The Electrical Grid: A Complex Network
The electrical grid is the interconnected network that delivers electricity from power plants to consumers. It has three main parts:
1.Generation: Power plants (e.g., coal, nuclear, hydroelectric, wind) produce electricity.
2.Transmission: High-voltage transmission lines carry the electricity over long distances.
3.Distribution: Lower-voltage distribution lines deliver the electricity to local neighborhoods and individual homes and businesses.
High-Voltage Transmission
Power is lost as heat in transmission lines due to the resistance of the wires. This power loss is given by the formula P_loss = I²R, where I is the current and R is the resistance.
To minimize this power loss, it is crucial to transmit electricity with the lowest possible current (I).
Since electrical power is also given by P_transmitted = IV, if we want to transmit the same amount of power with a very low current (I), we must use a very high voltage (V).
This is why electricity is 'stepped up' to very high voltages (e.g., hundreds of thousands of volts) for long-distance transmission.
Transformers
A transformer is a device that changes the voltage of an alternating current.
It consists of two coils of wire, a primary coil and a secondary coil, wrapped around a common iron core.
A changing current in the primary coil creates a changing magnetic field in the core, which in turn induces a current in the secondary coil (Faraday's Law of Induction).
Step-Up Transformer: Has more turns in the secondary coil than the primary. It increases voltage and decreases current. Used at power plants.
Step-Down Transformer: Has fewer turns in the secondary coil. It decreases voltage and increases current. Used on utility poles and at substations to deliver power safely to homes.
Transformers only work with Alternating Current (AC).
Alternating Current (AC) vs. Direct Current (DC)
Direct Current (DC): The electric charge flows in only one direction. This is the type of power produced by batteries.
Alternating Current (AC): The electric charge periodically reverses direction. The U.S. grid operates at a frequency of 60 Hz. AC is used for power grids primarily because its voltage can be easily changed with transformers, which is essential for efficient long-distance transmission.