In recent years, with the advancement of science and technology, the technological nation of household appliances, and the improvement of power requirements for electronic equipment, there are a large number of large-scale or ultra-large-scale integrated circuits that are very sensitive to overvoltage inside such electronic equipment, so that The loss caused by the voltage is increasing. Given this situation, the "Code for Lightning Protection Design of Buildings" GB50057-94 (2000 Edition) has added Chapter VI - Lightning Protection Electromagnetic Pulse. According to this requirement, some manufacturers have also introduced related overvoltage protection products, which we often call surge protectors. It is essential to set up a complete equipotential bonding system to protect electrical and electronic systems, including all active conductors in the electromagnetic compatibility protection zone. The physical characteristics of discharge components in different overvoltage protection devices have advantages and disadvantages in practical applications, so protection circuits using multiple parts are more widely used.
However, it can meet all the technical requirements of the lightning current arrester that can conduct 10/350μs pulse current with the contemporary technical level, the pluggable surge protector for secondary power distribution, the electrical power protection device, and the power filter. Therefore, the product line is scarce. Also, this product range should include arresters for all circuits, i.e., in addition to power supplies, for measurement, control, technical regulation circuits, electronic data processing transmission circuits, and wireless and wired communication, so that customers can use them.
A brief introduction to several commonly used surge protection products and a brief analysis of their characteristics and applicable occasions are given.
1 Equipotential bonding system
The basic principle of overvoltage protection is that transient overvoltage occurs at the instant (microsecond or nanosecond level). An equipotential should be achieved between all metal parts in the protected area. "Equipotential is the use of connecting wires or overvoltage protectors to connect lightning protection devices, metal structures of buildings, external conductors, electrical and telecommunication devices, etc., in the space where lightning protection is required." ( "Specifications for Lightning Protection Design of Buildings") (GB50057-94). "The purpose of equipotential bonding is to reduce the potential difference between metal parts and systems in spaces requiring lightning protection" (IEC13123.4). "Lightning Protection Design Code for Buildings" (GB50057-94) stipulates: "Article 3.1.2 For buildings equipped with lightning protection devices, when the lightning protection devices cannot be isolated from other facilities and people in the building, they should be Adopt equipotential bonding." When establishing this equipotential bonding network, care should be taken to keep the shortest distance between the electrical and electronic equipment that must exchange information and the connecting wires between the equipotential bonding belt.
According to the induction theorem, the larger the inductance, the higher the voltage generated by the transient current in the circuit; (U=L·di/dt> The inductance is mainly related to the length of the wire and has little to do with the cross-section of the wire. Therefore, it should be Kept the ground wire as short as possible. Furthermore, the parallel connection of several wires can significantly reduce the inductance of the potential compensation system. To put these two into practice, it is theoretically possible to connect all circuits that should be connected to the equipotential bonding device. It is connected to the same metal plate as the equipment. Based on the concept of the metal plate, the line, star, or mesh structure can be used when the equipotential bonding system is retrofitted. In principle, only mesh equipotentiality should be used when designing new equipment—link system.
2 Connect the power supply lines to the equipotential bonding system
The so-called transient voltage or transient current means that its existence time is only microseconds or nanoseconds. The basic principle of surge protection is to establish an equipotential between all conductive parts in the protected area for a brief period when the transient overvoltage exists. Such conductive elements also include power lines in electrical circuits. Therefore, one needs components that respond faster than microseconds, especially for electrostatic discharge.
To faster than nanoseconds. Such elements are capable of delivering mighty currents up to several times ten thousand amps in brief time intervals. Winds up to 50kA are calculated at 10/350μS pulses under expected lightning strike conditions. Through a complete equipotential bonding device, an equipotential island can be formed quickly, and the potential difference of this equipotential island to a distance can even be as high as hundreds of thousands of volts. However, what is essential is that in the area to be protected, all conductive parts can be considered to have nearly equal or equal potentials without significant potential differences.
3 Installation and function of surge protector
Surge protection electrical components are divided into soft and complex in terms of response characteristics. Discharge elements with hard response characteristics include gas discharge tubes and discharge gap dischargers, either angular spark gaps based on arc-chopping technology or coaxial discharge spark gaps. The discharge elements belonging to the soft response characteristics include varistors and suppressor diodes. (Our surge protector is a weak response.) The difference between these components is the discharge capability, response characteristics, and residual voltage. Since these components have advantages and disadvantages, people combine them into special protection circuits to promote strengths and avoid weaknesses. The commonly used surge protectors in civil buildings are mainly discharged gap type arresters and varistor type arresters.
