In electrical engineering, the power grid and power transmission is a core part of energy systems. The basis of the power grid is sinusoidal alternating current, to capitalise on the properties of transformers. The main function of the grid is to deliver power. We manipulate network voltages and currents with transformers to efficiently deliver desired levels of power.
The residential supply voltage in Canada and the US is 120 volts RMS.
Power transmission
One of the big problems of the modern power grid is that for long-distance transmission, power lines have a small amount of resistance that builds up, leading to larger drops in voltage.
For long-distance transmission, step-up transformers are used to raise the voltage (to at least 110 kV RMS). Local sub-stations will use step-down transformers to reduce the voltage for distribution.