A regional substation supplies a refrigerated distribution centre through a buried cable. The transmission potential difference is 132 kV132\ \mathrm{kV}132 kV and the total resistance of the cable is 3.0 Ω.
To keep cable heating within its design allowance, the power lost in the cable is capped at 27 kW.
| Operating plan | Input power |
|---|---|
| P | 9.24 MW9.24\ \mathrm{MW}9.24 MW |
| Q | 11.88 MW11.88\ \mathrm{MW}11.88 MW |
| R | 13.86 MW13.86\ \mathrm{MW}13.86 MW |
| S | 15.84 MW15.84\ \mathrm{MW}15.84 MW |
Which operating plan transfers the most power while keeping the cable loss within its design allowance?
Plan P, transferring an input power of 9.24 MW9.24\ \mathrm{MW}9.24 MW
Plan Q, transferring an input power of 11.88 MW11.88\ \mathrm{MW}11.88 MW
Plan R, transferring an input power of 13.86 MW13.86\ \mathrm{MW}13.86 MW
Plan S, transferring an input power of 15.84 MW15.84\ \mathrm{MW}15.84 MW
108 exam-style questions on Edexcel GCSE Physics 13.2 Transformers and the National Grid, covering 13.2.1 Transformers and induction, 13.2.2 The transformer turns-ratio equation, 13.2.3 The National Grid, 13.2.4 The transformer power equation, and 13.2.5 Advantages of high-voltage transmission. Each one has a worked solution and a mark scheme showing where the marks go.