Class: Senior Secondary School 1 (SS1 / SSS 1)
Term: 3rd Term
Week: 8
Age: 15 years
Duration: 45 minutes
Subject: Electrical Installation and Maintenance Work
Curriculum Theme: Technology
Previous Lesson: Introduction to Voltage Operated Circuit Breaker: Meaning and Principle.
Topic: INSTALLATION OF VOLTAGE OPERATED CIRCUIT BREAKER
Subject Matter: sketching voltage operated circuit breaker diagram, IEE regulation on circuit breaker installation, connecting 2 points of light to a single phase voltage operated circuit breaker, connecting to a 3 phase voltage operated circuit breaker, safety checks and testing

Specific Objectives

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

Cognitive Domain:

Define a Voltage Operated Circuit Breaker (VOCB).
State at least three IEE regulations concerning circuit breaker installation.
Explain the purpose of safety checks and testing after installation.

Affective Domain:

Appreciate the importance of safety measures during electrical installations.
Develop an interest in adhering to electrical wiring regulations.
Participate actively in classroom discussions and practical demonstrations.

Psychomotor Domain:

Sketch a simple diagram of a Voltage Operated Circuit Breaker (VOCB).
Connect two points of light to a single-phase voltage operated circuit breaker under supervision.
Connect two points of light to a three-phase voltage operated circuit breaker under supervision.
Perform basic safety checks on a circuit breaker installation.

Collaborate with peers during practical activities.
Share ideas and observations during demonstrations.

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.
Okoro, N. (2018). Electrical Installation Technology for Senior Secondary Schools. Evans Brothers (Nigeria Publishers) Limited.
https://www.iee.org.uk/
https://www.electrical-installation.org/

Instructional Materials

The teacher will teach this lesson with the aid of:

A single-phase voltage operated circuit breaker.
A three-phase voltage operated circuit breaker.
A wiring board.
Assorted electrical cables.
Two light bulb holders with bulbs.
Chalkboard/whiteboard and markers/chalk.
Relevant circuit diagrams.

Rationale for the Lesson

This lesson helps pupils understand how to correctly install voltage operated circuit breakers, which are essential for protecting electrical circuits and equipment. Proper installation ensures safety for users and prevents damage to electrical systems in homes and industries.

Prerequisite/Previous Knowledge

Pupils are expected to have basic knowledge of electrical circuits, different types of circuit breakers, and fundamental electrical safety precautions.

Lesson Content/Board Summary

INSTALLATION OF VOLTAGE OPERATED CIRCUIT BREAKER

Definition of Voltage Operated Circuit Breaker (VOCB)

A Voltage Operated Circuit Breaker (VOCB) is a safety device designed to protect electrical circuits from damage caused by overcurrent or short circuits. It automatically trips, or breaks, the circuit when an abnormal voltage or current condition is detected, cutting off power supply to prevent hazards.

Voltage Operated Circuit Breaker (VOCB) Diagram

A typical VOCB diagram shows input terminals (line/phase and neutral), output terminals for the load, and a tripping mechanism. The diagram illustrates how the incoming supply connects to the breaker and how the outgoing circuit connects from the breaker to the load.

IEE Regulations on Circuit Breaker Installation

The Institution of Electrical Engineers (IEE) Regulations (now BS 7671 Wiring Regulations) provide guidelines for safe electrical installations. For circuit breakers, important regulations include:

Circuit breakers must be correctly rated for the circuit current and fault level they protect.
They must be easily accessible for operation and maintenance.
Every circuit breaker must be clearly labelled to identify the circuit it controls.
Circuit breakers must be installed in appropriate enclosures to protect them from mechanical damage and environmental factors.
Correct earthing (grounding) practices must be followed for the entire installation.
The breaking capacity of the circuit breaker must be adequate for the prospective fault current at its point of installation.

Connecting 2 Points of Light to a Single Phase Voltage Operated Circuit Breaker

To connect two points of light to a single-phase VOCB, the incoming live (phase) wire is connected to the input terminal of the VOCB, and the neutral wire is connected to a neutral bar. The outgoing live wire from the VOCB is then run to the first light point, and from there, a parallel connection is made to the second light point. The neutral wires from both light points are connected back to the neutral bar.

Connecting to a 3 Phase Voltage Operated Circuit Breaker

For a three-phase VOCB, the three incoming phase wires (L1, L2, L3) are connected to the respective input terminals of the breaker. The neutral wire is connected to a neutral bar. The outgoing phase wires from the breaker are then distributed to the loads (e.g., lighting circuits or power circuits) as required, ensuring load balancing across the phases. The neutral wires from the loads return to the neutral bar.

Safety Checks and Testing after Installation

After installing a circuit breaker, it is important to perform safety checks and tests to ensure proper and safe operation. These include:

Visual Inspection: Checking for correct wiring, secure connections, proper labelling, and absence of physical damage.
Continuity Test: Verifying that all conductors are correctly connected and have no breaks.
Insulation Resistance Test: Measuring the resistance between conductors and earth to ensure proper insulation and prevent leakage currents.
Polarity Test: Confirming that switches and protective devices are connected in the phase conductor.
Earth Fault Loop Impedance Test: Ensuring that the earth fault current is sufficient to trip the protective device within the required time.
Functional Test: Manually operating the circuit breaker to ensure it trips and resets correctly.

