The role of the lightning protector is used to protect a variety of electrical equipment in the power system from lightning overvoltage, operational overvoltage, frequency transient overvoltage impact and damage to a kind of electrical appliances. Types of lightning protector mainly has protection gap, valve type lightning protector and zinc oxide lightning protector. Protection gap is mainly used to limit the atmospheric overvoltage, generally used in power distribution systems, lines and substations into the line section protection. Valve type lightning protection and zinc oxide lightning protection for substation and power plant protection, in 500KV and the following system is mainly used to limit the atmospheric overvoltage, in the ultra-high voltage system will also be used to limit the internal overvoltage or for internal overvoltage backup protection.
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Main parameters
1, nominal voltage Un: the normal withstand voltage of the equipment, no action. In line with the rated voltage of the system being protected, in the information technology system this parameter indicates the type of protector that should be selected, it marks the rms value of AC or DC voltage.
2, the rated voltage Uc: can be long applied to the specified end of the protector, without causing changes in the characteristics of the protector and activate the protection element of the maximum effective value of the voltage.
3, the rated discharge current Isn: also known as the nominal discharge current In, to the protector to apply the waveform of 8/20μs of the standard lightning wave impact 10 times, the protector of the maximum impact current peak value.
4, the maximum discharge current Imax: to the protector applied waveform 8/20μs standard lightning wave impact 1 time, the protector withstand the maximum peak impact current.
5, the voltage protection level Up: the maximum value of the protector in the following tests: 1KV / μs slope of the fire jumping voltage; rated discharge current residual voltage.
6, response time tA: the main reaction in the protector of the special protection components of the action sensitivity, breakdown time, in a certain period of time depends on du/dt or di/dt slope.
7, the data transmission rate Vs: expressed in one second to transmit how many bits of value, unit: bps; is the correct choice of data transmission system in the reference value of the lightning protector, lightning protection of the data transmission rate depends on the system's transmission mode.
8, insertion loss Ae: the ratio of voltage before and after insertion of the protector at a given frequency.
9, return loss Ar: indicates the front wave in the protection equipment (reflection point) is reflected in the proportion of the protection equipment is a direct measure of the protection equipment with the system impedance is compatible with the parameter.
10, the maximum longitudinal discharge current: refers to each line to the ground to impose a waveform of 8/20μs of the standard lightning wave impact 1 time, the protector of the maximum peak impact current.
11, the maximum lateral discharge current: refers to the line and the line between the waveform of 8/20 μs of the standard lightning wave applied to the impact of 1 time, the protector withstand the maximum peak impact current.
12, online impedance: refers to the nominal voltage Un flow through the protector of the circuit impedance and inductive impedance of the sum. Often called "system impedance".
13, peak discharge current: there are two kinds: rated discharge current Isn and maximum discharge current Imax.
14, leakage current: refers to 75 or 80 nominal voltage Un under the DC current flowing through the protector.
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Performance characteristics
l Single-phase integrated power supply lightning protection box using **** mode, differential mode full protection mode
l Single-phase integrated power supply lightning protection box using multi-stage pressure-sensitive embedded parallel technology
l Single-phase integrated power supply lightning protection box using a large amount of flux with a low residual voltage, fast response time
l Single-phase integrated Power lightning protection box with load overcurrent, overheating, failure separation device
l Single-phase integrated power lightning protection box
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Technical parameters
Application Notes Installed in the lightning protection partition LPZOA-2 interface
Tested according to EDIN VDE 0675-6:1989-11 and -6/AI: 1996-03
Rated voltage (maximum continuous operating voltage) Uc 275V~ 500V_
Maximum discharge current Imax 40KA
Voltage protection level UP ≤2.5KV
Response time tA ≤100ns
Maximum fuse strength 100AgL/gG
Short-circuit current strength 25KA/50Hz
Operating temperature range C -40C - +80C
Installation of L1, L2, L3, N conductor cross-section Parallel/multiple strand 10mm2
Installation of PE conductor cross-section Parallel/multiple strand 25mm2
Shell material Cold-rolled steel plate
Alarm function Function With fault telecommunication contact and Audible and visual alarm
Lightning strike count 0-99
Operating status Normal green, failure or fault red
Connection type Screw terminal
Protection class IP64
Mounting width (mm) 282mm×172mm×70mm
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Optionality
Options
Based on the lightning protection to achieve the desired results, should focus on "in the right place to reasonably install the right lightning protection," the choice of lightning protection is very important.
