In an
electric power system
An electric power system is a network of electrical components deployed to supply, transfer, and use electric power. An example of a power system is the electrical grid that provides power to homes and industries within an extended area. The e ...
, overcurrent or excess current is a situation where a larger than intended
electric current
An electric current is a flow of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is defined as the net rate of flow of electric charge through a surface. The moving particles are called charge c ...
exists through a
conductor, leading to excessive generation of heat, and the risk of fire or damage to equipment. Possible causes for overcurrent include
short circuit
A short circuit (sometimes abbreviated to short or s/c) is an electrical circuit that allows a current to travel along an unintended path with no or very low electrical impedance. This results in an excessive current flowing through the circuit ...
s, excessive load, incorrect design, an
arc fault, or a
ground fault.
Fuses
Munitions, Fuse or FUSE may refer to:
Devices
* Fuse (electrical), a device used in electrical systems to protect against excessive current
** Fuse (automotive), a class of fuses for vehicles
* Fuse (hydraulic), a device used in hydraulic systems ...
,
circuit breaker
A circuit breaker is an electrical safety device designed to protect an Electrical network, electrical circuit from damage caused by current in excess of that which the equipment can safely carry (overcurrent). Its basic function is to interr ...
s, and
current limiters are commonly used overcurrent protection (OCP) mechanisms to control the
risk
In simple terms, risk is the possibility of something bad happening. Risk involves uncertainty about the effects/implications of an activity with respect to something that humans value (such as health, well-being, wealth, property or the environ ...
s.
Circuit breakers, relays, and fuses protect circuit wiring from damage caused by overcurrent.
Overcurrent in an electrical grid
Overcurrent capabilities of
electrical generator
In electricity generation, a generator, also called an ''electric generator'', ''electrical generator'', and ''electromagnetic generator'' is an electromechanical device that converts mechanical energy to electrical energy for use in an extern ...
s are essential for the
power system operations. Lack of overcurrent capability (low
short circuit ratio) of a
weak grid creates a multitude of problems, including:
* transients during the large load changes will cause large variations of the grid voltage, causing problems with the loads (e.g., some motors might not be able to start in the
undervoltage condition);
* the grid protection devices are designed to be triggered by a sufficient level of overcurrent. In a weak system the short circuit current might be hard to distinguish from a normal transient overcurrent encountered during the load changes;
* during a
black start operation after a failure, large
inrush current might be needed to energize the system components. For example, if some loads in a weak system remain connected, and
inverter-based resource might not be able to start.
Related standards
*
IEC 60364-4-43: Electrical installations of buildings – Part 4-43: Protection for safety – Protection against overcurrent
See also
*
Current limiting
*
Electrical fault
In an electric power system, a fault is a defect that results in abnormality of electric current. A fault current is any abnormal electric current. For example, a short circuit in which a live wire touches a neutral or ground wire is a fault. An op ...
*
Electrical safety
*
Overvoltage
References
Sources
*
Electrical systems
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