Vocational Scenario:
You are a trainee laboratory technician working for local aluminium smelting works. The smelting works is a huge consumer of electricity and has its own hydroelectric generating plant. The hydroelectric plant sends excess electricity to the National Grid, which is in turn distributed to local homes. The plant also has an induction furnace to produce aluminium ingots after the aluminium has been smelted. As part of your training you have been asked by the Health and Safety committee of the company to develop an electrical safety awareness booklet for their employees.
Task 1
Prepare a booklet titled ‘Electrical Safety Awareness’ that has the following sections:
Section 1 – AC and DC current
Explain the differences and similarities of the properties of AC and DC current in simple circuits
How are they produced? Use diagrams based on simple laboratory experiments to illustrate.
Use laboratory based investigations to evaluate how to control the AC electricity produced by generators. Apply the application of Flemings’ rules to the operation of an electrical motor (left hand) and the operation of an AC generator (right hand) to explain the principles of a DC generator
Describe DC electricity can be stored.
This provides evidence for P3
Illustrate, with a fully labelled graph, the difference between AC and DC electricity using an oscilloscope.
For AC compare the calculated root mean square (RMS) and measured peak voltage to show the quantitative relationship of RMS and peak values for AC electricity
This provides evidence for M3
Section 2 – Effects of AC and DC electricity on the human physiology
In the context of the dangers of working with electricity, use a diagram of the body to illustrate specific points and supplementary notes to explain:
The typical resistance values or current pathways in the body. What are the implications of this and is it different for AC compared to DC electricity?
The consequence of skin resistance in different conditions e.g. in contact with the ground, when moist
The effect of the length of current exposure time and the amount of electrical current. How is this different for AC compared to DC electricity?
The safe levels of DC voltage
How the heart responds to electric shock and how is this applied to the principles of a defibrillator
This provides evidence for P4
Section 3 – The National Grid
Evaluate, using diagrams, how AC electricity is produced in a generator at the smelting works hydroelectric facility for use in homes and industry. Apply the fundamental aspects of Fleming’s right hand rule for the generator in the power station. You should include:
a reasoned argument as to why a high powered AC generator should be used rather than a low powered AC/DC turbine.
Evaluate how the AC electricity is transferred from hydroelectric plant to homes and industry. Mathematically account for the need for transformers and high voltages. You should include:
the required voltage for applications of AC electricity around the home and at the smelting plant.
the mathematical comparisons of energy/power loss of transmitting electricity at different voltages
a reasoned argument as to why the voltages used to transmit electricity through the national grid for a variety of uses have been selected and why they may be different at different points in the transfer system
a reasoned argument as to why certain components such as transformers are required in specific parts of the national grid and connections between the hydroelectric plant and the National Grid.
This provides evidence for D2
Section 4 -Using AC and DC electricity around the home
Discuss the principles of the ring main circuit found in houses. You should include:
what is the purpose of the residual current and earth leakage circuit breakers (RCCB and ELCB), and how do they operate?
kettles and hairdryers are often ‘double insulated”, what is the significance of this?
how do fuses work in domestic appliances and why are they necessary?
when using DC equipment such as tablets, games consoles and mobile phones, discuss the principles behind ‘charging them up’ from the AC mains supply.
what are the dangers and inbuilt safety? (NB whilst these questions give guidance to the range of considerations you should discuss, you must present this in a coherent way.)
This provides evidence for M4
Section 5 – Using AC and DC electricity in industry
It is essential that the smelting works protects its workers by applying the Electricity at Work Regulations 1989. Discuss the specific actions that should be taken and the safety devices that should be used to protect workers when operating and repairing the AC and DC equipment in the plant.
This provides evidence for M4
