P1.4.2 The National Grid

Question 1

What is the purpose of the National Grid?

Answer 1

The National Grid is the network of pylons and cables that covers the whole of Britain. Electricity is distributed from power stations to consumers along the National Grid. It enables power to be generated anywhere on the grid, and then be supplied anywhere else on the grid.

Question 2

Why is the voltage boosted up so high?

Answer 2

• To transmit the huge amount of power needed, you need either a high voltage or a high current (P = V x I).
• The problem with a high current is that you lose loads of energy through heat in the cables.
• Therefore, for a given power, increasing the voltage reduces the current required and this reduces the energy losses in the cable.

Question 3

Explain how the various changes in the National Grid.

Answer 3

• To get the voltage high enough requires transformers as well as big pylons with huge insulators, but it’s still cheaper.
• A step-up transformer increases the voltage at one end, for efficient transmission, and then a step-down transformer reduces it down again to safe, usable levels at the other end, to be supplied to consumers.

Question 4

Compare the advantages and disadvantages of overhead power lines to cables buried in the ground.

Answer 4

\+ Lower set up costs.
\+ Easy to access to repair faults.
\+ Easier to set up.
\+ Minimal disturbances to the land.
- Lots of maintenance needed.
- Visual pollution.
- Can be affected by the weather.
- Less reliable.

Question 5

Compare the advantages and disadvantages of cables buried in the ground to overhead power lines.

Answer 5

\+ Minimal maintenance needed.
\+ No visual pollution - it's hidden.
\+ Can't be affected by the weather.
\+ More reliable.
- Higher set up costs.
- Harder to access to repair faults.
- Harder to set up.
- Lots of disturbances to the land.

Question 6

Evaluate ways of matching supply with demand.

Answer 6

1. The energy supplied to the National Grid needs to be increased to meed these demands.
   - Supply can be increased by opening more power plants, or increasing their power output.
2. Or the energy demands of consumers will need to decrease.
   - Demand can be reduced by consumers using more energy-efficient appliances, and being more careful not wasting energy in the home.