Class: Senior Secondary School 1 (SS1 / SSS1)
Term: 3rd Term
Week: 9
Age: 15 years
Duration: 45 minutes
Subject: Electrical Installation and Maintenance Work
Curriculum Theme: Technology
Previous Lesson: Installation of Voltage Operated Circuit Breaker.
Topic: THE RELEVANT REGULATION IEE Regulation on protective Devices (Fuse Circuit Breaker)
Subject Matter: IEE regulation on protective devices, fuse regulation requirements, circuit breaker regulation requirements, interpreting circuit diagrams for protective devices, connecting voltage operated circuit diagram on wiring board

Specific Objectives

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

Cognitive Domain:

Define IEE regulations in relation to protective devices.
State the IEE regulation requirements for fuses.
Explain the IEE regulation requirements for circuit breakers.
Interpret circuit diagrams that include protective devices.

Affective Domain:

Appreciate the importance of adhering to IEE regulations for safety.
Develop an interest in safe electrical installation practices.

Psychomotor Domain:

Observe the connection of a voltage-operated circuit diagram on a wiring board.
Identify protective devices in a given circuit diagram.

Participate in discussions about electrical safety standards.
Collaborate with peers in identifying components on circuit diagrams.

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 School Electrical Installation and Maintenance Work.
The IEE Wiring Regulations Explained and Illustrated by Brian Scaddan.
https://www.iee.org.uk
https://www.bsigroup.com

Instructional Materials

The teacher will teach this lesson with the aid of:

Voltage operated circuit breaker.
Wiring board.
Charts showing IEE regulation requirements for fuses and circuit breakers.
Sketches of circuit diagrams with protective devices.
Whiteboard/blackboard and markers/chalk.

Rationale for the Lesson

This lesson helps pupils understand the rules for electrical protective devices, such as fuses and circuit breakers. Knowing these regulations is important for ensuring safe electrical installations and preventing accidents in homes and workplaces.

Prerequisite/Previous Knowledge

Pupils are expected to have basic knowledge of electricity, simple circuits, and common electrical components like conductors and insulators.

Lesson Content/Board Summary

IEE Regulation on Protective Devices (Fuse and Circuit Breaker)

Introduction to IEE Regulations

The Institution of Electrical Engineers (IEE) Regulations, now known as BS 7671 (Requirements for Electrical Installations), are a set of standards that ensure the safety of electrical installations. These regulations cover all aspects of electrical work, including the selection and installation of protective devices.

Importance of Protective Devices

Protective devices are essential for electrical safety. They protect electrical circuits and equipment from damage due to overcurrents (overload and short-circuit) and protect people from electric shock.

The following are reasons for using protective devices:

To prevent damage to electrical appliances and wiring.
To protect users from electric shock.
To isolate faulty circuits quickly.
To ensure the overall safety and reliability of an electrical installation.

Fuse Regulation Requirements

A fuse is a safety device that protects an electrical circuit from overcurrent. It contains a wire or filament that melts and breaks the circuit when the current exceeds a safe level.

The following are IEE regulation requirements for fuses:

Rating: Fuses must be correctly rated for the circuit they protect, matching the cable current-carrying capacity.
Breaking Capacity: The fuse must have a breaking capacity sufficient to safely interrupt the maximum prospective fault current at its point of installation.
Type: The correct type of fuse (e.g., cartridge, HRC) must be used for the specific application.
Accessibility: Fuses should be easily accessible for inspection and replacement.
Identification: Fuse holders should be clearly labelled with their current rating and the circuit they protect.

Circuit Breaker Regulation Requirements

A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overcurrent or short circuit. Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation.

The following are IEE regulation requirements for circuit breakers:

Rating: Circuit breakers must be selected with appropriate current ratings to protect the circuit conductors from overload.
Breaking Capacity: They must have a breaking capacity adequate for the maximum prospective fault current at their point of installation.
Type and Tripping Characteristics: The correct type of circuit breaker (e.g., Miniature Circuit Breaker (MCB), Residual Current Device (RCD), Residual Current Breaker with Overcurrent protection (RCBO)) with appropriate tripping characteristics (e.g., B, C, D curves) must be chosen based on the circuit’s load and fault conditions.
Discrimination: Protective devices should be coordinated to ensure that only the faulty part of the circuit is disconnected (discrimination).
Installation: Circuit breakers must be installed in suitable enclosures and be easily accessible for operation and inspection.

Interpreting Circuit Diagrams for Protective Devices

Circuit diagrams use standard symbols to represent electrical components, including protective devices. Understanding these symbols is important for identifying where fuses and circuit breakers are placed in a circuit and how they function.

The following are common symbols:

Fuse: A rectangle with a line through it, or a specific fuse symbol.
Circuit Breaker: A square with a diagonal line and an arc representing tripping mechanism.
RCD/RCCB: A circuit breaker symbol with an additional arc representing residual current detection.

