1. Complete the sentences:
The National _____ is a network of high voltage transmission lines that connect _________ _______ with substations around the country. The electricity is generated at __________ V, 1/3-phase. The electricity is stepped up using __________ transformers to _____ voltage. This means that the ________ is lower, so less energy is wasted.
3 sets of cables hang from the transmission towers, also called ___________. The currents and voltages are ___________, so that the current in the neutral wire is very small/big. At the sub-station, the voltage is stepped up/down by a transformer. Then _________ voltage cables connect the substation to factories and homes.
2. Draw a circuit diagram to show the idea of a star connection.
3. Draw a circuit diagram to show the idea of a delta connection.
4. Sketch a graph and a phasor diagram to show the idea of 3-phase electricity.
5. Explain why a 415 V 3-phase supply to a small factory unit shares the same cables as the homes around it.