Surge Protection Device SPD
Surge Protection Device SPD is also named surge arrester, All surge protectors for a specific purpose are actually a kind of rapid switch, and the surge protector is activated within a certain voltage range. After being activated, the suppression component of the surge protector will be disconnected from the high-impedance state, and the L pole will be turned into a low-resistance state. In this way, the local energy surge current in the electronic device can be vented. During the entire lightning process, the surge protector will maintain a relatively constant voltage across the pole. This voltage ensures that the surge protector is always on and can safely discharge the surge current to the earth. In other words, surge protectors protect sensitive electronic equipment from the effects of lightning events, switching activity on the public grid, power factor correction processes, and other energy generated by internal and external short-term activities.
Lightning has obvious threats to personal safety and poses a potential threat to various devices. The damage of power surges to equipment is not limited to direct lightning strikes. Close-range lightning strikes pose a huge threat to sensitive modern electronic devices; on the other hand, lightning activity in the distance and discharge between thunderclouds can create strong inrush currents in the power supply and signal loops, so that the normal flow equipment is normal. Run and shorten the life of the equipment. The lightning current flows through the earth due to the presence of ground resistance, which generates a high voltage. This high voltage not only jeopardizes the electronic equipment but also endangers human life due to the step voltage.
Surge, as the name suggests is a transient overvoltage that exceeds the normal operating voltage. In essence, a surge protector is a violent pulse that occurs in just a few millionths of a second and can cause surges: heavy equipment, short circuits, power switching, or large engines. Products containing surge arresters can effectively absorb sudden bursts of energy to protect connected equipment from damage.
A surge protector, also called a lightning arrester, is an electronic device that provides safety protection for various electronic devices, instruments, and communication lines. When a sudden current or voltage is suddenly generated in an electrical circuit or a communication line due to external interference, the surge protector can conduct the shunt in a very short time, thereby avoiding damage to other equipment in the circuit by the surge.
The surge protector has a large flow rate, a low residual voltage and a fast response time;
Use the latest arc extinguishing technology to completely avoid fires;
Temperature control protection circuit with built-in thermal protection;
With a power status indication indicating the working status of the surge protector;
The structure is rigorous and the work is stable and reliable.
1, Air-termination system
Surge protectors are used for metal objects and metal structures that directly accept or withstand lightning strikes, such as lightning rods, lightning protection belts (lines), lightning protection nets, etc.
2, Down conductor system
The surge protector connects the metal conductor of the lightning receptor to the grounding device.
3, Earth termination system
The sum of the Earth electrode and the Earth conductor.
4, Earth electrode
A metal conductor buried in the ground that is in direct contact with the earth. Also known as the grounding pole. Various metal members, metal facilities, metal pipes, metal equipment, etc. that directly contact the earth can also serve as an Earth electrode, which is called a natural Earth electrode.
5, Earth conductor
Connect the connecting wires or conductors of the grounding device from the grounding terminal of the electrical equipment to the connecting wires or conductors of the grounding device from the metal objects that need equipotential bonding, the total grounding terminal, the grounding summary board, the total grounding bar, and the equipotential bonding.
6, Direct lightning flash
Direct lightning strikes on real objects such as buildings, earth or lightning protection devices.
7, Back flashover
The lightning current passes through a grounding point or a grounding system to cause a change in the ground potential of the region. Ground potential counterattacks can cause changes in the grounding system potential, which may cause damage to electronic equipment and electrical equipment.
8, Lightning protection system (LPS)
Surge protectors reduce the damage caused by lightning to buildings, installations, etc., including external and internal lightning protection systems.
8.1 External lightning protection system
A lightning protection part of the exterior or body of a building. The surge protector usually consists of a lightning receptor, a down conductor and a grounding device to prevent direct lightning strikes.
8.2 Internal lightning protection system
The lightning protection part inside the building (structure), the surge protector usually consists of equipotential bonding system, common grounding system, shielding system, reasonable wiring, surge protector, etc., mainly used to reduce and prevent lightning current The electromagnetic effect generated in the protective space.
Lightning disasters are one of the most serious natural disasters. There are countless casualties and property losses caused by lightning disasters every year in the world. With a large number of applications of electronic and microelectronic integrated devices, the damage of systems and equipment caused by lightning overvoltage and lightning electromagnetic pulses is increasing. Therefore, it is very important to solve the lightning disaster protection problem of buildings and electronic information systems as soon as possible.
Surge protector lightning discharge may occur between clouds or clouds, or between clouds and ground; in addition to the internal surge caused by the use of many large-capacity electrical equipment, the power supply system (China’s low-voltage power supply system standard: AC 50Hz 220 /380V) and the impact of electrical equipment and protection against lightning and surge has become the focus of attention.
