![IMO SPD 40-275 Surge Protection Device E-Magnetica](https://upload.wikimedia.org/wikipedia/commons/0/08/IMO_SPD_40-275_Surge_Protection_Device_E-Magnetica.jpg)
A '
surge protector'' (or spike suppressor, surge suppressor, surge diverter, surge protection device (SPD) or transient voltage surge suppressor (TVSS) is an appliance or device intended to protect
electrical devices from
voltage spike
In electrical engineering, spikes are fast, short duration electrical transients in voltage (voltage spikes), current (current spikes), or transferred energy (energy spikes) in an electrical circuit.
Fast, short duration electrical transients ( ...
s in
alternating current
Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction. Alternating current is the form in whic ...
(AC) circuits. A voltage spike is a transient event, typically lasting 1 to 30 microseconds, that may reach over 1,000 volts. Lightning that hits a power line can give a spike of over 100,000 volts and can burn through wiring insulation and cause fires, but even modest spikes can destroy a wide variety of electronic devices, computers, battery chargers, modems and TVs etc, that happen to be plugged in at the time. Typically the surge device will trigger at a set voltage, around 3 to 4 times the mains voltage, and divert the current to earth. Some devices may absorb the spike and release it as heat. They are generally rated according to the amount of energy in joules they can absorb.
some company have surge protection device lik
OBO BETTERMANN DEHN.
CITEL The Inter-American Telecommunication Commission or ''Comisión Interamericana de Telecomunicaciones'' (CITEL) is an entity of the Organization of American States. It was originally created as the Inter-American Electrical Communication Commission a ...
Voltage spikes
In an AC circuit a voltage spike is a transient event, typically lasting 1 to 30 microseconds, that may reach over 1,000 volts. Lightning that hits a power line can give many thousands, sometimes 100,000 or more volts. A motor when switched off can generate a spike of 1,000 or more volts. Spikes can degrade wiring insulation and destroy electronic devices like
light bulbs
An electric light, lamp, or light bulb is an electrical component that produces light. It is the most common form of artificial lighting. Lamps usually have a base made of ceramic, metal, glass, or plastic, which secures the lamp in the soc ...
, battery chargers, modems, TVs, and other consumer electronics.
Spikes can also occur on telephone and data lines when AC main lines accidentally connect to them or lightning hits them, or if the telephone and data lines travel near lines with a spike and the voltage is induced.
A long term surge, lasting seconds, minutes, or hours, caused by power transformer failures such as a lost neutral or other power company error, are not protected by transient protectors. Long term surges can destroy the protectors in an entire building or area. Even tens of milliseconds can be longer than a protector can handle. Long term surges may or may not be handled by fuses and
overvoltage relays.
Surge currents
Surge currents are much lower in Category A locations than at Category B and C locations.
Category A loads are more than 60 feet of wire length from the service entrance to the load. Category A loads can be exposed to 6kV, 0.5kA surge currents.
Category B loads are more than 30 feet from the service entrance and less than 60 feet of wire length from the service entrance to the load. Category B loads can be exposed to 6kV, 3kA surge currents.
Category C loads are less than 30 feet from the service entrance to the load. Category C loads can be exposed to 20kV, 10kA surge currents.
A building's wiring adds impedance that limits the surge current that reaches the loads. There is less surge current at longer wire distances and where more impedance is present between the service entrance and the load.
A coiled extension cord can be used to increase the wire length to more than 60 feet and to increase the impedance between the service entrance and the load.
Definitions
The terms ''surge protection device'' (''SPD'') and ''transient voltage surge suppressor'' (''TVSS'') are used to describe electrical devices typically installed in power distribution panels,
process control systems, communications systems, and other heavy-duty industrial systems, for the purpose of protecting against electrical surges and spikes, including those caused by
lightning
Lightning is a naturally occurring electrostatic discharge during which two electric charge, electrically charged regions, both in the atmosphere or with one on the land, ground, temporarily neutralize themselves, causing the instantaneous ...
. Scaled-down versions of these devices are sometimes installed in residential service entrance electrical panels, to protect equipment in a household from similar hazards.
Protectors
A transient surge protector attempts to limit the
voltage
Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to m ...
supplied to an electric device by either blocking or
shorting
In finance, being short in an asset means investing in such a way that the investor will profit if the value of the asset falls. This is the opposite of a more conventional " long" position, where the investor will profit if the value of t ...
current to reduce the voltage below a safe threshold. Blocking is done by using inductors which inhibit a sudden change in current. Shorting is done by spark gaps, discharge tubes, zener-type semiconductors, and
metal-oxide varistors (MOVs), all of which begin to conduct current once a certain voltage threshold is reached, or by capacitors which inhibit a sudden change in voltage. Some surge protectors use multiple elements.
The most common and effective way is the shorting method in which the electrical lines are temporarily shorted together (as by a spark gap) or clamped to a target voltage (as by a MOV) resulting in a large current flow. The voltage is reduced as the shorting current flows through the resistance in the power lines. The spike's energy is dissipated in the power lines (and/or the
ground), or in the body of the MOV, converted to heat. Since a spike lasts only 10s of microseconds, the temperature rise is minimal. However, if the spike is large enough or long enough, like a nearby hit by lightning, there might not be enough power line or ground resistance and the MOV (or other protection element) can be destroyed and power lines melted.
Surge protectors for homes can be in power strips used inside, or a device outside at the power panel. Sockets in a modern house uses three wires: line, neutral and ground. Many protectors will connect to all three in pairs (line–neutral, line–ground and neutral–ground), because there are conditions, such as lightning, where both line and neutral have high voltage spikes that need to be shorted to ground.