1. The distribution of lightning current between the various facilities into the building is as follows: about 50% of the lightning current through the external lightning protection device is released into the ground, and the other 50% of the lightning current will be distributed throughout the system within the metal material. This *estimation model is used to estimate the through-current capacity and metallic conductor specifications of the lightning protection devices that are equipotentially connected at the junction of the LPAOA zone, the LPZOB zone, and the LPZ1 zone. The lightning current at this location is a 10/35μs current waveform. In the distribution of lightning current in each metal substance: each part of the lightning current amplitude depends on the distribution channel has the impedance and inductive impedance, the distribution channel refers to the distribution of lightning current may be allocated to the metal substance, such as power lines, signal lines, water pipes, metal frames and other metal pipe level and other grounding, generally only to the value of the respective grounding resistance can be roughly estimated. In the case can not be determined, can be considered to be connected to the resistance is equal, that is, each metal pipeline average distribution of current.
2. In the overhead introduction of power lines, and power lines may be struck by direct lightning, the lightning current into the protected area within the building depends on the external lead line, lightning protection device discharge branch circuit and the user side of the line impedance and inductive impedance. If the impedances of the inner and outer ends are the same, the power line is allocated half of the direct lightning current. In this case must be used with a lightning protector with the function of direct lightning protection.
3. The subsequent * estimate mode is used to * estimate the distribution of lightning current at the junction of the protection zone after the LPZ1 zone. As the user side of the insulation impedance is much greater than the impedance of the discharge branch of the lightning protector and the external lead line, into the subsequent lightning protection zone of the lightning current will be reduced in the numerical value does not require special estimates. General requirements for subsequent lightning protection area of the power supply lightning protection current capacity in the 20kA (8/20μs) below, do not need to use a large current capacity of the lightning protector.
Subsequent lightning protection area lightning protector selection should consider the energy distribution between levels and voltage coordination, in many factors is difficult to determine, the use of series-parallel power lightning protector is a good choice. Series-parallel type is based on modern lightning protection in many applications, protection range level distinction and other characteristics of the concept (relative to the traditional parallel lightning protector). In essence, it is an effective combination of multi-stage discharger and filter technology through energy matching and voltage distribution. Series-parallel lightning protection has the following characteristics: wide range of applications. Not only can be applied routinely, but also suitable for the protection zone is difficult to distinguish between the places. Inductive decoupling devices under the transient overvoltage voltage division, delay role to help achieve energy matching. Slow down the rising rate of transient interference to achieve low residual voltage and long life and very fast response time.
4. Other parameters of the lightning protector selection depends on the level of each protected object is located in the lightning protection zone, the operating voltage to be installed in the lead circuit of all components of the rated voltage shall prevail. Series-parallel lightning protector also need to pay attention to its rated current.
5. Other factors affecting the distribution of lightning current in the electronic line: the transformer end of the grounding resistance will reduce the distribution of current in the electronic line increases. Increase in the length of the power supply cable will make the distribution of current in the power line to reduce, and to make a few wires have a balanced current distribution. Too short a cable length and too low a neutral impedance will unbalance the current and cause differential mode interference. Power supply cable parallel connection of multiple users will reduce the effective impedance, resulting in an increase in the distribution of current, in the state of the power supply connected to the grid, the lightning temporary current mainly into the power line, which is most of the lightning damage occurs in the power line at the reason.
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Installation, use and maintenance
1. This series of single-phase power arrester adopts dark-colored all-metal shell, good sealing, safe and reliable.
2. This series of single-phase power arrester is connected with the protected equipment in parallel; do not disassemble this series of products without authorization.
3. Users according to the lightning arrester wiring signs on the correct wiring, grounding wire with a cross-sectional area of not less than 25mm insulated yellow-green copper wire.
The length of the grounding wire is as short as possible to reduce the grounding resistance.
4. This series of products are equipped with installation accessories, the user can be installed according to the actual situation, wiring, checking that there is no
wrong can be energized and put into operation.
5. Regularly check the work of the power arrester:
Surge arrester normal, the work indicator (green) is on, when the deterioration of the arrester on the indicator (red) is on, indicating that
The power arrester internal failure of the important components, then please replace immediately. 6. Power lightning protection box during use, should be regularly tested and viewed indicator working status: green indicator for the work of the instructions,
Lightning box work normally; red indicator does not light up during normal operation, when the lightning protection box failure, the red indicator is bright,
should be repaired or replaced in a timely manner.