The lightning strike between the cloud and the ground of the surge protector consists of one or several separate lightnings, each carrying a number of very high currents with very short durations. A typical lightning discharge will include two or three lightning strikes, approximately one-twentieth of a second between each lightning strike. Most lightning currents fall between 10,000 and 100,000 amps, and their duration is typically less than 100 microseconds.
The use of large-capacity equipment and inverter equipment in the surge protector power supply system has brought about an increasingly serious internal surge problem. We attribute it to the effects of transient overvoltage (TVS). The allowable range of the power supply voltage is present for any powered device. Sometimes even a very narrow overvoltage shock can cause power or damage to the equipment. This is the case with transient overvoltage (TVS) damage. Especially for some sensitive microelectronic devices, sometimes a small surge can cause fatal damage.
With the increasingly strict requirements for lightning protection of related equipment, the installation of Surge Protection Device (SPD) to suppress surges and transient overvoltages on the line and overcurrent on the bleeder line has become an important part of modern lightning protection technology. one.
1, lightning characteristics
Lightning protection includes external lightning protection and internal lightning protection. The external lightning protection is mainly used for lightning receptors (lightning rods, lightning protection nets, lightning protection belts, lightning protection lines), down conductors, and grounding devices. The main function of the surge protector is to ensure that the building body is protected from direct lightning strikes. Lightning bolts that may hit a building are discharged into the earth through lightning rods (belts, nets, wires), down conductors, etc. Internal lightning protection includes lightning protection, line surges, ground potential counterattacks, lightning wave intrusion, and electromagnetic and electrostatic induction. The method is based on equipotential bonding, including direct connection and indirect connection through SPD, so that the metal body, equipment line and the earth form a conditional equipotential body, and the internal facilities are shunted and induced by lightning and other surges. The lightning current or surge current is discharged into the earth to protect the safety of people and equipment in the building.
Lightning is characterized by very fast voltage rise (within 10μs), high peak voltage (tens of thousands to millions of volts), large current (tens to hundreds of thousands of amps), and short duration (tens to hundreds of microseconds) ), the transmission speed is fast (transmitting at the speed of light), the energy is very huge, and it is the most destructive one among the surge voltages.
2, classification of surge protectors
SPD is an indispensable device for lightning protection of electronic equipment. Its function is to limit the instantaneous overvoltage of the power line and signal transmission line to the voltage range that the equipment or system can withstand, or to discharge powerful lightning current into the ground. Protect protected equipment or systems from shocks.
2,1 Classification by working principle
Classified according to their working principle, SPD can be divided into voltage switch type, voltage limit type and combination type.
(1) Voltage switch type SPD. In the absence of transient overvoltage, it exhibits high impedance. Once it responds to lightning transient overvoltage, its impedance mutates to low impedance, allowing lightning current to pass through, also known as “short-circuit switch type SPD”.
(2) Pressure limiting SPD. When there is no transient overvoltage, it is high impedance, but as the surge current and voltage increase, its impedance will continue to decrease, and its current and voltage characteristics are strongly nonlinear, sometimes called “clamped type SPD”.
(3) Combined SPD. It is a combination of a voltage switching type component and a voltage limiting type component, which can be displayed as a voltage switching type or a voltage limiting type or both, depending on the characteristics of the applied voltage.
2.2 Classification by purpose
According to their use, SPD can be divided into power line SPD and signal line SPD.
2.2.1 Power Line SPD
Since the energy of lightning strikes is very large, it is necessary to gradually discharge the lightning strike energy to the earth by means of grading discharge. Install a surge protector or a voltage-limiting surge protector that passes the Class I classification test at the junction of the direct lightning protection zone (LPZ0A) or the direct lightning protection zone (LPZ0B) and the first protection zone (LPZ1). Primary protection, which discharges direct lightning current, or discharges large amounts of conducted energy when the power transmission line is subjected to direct lightning strikes. A voltage limiting surge protector is installed at the junction of each zone (including the LPZ1 zone) behind the first protection zone as a second, third or higher level of protection. The second-level protector is a protective device for the residual voltage of the pre-stage protector and the induced lightning strike in the area. When the lightning energy absorption of the front-stage is large, some parts are still quite large for the equipment or the third-level protector. The energy that is transmitted will require further absorption by the second level protector. At the same time, the transmission line of the first stage lightning arrester will also induce lightning electromagnetic pulse radiation. When the line is long enough, the energy of the induced lightning becomes large enough, and the second level protector is needed to further bleed the lightning energy. The third stage protector protects the residual lightning energy through the second stage protector. According to the withstand voltage level of the protected equipment, if the two-level lightning protection can achieve the voltage limit below the voltage level of the equipment, only two levels of protection are needed; if the equipment withstand voltage level is low, it may require four levels or even More levels of protection.
