Overvoltage
Encyclopedia
Voltage
Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...
in a circuit
Electrical network
An electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, voltage sources, current sources and switches. An electrical circuit is a special type of network, one that has a closed loop giving a return path for the current...
or part of it is raised above its upper design limit, this is known as overvoltage. The conditions may be hazardous. Depending on its duration, the overvoltage event can be transient
Transient (oscillation)
A transient event is a short-lived burst of energy in a system caused by a sudden change of state.The source of the transient energy may be an internal event or a nearby event...
—a voltage spike
Voltage spike
In electrical engineering, spikes are fast, short duration electrical transients in voltage , current , or transferred energy in an electrical circuit....
—or permanent, leading to a power surge
Power surge
Power surge or Powersurge may refer to:* Voltage spike* Power Surge , a 2002 DC Comics event* Power Surge , an amusement ride* Powersurge , an American power metal band* Powersurge , a Bangladeshi thrash/groove metal band...
.
Explanation
Electronic and electrical devices are designed to operate at a certain maximum supply voltage, and considerable damage can be caused by voltage that is higher than that for which the devices are rated.For example an electric light bulb
Incandescent light bulb
The incandescent light bulb, incandescent lamp or incandescent light globe makes light by heating a metal filament wire to a high temperature until it glows. The hot filament is protected from air by a glass bulb that is filled with inert gas or evacuated. In a halogen lamp, a chemical process...
has a wire in it that at the given rated voltage will carry a current
Electric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...
just large enough for the wire to get very hot (giving off light
Light
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
and heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
), but not hot enough for it to melt
Melting
Melting, or fusion, is a physical process that results in the phase change of a substance from a solid to a liquid. The internal energy of a substance is increased, typically by the application of heat or pressure, resulting in a rise of its temperature to the melting point, at which the rigid...
. The amount of current in a circuit depends on the voltage supplied: if the voltage is too high, then the wire may melt and the light bulb would have "burned out". Similarly other electrical devices may stop working, or may even burst into flame
Flame
A flame is the visible , gaseous part of a fire. It is caused by a highly exothermic reaction taking place in a thin zone...
s if an overvoltage is delivered to the circuit of which these devices are part.
Natural
A typical natural source of transient overvoltage events is lightningLightning
Lightning is an atmospheric electrostatic discharge accompanied by thunder, which typically occurs during thunderstorms, and sometimes during volcanic eruptions or dust storms...
. Bursts of solar wind
Solar wind
The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...
following solar flare
Solar flare
A solar flare is a sudden brightening observed over the Sun surface or the solar limb, which is interpreted as a large energy release of up to 6 × 1025 joules of energy . The flare ejects clouds of electrons, ions, and atoms through the corona into space. These clouds typically reach Earth a day...
s are also known to cause overvoltage in electrical circuits, especially onboard space satellite
Satellite
In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
s.
Man made
Man-made sources of spikes are usually caused by electromagnetic inductionElectromagnetic induction
Electromagnetic induction is the production of an electric current across a conductor moving through a magnetic field. It underlies the operation of generators, transformers, induction motors, electric motors, synchronous motors, and solenoids....
when switching on or off inductive loads (such as electric motor
Electric motor
An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...
s or electromagnet
Electromagnet
An electromagnet is a type of magnet in which the magnetic field is produced by the flow of electric current. The magnetic field disappears when the current is turned off...
s), or by switching heavy resistive AC loads when zero-crossing circuitry
Zero cross circuit
A zero cross circuit is an electrical circuit that starts operation with the AC load voltage at close to zero-phase. This is in relation to solid state relays, such as triacs and silicon controlled rectifiers...
is not used - anywhere a large change of current takes place. One of the purposes of electromagnetic compatibility
Electromagnetic compatibility
Electromagnetic compatibility is the branch of electrical sciences which studies the unintentional generation, propagation and reception of electromagnetic energy with reference to the unwanted effects that such energy may induce...
compliance is to eliminate such sources.
An important potential source of dangerous overvoltage is electronic warfare
Electronic warfare
Electronic warfare refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum, attack an enemy, or impede enemy assaults via the spectrum. The purpose of electronic warfare is to deny the opponent the advantage of, and ensure friendly...
. There is intensive military
Military
A military is an organization authorized by its greater society to use lethal force, usually including use of weapons, in defending its country by combating actual or perceived threats. The military may have additional functions of use to its greater society, such as advancing a political agenda e.g...
research in this field, whose goal is to produce various transient electromagnetic devices designed to generate electromagnetic pulse
Electromagnetic pulse
An electromagnetic pulse is a burst of electromagnetic radiation. The abrupt pulse of electromagnetic radiation usually results from certain types of high energy explosions, especially a nuclear explosion, or from a suddenly fluctuating magnetic field...
s that will disable an enemy's electronic equipment. A recent military development is that of the exploding capacitor
Capacitor
A capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...
designed to radiate a high voltage electromagnetic pulse. Another intense source of an electromagnetic pulse is a nuclear explosion.