7. Power lightning protection box lightning counter counter range of 0 to 99 times, counting the action current is not less than 5KA; power on
display for 00 times, when the power is no longer displayed, you can press the "read" button to display the number of lightning strikes. In the lightning protection box
The upper end of the counter is equipped with a zero button, view the counter can be zeroed at any time;
8. The grounding resistance is not greater than 4Ω.
9. Non-professionals should not disassemble.
The box is made of high-quality steel, flame retardant, anti-corrosion
l Single-phase integrated power supply lightning protection box using the work status indication and lightning strike counting, provide remote telecommunication, acoustic and visual alarm
l Single-phase integrated power supply lightning protection box using pressure-sensitive series connected to the gas discharge pipe to completely eliminate leakage currents, higher safety
Working principle
Single-phase integrated power supply lightning protection box is the most effective way to protect the power supply when induced lightning intrudes into the power supply, and the most effective way to protect the power supply. Lightning protection box is when the induced lightning invasion of power transmission lines, lightning arrester lightning protection components to nanosecond
(100 ns) response speed presents a low-resistance state, rapid discharge of lightning current to the earth, and the overvoltage caused by the lightning current
limit the protected equipment allowed to withstand the withstand voltage range to ensure the safe operation of the equipment, so that
protection equipment
protect the equipment from damage to the power supply. Free from damage
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Related standards
The common implementation of lightning protection standards (different countries requirements): IEC61643-1, GB18802.1-2002, UL1283Filter, UL1449.2nd.Edition
China's current lightning protection system is now implementing the Is the Chinese people *** and the Ministry of Construction on March 1, 2004 developed: GB50343-2004 "building electronic information systems lightning technical specifications" and the Chinese people *** and the Ministry of Construction on October 1, 2000 developed: GB50057-94 "building design lightning code".
IEC 62305-1-2006 Lightning protection
IEC/TR 61400-24-2002 Wind turbine generator systems. Part 24: Lightning protection IEC 61400-24
IEC 60364-5-54-2002 Electrical installations in buildings. Part 5-54: Selection and installation of electrical equipment. Earthing measures, protective conductors and protective jumper wires IEC60364-5-54
IEC 60099 Lightning arresters
GB 15599-1995 Code for safety of petroleum and petroleum facilities against lightning
GB 50057-1994 Code for lightning protection design for buildings (with explanations of provisions) (2000 edition)
GB 50343-2004 Technical Specification for Lightning Protection of Electronic Information Systems in Buildings (with Explanatory Notes)
GB/T 19271-2003 Protection against Electromagnetic Pulse of Lightning
GB/T 19663-2005 Protection against Electromagnetic Pulse of Lightning
GB/T 19663-2005 Terminology of Lightning Protection for Information Systems
GB/T 19856-2005 Protection against Lightning of Petroleum Facilities (2000 Edition)
GB/T 21431-2008 Technical specification for the detection of lightning protection devices in buildings
GB/T 21714-2008 Lightning protection
GB/T 2900.12-2008 Electrical terminology Lightning arrester, low-voltage surge protector and components
GB/T 7450-1987 Guidelines for lightning protection of electronic equipment
GJB 5080-2004 Design and use of military communications facilities lightning protection requirements
GJB 1210-1991 Grounding Overlap and shielding design implementation
GJB 2269-1996 Rear ammunition depot lightning protection technical requirements
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Famous brands
Famous brands
Famous brands
Electronic terminology
GB/T 2900-12-2008 Electrical terminology Low voltage surge protectors and components p>
Famous brands
Currently on the market more common lightning protection devices are:
Domestic: Haide Haide lightning protection
Foreign: DEHN, OBO, CAN, LEUTRON, etc.
(The above rankings are in no particular order)
Haide part of the products of the Haide lightning protection device
Power lightning protection module:
Three-phase B + C power lightning protection module B + C level power lightning protection module Step-by-step degradation of the power lightning protection module
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SPD selection
Sparkling arrester in the use of components
Power lightning arrester in the absorption of lightning energy, mainly zinc oxide piezoelectric resistor and gas discharge tube.
