13.6 Power Plants & The Electrical Grid
Efficiency was one of the main reasons why AC electricity won over DC.
Generators at today’s large scale power plants can produce huge amounts of
power; a significant amount of which can be lost to thermal energy as large
currents pass through transmission lines.
We can use the power equation, P = VI, and Ohm’s Law, R = V/I, to determine the
how much power is lost in transmission wires.
P = VI
P = (IR)(I) using Ohm’s Law
P = VI
P = (V)(V/R) using Ohm’s Law
P = I2R
P = V2/R
SP on p.610
13.6 Power Plants & The Electrical Grid
The Electrical Power Grid
13.6 Power Plants & The Electrical Grid
The generator produces 20 kV of AC, which is immediately stepped up to 230kV or
higher to minimize energy loss during transmission.
The electricity is then sent along power transmission lines supported by towers.
The electricity is gradually decreased in voltage; at a district transformer station,
local transformer station, substation, and finally a pole or ground transformer in
your neighbourhood.
Power plants only generate the amount of electricity that is needed because
electrical energy is difficult to store. Energy is fed into the grid on demand.
If more electrical energy is generated than needed, it is sold to other electrical
grids farther away. If more energy is needed than power plant capacity, it is
purchased from other grids at a higher cost.
13.6 Homework
Questions # 1-3 p.612