Question 1: Define the term 'National Grid' in the context of electricity supply.

Answer: The National Grid is a network of high-voltage power lines and substations that transmit electricity from power stations to consumers across the country.

Question 2: Explain why high voltage is used in the transmission of electricity in the National Grid.

Answer: High voltage reduces the current for a given power, thereby minimising energy loss as heat in the transmission lines.

Question 3: Describe the main components of the National Grid system.

Answer: Power stations, step-up transformers, high-voltage transmission lines, substations with step-down transformers, and distribution networks.

Question 1: A power station transmits electricity at a voltage of 400 kV with a current of 500 A. Calculate the power transmitted in megawatts (MW). (Use P = V × I).

Answer: P = 400,000 V × 500 A = 200,000,000 W = 200 MW

Question 2: If the transmission line has a resistance of 0.2 Ω per km and is 150 km long, what is the total resistance of the line? (Use R = resistance per km × length).

Answer: R = 0.2 Ω/km × 150 km = 30 Ω

Question 1: Identify three safety precautions that engineers should follow when working on high-voltage transmission lines.

Answer: Wearing insulated gloves and boots, ensuring equipment is properly grounded, and maintaining a safe distance from live conductors.

Question 2: Describe a basic procedure for safely switching off a section of the National Grid for maintenance.

Answer: The procedure involves notifying relevant authorities, isolating the section by opening circuit breakers, verifying the absence of voltage, and using appropriate personal protective equipment before maintenance.

Question 1: A particular transmission line operates at 400 kV and delivers 1500 MW of power. Calculate the current flowing through the line. (Use P = V × I, rearranged as I = P / V).

Answer: I = 1500,000,000 W / 400,000 V = 3750 A

Question 2: Discuss how increasing the transmission voltage impacts energy loss and the efficiency of power delivery.

Answer: Increasing transmission voltage reduces current for the same power, which decreases resistive energy losses and improves overall efficiency of power delivery.

Question 1: Explain why the National Grid uses transformers to step voltage levels up and down during transmission and distribution. (6 marks)

Answer: Transformers are used to increase voltage for long-distance transmission to reduce current and minimise energy loss as heat. Before reaching consumers, the voltage is stepped down to safer, usable levels. This process ensures efficient energy transfer over large distances while maintaining safety standards.

Question 1: Describe how the design of the National Grid helps prevent power outages and maintains supply stability during high demand periods.

Answer: The Grid uses multiple pathways and redundancy, along with real-time monitoring and automatic switching, to balance load and quickly reroute power if faults occur, ensuring a stable supply.

Question 2: Explain how advancements in smart grid technology could improve the efficiency and reliability of the National Grid in the future.

Answer: Smart grid technology allows for real-time data collection, automated control, and better demand management, leading to increased efficiency, reduced losses, and quicker responses to faults, improving overall reliability.