![Tricklestar Plug Strip](https://upload.wikimedia.org/wikipedia/commons/f/fa/Tricklestar_Plug_Strip.jpg)
Additionally, some consumer-grade protectors have ports for
Ethernet
Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 198 ...
and
coaxial
In geometry, coaxial means that several three-dimensional linear or planar forms share a common axis. The two-dimensional analog is ''concentric''.
Common examples:
A coaxial cable is a three-dimensional linear structure. It has a wire condu ...
cables, and plugging them in allows the surge protector to shield them from external electrical damage.
Transient voltage suppressor
A transient voltage suppressor or TVS is a general classification of electronic components that are designed to react to sudden or momentary
overvoltage
When the voltage in a circuit 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—a voltage spike—or perm ...
conditions. One such common device used for this purpose is known as the
transient voltage suppression diode
A transient-voltage-suppression (TVS) diode, also transil or thyrector, is an electronic component used to protect electronics from voltage spikes induced on connected wires.
Description
The device operates by shunting excess current when the ...
, a
Zener diode
A Zener diode is a special type of diode designed to reliably allow current to flow "backwards" (inverted polarity) when a certain set reverse voltage, known as the ''Zener voltage'', is reached.
Zener diodes are manufactured with a great varie ...
designed to protect
electronics
The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...
device against overvoltages. Another design alternative applies a family of products that are known as
metal-oxide varistor
A varistor is an electronic component with an electrical resistance that varies with the applied voltage. Also known as a voltage-dependent resistor (VDR), it has a nonlinear, non- ohmic current–voltage characteristic that is similar to that ...
s (MOV).
The characteristic of a TVS requires that it respond to overvoltages faster than other common overvoltage protection components such as
varistor
A varistor is an electronic component with an electrical resistance that varies with the applied voltage. Also known as a voltage-dependent resistor (VDR), it has a nonlinear, non- ohmic current–voltage characteristic that is similar to that ...
s or
gas discharge tube
A gas-filled tube, also commonly known as a discharge tube or formerly as a Plücker tube, is an arrangement of electrodes in a gas within an insulating, temperature-resistant envelope. Gas-filled tubes exploit phenomena related to electric d ...
s. This makes TVS devices or components useful for protection against very fast and often damaging
voltage spike
In electrical engineering, spikes are fast, short duration electrical transients in voltage (voltage spikes), current (current spikes), or transferred energy (energy spikes) in an electrical circuit.
Fast, short duration electrical transients ( ...
s. These fast overvoltage spikes are present on all distribution networks and can be caused by either internal or external events, such as
lightning
Lightning is a naturally occurring electrostatic discharge during which two electric charge, electrically charged regions, both in the atmosphere or with one on the land, ground, temporarily neutralize themselves, causing the instantaneous ...
or motor
arcing
An electric arc, or arc discharge, is an electrical breakdown of a gas that produces a prolonged electrical discharge. The electric current, current through a normally Electrical conductance, nonconductive medium such as air produces a plasma (p ...
.
Applications of transient voltage suppression diodes are used for unidirectional or bidirectional
electrostatic discharge
Electrostatic discharge (ESD) is a sudden and momentary flow of electric current between two electrically charged objects caused by contact, an short circuit, electrical short or dielectric breakdown. A buildup of static electricity can be caused ...
protection of transmission or data lines in electronic circuits. MOV-based TVSs are used to protect home electronics, distribution systems and may accommodate industrial level power distribution disturbances saving downtime and damage to equipment. The level of energy in a transient overvoltage can be equated to energy measured in
joule
The joule ( , ; symbol: J) is the unit of energy in the International System of Units (SI). It is equal to the amount of work done when a force of 1 newton displaces a mass through a distance of 1 metre in the direction of the force applied ...
s or related to
electric current
An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving pa ...
when devices are rated for various applications. These bursts of overvoltage can be measured with specialized electronic meters that can show power disturbances of thousands of volts amplitude that last for a few microseconds or less.
It is possible for a MOV to overheat when exposed to overvoltage sufficient for the MOV to start conducting, but not enough to totally destroy it, or to blow a house fuse. If the overvoltage condition persists long enough to cause significant heating of the MOV, it can result in thermal damage to the device and start a fire.
Comparison of transient suppressors
File:Transils-01.jpeg, TVS-diodes. The devices shown here are able to handle 1.5 kW of peak power for a short period.
File:Varistoren.jpg, Metal-oxide varistor
A varistor is an electronic component with an electrical resistance that varies with the applied voltage. Also known as a voltage-dependent resistor (VDR), it has a nonlinear, non- ohmic current–voltage characteristic that is similar to that ...
s
File:Gasableiter.jpg, Gas discharge tube
A gas-filled tube, also commonly known as a discharge tube or formerly as a Plücker tube, is an arrangement of electrodes in a gas within an insulating, temperature-resistant envelope. Gas-filled tubes exploit phenomena related to electric d ...
Domestic use
![SpikeStopperHomeWiki](https://upload.wikimedia.org/wikipedia/commons/0/03/SpikeStopperHomeWiki.jpg)
Many
power strip
A power strip is a block of electrical sockets that attaches to the end of a flexible cable (typically with a mains plug on the other end), allowing multiple electrical devices to be powered from a single electrical socket. Power strips are often ...
s have basic surge protection built in; these are typically clearly labeled as such. However, in unregulated countries there are power strips labelled as "surge" or "spike" protectors that only have a capacitor or RFI circuit (or nothing) that do ''not'' provide true (or any) spike protection.
