# Overcurrent

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Dangerous condition in electrical systems

 The inside of a voltmeter in which at least one of its resistors has burned out due to an overcurrent caused by exposing the voltmeter to a voltage (230 V) higher than the maximum expected (30 V)

In an [electric power system](/source/Electric_power_system), **overcurrent** or **excess current** is a situation where a larger than intended [electric current](/source/Electric_current) exists through a [conductor](/source/Electrical_conductor), leading to excessive generation of heat, and the risk of fire or damage to equipment. Possible causes for overcurrent include [short circuits](/source/Short_circuit), excessive load, incorrect design, an [arc fault](/source/Arc_fault), or a [ground fault](/source/Ground_fault). [Fuses](/source/Fuse_(electrical)), [circuit breakers](/source/Circuit_breaker), and [current limiters](/source/Current_limiter) are commonly used overcurrent protection (OCP) mechanisms to control the [risks](/source/Risk). Circuit breakers, relays, and fuses protect circuit wiring from damage caused by overcurrent.[1]

## Overcurrent in an electrical grid

Overcurrent capabilities of [electrical generators](/source/Electrical_generator) are essential for the [power system operations](/source/Power_system_operations). Lack of overcurrent capability (low [short circuit ratio](/source/Short_circuit_ratio_(electrical_grid))) of a [weak grid](/source/Weak_grid) creates a multitude of problems, including:[2]

- 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](/source/Undervoltage) condition);

- the grid [protection devices](/source/Protection_device) 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](/source/Black_start) operation after a failure, large [inrush current](/source/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](/source/Inverter-based_resource) might not be able to start.

## Related standards

- [IEC 60364](/source/IEC_60364)-4-43: Electrical installations of buildings – Part 4-43: Protection for safety – Protection against overcurrent

## See also

- [Current limiting](/source/Current_limiting)

- [Electrical fault](/source/Electrical_fault)

- [Electrical safety testing](/source/Electrical_safety_testing)

- [Overvoltage](/source/Overvoltage)

## References

1. **[^](#cite_ref-1)** Keller, Kimberley J. (2010). [*Overcurrent Protection*](https://www.sciencedirect.com/topics/engineering/overcurrent-protection). Butterworth-Heinemann. [ISBN](/source/ISBN_(identifier)) [978-1-85617-654-5](https://en.wikipedia.org/wiki/Special:BookSources/978-1-85617-654-5). Retrieved July 5, 2021. {{[cite book](https://en.wikipedia.org/wiki/Template:Cite_book)}}: |website= ignored ([help](https://en.wikipedia.org/wiki/Help:CS1_errors#periodical_ignored))

1. **[^](#cite_ref-FOOTNOTELiNieWang2022536_2-0)** [Li, Nie & Wang 2022](#CITEREFLiNieWang2022), p. 536.

## Sources

- Li, Haiguo; Nie, Cheng; Wang, Fred (2022). ["Grid Strengthening IBR: An Inverter-Based Resource Enhanced by a Co-Located Synchronous Condenser for High Overcurrent Capability"](https://doi.org/10.1109%2Fojpel.2022.3194849). *IEEE Open Journal of Power Electronics*. **3**. Institute of Electrical and Electronics Engineers (IEEE): 535–548. [doi](/source/Doi_(identifier)):[10.1109/ojpel.2022.3194849](https://doi.org/10.1109%2Fojpel.2022.3194849). [ISSN](/source/ISSN_(identifier)) [2644-1314](https://search.worldcat.org/issn/2644-1314). [S2CID](/source/S2CID_(identifier)) [251194445](https://api.semanticscholar.org/CorpusID:251194445).

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