Zinc oxide varistor is a voltage-limiting protection device, there is no pulse voltage presents a high resistance state, once the response to the pulse voltage, immediately limit the voltage to a certain value, the impedance of its impedance changes abruptly to a low resistance state. Compared with gas discharge tube, its biggest advantage is that when it absorbs the pulse voltage because the residual voltage is higher than the working voltage, it will not cause instantaneous short-circuit of the power supply, and will not generate the renewal current. The response time of zinc oxide varistors is faster than that of gas discharge tubes. The breakdown voltage of the gas discharge tube is very sensitive to the rate of rise of the pulse voltage, the faster the rate of voltage rise, the higher the ignition voltage, the faster the response time. Can correctly select the piezoresistors and gas discharge tubes of these two types of components, and the use of their respective advantages for the combination of power arrester, its overall performance is relatively good. Power lightning arrester requires zinc oxide varistor, with excellent energy withstand characteristics, and energy withstand characteristics are mainly used to describe the rated lightning impulse current, the maximum lightning impulse current and energy withstand three major indicators, these characteristics and the surface area of the zinc oxide varistor, and components of the heat dissipation conditions. The same specification of the varistor, due to different manufacturers of the manufacturing process, raw material formula, its energy withstand capacity will vary greatly.
The gas discharge tube has a strong ability to withstand large energy impact, but in specific use, because the gas discharge tube in the discharge of the residual voltage is extremely low, approximate short-circuit state, so can not be used in the power supply arrester alone, the gas discharge tube of the current-resistant ability and the diameter of the tube is related to the tube, the larger the tube diameter, the better the current-resistant ability. Gas discharge tube quality problems are mainly manifested in chronic leakage, long time use of reliability problems (i.e., suffered a number of lightning strikes, the DC breakdown voltage value shifts), photosensitive effect and discrete larger. Although in recent years the domestic gas discharge tube has improved greatly, the quality is gradually improved, but the overall quality problems still exist, especially reliability problems and chronic gas leakage. Therefore, the power supply arrester in the choice of imported brand-name gas discharge tube products should be preferred, and the gas discharge tube diameter in Ф8 ㎜ or more for good.
Power arrester capacitor and thermal fuse selection is also very important. Power arrester long-term work in the power grid, due to the quality of the capacitor caused by the power arrester machine damage in many cases, therefore, the capacitor voltage selection is very important, especially the ability to withstand the impact of pulse high voltage. In contrast, foreign products are better than domestic products, Hitachi, OKAYA's capacitor quality is good. Power arrester in the role of the thermal fuse is when the lightning current exceeds the maximum withstand capacity of the power arrester, due to overcurrent, the fuse can be disconnected, and at the same time, due to the overcutting of the zinc oxide varistor temperature can also be made to fuse disconnect, play a double role in overcurrent and temperature protection. As the power supply lightning arrester normal operating conditions, the current is very small, only in the lightning shock or pulse voltage shock, in the transient conditions of the protective effect, so the conditions of use with the conventional thermal fuse is different, so the power supply lightning arrester in the thermal fuse should have a unique performance, i.e., in the transient conditions of the melting characteristics.
Advanced design
Surge arrester design program with good components, advanced design program is to ensure the quality of the power supply arrester is necessary. According to the analysis and comparison of domestic and foreign products, in the design of power surge arrester should fully consider the following aspects. Power lightning arrester lightning current impact level of reasonable positioning, that is, the power arrester rated surge current value and the maximum surge current value determination. Now on the market, some power arrester manufacturers, in order to advertise and product competition and other commercial behavior, arbitrarily increase the level of resistance to lightning current impact, which is a very irresponsible attitude towards the user. Lightning disaster on modern electronic equipment is extremely destructive. The size of the lightning current in a certain area, due to the geographic environment, meteorological conditions and electronic equipment power wiring and many other uncertainties, it is difficult to determine a numerical amount, therefore, manufacturers of power supply lightning arrester design should have a large margin. General surge current design should be the maximum surge current value of the power arrester should be double the maximum surge current value should be the rated surge current value of the power arrester is double, such a design margin is responsible for the user's attitude. In the manufacturer's design of the specific line, should be used in multiple surge current absorption of redundant circuit structure, that is, when a surge current absorption circuit due to a component damage, automatically exit the power arrester circuit, does not affect the normal operation of the entire power arrester. As a result of the above design margins, even if there is a way, or even two absorption circuits out of the overall circuit, does not affect the lightning protection capability of the entire power supply arrester. This redundant design scheme will greatly improve the reliability of the power arrester, is the first choice of protection equipment for lightning protection of power lines in multiple minefields.