Industrial use
![Surge Arresters big](https://upload.wikimedia.org/wikipedia/commons/e/e3/Surge_Arresters_big.jpg)
A surge arrester, surge protection device (SPD) or transient voltage surge suppressor (TVSS), is used to protect equipment in power
transmission and
distribution Distribution may refer to:
Mathematics
*Distribution (mathematics), generalized functions used to formulate solutions of partial differential equations
* Probability distribution, the probability of a particular value or value range of a vari ...
systems. The energy criterion for various insulation material can be compared by impulse ratio. A surge arrester should have a low impulse ratio, so that a surge incident on the surge arrester may be bypassed to the ground instead of passing through the apparatus.
To protect a unit of equipment from transients occurring on an attached conductor, a surge arrester is connected to the conductor just before it enters the equipment. The surge arrester is also connected to
ground and functions by routing energy from an over-voltage transient to ground if one occurs, while isolating the conductor from ground at normal operating voltages. This is usually achieved through use of a
varistor
A varistor is an electronic component with an electrical resistance that varies with the applied voltage. Also known as a voltage-dependent resistor (VDR), it has a nonlinear, non- ohmic current–voltage characteristic that is similar to that ...
, which has substantially different resistances at different voltages.
Surge arresters are not generally designed to protect against a direct
lightning strike
A lightning strike or lightning bolt is an electric discharge between the atmosphere and the ground. Most originate in a cumulonimbus cloud and terminate on the ground, called cloud-to-ground (CG) lightning. A less common type of strike, ground- ...
to a conductor, but rather against electrical transients resulting from lightning strikes occurring in the vicinity of the conductor.
Lightning which strikes the earth results in ground currents which can pass over buried conductors and induce a transient that propagates outward towards the ends of the conductor. The same kind of induction happens in overhead and above ground conductors which experience the passing energy of an atmospheric
EMP caused by the lightning flash. Surge arresters only protect against induced transients characteristic of a lightning discharge's rapid rise-time and will not protect against electrification caused by a direct strike to the conductor. Transients similar to lightning-induced, such as from a high voltage system's fault switching, may also be safely diverted to ground; however, continuous
overcurrent
In an electric power system, overcurrent or excess current is a situation where a larger than intended electric current exists through a conductor, leading to excessive generation of heat, and the risk of fire or damage to equipment. Possible caus ...
s are not protected against by these devices. The energy in a handled transient is substantially less than that of a lightning discharge; however it is still of sufficient quantity to cause equipment damage and often requires protection.
Without very thick insulation, which is generally cost prohibitive, most conductors running more than minimal distances (greater than approximately 50 feet) will experience lightning-induced transients at some time during use. Because the transient is usually initiated at some point between the two ends of the conductor, most applications install a surge arrester just before the conductor lands in each piece of equipment to be protected. Each conductor must be protected, as each will have its own transient induced, and each SPD must provide a pathway to earth to safely divert the transient away from the protected component. The one notable exception where they are not installed at both ends is in high voltage distribution systems. In general, the induced voltage is not sufficient to do damage at the electric generation end of the lines; however, installation at the service entrance to a building is key to protecting downstream products that are not as robust.
Types
*Low-voltage surge arrester: Apply in Low-voltage distribution system, exchange of electrical appliances protector, low-voltage distribution transformer windings
*Distribution arrester: Apply in 3 kV, 6 kV, 10 kV AC power distribution system to protect distribution transformers, cables and power station equipment
*The station type of common valve arrester: Used to protect the 3 ~ 220 kV transformer station equipment and communication system
*Magnetic blow valve station arrester: Use to 35 ~ 500 kV protect communication systems, transformers and other equipment
*Protection of rotating machine using magnetic blow valve arrester: Used to protect the AC generator and motor insulation
*Line Magnetic blow valve arrester: Used to protect 330 kV and above communication system circuit equipment insulation
*DC or blowing valve-type arrester: Use to protect the DC system’s insulation of electrical equipment
*Neutral protection arrester: Apply in motor or the transformer’s neutral protection
*Fiber-tube arrester: Apply in the power station’s wires and the weaknesses protection in the insulated
*Plug-in Signal Arrester: Used to twisted-pair transmission line in order to protect communications and computer systems
![Gasableiter](https://upload.wikimedia.org/wikipedia/commons/7/7e/Gasableiter.jpg)
*High-frequency feeder arrester: Used to protect the microwave, mobile base stations satellite receiver, etc.
*Receptacle-type surge arrester: Use to Protect the terminal Electronic equipment
*Signal Arrester: Apply in MODEM, DDN line, fax, phone, process control signal circuit etc.
*Network arrester: Apply in servers, workstations, interfaces etc.
*Coaxial cable lightning arrester: Used on the coaxial cable to protect the wireless transmission and receiving system
Important specifications
These are some of the most prominently featured specifications which define a surge protector for AC mains, as well as for some data communications protection applications.
Clamping voltage
Also known as the let-through voltage, this specifies what spike voltage will cause the protective components inside a surge protector to short or clamp.
A lower clamping voltage indicates better protection, but can sometimes result in a shorter life expectancy for the overall protective system. The lowest three levels of protection defined in the
UL rating are 330 V, 400 V and 500 V. The standard let-through voltage for 120 V AC devices is 330 volts.
Underwriters Laboratories
The UL enterprise is a global safety science company headquartered in Northbrook, Illinois, composed of three organizations, UL Research Institutes, UL Standards & Engagement and UL Solutions.
Established in 1894, the UL enterprise was founded a ...
