An offshore wind farm located 100 km from the coast generates electrical power that must be integrated into the onshore National Grid. Due to the high capacitance between undersea cables and the surrounding seawater, a High Voltage Direct Current (HVDC) interconnector is used for the subsea leg, while the standard onshore transmission system utilizes High Voltage Alternating Current (HVAC).
Which row in the table correctly identifies the type of current used in the undersea transmission link and the typical potential difference of the onshore supergrid transmission lines?
Undersea transmission linkOnshore supergrid transmissionAd.c.230 V a.c.Ba.c.400 kV d.c.Cd.c.400 kV a.c.Da.c.230 V d.c. \begin{array}{|c|c|c|} \hline & \textbf{Undersea transmission link} & \textbf{Onshore supergrid transmission} \\ \hline \textbf{A} & \text{d.c.} & 230\text{ V a.c.} \\ \hline \textbf{B} & \text{a.c.} & 400\text{ kV d.c.} \\ \hline \textbf{C} & \text{d.c.} & 400\text{ kV a.c.} \\ \hline \textbf{D} & \text{a.c.} & 230\text{ V d.c.} \\ \hline \end{array} ABCDUndersea transmission linkd.c.a.c.d.c.a.c.Onshore supergrid transmission230 V a.c.400 kV d.c.400 kV a.c.230 V d.c.Row A: Undersea link is d.c.\text{d.c.}d.c., onshore supergrid is 230 V a.c.230\text{ V a.c.}230 V a.c.
Row B: Undersea link is a.c.\text{a.c.}a.c., onshore supergrid is 400 kV d.c.400\text{ kV d.c.}400 kV d.c.
Row C: Undersea link is d.c.\text{d.c.}d.c., onshore supergrid is 400 kV a.c.400\text{ kV a.c.}400 kV a.c.
Row D: Undersea link is a.c.\text{a.c.}a.c., onshore supergrid is 230 V d.c.230\text{ V d.c.}230 V d.c.
39 exam-style questions on OCR GCSE Physics Powering Earth. Each one has a worked solution and a mark scheme showing where the marks go.