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Generation, transmission and distributionWhy send electricity across the country at 400,000 volts?
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The question at the end: Why send electricity across the country at 400,000 volts? The answer is in the notes below.
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- Generate: fossil fuels or nuclear energy make steam, which drives a turbine and generator at about 25 kV. Solar and hydro are other sources.
- Step up to 400 kV (275 kV is also used) to transmit across the country, say from Cornwall to Birmingham. A higher voltage means lower current for the same power, so thinner cables and smaller losses.
- Regional transformers step down to 132 kV, then local ones to 33 kV or 11 kV. This is distribution. A big factory might take 11 kV directly.
- Step down again for streets: 230 V for domestic, and 400 V for commercial and industrial properties (shops, schools, factories).
| Learn these | Voltage |
|---|---|
| Generation voltage | 25 kV |
| Transmission voltage | 400 kV (also 275 kV) |
| Distribution voltages | 132 kV · 33 kV · 11 kV |
| Supply to buildings | 400 V 3-phase · 230 V single-phase |
Most houses have a 60, 80 or 100 A main fuse. Transformers only work on AC.
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