Every day we use all types of electrical equipment in the home or workplace. We assume that they are safe to use because they are earthed. Despite this, not everyone has a clear idea what it means when something is earthed. With no clear idea, it does lead to the question of what is the purpose of earthing electrical equipment.
Mains Electrical Supply
The UK mains electricity supply works in the region of 230V. Because of this, there is a risk that such a high voltage can kill if the equipment through which it passes is not safe to use. The power cord attached to an appliance has three inner wires with an outer plastic layer providing insulation. To help identify what each inner wire does they have their own unique colour coded insulation. The three wires are:
- Live (Brown)
- Neutral (Blue)
- Earth (Green and Yellow stripes)
Each wire has a specific purpose. The first is the live wire which delivers the electrical supply. The next is the neutral wire. This takes care of the return of the electricity by completing the electrical circuit. The last wire is the earth wire. This wire usually carries no electrical supply and is a safety measure.
What is Earthing?
In the United Kingdom, we have legislation that requires that the appliances we use in the home or workplace should be safe. The legislation sets out that an essential part of any electrical equipment, as well being a major safety feature, is that it should be earthed. Very simply this means that the appliance has a connection to the earth. The reason for such a connection is that the planet is a good conductor of electricity.
If your appliance such as a cooker or washing machine has a fault, there is a risk that you could get an electric shock. Earthing your device protects you from this shock. When you get an electric shock, the electric current will try and take the shortest path to the ground to complete the circuit. If you are touching a faulty appliance, then the electric current may use your body as a way to the earth. By earthing your electrical equipment, it protects you from an electric shock. The reason for this is that it provides a path (often referred to as a protective conductor) for the electric current to flow into the earth.
What is the purpose of earthing electrical equipment?
Electricity has the potential to kill. As a result, when using the electrical equipment we need something that will keep us safe. By earthing electrical equipment, it protects us. It provides three things:
- Keeps people safe.
- Protects electrical equipment from excessive damage. Makes sure that equipment is safe.
- Disables the passage of any excess voltage through the equipment.
In the home or workplace, many of the electrical appliances we use every day have some form of metal case. Good examples include cookers, washing machines, and fridges. If the live wire inside the equipment comes loose and touches the metal casing, you will receive an electric shock if the appliance has not been properly earthed. The purpose of the earth wire is to provide a safe route for any current to pass along should the live wire touch the electrical equipment’s metal case. It does this by completing an electrical circuit. The outcome is that the resulting large current will blow the fuse in the equipment’s plug. This separates the appliance from the power supply. Both the earth wire and fuse protect the electrical equipment from giving someone an electrical shock as well as overheating and possibly causing a fire.
Is earthing necessary?
It is not always the case that an appliance has to have an earth wire. Appliances like vacuum cleaners and electric drills are not always earthed. There are two reasons for this. One is that they have a plastic rather than a metal casing, the second is that the design of the equipment provides a way so that the live wire cannot make contact with the housing. Because of this, the person using the equipment cannot receive an electric shock.
While we all know the benefits of electricity in being able to power devices, it comes with a risk in that it has the potential to kill us. This is where the need for earthing comes in. To summarise, the purpose of earthing electrical equipment is safety. When it comes to using appliances in the home or workplace, earthing keeps us safe.