questions would qualify. The individual voltage tag is also odd but I see we'd like to off that one altogether: Tags: Voltage, current, and power (oh my)

I'd, possibly, like to offer some alternatives. We currently have high-voltage and low-voltage tags according to the IEC definitions but we don't have extra-low-voltage to round out the classes. Those three tags would leave us with a split of

  1. (HV) >1000 V
  2. (LV) 50-1000 V
  3. (ELV) <50 V

These are nice but I don't think these lines drawn in the sand by IEC play nicely with the questions on EE.SE. Namely, there's too many questions that hover in that 30-60 V range that shouldn't be lumped in with 750 Vrms questions. I think we would actually benefit from using some more intuitive voltage categories instead. Something like this:

  1. high-voltage (>1000 V)
  2. industrial-voltage (208, 347, 480, 600 V)
  3. mains-voltage (120 V, 240 V)
  4. low-voltage (0 to 50 V)

For the purpose of the site, I don't think it's necessary to delineate medium voltage, high, extra, ultra high voltage, transmission, or distribution levels. Anyone asking those questions will likely get the attention of the right people by tagging high-voltage or power-engineering.

Ultimately, I'd just let to set up a watch on actual industrial and high voltage level questions, occasionally look at some mains levels, and ignore questions tagged as high-voltage when someone is using 24 V with a some micro-controller.

  • \$\begingroup\$ Something like your latter categories seems better AS eg ELV is by no means as low as 50V in some administrations and AC and DC vary and ... . \$\endgroup\$
    – Russell McMahon Mod
    Aug 18, 2022 at 13:00
  • \$\begingroup\$ With IEC 61010, the dividing line is at 63 volts between dangerous and non dangerous voltage \$\endgroup\$
    – Voltage Spike Mod
    Aug 18, 2022 at 14:17
  • \$\begingroup\$ Definitely a few standards that try to wedge some definitions in. Regardless, the high-voltage tag is used improperly. There's a handful of proper high voltage questions. There is no ELV tag at present, meaning everything else would just be tagged as low-voltage... making it as meaningful as voltage, IMO. \$\endgroup\$
    – user199402
    Aug 18, 2022 at 14:22
  • \$\begingroup\$ There are always additional tags for clarity but something like induction-motor low-voltage and induction-motor industrial-voltage are usually handled by two different engineers with experience in two different skillsets. Common theory definitely overlaps but not necessarily the standards or practices. Just food for thought. Tags are definitely cluttered already so I also understand not wanting to add more! \$\endgroup\$
    – user199402
    Aug 18, 2022 at 14:26
  • \$\begingroup\$ In my jurisdiction, the boundary between ELV and LV is at "50 volts AC or 120 volts ripple-free DC"... (HV is still anything over 1,000 V.) \$\endgroup\$ Aug 20, 2022 at 9:42
  • \$\begingroup\$ @Li-aungYip, I believe that's the same as IEC, I just didn't write in any DC values. \$\endgroup\$
    – user199402
    Aug 20, 2022 at 16:13
  • \$\begingroup\$ The European LVD Directive makes the distinction 50 VAC or 75 VDC. \$\endgroup\$
    – Lundin
    Aug 22, 2022 at 13:28
  • \$\begingroup\$ Regarding mains voltage, that's traditionally somewhere between 220VAC and 240VAC, I'd say 230VAC 50Hz is most common nowadays. See en.wikipedia.org/wiki/Mains_electricity_by_country. North/Central America stands out a bit. \$\endgroup\$
    – Lundin
    Aug 22, 2022 at 13:37
  • \$\begingroup\$ Well, high-voltage is 12V in my TTL world. So I guess YMMV, and depends on context. \$\endgroup\$ Aug 30, 2022 at 20:53

2 Answers 2


While I, personally, like and use the low, mains, industrial, high descriptions, there is a big problem with 'low voltage' being used differently in this context, and in the IEC context. That would lead to confusion, and bring our tags into disrepute.

Rather than argue about what 'low voltage' should mean, how about being numerically explicit? Not only is below 50 V explicit, it's self descriptive, and it's not a recognised description, so it doesn't conflict with IEC nomenclature, or any of the other electrical authorities.