(UL), a global independent safety science company, defines how a protector may be used safely. UL 1449 became compliance mandatory in jurisdictions that adopted the NEC with the 3rd edition in September 2009 to increase safety compared to products conforming to the 2nd edition. A measured limiting voltage test, using six times higher current (and energy), defines a voltage protection rating (VPR). For a specific protector, this voltage may be higher compared to a Suppressed Voltage Ratings (SVR) in previous editions that measured let-through voltage with less current. Due to non-linear characteristics of protectors, let-through voltages defined by 2nd edition and 3rd edition testing are not comparable.
A protector may be larger to obtain a same let-through voltage during 3rd edition testing. Therefore, a 3rd edition or later protector should provide superior safety with increased life expectancy.
A protector with a higher let-through voltage, e.g.400 V vs 330 V, will pass a higher voltage to the connected device. The design of the connected device determines whether this pass-through spike will cause damage. Motors and mechanical devices are usually not affected. Some (especially older) electronic parts, like chargers, LED or CFL bulbs and computerized appliances are sensitive and can be compromised and have their life reduced.
Joule rating
The Joule rating number defines how much energy a
MOV-based surge protector can theoretically absorb in a single event, without failure. Better protectors exceed ratings of 1,000 joules and 40,000 amperes. Since the actual duration of a spike is only about 10 microseconds, the actual dissipated energy is low. Any more than that and the MOV will fuse, or sometimes short and melt, hopefully blowing a fuse, disconnecting itself from the circuit.
The MOV (or other shorting device) requires resistance in the supply line in order to limit the voltage. For large, low resistance power lines a higher joule rated MOV is required. Inside a house, with smaller wires that have more resistance, a smaller MOV is acceptable.
Every time a MOV shorts, its internal structure is changed and its threshold voltage reduced slightly. After many spikes the threshold voltage can reduce enough to be near the line voltage, i.e. 120 vac or 240 vac. At this point the MOV will partially conduct and heat up and eventually fail, sometimes in a dramatic meltdown or even a fire. Most modern surge protectors have circuit breakers and temperature fuses to prevent serious consequences. Many also have an LED light to indicate if the MOVs are still functioning.
The joule rating is commonly quoted for comparing MOV-based surge protectors. An average surge (spike) is of short duration, lasting for nanoseconds to microseconds, and experimentally modeled surge energy can be less than 100 joules. Well-designed surge protectors consider the resistance of the lines that supply the power, the chance of lightning or other seriously energetic spike, and specify the MOVs accordingly. A little battery charger might include a MOV of only 1 watt, whereas a surge strip will have a 20 watt MOV or several of them in parallel. A house protector will have a large block-type MOV.
Some manufacturers commonly design higher joule-rated surge protectors by connecting multiple MOVs in parallel and this can produce a misleading rating. Since individual MOVs have slightly different voltage thresholds and non-linear responses when exposed to the same voltage curve, any given MOV might be more sensitive than others. This can cause one MOV in a group to conduct more (a phenomenon called
current hogging
Thermal runaway describes a process that is accelerated by increased temperature, in turn releasing energy that further increases temperature. Thermal runaway occurs in situations where an increase in temperature changes the conditions in a way t ...
), leading to possible overuse and eventual premature failure of that component. However the other MOVs in the group do help a little as they start to conduct as the voltage continues to rise as it does since a MOV does not have a sharp threshold. It may start to short at 270 volts but not reach full short until 450 or more volts. A second MOV might start at 290 volts and another at 320 volts so they all can help clamp the voltage, and at full current there is a series ballast effect that improves current sharing, but stating the actual joule rating as the sum of all the individual MOVs does not accurately reflect the total clamping ability. The first MOV may bear more of the burden and fail earlier. One MOV manufacturer recommends using fewer but bigger MOVs (e.g.60 mm vs 40 mm diameter) if they can fit in the device and to match them and derate them. In some cases it may take four 40 mm MOVs to be equivalent to one 60 mm MOV.
A further problem is that if a single inline fuse is placed in series with a group of paralleled MOVs as a disconnect safety feature, it will open and disconnect all remaining working MOVs.
The ''effective'' surge energy absorption capacity of the entire system is dependent on the MOV matching so derating by 20% or more is usually required. This limitation can be managed by using carefully ''matched sets'' of MOVs, matched according to manufacturer's specification.
[ See pages 7-8, "Parallel Operation of Varistors"]
According to industry testing standards, based on IEEE and ANSI assumptions, power line surges inside a building can be up to 6,000 volts and 3,000 amperes, and deliver up to 90 joules of energy, including surges from external sources not including lightning strikes.
The common assumptions regarding lightning specifically, based ANSI/IEEE C62.41 and UL 1449 (3rd Edition) at time of this writing, are that minimum lightning-based power line surges inside a building are typically 10,000 amperes or 10 kiloamperes (kA). This is based on 20 kA striking a power line, the imparted current then traveling equally in both directions on the power line with the resulting 10 kA traveling into the building or home. These assumptions are based on an average approximation for testing minimum standards. While 10 kA is typically good enough for minimum protection against lightning strikes it is possible for a lightning strike to impart up to 200 kA to a power line with 100 kA traveling in each direction.
Lightning and other high-energy transient voltage surges can be suppressed with pole mounted suppressors by the utility, or with an owner supplied whole house surge protector. A whole house product is more expensive than simple single-outlet surge protectors and often needs professional installation on the incoming electrical power feed; however, they prevent power line spikes from entering the house. Damage from direct lightning strikes via other paths must be controlled separately.
Response time
Surge protectors don't operate instantaneously; a slight delay exists, some few nanoseconds. With longer response time and depending on system impedance, the connected equipment may be exposed to some of the surge. However, surges typically are much slower and take around a few
microsecond
A microsecond is a unit of time in the International System of Units (SI) equal to one millionth (0.000001 or 10−6 or ) of a second. Its symbol is μs, sometimes simplified to us when Unicode is not available.
