Class: Senior Secondary School 1 (SS1 / SSS 1)
Term: Second Term
Week: 2
Age: 15 years
Duration: 45 minutes
Subject: Electrical Installation and Maintenance Work
Curriculum Theme: Technology
Previous Lesson: Generation: Meaning and Types of Generating Stations.
Topic: TRANSMISSION
Subject Matter: Meaning of electrical power transmission, types of transmission, transmission accessories such as pylon, overhead transmission lines, basic transmission station concept.

Specific Objectives

By the end of the lesson, pupils should be able to:

Cognitive Domain:

Define electrical power transmission.
State different types of electrical power transmission.
Identify various accessories used in electrical power transmission.

Affective Domain:

Appreciate the importance of electrical power transmission in daily life.
Participate actively in discussions about transmission concepts.

Psychomotor Domain:

Sketch a simple diagram showing overhead transmission lines.
Point out transmission accessories from a given picture or chart.

Discuss the role of transmission stations in power delivery.
Collaborate with peers to identify components of a transmission system.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum for Electrical Installation and Maintenance Work.
State Unified Scheme of Work for Senior Secondary Schools.
Electrical Installation and Maintenance Work for Senior Secondary Schools, Book 1.

Instructional Materials

The teacher will teach this lesson with the aid of:

Pictures of a transmission station.
Charts showing different types of transmission lines and accessories.

Rationale for the Lesson

This lesson helps pupils understand how electricity generated in power stations reaches their homes and workplaces. Understanding transmission systems enables pupils to appreciate the complex process of power delivery and the importance of safety around electrical infrastructure.

Prerequisite/Previous Knowledge

Pupils should have basic knowledge of electricity generation and simple electrical circuits.

Lesson Content/Board Summary

Electrical Power Transmission

Meaning of Electrical Power Transmission

Electrical power transmission is the bulk transfer of electrical energy from generating power plants to electrical substations located near demand centers. This process involves high voltages to minimize energy loss over long distances.

Types of Electrical Power Transmission

The following are the main types of electrical power transmission:

Overhead Transmission: This is the most common method, involving conductors suspended by towers or poles above the ground.
Underground Transmission: This method uses insulated cables buried beneath the ground. It is often used in urban areas where overhead lines are impractical or undesirable.
Submarine Transmission: This involves cables laid on the seabed to transmit power across bodies of water, such as between islands or countries.

Transmission Accessories

Transmission accessories are components that support and protect the transmission lines. The following are common transmission accessories:

Pylons (Transmission Towers): Tall structures, usually made of steel lattice, that support overhead transmission lines.
Conductors: Wires or cables that carry the electrical current. They are typically made of aluminum with steel reinforcement (ACSR).
Insulators: Devices made of ceramic or glass that prevent the electrical current from flowing from the conductors to the pylon or ground.
Ground Wires (Shield Wires): Wires placed at the top of the pylons to protect the main conductors from lightning strikes.
Cross-Arms: Horizontal structures on pylons that hold the insulators and conductors.
Vibration Dampers: Devices attached to conductors to reduce vibrations caused by wind, which can lead to fatigue and damage.

Overhead Transmission Lines

Overhead transmission lines consist of conductors supported by pylons or poles. They operate at very high voltages (e.g., 132kV, 330kV) to reduce current and thus minimize power loss (I²R loss) during transmission over long distances. The conductors are bare (uninsulated) and separated by air, with insulators at the points of attachment to the pylons.

Basic Transmission Station Concept

A transmission station (or substation) is a facility that forms part of the electrical power transmission system. It transforms voltage from high to low, or vice-versa, and performs other important functions like switching, voltage regulation, and protection of the system. Transmission stations connect different parts of the power grid, ensuring efficient and reliable power delivery.