If done purely numerically, there is a potentially problematic overlap between the 51 V to mains 240 V and industrial from 208 V. However, here we want to catch people handling 'domestic mains', as distinct to 'industrial mains', which incidentally will often be three phase.

There is no need to be consistent and use only numerical or only descriptive tags, a hybrid approach would be fine.

below 50
50 to mains
industrial - perhaps this one is superfluous?
50 to 1000
above 1000

I feel it would be useful to distinguish between domestic mains, and industrial mains, from the point of view of assessing the skill level of the OP. The former will tend to not know what they are doing, yet still be wanting to mess with lethal voltages. The latter should know what they are doing from a physics/electricity point of view, but may not have the required certifications in order to make those changes at a 'place of work', which will often have safety regulations that must be adhered to.

There's another physically useful boundary at 10 kV (ish) where corona control starts to become significant (the ozone-smelly stuff, not the virus).

  • \$\begingroup\$ We do already have an industrial tag so it may be superfluous. A questions tagged with the numerical voltage along with industrial would likely have the same effect. \$\endgroup\$
    – user199402
    Aug 20, 2022 at 22:58
  • \$\begingroup\$ Industrial could be anything, there are lots of more or less standardized supplies depending on what equipment you work with. For example a machine can be powered with some high voltage and 3 phase, but electrical subsystems on that machine may be powered with 230VAC or 24VDC. \$\endgroup\$
    – Lundin
    Aug 22, 2022 at 13:32
  • \$\begingroup\$ I'd drop the industrial, lump it together with mains. That's what it is after all. \$\endgroup\$
    – Mast
    Aug 23, 2022 at 18:45
  • \$\begingroup\$ I've been informed by top social media personalities and many politicians that corona control is, in fact, a communist plot to destroy the economy. \$\endgroup\$
    – user253751
    Aug 24, 2022 at 12:35
  • \$\begingroup\$ @user253751 citation needed \$\endgroup\$
    – Neil_UK
    Aug 24, 2022 at 12:58
  • \$\begingroup\$ @Mast I feel the need to distinguish, or at least give the users themselves the opportunity to distinguish, between domestic mains, ie people who don't know what they're doing f*'ing around with lethal voltages, and industrial mains, which is people who ought to know what they're doing, f*'ing around (possibly in contravention of safety at work regulations) with lethal voltages. \$\endgroup\$
    – Neil_UK
    Aug 24, 2022 at 13:01
  • \$\begingroup\$ @Neil_UK example: nbcnews.com/news/us-news/… :) \$\endgroup\$
    – user253751
    Aug 24, 2022 at 13:02
  • \$\begingroup\$ @user253751 Oh, that corona, love it! \$\endgroup\$
    – Neil_UK
    Aug 24, 2022 at 13:03
  • \$\begingroup\$ @Neil_UK -- that's what I was trying to split in my original question as well. Or the difference between someone using mains for a commercial product vs mains in a factory. Maybe we just change the tag to read like high-current: "this means a lot of things, add your current into the question" haha \$\endgroup\$
    – user199402
    Aug 30, 2022 at 16:53

The tag description seems to say "yeah, that's the IEC definition, but there are many definitions".

I think the tag is fine, in that you'd be hard-pressed to find a better tag in many situations.

As an example, if I see something tagged [op-amp] [high-voltage], I probably know what I will find in such a question, regardless of any IEC definition.

  • \$\begingroup\$ Right -- in that scenario, you're likely to find a question where the user has an op-amp and 120V. In my opinion, 120V is not high-voltage at all, it's low-voltage. I understand that's splitting hairs and if the consensus is that people don't really care then we can just leave it. \$\endgroup\$
    – user199402
    Aug 30, 2022 at 16:44
  • \$\begingroup\$ On the flip side, if high-voltage is whatever the OP deems as high (24V car battery, 50VDC, 120VAC mains, 4kV) then it's as useless as voltage. \$\endgroup\$
    – user199402
    Aug 30, 2022 at 16:46

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