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Miniature circuit breakers and fuses may be rated to interrupt as little as 85 amperes and are intended for supplementary protection of equipment, not the primary protection of a building wiring system. In North American practice, approved general-purpose low-voltage fuses must interrupt at least 10,000 amperes.
A small circuit breaker typically has a manual control lever to switch the circuit off or reset a tripped breaker, while a larger unit may use a solenoid to trip the mechanism, and an electric motor to restore energy to springs (which rapidly separate contacts when the breaker is tripped).
Appliance classes (also known as protection classes) specify measures to prevent dangerous contact voltages on unenergized parts, such as the metallic casing, of an electronic device. In the electrical appliance manufacturing industry, the following appliance classes are defined in IEC 61140 and used to differentiate between the protective ...
Power system protection is a branch of electrical power engineering that deals with the protection of electrical power systems from faults [citation needed] through the disconnection of faulted parts from the rest of the electrical network. The objective of a protection scheme is to keep the power system stable by isolating only the components ...
In terms of protection response time, fuses tend to isolate faults more quickly (depending on their operating time) than circuit breakers. A fuse can clear a fault within a quarter cycle of the fault current, while a circuit breaker may take around half to one cycle to clear the fault.
A problem arises if the electricity supply is upgraded, by adding new generation capacity or by adding cross-connections. Because these increase the amount of power that can be supplied, all of the branch circuits must have their bus bars and circuit breakers upgraded to handle the new higher fault current limit. [citation needed]
A residual-current device (RCD), residual-current circuit breaker (RCCB) or ground fault circuit interrupter (GFCI) [a] is an electrical safety device, more specifically a form of Earth-leakage circuit breaker, that interrupts an electrical circuit when the current passing through line and neutral conductors of a circuit is not equal (the term residual relating to the imbalance), therefore ...
A distribution board (also known as panelboard, circuit breaker panel, breaker panel, electric panel, fuse box or DB box) is a component of an electricity supply system that divides an electrical power feed into subsidiary circuits while providing a protective fuse or circuit breaker for each circuit in a common enclosure.