A microsecond is equal to 1000 n ...
s to reach their peak voltage, and a surge protector with a
nanosecond
A nanosecond (ns) is a unit of time in the International System of Units (SI) equal to one billionth of a second, that is, of a second, or 10 seconds.
The term combines the SI prefix ''nano-'' indicating a 1 billionth submultiple of an SI unit ( ...
response time would kick in fast enough to suppress the most damaging portion of the spike.
Thus response time under standard testing is not a useful measure of a surge protector's ability when comparing MOV devices. All MOVs have response times measured in nanoseconds, while test waveforms usually used to design and calibrate surge protectors are all based on modeled waveforms of surges measured in microseconds. As a result, MOV-based protectors have no trouble producing impressive response-time specs.
Slower-responding technologies (notably, GDTs) may have difficulty protecting against fast spikes. Therefore, good designs incorporating slower but otherwise useful technologies usually combine them with faster-acting components, to provide more comprehensive protection.
Standards
Some frequently listed standards include:
*
IEC
The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization that prepares and publishes international standards for all electrical, electronic and r ...
61643-11 Low-voltage surge protective devices - Part 11: Surge protective devices connected to low-voltage power systems - Requirements and test methods (replaces IEC 61643-1)
*
IEC
The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization that prepares and publishes international standards for all electrical, electronic and r ...
61643-21 Low voltage surge protective devices - Part 21: Surge protective devices connected to telecommunications and signalling networks - Performance requirements and testing methods
*
IEC
The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization that prepares and publishes international standards for all electrical, electronic and r ...
61643-22 Low-voltage surge protective devices - Part 22: Surge protective devices connected to telecommunications and signalling networks - Selection and application principles
*
EN 61643-11, 61643-21 and 61643-22
*
Telcordia Technologies
iconectiv is a supplier of network planning and network management services to telecommunications providers. Known as Bellcore after its establishment in the United States in 1983 as part of the break-up of the Bell System, the company's name ...
Technical Referenc
TR-NWT-001011*
ANSI
The American National Standards Institute (ANSI ) is a private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organi ...
/
IEEE
The Institute of Electrical and Electronics Engineers (IEEE) is a 501(c)(3) professional association for electronic engineering and electrical engineering (and associated disciplines) with its corporate office in New York City and its operation ...
C62.xx
*
Underwriters Laboratories
The UL enterprise is a global safety science company headquartered in Northbrook, Illinois, composed of three organizations, UL Research Institutes, UL Standards & Engagement and UL Solutions.
Established in 1894, the UL enterprise was founded a ...
(UL) 1449.
*
AS/NZS 1768
Each standard defines different protector characteristics, test vectors, or operational purpose.
The 3rd Edition of UL Standard 1449 for SPDs was a major rewrite of previous editions, and was also accepted as an ANSI standard for the first time.
A subsequent revision in 2015 included the addition of low-voltage circuits for
USB
Universal Serial Bus (USB) is an industry standard that establishes specifications for cables, connectors and protocols for connection, communication and power supply (interfacing) between computers, peripherals and other computers. A broad ...
charging ports and associated batteries.
EN 62305 and ANSI/IEEE C62.xx define what spikes a protector might be expected to divert. EN 61643-11 and 61643-21 specify both the product's performance and safety requirements. In contrast, the IEC only writes standards and does not certify any particular product as meeting those standards. IEC Standards are used by members of the CB Scheme of international agreements to test and certify products for safety compliance.
None of those standards guarantee that a protector will provide proper protection in a given application. Each standard defines what a protector should do or might accomplish, based on standardized tests that may or may not correlate to conditions present in a particular real-world situation. A specialized engineering analysis may be needed to provide sufficient protection, especially in situations of high
lightning
Lightning is a naturally occurring electrostatic discharge during which two electric charge, electrically charged regions, both in the atmosphere or with one on the land, ground, temporarily neutralize themselves, causing the instantaneous ...
risk.
In addition, the following standards are not standards for standalone surge protectors, but are instead meant for testing surge immunity in electrical and electronic equipment as a whole. Thus, they're frequently used in the design and test of surge protection circuitry.
*
IEC
The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization that prepares and publishes international standards for all electrical, electronic and r ...
61000-4-2 Electrostatic discharge immunity test
*
IEC
The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization that prepares and publishes international standards for all electrical, electronic and r ...
61000-4-4 Electrical fast transient/burst immunity test
*
IEC
The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization that prepares and publishes international standards for all electrical, electronic and r ...
61000-4-5 Surge immunity test
Primary components
Systems used to reduce or limit high-voltage surges
can include one or more of the following types of
electronic component
An electronic component is any basic discrete device or physical entity in an electronic system used to affect electrons or their associated fields. Electronic components are mostly industrial products, available in a singular form and are not ...
s. Some surge suppression systems use multiple technologies, since each method has its strong and weak points.
[ Includes extensive comparison of design tradeoffs among various surge suppression technologies.][ Connection of MOVs and GDTs in series]
The first six methods listed operate primarily by diverting unwanted surge energy away from the protected load, through a protective component connected in a ''parallel'' (or shunted) topology. The last two methods also block unwanted energy by using a protective component connected in ''series'' with the power feed to the protected load, and additionally may shunt the unwanted energy like the earlier systems.