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, reviews the previous lesson briefly, and then introduces the new topic: “Installation of Voltage Operated Circuit Breaker.” The teacher explains that this lesson is important for understanding how to protect electrical circuits.
Pupils’ Activity: Pupils respond to greetings, recall the previous lesson, and listen attentively to the introduction of the new topic.
Learning Point: Pupils are prepared for the day’s lesson and understand its relevance.

Step 2: Sketching VOCB Diagram

Time: 8 minutes
Teaching Skill: Illustration/Explanation
Teacher’s Activity: The teacher sketches a simple diagram of a Voltage Operated Circuit Breaker on the board, pointing out the input, output, and tripping mechanism. The teacher briefly explains its function.
Pupils’ Activity: Pupils observe the diagram carefully, ask questions for clarification, and make notes.
Learning Point: Pupils can identify the main parts of a VOCB and understand its basic operation.

Step 3: Explaining IEE Regulations on Circuit Breaker Installation

Time: 7 minutes
Teaching Skill: Explanation/Lecture
Teacher’s Activity: The teacher explains key IEE regulations that govern the installation of circuit breakers, emphasizing correct rating, accessibility, labelling, and earthing. The teacher highlights why these regulations are important for safety.
Pupils’ Activity: Pupils listen, take notes, and may ask questions regarding specific regulations or their application.
Learning Point: Pupils understand the importance of following IEE regulations for safe electrical installations.

Step 4: Demonstrating Single Phase Connection

Time: 8 minutes
Teaching Skill: Demonstration/Practical
Teacher’s Activity: Using the wiring board, a single-phase VOCB, and cables, the teacher demonstrates how to connect two points of light to the single-phase circuit breaker. The teacher explains each connection step clearly.
Pupils’ Activity: Pupils observe the demonstration keenly, paying attention to the connections and the teacher’s explanations.
Learning Point: Pupils observe the practical connection of a single-phase VOCB to a load.

Step 5: Demonstrating Three Phase Connection

Time: 7 minutes
Teaching Skill: Demonstration/Practical
Teacher’s Activity: The teacher then uses a three-phase VOCB and the wiring board to demonstrate how to connect a load (representing two points of light) to the three-phase circuit breaker, explaining the distribution of phases.
Pupils’ Activity: Pupils continue to observe the demonstration, noting the differences between single-phase and three-phase connections.
Learning Point: Pupils observe the practical connection of a three-phase VOCB to a load.

Step 6: Discussing Safety Checks and Testing

Time: 5 minutes
Teaching Skill: Discussion/Explanation
Teacher’s Activity: The teacher leads a discussion on the various safety checks and tests that must be performed after installing a circuit breaker, such as visual inspection, continuity test, and insulation resistance test. The teacher explains the purpose of each test.
Pupils’ Activity: Pupils contribute to the discussion, ask questions, and take notes on the safety procedures.
Learning Point: Pupils understand the importance of and procedures for safety checks after VOCB installation.

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

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

What is a Voltage Operated Circuit Breaker (VOCB)?
Mention three IEE regulations for circuit breaker installation.
Briefly explain how to connect two points of light to a single-phase VOCB.
List at least three safety checks to perform after installing a circuit breaker.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 2 minutes
Teaching Skill: Summarization
Teacher’s Activity: The teacher summarizes the key points of the lesson, reiterating the importance of correct VOCB installation and safety. The teacher assigns homework, asking pupils to draw a neat diagram of a single-phase VOCB connection.
Pupils’ Activity: Pupils listen to the summary, ask any final questions, and note down the homework assignment.
Learning Point: Pupils consolidate their understanding and are given an opportunity for further practice.

Lesson Keywords

Voltage Operated Circuit Breaker (VOCB) – An electrical safety device that automatically cuts off power when abnormal voltage or current is detected.
IEE Regulations – Guidelines set by the Institution of Electrical Engineers for safe electrical installations.
Single Phase – An electrical power system where voltage varies in unison, typically used for domestic applications.
Three Phase – An electrical power system with three alternating currents, each peaking at different times, commonly used for industrial power.
Circuit Breaker – An automatic switch designed to protect an electrical circuit from damage caused by overcurrent or short circuit.

Differentiation

For pupils who grasp concepts quickly, the teacher will encourage them to research advanced types of circuit breakers or more complex three-phase wiring scenarios. For pupils who require more support, the teacher will provide additional one-on-one guidance during practical demonstrations and simplify explanations.

Note for teachers using this lesson plan

Teachers should ensure all instructional materials are available and in good working condition before the lesson. Safety precautions must be strictly observed during all practical demonstrations. Encourage pupils to ask questions and participate actively to ensure a thorough understanding of the topic.