Class: Senior Secondary School 2 (SS2 / SSS2)
Term: 1st Term
Week: 4
Age: 16 years
Duration: 45 minutes
Subject: Basic Electricity
Curriculum Theme: Electrical Power Systems
Previous Lesson: Transmission of Electricity: Meaning and National Grid.
Topic: TRANSMISSION OF ELECTRICITY
Subject Matter: Components of transmission system (conductors, insulators, protective devices), functions of components of transmission system (carrying, supporting and protecting power lines), general layout for transmission of electric power (from generating station to substation)

Specific Objectives

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

Cognitive Domain:

Identify the main components of an electric power transmission system.
Explain the function of each component in the transmission system.
Describe the general layout for the transmission of electric power.

Affective Domain:

Appreciate the importance of a reliable power transmission system.
Show interest in how electricity is delivered to homes and industries.

Psychomotor Domain:

Sketch a simple block diagram illustrating the general layout of electric power transmission.
Relate the displayed components to their actual use in the field.

Discuss the impact of efficient power transmission on community development.
Collaborate in identifying and explaining transmission components.

Reference Materials

The following resources were used in planning this lesson:

Senior Secondary Schools Education Curriculum
State Unified Scheme of Work
Basic Electricity for Senior Secondary Schools by P.N. Okeke

Instructional Materials

The teacher will teach this lesson with the aid of:

Samples of electrical conductors (e.g., copper wire, aluminum cable)
Samples of insulators (e.g., ceramic insulator, glass insulator)
Images or charts showing various protective devices (e.g., circuit breaker, fuse, lightning arrester)
Charts illustrating the general layout of an electric power transmission system

Rationale for the Lesson

This lesson helps pupils understand how electricity generated in power stations is safely and efficiently delivered to consumers over long distances. It enables pupils to appreciate the complex system required to provide reliable electrical power for daily use and national development.

Prerequisite/Previous Knowledge

Pupils have prior knowledge of basic electrical concepts such as current, voltage, and simple circuits.

Lesson Content/Board Summary

TRANSMISSION OF ELECTRICITY

Components of Electric Power Transmission System

The transmission system is a network of components used to transfer electricity from power generating stations to substations near consumption areas. Key components include:

Conductors: Materials that allow electric current to flow easily, typically made of aluminum or copper.
Insulators: Materials that prevent the flow of electricity, used to support conductors and prevent current leakage to the ground or tower. Common types are ceramic, glass, and polymer insulators.
Protective Devices: Equipment designed to detect faults and automatically disconnect faulty sections of the power system to prevent damage and ensure safety. Examples include circuit breakers, fuses, and lightning arresters.
Support Structures: Towers or poles made of steel, concrete, or wood that hold the conductors at safe heights above the ground.
Transformers: Devices used to step up or step down voltage levels for efficient transmission and distribution.

Functions of Components of Transmission System

Conductors: Their primary function is to carry the high-voltage electric current from generating stations to load centers.
Insulators: They provide electrical isolation for the conductors from the support structures and the ground, preventing short circuits and ensuring safe operation. They also support the power lines.
Protective Devices: These devices protect the power lines, equipment, and personnel from damage due to overcurrents, short circuits, lightning strikes, and other electrical faults.
Support Structures: They provide the physical support for the overhead transmission lines, maintaining adequate clearance from the ground and other objects.
Transformers: Step-up transformers increase the voltage for efficient long-distance transmission, while step-down transformers reduce the voltage for distribution and safe use.

General Layout for Transmission of Electric Power

The transmission of electric power typically follows a sequence from the generating station to the consumer:

Generating Station: Electricity is produced at relatively low voltages (e.g., 11kV to 25kV).
Step-Up Substation: Near the generating station, transformers step up the voltage to very high levels (e.g., 132kV, 330kV, 765kV) for efficient long-distance transmission, minimizing power loss.
Transmission Lines: High-voltage electricity is carried over long distances using overhead conductors supported by large towers. This forms the “grid.”
Primary Step-Down Substation: Located near major load centers, transformers reduce the high transmission voltage to a lower sub-transmission voltage (e.g., 33kV, 11kV).
Distribution Lines: The lower voltage electricity is then distributed through a network of smaller lines to local substations and eventually to consumers.