Metal oxide varistor
A
metal oxide varistor (MOV) consists of a bulk
semiconductor
A semiconductor is a material which has an electrical resistivity and conductivity, electrical conductivity value falling between that of a electrical conductor, conductor, such as copper, and an insulator (electricity), insulator, such as glas ...
material (typically
sintered granular
zinc oxide
Zinc oxide is an inorganic compound with the formula . It is a white powder that is insoluble in water. ZnO is used as an additive in numerous materials and products including cosmetics, food supplements, rubbers, plastics, ceramics, glass, cemen ...
) that can conduct large currents when presented with a voltage above its rated voltage.
MOVs typically limit voltages to about 3 to 4 times the normal circuit voltage by diverting surge current elsewhere than the protected load. MOVs may be connected in parallel to increase current capability and life expectancy, providing they are ''matched sets''.
MOVs have finite life expectancy and degrade when exposed to a few large transients, or many small transients.
[Walaszczyk, et al. 2001 "Does Size Really Matter? An Exploration of ... Paralleling Multiple Lower Energy Movs".](_blank)
See Figures 4 & 5 for Pulse Life Curves. Every time an MOV activates its threshold voltage reduces slightly. After many spikes the threshold voltage can reduce enough to be near the protection voltage, either mains or data. At this point the MOV conducts more and more often, heats up and finally fails. In data circuits, the data channel becomes shorted and non-functional. In a power circuit, you may get a dramatic meltdown or even a fire if not protected by a fuse of some kind.
Modern surge strips and house protectors have circuit breakers and temperature fuses to prevent serious consequences. A thermal fuse disconnects the MOV when it gets too hot. Only the MOV is disconnected leaving the rest of the circuit working but without surge protection. Often there is an LED light to indicate if the MOVs are still functioning. Older surge strips had no thermal fuse and relied on a 10 or 15 amp circuit breaker which usually blew only after the MOVs had smoked, burned, popped, melted and permanently shorted.
A failing MOV is a fire risk, which is a reason for the National Fire Protection Association's (NFPA) UL1449 in 1986 and subsequent revisions in 1998, 2009 and 2015. NFPA's primary concern is protection from fire.
Therefore, all MOV-based protectors intended for long-term use should have an indicator that the protective components have failed, and this indication must be checked on a regular basis to ensure that protection is still functioning.
Because of their good
price–performance ratio
In economics, engineering, business management and marketing the price–performance ratio is often written as cost–performance, cost–benefit or capability/price (C/P), refers to a product's ability to deliver performance, of any sort, for it ...
, MOVs are the most common protector component in low-cost basic AC power protectors.
Transient voltage suppression diode
A
transient-voltage-suppression diode
A transient-voltage-suppression (TVS) diode, also transil or thyrector, is an electronic component used to protect electronics from voltage spikes induced on connected wires.
Description
The device operates by shunting excess current when the ...
(TVS diode) is a type of
avalanche diode
In electronics, an avalanche diode is a diode (made from silicon or other semiconductor) that is designed to experience avalanche breakdown at a specified reverse bias voltage. The junction of an avalanche diode is designed to prevent current co ...
which can limit voltage spikes. These components provide the fastest limiting action of protective components (theoretically in
picoseconds
A picosecond (abbreviated as ps) is a unit of time in the International System of Units (SI) equal to 10−12 or (one trillionth) of a second. That is one trillionth, or one millionth of one millionth of a second, or 0.000 000 000&nbs ...
), but have a relatively low energy-absorbing capability. Voltages can be clamped to less than twice the normal operation voltage. If current impulses remain within the device ratings, life expectancy is exceptionally long. If component ratings are exceeded, the diode may fail as a permanent short circuit; in such cases, protection may remain but normal circuit operation is terminated in the case of low-power signal lines. Due to their relatively limited current capacity, TVS diodes are often restricted to circuits with smaller current spikes. TVS diodes are also used where spikes occur significantly more often than once a year, since this component will not degrade when used within its ratings. A unique type of TVS diode (trade names Transzorb or
Transil
A transient-voltage-suppression (TVS) diode, also transil or thyrector, is an electronic component used to protect electronics from voltage spikes induced on connected wires.
Description
The device operates by shunting excess current when the ...
) contains reversed paired ''series'' avalanche diodes for bi-polar operation.
TVS diodes are often used in high-speed but low-power circuits, such as occur in data communications. These devices can be paired in ''series'' with another diode to provide low capacitance as required in communication circuits.
Thyristor surge protection device (TSPD)
A
Trisil
Trisil is a trade name for a thyristor surge protection device, an electronic component designed to protect electronic circuits against overvoltage. Unlike a transient voltage suppression diodes, such as Transil, a Trisil acts as a crowbar devic ...
is a type of thyristor surge protection device (TSPD), a specialized solid-state electronic device used in
crowbar circuits to protect against overvoltage conditions. A
SIDACtor is another
thyristor
A thyristor () is a solid-state semiconductor device with four layers of alternating P- and N-type materials used for high-power applications. It acts exclusively as a bistable switch (or a latch), conducting when the gate receives a current ...
type device used for similar protective purposes.
These thyristor-family devices can be viewed as having characteristics much like a
spark gap
A spark gap consists of an arrangement of two conducting electrodes separated by a gap usually filled with a gas such as air, designed to allow an electric spark to pass between the conductors. When the potential difference between the conduct ...
or a
GDT, but can operate much faster. They are related to TVS diodes, but can "break over" to a low clamping voltage analogous to an ionized and conducting spark gap. After triggering, the low clamping voltage allows large current surges while limiting heat dissipation in the device.
Gas discharge tube (GDT) spark gap
A gas discharge tube (GDT) is a sealed glass-enclosed device containing a special gas mixture trapped between two electrodes, which conducts electric current after becoming
ionized
Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule ...
by a high voltage spike.
