4.6 The National Grid
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The national grid. On the left we have the method that generates the electricity (nuclear, coal power station, wind turbine, hydroelectric power station etc.), then a step-up transformer, electrical cables, step-down transformer and then the final consumer of electricity.
The National Grid takes energy from where it has been produced to anywhere that it is needed. It facilitates a variety of energy resources to be fed into the grid.
Transformers
The National Grid uses cables to transport energy from where it has been produced to where it is needed. To transform a large amount of power, you need a high voltage or a high current (EXPLAIN WHAT THESE MEAN). The issue with a high current is that a significant amount of energy is lost through the cables heating up as electricity travels through it. Therefore, the National Grid chooses to have a high voltage and a low current.
Transformers on the grid allow the voltage and current to be changed. There are two types of transformers. The first is a step-up transformer. A step-up transformer increases the voltage to 400,000 V, 275,000 V or 132,000 V. At these voltages the amount of energy lost through heat in the electrical lines is reduced. Power stations tend to produce electricity at 25,000 V, which is why step-up transformers are needed. After the electricity has passed through the step-up transformer it will travel through high voltage transmission lines to where it is required. Emphasise this point!!!
When the electricity has got to where it is going to be used, it goes through a second transformer, which reduces the voltage of the electricity to a safe level. The voltage of household electricity is about 230 V. The second transformer is known as a step-down transformer.
The National Grid uses cables to transport energy from where it has been produced to where it is needed. To transform a large amount of power, you need a high voltage or a high current (EXPLAIN WHAT THESE MEAN). The issue with a high current is that a significant amount of energy is lost through the cables heating up as electricity travels through it. Therefore, the National Grid chooses to have a high voltage and a low current.
Transformers on the grid allow the voltage and current to be changed. There are two types of transformers. The first is a step-up transformer. A step-up transformer increases the voltage to 400,000 V, 275,000 V or 132,000 V. At these voltages the amount of energy lost through heat in the electrical lines is reduced. Power stations tend to produce electricity at 25,000 V, which is why step-up transformers are needed. After the electricity has passed through the step-up transformer it will travel through high voltage transmission lines to where it is required. Emphasise this point!!!
When the electricity has got to where it is going to be used, it goes through a second transformer, which reduces the voltage of the electricity to a safe level. The voltage of household electricity is about 230 V. The second transformer is known as a step-down transformer.
Overhead power cables.
Overhead vs Underground Cables
Electricity is transported by high voltage transmission lines. We can have underground cables or overhead cables that are held up by pylons. There are advantages and disadvantages of each.
Electricity is transported by high voltage transmission lines. We can have underground cables or overhead cables that are held up by pylons. There are advantages and disadvantages of each.
- Overhead Cables:
- Advantages: cheaper, easy to set up and fix
- Disadvantages: look ugly, affected by weather (blow over in the wind/ trees fall on them) and need lots of maintenance
- Underground Cables
- Advantages: more reliable, less effected by weather, less maintenance and are unseen so no visual impact
- Disadvantage: more expensive (significantly more), hard to access if there is an issue, harder to set up and a bigger disturbance on the land