Lightning currents and post-lightning currents require extremely strong dischargers. To conduct the lightning current through the equipotential bonding system into the grounding device, it is recommended to use current lightning arresters with angular spark gaps according to the arc chopping technique. Only it can conduct 10/350μs pulse current greater than 50kA and realize automatic arc extinguishing. The rated voltage of this product application can reach 400V. In addition, this arrester will not cause a fuse rated at 125A to blow when the short circuit current goes 4kA.
Due to its good performance, the uninterrupted working characteristics of instruments and equipment installed in the protected area are greatly improved. However, it should be pointed out that not only the current with high amplitude can be processed, but more importantly, the pulse form of the current plays a decisive role. Both must be considered simultaneously. Therefore, although the angular spark gap can also conduct currents up to 100kA, its pulse form is shorter (8/80μs). Such pulses are impulse current pulses, which until October 1992 were the design basis for the development of current lightning arresters.
Although the lightning current arrester has a good discharge capacity, it always has its shortcomings: its residual voltage is as high as 2.5~3.5kV. Therefore, when the lightning current arrester is installed as a whole, it needs to be used in combination with other arresters.
Such products mainly include Limitor MB, Limitor NB-B, LimitorG-B, Limited GN-B of Asia Brown Boffary (ABB) company; DEHNportMaxi (10/350μs, 50kA/ phase), DEHNport255 (10/350μs, 75kA/phase); Germany PHOENIX angle spark gap: FLT60-400 (10/350μs, 60kA phase), FLT25-400 (10/350μs, 25kA phase); Schneider's PRF1 surge Protector; MOELLER's VBF-Series.
Varistors function as many bidirectional suppressor diodes in series and parallel and work like voltage-dependent resistors. When the voltage exceeds the specified voltage, the varistor can conduct electricity; when the voltage is lower than the specified voltage, the varistor does not conduct electricity. In this way, the varistor can play a perfect voltage limiting role. Varistors work extremely quickly, with response times in the low nanosecond range.
The varistor commonly used in the power supply can conduct current with a limit of 40kA8/20us pulse, so it is very suitable for the second-stage discharger of the power supply. But it is not ideal as a lightning current arrester. It is recorded in the document IEC1024-1 of the International Electron Technology Committee that the charge amount to be processed is 10/350μs, which is equivalent to 20 times the charge amount in the case of an 8/20μs pulse.
( 10/350) μs=20xQ(8/20) μs
It can be seen from this formula that it is essential not only to pay attention to the amplitude of the discharge current but also to pay attention to the pulse form. The disadvantage of the varistor is that it is easy to age and has high capacitance. In addition, the diode element is broken down. Since, in most cases, a short circuit occurs when the PN junction is overloaded, depending on how frequently it is loaded, the varistor begins to draw leakage currents that can cause errors in measurement data insensitive test circuits. At the same time, especially at high-rated voltages, it will generate an intense heat in the course.
The high capacitance of the varistor makes it impossible to use in signal transmission lines in many cases. The capacitance and wire inductance form a low-pass circuit that significantly attenuates the signal. But the attenuation below about 30kHz is negligible. Such products mainly include ABB's Limitor V, Limited VTS, Limitor VE, Limitor VETS, LimitorGE-S; Schneider's PRD series replaceable surge protectors; MOELLER's VR7-, VS7-series products; Germany DEHN's DEHNguard385 ( 8/20μs, 40kA phase), DEHNguard275 (8/20μs, 40kA phase); VAL-MS400ST (8/20μs, 40kA phase), VAL-ME400ST/FM (8/20μs, 40kA/phase) from PHOENIX, Germany; Ma Shen DB30-4A/B (8/20μs, 30kA/phase), DB40-4A/B (8/20μs, 40kA phase).
4 Install a surge protector according to the overvoltage protection scheme
An assembly (rail mounting type, power socket type, adapter) that contains a single protection element or a combined protection circuit integrated according to the technical installation conditions is called a discharger.
Overvoltage protection in almost all cases should be divided into at least two levels. For example, each arrester containing only one level of security can be installed in different locations in the power supply. The same arrester may also have multiple levels of protection. To achieve adequate overvoltage protection, people will need to protect the range of different electromagnetic compatibility divisions, this protection range, including from lightning protection zone 0 overvoltage protection zone 1 to 3, until the interference voltage protection zone has a higher serial number. Electromagnetic compatibility protection zones 0 to 3 are set to avoid equipment damage due to high-energy coupling. The electromagnetic compatibility protection with a higher serial number is set up to prevent information distortion and loss. The higher the protection zone number, the lower the expected disturbance energy and disturbance voltage level. The electrical and electronic equipment that needs protection is installed in a very effective protection ring. Such a protection ring can be for a single piece of electronic equipment, a space with multiple electronic types of equipment, or even a whole building passing through. Wires that usually have a space-shielded protective ring are connected to the voltage protection arrester at the same time as the peripheral equipment of the protective circle.