A simple block diagram illustrating this flow is shown below:

Generating Station → Step-Up Transformer → High-Voltage Transmission Line → Step-Down Substation → Distribution Network → Consumers

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 greets the pupils and asks them how electricity gets to their homes from the power station.
Pupils’ Activity: Pupils respond by offering various ideas about how electricity travels.
Learning Point: Pupils are introduced to the concept of electricity transmission.

Step 2: Presentation of Components

Time: 7 minutes
Teaching Skill: Demonstration/Identification
Teacher’s Activity: The teacher displays samples or charts of conductors, insulators, and protective devices, asking pupils to identify them.
Pupils’ Activity: Pupils observe the materials and identify the various components based on their prior knowledge.
Learning Point: Pupils identify the physical components used in power transmission.

Step 3: Explanation of Functions

Time: 10 minutes
Teaching Skill: Explanation/Lecture
Teacher’s Activity: The teacher explains the specific function of each identified component (conductors, insulators, protective devices, support structures, transformers) in the transmission system.
Pupils’ Activity: Pupils listen attentively, take notes, and ask questions for clarification.
Learning Point: Pupils understand the role each component plays in transmitting electricity.

Step 4: Discussion of Protective Devices

Time: 7 minutes
Teaching Skill: Discussion/Elaboration
Teacher’s Activity: The teacher elaborates on the importance of protective devices like circuit breakers, fuses, and lightning arresters in ensuring safety and system reliability.
Pupils’ Activity: Pupils discuss the dangers of electricity and the necessity of protective measures.
Learning Point: Pupils learn about the safety aspects and protective mechanisms in power transmission.

Step 5: General Layout Description

Time: 8 minutes
Teaching Skill: Description/Visualisation
Teacher’s Activity: The teacher describes the general layout of electric power transmission, explaining the journey of electricity from the generating station to the substation using a chart.
Pupils’ Activity: Pupils follow the explanation on the chart and visualize the entire transmission process.
Learning Point: Pupils grasp the sequence and stages of power transmission.

Step 6: Diagrammatic Representation

Time: 5 minutes
Teaching Skill: Guided Practice
Teacher’s Activity: The teacher guides pupils to sketch a simple block diagram illustrating the general layout of electric power transmission in their notebooks.
Pupils’ Activity: Pupils attempt to draw the transmission layout under the teacher’s guidance.
Learning Point: Pupils practice representing the transmission system diagrammatically.

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

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

List three main components of an electric power transmission system.
State the primary function of an insulator in a power line.
Describe the general path electricity takes from a generating station to a primary step-down substation.
Why are protective devices important in electricity transmission?

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 3 minutes
Teaching Skill: Summarization/Assignment
Teacher’s Activity: The teacher summarizes the key points of the lesson and assigns homework for pupils to research different types of overhead line support structures.
Pupils’ Activity: Pupils listen to the summary and copy the homework assignment.
Learning Point: Pupils consolidate their learning and prepare for further study.

Lesson Keywords

Transmission – The process of sending electric power over long distances.
Conductor – A material that allows electricity to flow through it easily.
Insulator – A material that resists the flow of electricity.
Substation – A facility that transforms voltage from high to low, or vice versa.
Grid – A network of transmission lines connecting power plants and consumers.
Protective device – Equipment that safeguards electrical systems from faults.

Differentiation

For pupils who are struggling, the teacher will provide simplified diagrams and focus on identifying components and their basic functions. More advanced pupils will be challenged to explain the reasons for high-voltage transmission and discuss the economic implications of power loss during transmission.

Note for teachers using this lesson plan

Teachers should ensure that actual samples of conductors and insulators are available for pupils to observe. If actual samples are not available, clear and large charts or digital images should be used. Emphasize the safety aspects of high-voltage transmission. Encourage pupils to draw the layout in their notebooks to reinforce learning.