Production process and quality management system
Reasonable and scientific production process is to ensure that the quality of the power arrester to ensure the conditions. In the power arrester production process, manufacturers should pay attention to the following aspects of the problem. Moisture and heat has been an important reason for the failure of varistors, which is manifested in the phenomenon of varistors under the influence of long-term humid environment, the leakage current rises significantly, the value of the pressure-sensitive voltage drops significantly. For the entire power arrester, due to the influence of humid environment, once the power grid transient overvoltage or lightning current impact, it is likely to cause a local short circuit and damage to the phenomenon. As the thunderstorm season
season is often a hot and humid meteorological conditions, so the power supply arrester anti-moisture and heat process is very important. Usually manufacturers use epoxy resin potting production process. Some manufacturers can be in the process of epoxy resin potting vacuum pumping, the effect is better. Therefore, in the selection of power supply arrester, in addition to watching the manufacturer's choice of components, design programs and production processes, quality management is also very important. This includes component procurement, storage, inspection, assembly, aging, residual voltage and leakage current testing system, safety system and other aspects.
In summary, the choice of good quality power arrester, can not just stay in the manufacturer's advertising, but also to the manufacturer for the above aspects to take a look, especially the selection of key components, design programs, production processes are the focus of understanding. In addition, the local meteorological conditions, the number of days of annual thunderstorms and thunderstorms caused by property damage should also be and choose the level of protection of the power supply lightning arrester for comprehensive consideration.
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Design principle
There are a variety of lightning arrester on the market now, the quality is uneven, and some have not even heard of asking (such as: do not have to ground the lightning arrester, up to now, can not figure out how it works), therefore, through the introduction of lightning arrester principle of operation and composition of the customer to identify the true and false, good and bad, to help.
Surge arrester components from the response characteristics, there are two kinds of soft and hard. Belong to the hard response characteristics of the discharge element has a spark gap (based on chopping arc technology angle type spark gap and coaxial discharge spark gap) and gas discharge tube, belongs to the soft response characteristics of the discharge element has a metal oxide varistor and transient suppression diode. The difference between these components is the discharge capacity, response characteristics and residual voltage, lightning arrester is the use of their different strengths and weaknesses, to avoid the shortcomings, combined into a variety of lightning arrester, protection circuit.
Spark gap (Arc chopping)
1, discharge gap: the principle of two such as the status quo of the horn electrode, the distance is very short, separated by insulating materials, when the two electrodes between the strength of the electric field reaches the strength of the breakdown, the electrode between the formation of the current path. When the lightning wave comes to the first in the gap at the time of breakdown, so that the gap of the air ionization, the formation of a short circuit, lightning current flow through the gap into the earth, and at this time the gap at both ends of the voltage is very low, so as to achieve the purpose of protecting the line. Electric field strength is lower than the breakdown gap, the discharge gap type lightning arrester and restore the insulation state. Commonly used in high-voltage line lightning protection. In the low-voltage system, often used in the power supply of the front protection.
Spark gap type lightning arrester product advantages and disadvantages, is made of electrode materials, gap distance and insulation materials.
Advantages: strong discharge capability, large flux, 10/350μs pulse waveform can channel 50KA pulse current, for 8/20μs pulse current, can be greater than 100KA, high insulation resistance and very small parasitic capacitance, small leakage current. It will not bring any harmful effects to the normal operation of the equipment.
Disadvantages: high residual voltage (2.5~3.5KV), long response time (≦100ns), low accuracy of the action voltage, there is an industrial frequency current, so in the protection circuit should be connected in series with a fuse, so that the industrial frequency current is quickly cut off.
Note: As two discharge tubes were installed in a circuit of two wires, sometimes will not be discharged at the same time, so that the potential difference between the two wires, in order to make the two wires on the discharge tube can be close to a uniform time to discharge, reduce the potential difference between the two wires, but also the development of a three-stage discharge tube. It can be regarded as two secondary discharge tubes merged together. Three discharge tube in the middle of a level as a public **** ground, the other two levels were connected to the circuit of the two wires.