However, it can meet all the technical requirements of the lightning current arrester that can conduct 10/350μs pulse current with the contemporary technical level, the pluggable surge protector for secondary power distribution, the electrical power protection device, and the power filter. Therefore, the product line is scarce. Also, this product range should include arresters for all circuits, i.e., in addition to power supplies, for measurement, control, technical regulation circuits, electronic data processing transmission circuits, and wireless and wired communication, so that customers can use them.
A brief introduction to several commonly used surge protection products and a brief analysis of their characteristics and applicable occasions are given.
1 Equipotential bonding system
The basic principle of overvoltage protection is that transient overvoltage occurs at the instant (microsecond or nanosecond level). An equipotential should be achieved between all metal parts in the protected area. "Equipotential is the use of connecting wires or overvoltage protectors to connect lightning protection devices, metal structures of buildings, external conductors, electrical and telecommunication devices, etc., in the space where lightning protection is required." ( "Specifications for Lightning Protection Design of Buildings") (GB50057-94). "The purpose of equipotential bonding is to reduce the potential difference between metal parts and systems in spaces requiring lightning protection" (IEC13123.4). "Lightning Protection Design Code for Buildings" (GB50057-94) stipulates: "Article 3.1.2 For buildings equipped with lightning protection devices, when the lightning protection devices cannot be isolated from other facilities and people in the building, they should be Adopt equipotential bonding." When establishing this equipotential bonding network, care should be taken to keep the shortest distance between the electrical and electronic equipment that must exchange information and the connecting wires between the equipotential bonding belt.
According to the induction theorem, the larger the inductance, the higher the voltage generated by the transient current in the circuit; (U=L·di/dt> The inductance is mainly related to the length of the wire and has little to do with the cross-section of the wire. Therefore, it should be Kept the ground wire as short as possible. Furthermore, the parallel connection of several wires can significantly reduce the inductance of the potential compensation system. To put these two into practice, it is theoretically possible to connect all circuits that should be connected to the equipotential bonding device. It is connected to the same metal plate as the equipment. Based on the concept of the metal plate, the line, star, or mesh structure can be used when the equipotential bonding system is retrofitted. In principle, only mesh equipotentiality should be used when designing new equipment—link system.
2 Connect the power supply lines to the equipotential bonding system
The so-called transient voltage or transient current means that its existence time is only microseconds or nanoseconds. The basic principle of surge protection is to establish an equipotential between all conductive parts in the protected area for a brief period when the transient overvoltage exists. Such conductive elements also include power lines in electrical circuits. Therefore, one needs components that respond faster than microseconds, especially for electrostatic discharge.
To faster than nanoseconds. Such elements are capable of delivering mighty currents up to several times ten thousand amps in brief time intervals. Winds up to 50kA are calculated at 10/350μS pulses under expected lightning strike conditions. Through a complete equipotential bonding device, an equipotential island can be formed quickly, and the potential difference of this equipotential island to a distance can even be as high as hundreds of thousands of volts. However, what is essential is that in the area to be protected, all conductive parts can be considered to have nearly equal or equal potentials without significant potential differences.
3 Installation and function of surge protector
Surge protection electrical components are divided into soft and complex in terms of response characteristics. Discharge elements with hard response characteristics include gas discharge tubes and discharge gap dischargers, either angular spark gaps based on arc-chopping technology or coaxial discharge spark gaps. The discharge elements belonging to the soft response characteristics include varistors and suppressor diodes. (Our surge protector is a weak response.) The difference between these components is the discharge capability, response characteristics, and residual voltage. Since these components have advantages and disadvantages, people combine them into special protection circuits to promote strengths and avoid weaknesses. The commonly used surge protectors in civil buildings are mainly discharged gap type arresters and varistor type arresters.
Lightning currents and post-lightning currents require extremely strong dischargers. To conduct the lightning current through the equipotential bonding system into the grounding device, it is recommended to use current lightning arresters with angular spark gaps according to the arc chopping technique. Only it can conduct 10/350μs pulse current greater than 50kA and realize automatic arc extinguishing. The rated voltage of this product application can reach 400V. In addition, this arrester will not cause a fuse rated at 125A to blow when the short circuit current goes 4kA.