GDTs can conduct more current for their size than other components. Like MOVs, GDTs have a finite life expectancy, and can handle a few very large transients or a greater number of smaller transients. The typical failure mode occurs when the triggering voltage rises so high that the device becomes ineffective, although lightning surges can occasionally cause a dead short.
GDTs take a relatively long time to trigger (longer than a lightning strike of 60 ns to 70 ns), permitting a higher voltage spike to pass through before the GDT conducts significant current. It is not uncommon for a GDT to let through pulses of 500 V or more of 100 ns in duration. In some cases, additional protective components are necessary to prevent damage to a protected load, caused by high-speed let-through voltage which occurs before the GDT begins to operate. The triggering voltages are typically 400–600 volts for gas tubes and those that are UL Standard 497 listed typically have high surge current ratings, 5,000 to 10,000 amperes (8x20 µs).
GDTs create an effective short circuit when triggered, so that if any electrical energy (spike, signal, or power) is present, the GDT will short this. Once triggered, a GDT will continue conducting (called follow-on current) until all electric current sufficiently diminishes, and the gas discharge quenches. Unlike other shunt protector devices, a GDT once triggered will continue to conduct at a voltage ''less than'' the high voltage that initially ionized the gas; this behavior is called
negative resistance
In electronics, negative resistance (NR) is a property of some electrical circuits and devices in which an increase in voltage across the device's terminals results in a decrease in electric current through it.
This is in contrast to an ordina ...
. Additional auxiliary circuitry may be needed in DC (and some AC) applications to suppress follow-on current, to prevent it from destroying the GDT after the initiating spike has dissipated. Some GDTs are designed to deliberately short out to a grounded terminal when overheated, thereby triggering an external fuse or circuit breaker.
Many GDTs are light-sensitive, in that exposure to light lowers their triggering voltage. Therefore, GDTs should be shielded from light exposure, or opaque versions that are insensitive to light should be used.
The CG2 SN series of surge arrestors, formerly produced by C P Clare, are advertised as being non-radioactive, and the datasheet for that series states that some members of the CG/CG2 series (75-470V) are radioactive.
Due to their exceptionally low capacitance, GDTs are commonly used on high frequency lines, such as those used in telecommunications equipment. Because of their high current-handling capability, GDTs can also be used to protect power lines, but the follow-on current problem must be controlled.
Selenium voltage suppressor
An "overvoltage clamping" bulk semiconductor similar to an MOV, though it does not clamp as well. However, it usually has a longer life than an MOV. It is used mostly in high-energy DC circuits, like the exciter field of an
alternator
An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature.Go ...
. It can dissipate power continuously, and it retains its clamping characteristics throughout the surge event, if properly sized.
Carbon block spark gap overvoltage suppressor
A
spark gap
A spark gap consists of an arrangement of two conducting electrodes separated by a gap usually filled with a gas such as air, designed to allow an electric spark to pass between the conductors. When the potential difference between the conduct ...
is one of the oldest protective electrical technologies still found in telephone circuits, having been developed in the nineteenth century. A carbon rod electrode is held with an insulator at a specific distance from a second electrode. The gap dimension determines the voltage at which a spark will jump between the two parts and short to ground. The typical spacing for telephone applications in North America is (0.003 inches). Carbon block suppressors are similar to gas arrestors (GDTs) but with the two electrodes exposed to the air, so their behavior is affected by the surrounding atmosphere, especially the humidity. Since their operation produces an open spark, these devices should ''never'' be installed where an explosive atmosphere may develop.
Inductors, line reactors, chokes, capacitors
Inductors, Line Reactors, Chokes and Capacitors are used to limit fault currents and can reduce or prevent overvoltage events. In applications that limit fault currents, inductors are more commonly known as an electrical line reactors or a choke. Line reactors can prevent overvoltage trips, increase the reliability and life of solid state devices, and reduce nuisance trips.
Marshalling cabinet panels with surge protectors
Metal marshalling cabinet panels can allow surge protection device (SPD) failures to be contained remotely from digital devices and electrical controllers. Direct flashes of lightning and lightning surge on secondary systems can cause catastrophic failures of SPDs. Catastrophic failures of SPDs can release fireballs of metal fragments and clouds of conductive carbon soot. Marshalling panels keep such hazards from reaching the digital and control devices that are mounted in the remote main control panels. Marshalling cabinet panels are used for digital system panels (fire alarm, security access control, computer clean power, etc.). Wiring and cables to be protected include both the power supply and any wiring (signaling circuit, initiating device circuit, shields, etc.), which extend beyond the building by underground, overhead or other means, such as walkways, bridges, etc. In addition, it should include the wiring of devices located in high places such as attics, roof levels of parking lots, parking lights, etc. After passing through the SPDs in the marshalling cabinets the wiring can pass through conduits into other remote, nearly adjacent, cabinets that contain the input & output connections to for digital system panels (fire alarm, security access control, computer clean power,
programmable logic controllers
A programmable logic controller (PLC) or programmable controller is an industrial computer that has been ruggedized and adapted for the control of manufacturing processes, such as assembly lines, machines, robotic devices, or any activity t ...
(PLCs), etc.
