National Grid Physics

You have probably interacted with the national grid in some way or another in order for you to read this article. The grid exists to get electricity from where it is generated to where it is needed or required, so you probably used the national grid to charge your phone this morning, or it's even powering the computer that you are using right now! We're going to discuss what is involved within the national grid, as well as how it works to transport massive amounts of electricity across the country.

What is the meaning of the national grid?

All of the electricity in the country has to be generated somewhere, which is usually within power plants around the country. The main way this electricity gets from power stations to users is via the national grid.

The vast majority of the electricity in the national grid is transferred via overhead transmission cables, where the current must be kept low in order to have minimal energy loss to heat within the wires.

What does the national grid system do?

The national grid isn't just a web of connections all over the country. It is also important for making sure that electricity production keeps up with demand. You see, the amount of electricity being used changes throughout the day, as people wake up, go to work and come home. The operators of the national grid can predict when large amounts of electricity are going to be required, and adjust the amount of electricity being produced and transported accordingly.

Most of the time, power plants are running at below their maximum operating capacity, and can therefore generate a lot more electricity when the national grid demands it. Several smaller power stations are kept in a standby state that can be spun up relatively quickly if the demand is even higher than the standard power plants can supply.

What are some features of the national grid?

The most obvious and widely observed features of the national grid are the overhead cables, called powerlines, that span the British countryside, like the one shown below. There are a few different types of overhead cabling that you will see around the UK, but not all of them carry electricity. The easiest way to tell if an overhead cable is carrying electricity is by listening for the constant buzz that they make as you get closer to the pylons.

A typical overhead powerline in Kent, Wikimedia Commons CC BY-SA 2.0.

As well as these overhead transmission cables, the national grid is made up of buildings called transformers. There are two types of transformers within the national grid: step-up transformers and step-down transformers. A step-up transformer takes the electricity generated by a power station and prepares it for transmission across the country by increasing the voltage, whereas a step-down transformer takes electricity from overhead wires and makes it usable by consumers by decreasing the voltage. The buildings that house these transformers are often called substations, and electricity can flow through any number of substations between the power plant and the user of the electricity.

A typical electrical substation, Wikimedia Commons.

A diagram of the national grid

To help you to understand how the national grid works, there is a simple diagram below that shows you what the national grid does, and the order from electricity producer to consumer. Summarised, we have the following.

1. Electricity (electrical power) is produced in a power station.
2. A step-up transformer increases the voltage such that the same amount of power can be transported with a smaller current, decreasing the energy losses to heat.
3. The power lines transport the electricity from place to place.
4. A step-down transformer decreases the voltage to a much lower value such that households can safely use the electricity provided.
5. Households receive the low-voltage electricity.

A simplified version of the national grid, StudySmarter Originals.

Electricity transfer methods in the national grid

So, we've already discussed what hardware makes up the national grid. Now, let's discuss how electricity gets around. The national grid system aims to get electricity to consumers with as little waste heat as possible. Waste heat is bad for an electricity transmission system, as it cuts the efficiency and decreases the amount of electricity getting from the producers to the consumers. The easiest way to reduce the amount of energy lost to heat is to decrease the amount of heat generated by transmission via overhead cables!

The best way to reduce this heat is by reducing the current within the overhead and long-distance transmission cables. The national grid uses an extremely high potential difference alongside a very low current. This does, however, keep the amount of power travelling through the cables the same, thanks to the power equation

,

whereis power,is voltage, andis current. A step-up transformer takes the voltage of the power plant (which is around) as an input, and outputs electricity at a voltage of about, with a current of about. At the other end of the power network, where a consumer would like to use this electricity, the voltage needs to be returned to a safer level, at about. A step-down transformer is used to convertto, after which the electricity is distributed to a large number of consumers in the area. This ensures that the national grid is an efficient way of transferring electricity across the country.