Teaching Methods/Instructional Techniques

Discussion, Lecture, Demonstration, Question and Answer, Visual Aids

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher displays pictures of a power generation plant and a transmission station with pylons. The teacher asks pupils what they think happens to electricity after it is generated and how it reaches distant places.
Pupils’ Activity: Pupils observe the pictures and offer initial thoughts on how electricity travels from power plants to homes.
Learning Point: Pupils are introduced to the concept of electricity movement and stimulated to learn about transmission.

Step 2: Meaning of Electrical Power Transmission

Time: 8 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher explains the meaning of electrical power transmission, emphasizing its role in transferring bulk energy from generation sites to demand centers using high voltages. The teacher writes the definition on the board.
Pupils’ Activity: Pupils listen attentively, ask questions for clarity, and copy the definition into their notebooks.
Learning Point: Pupils understand what electrical power transmission is.

Step 3: Types of Electrical Power Transmission

Time: 8 minutes
Teaching Skill: Elucidation/Categorization
Teacher’s Activity: The teacher explains and lists the different types of electrical power transmission (overhead, underground, submarine), providing brief descriptions and examples for each. The teacher uses charts to illustrate these types.
Pupils’ Activity: Pupils observe the charts, listen to the explanations, and note down the different types of transmission.
Learning Point: Pupils can identify and differentiate between various types of electrical power transmission.

Step 4: Transmission Accessories

Time: 8 minutes
Teaching Skill: Identification/Listing
Teacher’s Activity: The teacher discusses common transmission accessories such as pylons, conductors, insulators, and ground wires. The teacher points out these accessories on the displayed pictures and charts, explaining their functions.
Pupils’ Activity: Pupils identify the accessories on the visual aids and ask questions about their specific roles. They list the accessories in their notes.
Learning Point: Pupils can name and describe the function of key transmission accessories.

Step 5: Overhead Transmission Lines

Time: 5 minutes
Teaching Skill: Detailed Explanation
Teacher’s Activity: The teacher provides a detailed explanation of overhead transmission lines, focusing on why high voltages are used and how power loss is minimized. The teacher can draw a simple sketch on the board.
Pupils’ Activity: Pupils pay attention to the explanation and observe the sketch, understanding the principles behind overhead lines.
Learning Point: Pupils understand the operational principles and components of overhead transmission lines.

Step 6: Basic Transmission Station Concept

Time: 6 minutes
Teaching Skill: Conceptual Understanding
Teacher’s Activity: The teacher explains the basic concept of a transmission station, highlighting its role in voltage transformation and connecting different parts of the power grid.
Pupils’ Activity: Pupils listen and understand the function of a transmission station in the overall power system.
Learning Point: Pupils grasp the role and importance of transmission stations.

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

Define electrical power transmission.
Mention three types of electrical power transmission.
List four accessories used in electrical power transmission.
State one importance of a transmission station.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 5 minutes
Teaching Skill: Summarization
Teacher’s Activity: The teacher summarizes the key points of the lesson, reiterating the meaning of transmission, its types, and the essential accessories. The teacher assigns homework: “Draw and label a simple diagram showing an overhead transmission line with its main components.”
Pupils’ Activity: Pupils listen to the summary and copy the homework assignment.
Learning Point: Pupils consolidate their understanding of the lesson and prepare for further study.

Lesson Keywords

Transmission – The process of moving electrical energy in bulk from generating power plants to substations.
Pylon – A tall structure, usually made of steel, used to support overhead electrical power lines.
Conductor – A material, typically metal wire, that allows electricity to flow through it easily.
Insulator – A material that does not allow electricity to flow through it, used to prevent current leakage.
Substation – A facility that transforms voltage from high to low, or vice versa, in an electrical grid.

Differentiation

For pupils who grasp concepts quickly, the teacher can ask them to research the environmental impact of different transmission types. For those who require more support, the teacher will provide simplified diagrams and allow for peer-assisted learning during activities.

Note for teachers using this lesson plan

Ensure that the pictures and charts used are clear and large enough for all pupils to see. Encourage pupils to ask questions and relate the concepts to their local environment where transmission lines might be visible. Emphasize safety aspects related to high-voltage transmission lines.