Description of safety devices
Circuit breakers: The purpose of a circuit breaker is for it to break the circuit when the current in the circuit exceeds the maximum value, and is no longer considered safe. To do this there is an electromagnet that will physically break the circuit when it detects that the current has exceeded its maximum.
Fuses: Fuses are like circuit breakers in that they will break a circuit when it detects that it is too dangerous to operate. Fuses use a resistance wire with a low melting point instead of an electromagnet, and when the current is too great the wire melts and the circuit will is broken. As the fuse melts every time the current is too great, it must be replaced, unlike the circuit breaker, which can be reset after it breaks the circuit.
Earthing: In Australia there are three wires that supply power to households. These are the active, neutral and earth wires. Earth wires are put in so that electric shocks can be avoided when people come into contact with an active wire that is in contact with the casing of any connected appliances. If there was no earth wire a person would complete the circuit between the appliances and the ground, and would receive an electric shock. To reduce the chance of this happening, the earth wire provides a better conductive path for the current. If the current comes into contact with the casing of an appliance, the earth wire will create a conductive path from the appliance to the earth, and a large current will flow to the earth through this connection. This large current will also blow any fuses or trip any circuit breakers, so that the circuit is not complete, and any person touching the appliance will not receive an electric shock.
Double insulation: Insulation is installed so that wiring and electric appliances are covered so that the current will only go through its intended path. The insulation is made out of an extremely poor conductor in order to create a safe path for the current to flow through. To increase the safety from insulation, a second layer of insulation can be installed, so that if one of the layers fails to properly insulate the circuit, the second layer will still be able to protect it.
Residual current devices: RCDs are designed so that they can stop a current before it becomes harmful to a person. It does this by detecting any leakages from the circuit through a differential current transformer, that will compare the current flowing through the live and neutral conductor, and if there is a difference it quickly shuts down the current. It typically shuts it down in 25-40 milliseconds after a leakage conductor, to minimise the damage done to the body.
Fuses: Fuses are like circuit breakers in that they will break a circuit when it detects that it is too dangerous to operate. Fuses use a resistance wire with a low melting point instead of an electromagnet, and when the current is too great the wire melts and the circuit will is broken. As the fuse melts every time the current is too great, it must be replaced, unlike the circuit breaker, which can be reset after it breaks the circuit.
Earthing: In Australia there are three wires that supply power to households. These are the active, neutral and earth wires. Earth wires are put in so that electric shocks can be avoided when people come into contact with an active wire that is in contact with the casing of any connected appliances. If there was no earth wire a person would complete the circuit between the appliances and the ground, and would receive an electric shock. To reduce the chance of this happening, the earth wire provides a better conductive path for the current. If the current comes into contact with the casing of an appliance, the earth wire will create a conductive path from the appliance to the earth, and a large current will flow to the earth through this connection. This large current will also blow any fuses or trip any circuit breakers, so that the circuit is not complete, and any person touching the appliance will not receive an electric shock.
Double insulation: Insulation is installed so that wiring and electric appliances are covered so that the current will only go through its intended path. The insulation is made out of an extremely poor conductor in order to create a safe path for the current to flow through. To increase the safety from insulation, a second layer of insulation can be installed, so that if one of the layers fails to properly insulate the circuit, the second layer will still be able to protect it.
Residual current devices: RCDs are designed so that they can stop a current before it becomes harmful to a person. It does this by detecting any leakages from the circuit through a differential current transformer, that will compare the current flowing through the live and neutral conductor, and if there is a difference it quickly shuts down the current. It typically shuts it down in 25-40 milliseconds after a leakage conductor, to minimise the damage done to the body.
![Picture](/uploads/2/2/5/9/22598200/380582195.jpg?794)
Diagram of how a RCD operates.