I want to transmit data and power over 10 meters at 12 volts with 1 amp. I don't know if I could do it using UTP, because that's a standard for other things. Which standard should I choose? Number of cables needed 4 at least. Frequency irrelevant, slow. The question is; I'm not following the rules of UTP I'm making my own rules, so I suppose I cannot use UTP even if it fits my needs because if someone plugs a computer there it can be damaged. Is there a general purpose standard?
You should consider Fast Ethernet (100Base-Tx) with power over Ethernet (PoE). You can use a 4 wire UTP for that without the possibility to damage a computer at the other side, but you have to be careful with your current of 1 A. When using PoE, the current flows through the coupling transformers windings and 1 A will probably be to much.
If you are looking for a simpler solution you should have a look at the AS interface (ASI bus).
Or build a custom solution which is a little fiddly and could involve capacitive coupling like shown below (DC free channel coding required).
Answer to your updated question:
UTP is just a standard for wires and does not describe the kind of connector that is attached to it (western RJ45 for Ethernet connections to computers). Therefore you can use UTP without doubts. Aggreed?