2, gas discharge tube (Gas discharge tube, GDT): is a ceramic or glass package, the tube is then filled with a certain pressure of inert gas (such as argon), switching type of protection components, two electrodes and three electrodes two structures. When the electric field strength reaches the strength of the breakdown inert gas, it causes the gap discharge, thus limiting the voltage between the poles. 8/20μs pulse current is able to channelize 10KA. the discharge voltage is unstable, when the voltage is greater than 12V, the current voltage of 100mA, it will produce the subsequent current. It is usually used in measuring, controlling and regulating technical circuits and electronic data processing transmission circuits.
Metal oxide varistor
Metal oxide varistor (Metal oxide varistor, MOV)
Metal oxide semiconductor nonlinear resistor with zinc oxide as the main component, when the voltage added to the resistor terminals is less than the varistor voltage, the varistor is a high-resistance state, and if it is connected in parallel to the circuit, the varistor is a disconnected state. When the voltage added to both ends of the varistor is greater than the voltage of the varistor, the varistor will break down, presenting a low resistance, or even close to the short circuit state. This kind of breakdown state of the varistor can be restored, when the voltage higher than the voltage-sensitive voltage is withdrawn, it returns to the high resistance state. When the power line is struck by lightning, the high voltage of the lightning wave causes the varistor to break down, and the lightning current flows through the varistor into the earth, so that the class voltage on the power line is clamped within the safety range.
Zinc oxide varistor lightning arrester, now on the market circulation of many, our country in the late 1980s only mass production, is currently considered the latest type, the most advanced technology, will do a special detailed introduction. Now China's transmission line lightning arrester, are used zinc oxide lightning arrester.
Advantages: wide range of switching voltage: 6V ~ 1.5KV, fast response speed (25ns), low residual voltage (can reach the safety of the terminal equipment working voltage), throughput (2KA/cm2), no renewal, long life.
Disadvantage: Easy to age, after a few actions, the leakage current will increase, which will lead to overheating of the varistor, and eventually lead to aging failure.
Capacitance is large, in many cases not in high frequency, ultra-high frequency system. This capacitance, in turn, forms a low pass with the wire capacitance. The low-pass can cause serious signal attenuation. But at frequencies below 30KHZ, this attenuation can be ignored.
Transient suppression diode
Transient suppression diode (Transient voltage suppressor, TVS):
1, bipolar discharge tubes: there are two forms: one is a Zener-type (for the unidirectional avalanche breakdown), and the second is a bi-directional silicon-voltage-sensitive resistor. Performance similar to switching diodes. Under the action of the specified reverse voltage, the two-terminal voltage is greater than the threshold voltage, its working impedance can be immediately reduced to a very low level to allow large currents to pass, and clamp the two-terminal voltage at a very low level, thus effectively protecting the end of the electronic products in the precision components to avoid damage. Bidirectional TVS can absorb instantaneous large pulsating power in both positive and negative directions, and clamp the voltage at a predetermined level. Suitable for AC circuits.
Advantages: Very fast action time, up to picoseconds. Low limiting voltage, low breakdown voltage, used in various electronic fields.
Disadvantages: small current load, capacitance is quite high, generally below 20pF, now the ceramic discharge tube can do 3 ~ 5pF.
Electronic information systems required by the surge protection system is generally used in two or three-stage composition. The use of gas discharge tubes, varistors and suppressor diodes, and the use of a variety of surge suppressor characteristics, to achieve reliable protection. Gas discharge tube is generally placed on the line input as a primary surge protection device, withstand large surge current, belongs to the current drain device. Secondary protection devices using varistors, can be in a very short period of time (ns) will be limited to a lower level of surge voltage. For highly sensitive electronic circuits, can be used to suppress the diode as the third level of protection. In a shorter period of time the surge voltage is limited to the end of the insulation level of electronic equipment. As shown in the figure, when lightning and other surges come, suppressor diode first conductive, the instantaneous overvoltage is precisely controlled at a certain level, if the surge current is large, the varistor start and discharge a certain amount of inrush current, then the voltage at both ends of the varistor will be increased, until the promotion of the front gas discharge tube discharge, the large current drain to ground. When the distance between the three devices in the line is farther, the conduction order will start from the gas discharge tube, conduction in turn.
Surge arrester work, from the fastest reaction time, the most end of the equipment to start, and then step by step to the front end of the start.