Quarter-wave coaxial surge arrestor
Used in RF signal transmission paths, this technology features a tuned quarter-wavelength short-circuit stub that allows it to pass a bandwidth of frequencies, but presents a short to any other signals, especially down towards DC. The passbands can be narrowband (about ±5% to ±10% bandwidth) or wideband (above ±25% to ±50% bandwidth). Quarter-wave coax surge arrestors have coaxial terminals, compatible with common coax cable connectors (especially
N or
7-16 types). They provide the most rugged available protection for RF signals above ; at these frequencies they can perform much better than the gas discharge cells typically used in the universal/broadband coax surge arrestors. Quarter-wave arrestors are useful for
telecommunications
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...
applications, such as
Wi-Fi
Wi-Fi () is a family of wireless network protocols, based on the IEEE 802.11 family of standards, which are commonly used for local area networking of devices and Internet access, allowing nearby digital devices to exchange data by radio wave ...
at 2.4 or but less useful for TV/
CATV
Cable television is a system of delivering television programming to consumers via radio frequency (RF) signals transmitted through coaxial cables, or in more recent systems, light pulses through fibre-optic cables. This contrasts with broadc ...
frequencies. Since a quarter-wave arrestor shorts out the line for low frequencies, it is not compatible with systems which send DC power for a
LNB up the coaxial downlink.
Series mode (SM) surge suppressors
These devices are not rated in
joule
The joule ( , ; symbol: J) is the unit of energy in the International System of Units (SI). It is equal to the amount of work done when a force of 1 newton displaces a mass through a distance of 1 metre in the direction of the force applied ...
s because they operate differently from the earlier suppressors, and they do not depend on materials that inherently wear out during repeated surges. SM suppressors are primarily used to control transient voltage surges on electrical power feeds to protected devices. They are essentially heavy-duty
low-pass filter
A low-pass filter is a filter that passes signals with a frequency lower than a selected cutoff frequency and attenuates signals with frequencies higher than the cutoff frequency. The exact frequency response of the filter depends on the filter des ...
s connected so that they allow 50 or 60 Hz line voltages through to the load, while blocking and diverting higher frequencies. This type of suppressor differs from others by using banks of
inductor
An inductor, also called a coil, choke, or reactor, is a passive two-terminal electrical component that stores energy in a magnetic field when electric current flows through it. An inductor typically consists of an insulated wire wound into a c ...
s,
capacitor
A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals.
The effect of ...
s and
resistor
A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active el ...
s that suppress voltage surges and inrush current to the
neutral wire, whereas other designs shunt to the
ground wire
In electrical engineering, ground or earth is a reference point in an electrical circuit from which voltages are measured, a common return path for electric current, or a direct physical connection to the Earth.
Electrical circuits may be connec ...
. Surges are not diverted but actually suppressed. The inductors slow down the energy. Since the inductor in series with the circuit path slows the current spike, the peak surge energy is spread out in the
time domain
Time domain refers to the analysis of mathematical functions, physical signals or time series of economic or environmental data, with respect to time. In the time domain, the signal or function's value is known for all real numbers, for the cas ...
and harmlessly absorbed and slowly released from a capacitor bank.
Experimental results show that most surge energies occur at under 100 joules, so exceeding the SM design parameters is unlikely. SM suppressors do not present a fire risk should the absorbed energy exceed design limits of the
dielectric
In electromagnetism, a dielectric (or dielectric medium) is an electrical insulator that can be polarised by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the mate ...
material of the components because the surge energy is also limited via arc-over to ground during
lightning
Lightning is a naturally occurring electrostatic discharge during which two electric charge, electrically charged regions, both in the atmosphere or with one on the land, ground, temporarily neutralize themselves, causing the instantaneous ...
strikes, leaving a surge remnant that often does not exceed a theoretical maximum (such as 6000 V at 3000 A with a modeled shape of 8 × 20 microsecond waveform specified by IEEE/ANSI C62.41). Because SMs work on both the current rise and the voltage rise, they can safely operate in the worst surge environments.
SM suppression focuses its protective philosophy on a ''power supply input'', but offers nothing to protect against surges appearing between the input of an SM device and ''data lines'', such as antennae, telephone or
LAN connections, or multiple such devices cascaded and linked to the primary devices. This is because they do not divert surge energy to the ground line. Data transmission requires the ground line to be clean in order to be used as a reference point. In this design philosophy, such events are already protected against by the SM device before the power supply. NIST reports that "Sending them
urgesdown the drain of a grounding conductor only makes them reappear within a microsecond about 200 meters away on some other conductor."
So having protection on a data transmission line is only required if surges are diverted to the ground line.
SM devices tend to be bulkier and heavier than devices utilizing other surge suppression technologies. The initial costs of SM filters are higher, typically and up, but a long service life can be expected if they are used properly. In-field installation costs can be higher, since SM devices are installed in ''
series
Series may refer to:
People with the name
* Caroline Series (born 1951), English mathematician, daughter of George Series
* George Series (1920–1995), English physicist
Arts, entertainment, and media
Music
* Series, the ordered sets used in ...
'' with the power feed, requiring the feed to be cut and reconnected.
See also
*
Lightning arrester
A lightning arrester (alternative spelling lightning arrestor) (also called lightning isolator) is a device, essentially an air gap between an electric wire and ground, used on electric power transmission and telecommunication systems to protect ...
*
Lightning rod
A lightning rod or lightning conductor (British English) is a metal rod mounted on a structure and intended to protect the structure from a lightning strike. If lightning hits the structure, it will preferentially strike the rod and be conducte ...
Notes
References
External links
*
Surge Protection in Low-Voltage AC Power Circuits: An 8-part AnthologyA comprehensive compilation of papers and articles published 1963-2003, hosted by the National Institute of Standards and Technology (NIST), an agency of the US Commerce Department.
NEMA Surge Protection InstituteImportant Points About Surge Protectors Surgege Protector Tech.
Intro to TVS on AllAboutCircuits''Inductive Load Arc Suppression''
{{DEFAULTSORT:Surge Protector
Consumer electronics
Computer peripherals
Electric power systems components
Voltage stability