I was looking at an electrical installation and came across unfamiliar symbols on the front of a pair of meters.

These are from three-phase 240v meters running on a timed system. One each for peak/off-peak usage.

On the first image, I recognise part of the lower row: indicating 50Hz frequency, Unknown symbol Double insulated CE safety mark

I don't however recognise the line-and-circle symbols nor the ratchet-type symbol. I have been unable to find search terms to even start looking them up?

My best guess is that it has something to do with supported wiring schemes for the meters.

Can anyone shed some light as to what these are called and what they mean?

Thank you.

Image 1 Image 2

  • 1
    \$\begingroup\$ Is it power meter? Probably means the mechanism can not go in reverse. \$\endgroup\$
    – user263983
    Commented Apr 9, 2021 at 11:17
  • 1
    \$\begingroup\$ Hmmm The cog and wedge symbol I would assume means the meter is non reversible so you can't roll it back. The line and dot diagrams from the bottom white diagram in order look like 3 phase, single phase, single phase line to line, two phases of 3 phase, and the V and L shaped I'm not sure of. A 90 degree angle may indicate true vs reactive or something, but the 60 degree angle... hmmm. \$\endgroup\$
    – K H
    Commented Apr 9, 2021 at 11:49

2 Answers 2


Below are my interpretations of the various symbols. I included more than just the line-and-circle symbols, for the benefit of future visitors:

50 Hz AC:

50 Hz AC

Double Insulated:

Double insulated

Non-reversing (not suitable for power export or net-metering):


CE Marking (meets European Community standards):


Three-phase Wye:

Three-phase Wye

Single-phase plus grounded neutral:

Single-phase plus grounded neutral

Single-phase ungrounded:

Single-phase ungrounded

Single phase with center tap neutral:

Single phase with center tap neutral

Two phases of 3-phase system, plus neutral (This would give you 230V from phase to neutral, or 400V between phases, but no three-phase):

Two phases of 3-phase system, plus neutral

Corner-grounded 3-phase open delta:

Corner-grounded delta

Quadrature (phases 90° apart):


Contains lithium battery (probably for backup or to power a communications device):

Lithium Battery

  • \$\begingroup\$ Instead of "Single Phase Ungrounded" could you say "Single Phase Line to Line"? The system should still be bonded and grounded, even if no neutral is present or system is isolated. Nice answer. \$\endgroup\$
    – K H
    Commented Apr 9, 2021 at 21:59
  • 1
    \$\begingroup\$ @KH It's entirely possible for it to be ungrounded - not everything is a residential service. Isolated systems exist, usually in situations where continued service through a fault is desired. It could just be a single-phase without the meter seeing a neutral, but the meter doesn't care whether it's grounded or not. \$\endgroup\$ Commented Apr 10, 2021 at 3:23
  • \$\begingroup\$ @SomeoneSomewhereSupportsMonica Non current carrying parts are usually bonded, grounded or isolated, and an isolated system where they didn't bond and ground the non current carrying parts would be rare. There was a question recently about a shipboard system for example that used isolated 480V delta with ground fault detection. If the system is not bonded and grounded, ground fault detection does not work in that case. Even without a grounded neutral/identified conductor, saying "ungrounded" is a misnomer and untrue, and "line to line" more clear. \$\endgroup\$
    – K H
    Commented Apr 10, 2021 at 3:39
  • \$\begingroup\$ Who is Monica? Is there some sort of ancient grass roots political movement going on around here? \$\endgroup\$
    – K H
    Commented Apr 10, 2021 at 3:41
  • 2
    \$\begingroup\$ @KH Here's a thread that describes the events of late 2019 relating to Monica Cellio, which prompted a lot of users to add messages supportive of her to their display names: meta.stackexchange.com/questions/334399/… \$\endgroup\$ Commented Apr 10, 2021 at 6:51

In order of appearance:

  • Three-phase star (wye) connection.
  • Two-phase and neutral. (Note that if neutral isn't present then it would be a single-phase connection.)
  • Quadrature (90°) phases and neutral.
  • Split phase (180°) and neutral.
  • Single phase and neutral.

The ratchet symbol indicates that the meter won't run backwards and so won't register exported energy. This is common because there would be a different tariff for consumption and supply. Import and export could be monitored by connecting two of these meters back to back.


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