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{{short description|Short duration voltage transient in an electrical circuit}}
{{Redirect|Reverse surge||Surge (disambiguation){{!}}Surge}}
{{more citations needed|December 2022|date=January 2023}}
[[File:Transients.svg|alt=|thumb|Voltage spikes]]
In [[electrical engineering]], '''spikes''' are fast, short duration electrical [[transient (electricity)|transient]]s in voltage ('''voltage spikes'''),<ref>{{cite web |url=https://study.com/academy/lesson/voltage-spike-definition-causes-protection.html |title=What Causes Voltage Spikes & Power Surges? |access-date=December 31, 2022}}</ref> current ('''current spikes'''), or transferred energy ('''energy spikes''') in an electrical circuit.

Fast, short duration electrical transients ([[overvoltage]]s) in the [[electric potential]] of a [[electrical network|circuit]] are typically caused by<ref>{{cite web |url=https://www.sweetwater.com/insync/voltage-spike/ |title=Voltage Spike |date=February 12, 2008 |publisher=InSync |access-date=December 31, 2022}}</ref>
* [[Lightning]] strikes
* [[Power outage]]s
* Tripped [[circuit breaker]]s
* [[Short circuit]]s
* Power transitions in other large equipment on the same power line
* Malfunctions caused by the power company
* [[Electromagnetic pulse]]s (EMP) with [[electromagnetism|electromagnetic]] energy distributed typically up to the 100&nbsp;kHz and 1&nbsp;MHz frequency range.
* [[Inductance|Inductive]] spikes

In the design of critical infrastructure and military hardware, one concern is of pulses produced by [[nuclear explosion]]s, whose nuclear electromagnetic pulses distribute large energies in frequencies from 1&nbsp;kHz into the [[gigahertz]] range through the atmosphere.

The effect of a voltage spike is to produce a corresponding increase in [[electric current|current]] ('''current spike'''). However some voltage spikes may be created by current sources.  Voltage would increase as necessary so that a constant current will flow. Current from a discharging [[inductor]] is one example.

For sensitive [[electronics]], excessive current can flow if this voltage spike exceeds a material's [[electrical breakdown|breakdown]] voltage, or if it causes [[avalanche breakdown]]. In [[semiconductor]] [[p-n junction|junctions]], excessive electric current may destroy or severely weaken that device.  An [[avalanche diode]], [[transient voltage suppression diode]], [[varistor]], overvoltage [[crowbar (circuit)|crowbar]], or a range of other [[overvoltage]] protective devices can divert ([[shunt (electrical)|shunt]]) this transient current thereby minimizing voltage.<ref>{{cite web |url=https://www.daycounter.com/Articles/Inductive-Voltage-Spike.phtml |title=Inductive Voltage Spike |last=Daycounter |first=Tim |access-date=December 31, 2022}}</ref>

Voltage spikes, also known as surges, may be created by a rapid buildup or decay of a magnetic field, which may [[Electromagnetic induction|induce]] energy into the associated circuit. However voltage spikes can also have more mundane causes such as a fault in a [[transformer]] or higher-voltage (primary circuit) power wires falling onto lower-voltage (secondary circuit) power wires as a result of accident or storm damage.

Voltage spikes may be longitudinal (common) mode or metallic (normal or differential) mode.  Some equipment damage from surges and spikes can be prevented by use of [[surge protector|surge protection]] equipment.  Each type of spike requires selective use of protective equipment. For example, a [[common-mode signal|common mode]] voltage spike may not even be detected by a protector installed for normal mode transients.

Power increases or decreases which last multiple cycles are called swells or sags, respectively. An uninterrupted voltage increase that lasts more than a minute is called an overvoltage.  These are usually caused by malfunctions of the [[electric power distribution]] system.

==See also==
* {{annotated link|Uninterruptible power supply}}
* {{annotated link|Electric power quality}}
* {{annotated link|Surge protector}}
* {{annotated link|Flyback diode}}  - a device to channel inductive spikes back through the coil producing them
* {{annotated link|Voltage swell}}

==References==
{{Reflist}}

{{DEFAULTSORT:Voltage Spike}}
[[Category:Power electronics]]
[[Category:Voltage stability|Spike]]

[[pl:Przepięcie]]