Due to its good performance, the uninterrupted working characteristics of instruments and equipment installed in the protected area are greatly improved. However, it should be pointed out that not only the current with high amplitude can be processed, but more importantly, the pulse form of the current plays a decisive role. Both must be considered simultaneously. Therefore, although the angular spark gap can also conduct currents up to 100kA, its pulse form is shorter (8/80μs). Such pulses are impulse current pulses, which until October 1992 were the design basis for the development of current lightning arresters.
Although the lightning current arrester has a good discharge capacity, it always has its shortcomings: its residual voltage is as high as 2.5~3.5kV. Therefore, when the lightning current arrester is installed as a whole, it needs to be used in combination with other arresters.
Such products mainly include Limitor MB, Limitor NB-B, LimitorG-B, Limited GN-B of Asia Brown Boffary (ABB) company; DEHNportMaxi (10/350μs, 50kA/ phase), DEHNport255 (10/350μs, 75kA/phase); Germany PHOENIX angle spark gap: FLT60-400 (10/350μs, 60kA phase), FLT25-400 (10/350μs, 25kA phase); Schneider's PRF1 surge Protector; MOELLER's VBF-Series.
Varistors function as many bidirectional suppressor diodes in series and parallel and work like voltage-dependent resistors. When the voltage exceeds the specified voltage, the varistor can conduct electricity; when the voltage is lower than the specified voltage, the varistor does not conduct electricity. In this way, the varistor can play a perfect voltage limiting role. Varistors work extremely quickly, with response times in the low nanosecond range.
The varistor commonly used in the power supply can conduct current with a limit of 40kA8/20us pulse, so it is very suitable for the second-stage discharger of the power supply. But it is not ideal as a lightning current arrester. It is recorded in the document IEC1024-1 of the International Electron Technology Committee that the charge amount to be processed is 10/350μs, which is equivalent to 20 times the charge amount in the case of an 8/20μs pulse.
( 10/350) μs=20xQ(8/20) μs
It can be seen from this formula that it is essential not only to pay attention to the amplitude of the discharge current but also to pay attention to the pulse form. The disadvantage of the varistor is that it is easy to age and has high capacitance. In addition, the diode element is broken down. Since, in most cases, a short circuit occurs when the PN junction is overloaded, depending on how frequently it is loaded, the varistor begins to draw leakage currents that can cause errors in measurement data insensitive test circuits. At the same time, especially at high-rated voltages, it will generate an intense heat in the course.
The high capacitance of the varistor makes it impossible to use in signal transmission lines in many cases. The capacitance and wire inductance form a low-pass circuit that significantly attenuates the signal. But the attenuation below about 30kHz is negligible. Such products mainly include ABB's Limitor V, Limited VTS, Limitor VE, Limitor VETS, LimitorGE-S; Schneider's PRD series replaceable surge protectors; MOELLER's VR7-, VS7-series products; Germany DEHN's DEHNguard385 ( 8/20μs, 40kA phase), DEHNguard275 (8/20μs, 40kA phase); VAL-MS400ST (8/20μs, 40kA phase), VAL-ME400ST/FM (8/20μs, 40kA/phase) from PHOENIX, Germany; Ma Shen DB30-4A/B (8/20μs, 30kA/phase), DB40-4A/B (8/20μs, 40kA phase).
4 Install a surge protector according to the overvoltage protection scheme
An assembly (rail mounting type, power socket type, adapter) that contains a single protection element or a combined protection circuit integrated according to the technical installation conditions is called a discharger.
Overvoltage protection in almost all cases should be divided into at least two levels. For example, each arrester containing only one level of security can be installed in different locations in the power supply. The same arrester may also have multiple levels of protection. To achieve adequate overvoltage protection, people will need to protect the range of different electromagnetic compatibility divisions, this protection range, including from lightning protection zone 0 overvoltage protection zone 1 to 3, until the interference voltage protection zone has a higher serial number. Electromagnetic compatibility protection zones 0 to 3 are set to avoid equipment damage due to high-energy coupling. The electromagnetic compatibility protection with a higher serial number is set up to prevent information distortion and loss. The higher the protection zone number, the lower the expected disturbance energy and disturbance voltage level. The electrical and electronic equipment that needs protection is installed in a very effective protection ring. Such a protection ring can be for a single piece of electronic equipment, a space with multiple electronic types of equipment, or even a whole building passing through. Wires that usually have a space-shielded protective ring are connected to the voltage protection arrester at the same time as the peripheral equipment of the protective circle.