In this schematic, I am demonstrating the advantage of using higher voltage to transmit power to a load. Each load is a 1kW bulb. I included the equivalent resistor on the double-throw switch feeding each load.
The double-throw switch between the two at the loads should be changed to the bottom position when using the high-voltage power source, and the top position when using the lower voltage source. The switch at the power sources switches between high and low voltage.
Each resistor in the transmission lines represents one mile of resistance of an aluminum transmission line. This schematic shows a 1kW load 15 miles from the power source.
Notice the voltage drop across each load and each resistor in the transmission lines when using high vs. low voltage. Also notice the amount of current flowing to achieve the load's power rating. In the low-voltage circuit, almost half of the power consumed is lost in the transmission lines as heat. If you calculate the power consumed at the load you notice the desired power output is substantially reduced in the low-voltage example, where the load in the high-voltage circuit still produces 974 of the 1000 watts. The low-voltage power supply would have to produce almost double the power required to obtain the desired power-rating of the load. If you change the low voltage from 120V to 233V, the load will produce 1kW.