,Simply using gas discharge tubes to protect the back end of the equipment will have the following problems: on-time is too long, the residual voltage is too large, may exceed the back end of the equipment voltage level. After discharging, it will generate the industrial frequency renewal current. In order to avoid the above problems, another circuit (Figure 3) is used. In order to solve the problem of generating industrial frequency continuous current, but also to avoid the varistor due to leakage current is too large and heat self-destruct or aging, we in the gas discharge tube in series with a varistor, so that can avoid generating industrial frequency continuous current, but also to prevent the varistor due to leakage current and self-destruct, aging. But the new problem arises, so that the lightning arrester action time for the gas discharge tube on-time and varistor on-time sum. Assuming that the on-time of the gas discharge tube for 100ns, varistor on-time for 25ns, then their total response time of 125ns. in order to reduce the response time, in the circuit and into a varistor, so that the total response time of 25ns.
:When the overvoltage occurs, suppressor diode as the fastest component of the action of the first action, the line is designed to be, before the possible destruction of the suppressor diode, the line is designed to, in the Before the suppression diode may be destroyed, the discharge current that is with the amplitude of the rise of the conversion to the front discharge path, that is, the inflatable discharge path.
Us+△u≥Ug
Us: voltage on the suppression diode
△u: voltage on the decoupling inductor coil
Ug: action voltage of the gas discharge tube
If the discharge current is less than this value, the inflatable discharge tube does not operate. The use of this line can not only in the low level of protection conditions to take advantage of the rapid action of the discharger, but also to achieve a very high discharge capacitance. This will eliminate the inhibition of diode overload level fuse in the emergence of power supply when the shortcomings of the circuit is frequently cut off.
Higher-frequency lines can also use ohmic resistors as decoupling elements, and low-capacitance bridging line **** with the use.
2, three-pole discharge tube: in the two wires, the installation of two dipole discharge tube, there will be a potential difference, so there is a three-pole discharge tube, more than one pole to do the public **** grounding can reduce the time difference (0.15 ~ 0.2μs), and the resulting amplitude of the lateral lightning voltage.
Ordinary power arrester devices on the market generally use varistors for primary, secondary and tertiary power supply. This combination in the distance of more than 5 meters, the on-time from the first level of gradual backward conduction.
If the first level of gas discharge tubes, the second and third level of varistors, it must meet the first level and the second level to meet the distance greater than ten meters, the second level and the third level to meet the distance greater than 5 meters, so as to ensure that the first level of the first action. Otherwise, it may lead to the first level of the phenomenon of inactivity, and the second and third lightning arrester is not as large as the flux, resulting in lightning arrester can not effectively protect the equipment. This point in the engineering design must pay attention to.
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Surge Protector Classification
Surge Protector has a high-voltage and low-voltage lightning protection, this section introduces the low-voltage power distribution system in the lightning protector (surge protector SPD)
1. Types of surge protectors a wide range of surge protectors in China's market has exceeded hundreds of species, how to different brands, different models of the surge protector Classification may be in front of us.
From the combination of structural points; now on the market there are several types of lightning arrester:
1) Gap class ---- open gap, closed gap
2) Discharge tube class - - - open discharge tube sealed discharge tube
3) varistor class - single, multi-chip
4) suppressor diode class
5) varistor / gas discharge tube combination class ---- simple combination, Complex combination
6) silicon carbide class
In accordance with the nature of its protection can be divided into: open-circuit lightning arrester, short-circuit lightning arrester or switching type, voltage-limiting type;
According to the state of work (installation form) can be divided into: parallel lightning arrester and series lightning arrester.
2. structure and characteristics of lightning arrester
2.1.1 open gap arrester
Gap arrester working principle: based on arc discharge technology, when the voltage between the electrodes reaches a certain level, the breakdown of the air arc in the electrodes for the climb.
Advantages: strong discharge capacity, large throughput (can reach 100KA) leakage current is small
Good thermal stability
Disadvantages: high residual voltage, slow reflection time, the existence of renewed
Process characteristics: as the metal electrodes are subjected to large currents in the discharge, so it is easy to cause sublimation of the metal, so that the discharge cavity to form a metal coating affects the lightning arrester's Start and normal use. Discharge electrode production is still mainly concentrated in some foreign lightning arrester production enterprises, the main component of the electrode is tungsten metal alloy.
Engineering applications: the structure of the lightning arrester is mainly used in the power supply system to do B-level lightning arrester use. But due to the lightning arrester itself is easy to cause fire, lightning arrester action (fly out) out of the distribution panel and other accidents. According to the different models suitable for a variety of power distribution system.
When installing the project, we must consider the installation distance to avoid unnecessary losses and accidents.