Conduction path
The transient pulses can get into the equipment either by power or data lines, or directly through space from a strong electromagnetic fieldElectromagnetic field
An electromagnetic field is a physical field produced by moving electrically charged objects. It affects the behavior of charged objects in the vicinity of the field. The electromagnetic field extends indefinitely throughout space and describes the electromagnetic interaction...
change - an electromagnetic pulse
Electromagnetic pulse
An electromagnetic pulse is a burst of electromagnetic radiation. The abrupt pulse of electromagnetic radiation usually results from certain types of high energy explosions, especially a nuclear explosion, or from a suddenly fluctuating magnetic field...
(EMP). Filters
Electronic filter
Electronic filters are electronic circuits which perform signal processing functions, specifically to remove unwanted frequency components from the signal, to enhance wanted ones, or both...
are used to prevent spikes entering or leaving the equipment through wires, and the devices coupled electromagnetically to space (such as radio-frequency
Radio frequency
Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...
pick-up coils in MRI scanners) are protected by shielding
Electromagnetic shielding
Electromagnetic shielding is the process of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive and/or magnetic materials. Shielding is typically applied to enclosures to isolate electrical devices from the 'outside world' and to cables to isolate...
.
Overvoltage protection devices
- Arcing hornsArcing hornsArcing horns are projecting conductors used to protect insulators on high voltage electric power transmission systems from damage during flashover. Overvoltages on transmission lines, due to atmospheric electricity, lightning strikes, or electrical faults, can cause arcs across insulators that...
- Zener diodeZener diodeA Zener diode is a special kind of diode which allows current to flow in the forward direction in the same manner as an ideal diode, but will also permit it to flow in the reverse direction when the voltage is above a certain value known as the breakdown voltage, "Zener knee voltage" or "Zener...
- Avalanche diodeAvalanche diodeIn electronics, an avalanche diode is a diode that is designed to go through avalanche breakdown at a specified reverse bias voltage. The junction of an avalanche diode is designed to prevent current concentration at hot spots, so that the diode is undamaged by the breakdown...
- Transil
- TrisilTrisilA Trisil is trade name for a thyristor surge protection device, an electronic component designed to protect electronic circuits against overvoltage...
- Spark gap
- Gas filled tubeGas filled tubeA gas-filled tube, also known as a discharge tube, is an arrangement of electrodes in a gas within an insulating, temperature-resistant envelope. Although the envelope is typically glass, power tubes often use ceramics, and military tubes often use glass-lined metal...
- Metal Oxide Varistor
- SiBar Thyristor
See also
- Overvolting
- Crowbar (circuit)Crowbar (circuit)A crowbar circuit is an electrical circuit used to prevent an overvoltage condition of a power supply unit from damaging the circuits attached to the power supply. It operates by putting a short circuit or low resistance path across the voltage source, much as if one dropped a tool of the same name...
- Uninterruptible power supplyUninterruptible power supplyAn uninterruptible power supply, also uninterruptible power source, UPS or battery/flywheel backup, is an electrical apparatus that provides emergency power to a load when the input power source, typically mains power, fails...
- Transient (oscillation)Transient (oscillation)A transient event is a short-lived burst of energy in a system caused by a sudden change of state.The source of the transient energy may be an internal event or a nearby event...
- Voltage spikeVoltage spikeIn electrical engineering, spikes are fast, short duration electrical transients in voltage , current , or transferred energy in an electrical circuit....
- Surge suppressor
- Electronic warfareElectronic warfareElectronic warfare refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum, attack an enemy, or impede enemy assaults via the spectrum. The purpose of electronic warfare is to deny the opponent the advantage of, and ensure friendly...
- Electronic countermeasuresElectronic countermeasuresAn electronic countermeasure is an electrical or electronic device designed to trick or deceive radar, sonar or other detection systems, like infrared or lasers. It may be used both offensively and defensively to deny targeting information to an enemy...
- Electronic countermeasures
- Electromagnetic pulseElectromagnetic pulseAn electromagnetic pulse is a burst of electromagnetic radiation. The abrupt pulse of electromagnetic radiation usually results from certain types of high energy explosions, especially a nuclear explosion, or from a suddenly fluctuating magnetic field...
- Transient electromagnetic device
- LightningLightningLightning is an atmospheric electrostatic discharge accompanied by thunder, which typically occurs during thunderstorms, and sometimes during volcanic eruptions or dust storms...
- Electrostatic dischargeElectrostatic dischargeElectrostatic discharge is a serious issue in solid state electronics, such as integrated circuits. Integrated circuits are made from semiconductor materials such as silicon and insulating materials such as silicon dioxide...
- Electromagnetic shieldingElectromagnetic shieldingElectromagnetic shielding is the process of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive and/or magnetic materials. Shielding is typically applied to enclosures to isolate electrical devices from the 'outside world' and to cables to isolate...