They tell people about the electrical utility infrastructure and warn them that there are serious electrical hazards around. This includes things like utility poles, transformers, substations, metering equipment, switchgear, and power distribution components.

These signs are used by electrical utilities, municipalities, industrial facilities with their own electrical infrastructure, commercial property owners with pad-mounted transformers or switch-gear, construction companies that work near utility equipment and anyone who manages electrical distribution assets that the public or workers might come into contact with.

You should put them on transformer enclosures and pad-mounted equipment, at substation fencing and gates, on utility poles where people can see them, on vaults and manholes, on metering cabinets and at any point where someone might try to get into the electrical utility infrastructure without permission.

There are rules like OSHA 29 CFR 1910.303 through 1910.335 that cover safety in general industry. There are also rules like OSHA 29 CFR 1926.950 through 1926.960 that cover safety for construction work near utility lines and equipment. Then there is NFPA 70E, which talks about work practices near energized utility equipment. OSHA 29 CFR 1910.145 covers signs and tags that prevent accidents.

For equipment that the public can see, like pad-mounted transformers and utility poles, it is standard to mention the voltage on the sign. For signs inside a facility near equipment, if people already know about the voltage, it might be written down, but putting it on the sign gives people more information when they approach it.

Yes, they are. Enclosures and fencing are barriers that stop people from getting to the equipment. Signs tell people why those barriers are there and what might happen if they bypass them. Both barriers and signs are necessary for electrical utility equipment.

Yes, they can. The signs are made of vinyl that can handle sunlight, rain, wind, and very hot or cold temperatures without fading or peeling. Since electrical utility equipment is often outside all year, the signs need to be able to withstand the elements.