Why all country have different standard voltage?

(1)Is standard voltage depend upon the source from electrical enery produce?

(2) which standard voltage and frequency is best...

220v is best or 110v?

---The voltage does not depend of the source, depends of the transmission lines.

The voltage of the source can be changed to any other voltage with a transformer.

When you have 3 phases, you have 220V having contact with 2 of this 3 phases, the source of this voltage is a DELTA transformer.

When you have 4 phases (included ground or zero) you need to have contact with one of this phases with voltage and phase zero. As result you obtain 127V and the source of this voltage is a Y transformer. Also you can have the 220V service when electric company installs you to two phases with voltage.

---In the countries with 4 lines of transmission (Y trasformer), you can have both voltages. The home service is 127V and industrial service is 220V. (Also there are a lot of more different voltages).

---220V service is better because you can use more power with less amperage.
The standard voltage is set by the electricity generator. Since different countries designed their systems independently, each one came up with a different standard. Gradually countries changed until there are only a few standards left.

America 110
Europe 230 (was 220 and 240 until a few years ago)

I think most of the rest of the world use 220.

Which is best?

Low voltage means you're not as likely to be killed if you get a shock, but that there are likely to be more fires due to wires overheating.
220 is best. U.S. standard is 120 for household. Consider that half of the copper in U.S. household and office wiring could have been saved if we had gone 220. That is a lot of copper. I believe, historically, that there was a rush to a standard. Edison's first electrical system was (I'm just making an educated guess here) 100 volts because it is a nice round number. But, being DC and having no possibility of using transformers, as you got farther from the generator the voltage would drop. Incandescent bulbs (Edison's light) are very sensitive to voltage and get quite dim at lower voltages, so the U.S. standard went (in my lifetime) from 110 to 115, briefly 117, and now is 120. Edison and his DC have been history for a long time, but the legacy hangs on. Europe and just about the entire rest of the world waited a bit and went 220. Is it more dangerous than 120? Well, you get killed faster and more certainly, if that matters. The Europeans also went with 50 cycles instead of 60. I have no idea why. Transformers and motors take more iron, I believe, at lower frequencies, so it would not seem to be an advantage. Maybe another "nice round number" situation.
Due to the local evolution of the power grids in that area.
Rule of thumb, higher the voltage, lower the cost to transmit the power to the end user. This is due to smaller wire diameter needed to carry the same amperage.

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