ISO/IEC Power/Ground Symbol in schematics?

Question

Yet again, we are debating with colleagues to choose the correct power symbols in our schematics.

Some argue that using the horizontal 4-lines symbol for GND is a misunderstanding because this is not a real ground. Others say that only arrows are valid. On the 60617-2 snippet below, one can see that in French, the 02-15-01 symbol is named "Terre" (Earth) in french, but "Earth/Ground" in english. Thus, I am used to using this symbol when something is physically connected to the Earth.

So my question would be: is there an ISO/IEC standard about power symbols used in EDA, and which symbol is used to differentiate signal "GND" from power ground connected to Earth?

Here are some examples in my EDA software:

In ISO/IEC 60617-2:1996 I only found these references. It seems that all other symbols are not standard. Is that correct?

Answer 1

I’d like to add that the IEC 60617 “Frame/chassis” symbol had once been obsoleted in 2001, and has been revived and renamed to “Functional equipotential bonding.” Now it stands for more general things.

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IEC 60417 does not contain schematic diagram symbols.

Note that the icons in IEC 60417 are irrelevant as for schematic drawings.

IEC explains:

IEC 60417 graphical symbols are primarily intended to:

• identify the equipment or a part of the equipment (e.g. a control or display);
• indicate a functional state (e.g. on, off, alarm);
• designate connections (e.g. terminals, filling points for materials);
• provide information on packaging (e.g. identification of contents, instructions for handling);
• provide instruction for the operation of the equipment (e.g. limitations of use).

IEC 60417 does not apply to symbol originals for:

• safety signs;
• use on drawings and diagrams;
• use in technical documentation of products and in technical product documentation;
• use for public information.

Answer 2

Based on IEC 60617 you have 5 symbols (02-15-01 to 02-15-05) for ground reference.

• is referred to as "earth general symbol". A note says: supplementary information might be given if the status or purpose is not apparent.
• is frame or chassis, the hatching may be omitted, but then the line representing the frame must be thicker (looks like your leftmost symbol but with a thicker line at the bottom)
• is equipotentiality.

Then there are two variants of the earth symbol with circles:

• full circle encloses earth symbol: protective earth
• semicircle above earth: noiseless earth

Practice probably differs always a bit. I've seen the leftmost symbol used for the primary side reference point and the rightmost for secondary side reference point. Or the other way round.

The first symbol could be used in any way and I'd not interpret any special meaning into it, until the schematic shows me otherwise, but the close resemblance to protective earth makes me not use it on my own schematics.

I think only the frame and protective earth symbol have been used correctly in all the schematics I've seen...