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Why do power lines use high voltages for long-distance transmission?

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Study how a series of gears in a waterwheel translates a stream's energy to a millstone — energy conversion Before the Industrial Revolution, power came from three main sources: humans, draft animals, and water.
The ingenuity people used in harnessing waterpower can be seen in this medieval-style mill. The waterwheel is turned by a stream and is connected to a shaft that leads into the building. At the other end of the shaft is a gear. The connection of a series of gears translates the power from the stream to a shaft that drives a millstone, which grinds flour from grain.
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Power lines use high voltages for long-distance transmission primarily to minimize energy loss caused by electrical resistance in the wires.12

According to Joule's law, the power lost as heat in a conductor is calculated as $P = I^{2} R$ , where $I$ is the current and $R$ is the resistance. Because the power loss is proportional to the square of the current, even small reductions in current lead to significant decreases in energy waste.34

Since the total power transmitted is the product of voltage and current, increasing the voltage allows the same amount of power to be delivered at a much lower current. By using transformers to step up the voltage at the generating station, utility companies can transmit electricity over vast distances with far greater efficiency than would be possible at lower voltages. Once the power reaches its destination, it is stepped down to safer, lower voltages for consumer use.12