At its most basic, circuit protection is the purposeful inclusion of a "weak link" in an electrical circuit. In the case of a fault, such as high temperature, excessive current, or a short circuit in a conductor, this connection will be severed, saving the electrical circuit it is a part of from damage.
The three main types of circuit protection are fuse boxes, breaker panels, and ground fault interrupt circuits (GFI). Fuse boxes and breaker panels are integral parts of an electrical system that provide several outlets for connecting up to 14 wires into those outlets. Each outlet has two pins that must be connected to a wire inside the box or panel. A GFI device allows electricity to flow through it if no other conductor is available, such as when touching a metal object after breaking contact with another source of power. This type of device will stop the flow of current through it if another conductor is detected, such as by a spark between two pins. These devices should be installed in any area where there is a risk of someone being injured by electric shock.
You may have noticed that some conductors are marked with red tape to indicate they are required for service work. These cables are called "hot" wires because they carry a live current from your electric meter to your house. The black cable carrying neutral voltage from the transformer to your meter is also called the "hot" cable because it too carries a live current. Both cables must be protected by a proper electrical system.
Circuit protection devices, such as fuses and circuit breakers, are used to safeguard the wires and components of a circuit from overload. An overload occurs when too much current passes through the wire or device in a short period of time. This can happen if a person or animal contacts both a live and dead end of a circuit, creating a short circuit. The overloaded section of the circuit may begin to smoke, which could lead to a fire.
Overloaded circuits need to be replaced so that those parts of the circuit that are not damaged by the overload can be used again. Circuit protection devices act like shutters for opening and closing when excessive current flows through them. For example, if a fuse blows out, you will need to replace it before more damage occurs to other parts of the circuit. Damaged wiring may also have to be replaced so that it does not cause further problems for future customers.
Resistors come in many different sizes and with different resistance values. Care should be taken not to put objects into electrical outlets or use appliances without power connectors when there are broken or missing resistors in an extension cord or power strip.
Circuit protection devices prevent a harmful or excessive quantity of current or a short circuit in an electrical conductor automatically. The device uses the current itself to produce an open circuit or break the connection between its terminals, thereby preventing damage to or destruction of surrounding material. Circuit protectors are used in power supplies, battery chargers, and other equipment that can be damaged by excessive currents.
The three main types of circuit protectors are thermal cut-offs, magnetic cut-outs, and mechanical shutters. Thermal cut-offs use the heat from overload currents to destroy a link in a circuit breaker's trip mechanism, thus opening the circuit. Magnetic cut-outs use a magnetic field generated by an electric current to trigger an action that opens the circuit. Mechanical shutters use a spring or some other form of mechanical energy to close the circuit after it has been opened by the removal of the load. Most circuit protectors also have an indicator light that goes out when the circuit is closed or open.
Thermal cut-offs are usually built into large metal boxes that contain the wiring leading to appliances such as heaters, air conditioners, and dryer vents. These boxes must be mounted near the source of the danger so they can function properly.
Circuit protection's fundamental aims are to 1 identify and isolate the condition or fault and 2 avoid and limit any unneeded power loss. Several sorts of abnormal circumstances may develop over the life of a structure, and an electrical system must be built to repair or overcome them. Circuit breakers serve as the first line of defense by shutting off the power before any serious damage can occur.
The most common sort of circuit breaker is the single-pole, double-throw (SPDT) unit. It has two sets of contacts, one for normal operation and another for outage or emergency conditions. The SPDT unit can be activated either manually by pressing a button on its face, or automatically in response to certain abnormalities detected by sensors located around the circuit breaker panel.
Automatic transfer switches (ATSs) are similar to SPDT circuit breakers in function and application. However, they are controlled by signals from remote transmitters instead of personnel. Thus, they provide fail-safe power supply in case of manual switch action. ATSs are commonly used in industrial settings where malfunctioning equipment needs to be shut down quickly to prevent damage or injury. In residential applications, ATSs are often found in high-risk areas such as laundries, kitchens, and bathrooms.
Load centers are a type of circuit breaker designed to replace fuse boxes for large loads like motors, heaters, and air conditioners.