Lesson Notes By Weeks and Term v4 - SHS 1
ELECTRICAL SYSTEMS DESIGN
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
ELECTRICAL SYSTEMS DESIGN
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: Applied Technology
Class: SHS 1
Term: 1st Term
Week: 20
Grade code: 1.3.1.LI.2
Strand code: 3
Sub-strand code: 1
Content standard code: 1.3.1.CS.1
Indicator code: 1.3.1.LI.2
Theme: ELECTRICAL AND ELECTRONIC TECHNOLOGY
Subtheme: ELECTRICAL SYSTEMS DESIGN
This page supports the lesson note with a companion video and a short classroom-ready summary.
For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.
Good day, class. Every time we switch on a light, charge our phones, or watch television, we are using electrical power. But have you ever stopped to think about where this power comes from and how it gets to our homes, schools, and businesses? It's not magic! It's a carefully designed system. The electricity might be generated far away at the Akosombo Dam, the Bui Dam, or a thermal plant in Tema, but it travels hundreds of kilometres to reach us. Today, we will explore this incredible journey.
This section breaks down the entire journey of electricity into four main stages: Generation, Transmission, Distribution, and Utilisation. Stage 1: Power Generation
This is where electricity is created. In Ghana, power is generated from several sources: Hydroelectric Power: Using the force of water from dams (e.g., Akosombo Dam, Bui Dam). Thermal Power: Burning natural gas or other fuels to create steam that turns turbines (e.g., Aboadze Thermal Power Plant, Kpone Thermal Power Plant). Solar Power: Converting sunlight into electricity (e.g., Navrongo Solar Power Station).
The electricity generated at these plants is at a medium voltage, typically between 11kV and 25kV (1kV = 1,000 Volts). Stage 2: Power Transmission (The Electrical Highway)
Once electricity is generated, it needs to be transported over long distances to towns and cities. This is called transmission. The Role of GRIDCo: In Ghana, the company responsible for transmitting this power is the Ghana Grid Company (GRIDCo). They manage the big transmission lines and towers you see across the country. Why Use High Voltage? Before transmission, the voltage from the power plant is "stepped-up" (increased) to a very high level by a step-up transformer. This is the most important concept in efficient power transmission. The Problem: When electricity flows through a wire, some energy is lost as heat. This is called Power Loss. The formula for this loss is P_loss = I²R, where 'I' is the current and 'R' is the resistance of the wire. The Solution: To reduce power loss, we must reduce the current (I). We know that Power (P) = Voltage (V) × Current (I), or P = VI. This means for the same amount of power, if we increase the voltage (V) massively, the current (I) will become very small. Example: Imagine we need to transmit 1,000,000 Watts of power. At 10,000V: Current (I) = P/V = 1,000,000W / 10,000V = 100A. Power loss would be proportional to 100². At 400,000V: Current (I) = P/V = 1,000,000W / 400,000V = 2.5A. Power loss would be proportional to 2.5². As you can see, the current is much lower at the higher voltage, which means the power lost as heat in the transmission lines is significantly reduced. Advantages of High Voltage Transmission: Minimises Power Loss: Less electricity is wasted as heat over long distances. Allows for Thinner Cables: Lower current means the transmission wires don't need to be as thick, which saves money on materials (copper or aluminium). Increases Efficiency: More of the power generated reaches the consumer. Disadvantages of High Voltage Transmission: Requires Large Insulators: To prevent the high voltage electricity from jumping to the tower, large, expensive insulators are needed. Increased Safety Risk: High voltage lines are extremely dangerous and require large, tall towers to keep them far from the public. Typical Transmission Voltages in Ghana (managed by GRIDCo): 400kV (400,000V): Used for major, long-distance power transmission across the country. 275kV (275,000V): Also used for the national grid. 161kV (161,000V): A very common transmission voltage in Ghana, connecting major substations. 132kV (132,000V): Another common transmission voltage. Stage 3: Power Distribution (The Local Roads)