Circuit protection is employed to protect wires and other circuit components from damage in the event of a power overload or voltage spike. Lightning storms, overloaded power outlets, or a sudden electrical surge when large appliances or equipment suddenly switch on may result in a dangerous situation with the potential to cause fires or damage. Circuit protection negates this damage before it occurs by cutting off the power to the circuit.
One of the first forms of circuit protection is the fuse. This component protects circuits by heating up and melting when abnormal amounts of power flow through it. Fuses are designed to withstand a specific amount of current before the filament melts and breaks the circuit.
While fuses can protect a circuit from damage, they are a single-use item. Fuses often burn out, so it is always a good idea to have replacement fuses on hand. If a replacement fuse is unavailable for one reason or another, the circuit will not function. This makes the fuse unsafe for protecting circuit set-ups in situations that may result in grave difficulty or harm when electrical power malfunctions. Such may be the case for medical buildings or other facilities that depend on constant electrical function.
To avoid the problem of burnt fuses, most electricians now install a circuit breaker box with individual breakers, or circuit protectors, for each electrical circuit. A circuit breaker is a protection device that operates in much the same way as the fuse, except that it trips the breaker when it senses abnormal electric current, thus opening the circuit. The circuit breaker looks like a wall switch, and can be reset by switching it completely to the off position and then back to the on position. In some cases, it may also have an indicator that changes color to make identification of the tripped circuit easier.
In modern construction, the ground fault interrupter (GFI) is a popular method of circuit protection. Primarily used to protect circuit set-ups in which there is a danger of water coming into contact with an outlet, the GFI functions as its own circuit breaker. It can detect the difference in current flow when the current is diverted to the ground wire. In this event, the GFI then trips the internal circuit breaker to protect the circuit and avoid dangerous shock hazard conditions.
To further protect the devices on a circuit, many people install surge protectors. These devices protect sensitive electronic equipment from power surges and, in some cases, from all but direct hits by lightning. The surge protector uses a component called a transient voltage suppressor, which is a type of gas-filled diode that reacts to abnormal current much faster than other circuit protection devices.