Connecting Voltage Operated Circuit Diagram on Wiring Board

Connecting a voltage-operated circuit involves wiring components according to a circuit diagram. This practical skill reinforces the understanding of how protective devices are physically integrated into an electrical system.

The steps generally involve:

Understanding the circuit diagram.
Identifying the terminals of each component (e.g., voltage-operated circuit breaker, load, power supply).
Connecting wires between components as indicated by the diagram, ensuring proper polarity and secure connections.
Testing the circuit for correct operation and protection.

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 to mention some common electrical hazards they know. The teacher then asks what devices are used to prevent these hazards in electrical installations.
Pupils’ Activity: Pupils respond by mentioning hazards like electric shock, fire, and devices such as fuses and circuit breakers.
Learning Point: Pupils recall prior knowledge of electrical hazards and protective devices.

Step 2: Explanation of IEE Regulations and Protective Devices

Time: 8 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher introduces the IEE Regulations (BS 7671) and explains their purpose in ensuring electrical safety. The teacher then defines what protective devices are and why they are essential in electrical circuits.
Pupils’ Activity: Pupils listen attentively, take notes, and ask questions for clarification.
Learning Point: Pupils understand the role of IEE regulations and the importance of protective devices.

Step 3: Fuse Regulation Requirements

Time: 8 minutes
Teaching Skill: Elucidation/Listing
Teacher’s Activity: The teacher explains the specific IEE regulation requirements for fuses, covering aspects like rating, breaking capacity, type, and identification. The teacher may show examples of different fuse types.
Pupils’ Activity: Pupils listen, observe the fuse examples, and note down the requirements.
Learning Point: Pupils learn the specific regulations governing the use of fuses.

Step 4: Circuit Breaker Regulation Requirements

Time: 8 minutes
Teaching Skill: Elucidation/Comparison
Teacher’s Activity: The teacher explains the IEE regulation requirements for circuit breakers, including rating, breaking capacity, type, tripping characteristics, and discrimination. The teacher highlights differences and similarities with fuses.
Pupils’ Activity: Pupils listen, compare information with fuses, and record notes.
Learning Point: Pupils understand the specific regulations for circuit breakers and how they differ from fuses.

Step 5: Interpreting Circuit Diagrams for Protective Devices

Time: 8 minutes
Teaching Skill: Demonstration/Interpretation
Teacher’s Activity: The teacher sketches simple circuit diagrams on the board or uses charts to show where fuses and circuit breakers are placed. The teacher explains the standard symbols used for these devices and guides pupils on how to interpret them in a diagram.
Pupils’ Activity: Pupils observe the diagrams, identify the symbols for protective devices, and practice interpreting their placement.
Learning Point: Pupils develop the skill of interpreting circuit diagrams with protective devices.

Step 6: Practical Demonstration – Connecting a Voltage Operated Circuit

Time: 8 minutes
Teaching Skill: Demonstration/Practical Application
Teacher’s Activity: The teacher demonstrates how to connect a simple voltage-operated circuit diagram, including a protective device, on the wiring board. The teacher points out the correct wiring procedures and safety precautions.
Pupils’ Activity: Pupils observe the teacher’s demonstration carefully, noting the connections and safety practices.
Learning Point: Pupils observe the practical application of protective devices in a circuit.

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 are IEE Regulations and why are they important for electrical installations?
State three IEE regulation requirements for fuses.
Mention three IEE regulation requirements for circuit breakers.
How do you identify a fuse symbol in a circuit diagram?

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
Teacher’s Activity: The teacher summarizes the key learning points about IEE regulations, fuse, and circuit breaker requirements, emphasizing the importance of safety. The teacher then gives pupils a take-home assignment to draw a simple circuit diagram containing a fuse and a circuit breaker.
Pupils’ Activity: Pupils listen to the summary and copy the assignment.
Learning Point: Pupils consolidate their understanding and are given a task to reinforce learning.

Lesson Keywords

IEE Regulations – Standards for safe electrical installations.
Protective Device – A component that protects electrical circuits and users from faults.
Fuse – A safety device with a wire that melts to break a circuit during overcurrent.
Circuit Breaker – An automatic switch that interrupts an electrical circuit during overcurrent or fault conditions and can be reset.
Breaking Capacity – The maximum current a protective device can safely interrupt without damage.
Rating – The specified current or voltage for which a device is designed.

Differentiation

For pupils who grasp concepts quickly, the teacher can provide more complex circuit diagrams for interpretation or challenge them to research specific types of RCDs. For pupils needing more support, the teacher can provide simplified diagrams, review key terms, and offer one-on-one guidance during practical observation.

Note for teachers using this lesson plan

Ensure all instructional materials, especially the voltage-operated circuit breaker and wiring board, are in good working condition and correctly set up before the lesson. Emphasize safety precautions throughout the practical demonstration. Encourage pupils to ask questions and participate actively. Consider dividing the class into small groups for hands-on practice with the wiring board if time and resources allow in subsequent lessons.