This deep dive covers How the National Grid Works within National Grid & Transformers for GCSE Physics. Revise National Grid & Transformers in Extra Topics for GCSE Physics with 13 exam-style questions and 12 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 2 of 12 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 2 of 12
Practice
13 questions
Recall
12 flashcards
🧲 How the National Grid Works
Figure 1: The National Grid — step-up transformers increase voltage for efficient transmission, then step-down transformers reduce it for safe use
The National Grid is the network of cables that distributes electrical power across the UK. It works through a series of voltage changes:
- Power station generates electricity at about 25,000 V (25 kV)
- Step-up transformer increases voltage to 275,000 V or 400,000 V for long-distance transmission
- Transmission cables (on pylons) carry power across the country at high voltage, low current
- Grid substation (step-down) reduces to 33,000 V for heavy industry
- Local substation (step-down) reduces to 11,000 V then to 230 V for homes
Why High Voltage for Transmission?
The equation P = I²R shows that power wasted in the cables depends on current squared. If you halve the current, you quarter the power loss. The National Grid transmits at very high voltage (and therefore very low current) to minimise this wastage. A cable that would lose 50% of the power at low voltage loses less than 2% at 400,000 V.