Choose SPD, you need to understand some parameters and how they work.
(1) The 10/350μs wave is a waveform that simulates a direct lightning strike, and the waveform energy is large; the 8/20μs wave is a waveform that simulates lightning induction and lightning conduction.
(2) The nominal discharge current In refers to the peak current flowing through the SPD and 8/20 μs current wave.
(3) The maximum discharge current Imax, also known as the maximum flow rate, refers to the maximum discharge current that can be withstood by the SPD with a current wave of 8/20μs.
(4) The maximum continuous withstand voltage Uc(rms) refers to the maximum AC voltage rms or DC voltage that can be continuously applied to the SPD.
(5) The residual voltage Ur refers to the residual pressure value at the rated discharge current In.
(6) The protection voltage Up characterizes the voltage characteristic parameter between the SPD limit terminals, and its value can be selected from the list of preferred values, which should be greater than the highest value of the limit voltage.
(7) The voltage switch type SPD mainly discharges 10/350μs current wave, and the voltage limiting type SPD mainly discharges 8/20μs current wave.
2.2.2 Signal Line SPD
The signal line SPD is actually a signal lightning arrester installed in the signal transmission line, generally at the front end of the device, to protect subsequent devices and prevent lightning waves from influencing the damaged device from the signal line.
1) Selection of voltage protection level (Up)
The Up value should not exceed the rated voltage rating of the protected equipment. Up requires that the SPD be well matched to the insulation of the equipment being protected.
In the low-voltage power supply and distribution system, the equipment should have a certain ability to withstand surge, that is, the ability to withstand shock and overvoltage. When the impact overvoltage value of various equipment of 220/380V three-phase system cannot be obtained, it can be selected according to the given indicators of IEC 60664-1.
2) Selection of the nominal discharge current In (impact flow capacity)
The peak current flowing through the SPD, 8/20 μs current wave. It is used for the Class II classification test of SPD and also for the pretreatment of SPD for Class I and Class II classification tests.
In fact, In is the maximum peak value of the surge current that can pass the specified number of times (usually 20 times) and the specified waveform (8/20 μs) without substantial damage to the SPD.
3) Selection of maximum discharge current Imax (limit shock flow capacity)
The peak current flowing through the SPD, 8/20 μs current wave, is used for the Class II classification test. Imax has many similarities with In, which use a peak current of 8/20 μs current wave to perform a Class II classification test on SPD. The difference is also obvious. Imax only performs an impact test on SPD, and SPD does not cause substantial damage after the test, and In can do 20 such tests, and SPD cannot be substantially destroyed after the test. Therefore, Imax is the current limit of the impact, so the maximum discharge current is also called the ultimate impulse flow capacity. Obviously, Imax>In.
Surge Protection Device is an indispensable device for lightning protection of electronic equipment. It used to be called “arrester” or “overvoltage protector”. English is abbreviated as SPD. The role of the surge protector is to The transient overvoltage into the power line and the signal transmission line is limited to the voltage range that the equipment or system can withstand, or the powerful lightning current is discharged into the ground to protect the protected equipment or system from impact and damage.
The type and structure of the surge protector vary from application to application, but it should contain at least one non-linear voltage limiting component. The basic components used in surge protectors are discharged gap, gas-filled discharge tube, varistor, suppression diode and the choke coil.
1. Discharge gap (also known as protection gap):
It is generally composed of two metal rods separated by a certain gap exposed to the air, one of which is connected to the power supply phase line L or the neutral line (N) of the required protection device, and the other metal rod and the ground line ( PE) is connected. When the transient overvoltage strikes, the gap is broken down, and a part of the overvoltage charge is introduced into the earth, which avoids the voltage rise on the protected device. The distance between the two metal rods of the discharge gap can be adjusted as needed, and the structure is relatively simple, and the disadvantage is that the arc extinguishing performance is poor. The improved discharge gap is an angular gap, and its arc-extinguishing function is better than that of the former. It is caused by the action of the electric power F of the circuit and the rising of the hot air flow to extinguish the arc.
2. Gas discharge tube:
It consists of a pair of cold negative plates that are separated from each other and enclosed in a glass tube or ceramic tube filled with a certain inert gas (Ar). In order to increase the trigger probability of the discharge tube, a triggering agent is also provided in the discharge tube. This type of gas-filled discharge tube has a two-pole type and a three-pole type.
The technical parameters of the gas discharge tube are: DC discharge voltage Udc; shock discharge voltage Up (Generally, Up≈(2~3)Udc; power frequency withstand current In; impulse withstand current Ip; insulation resistance R (>109Ω) ); interelectrode capacitance (1-5PF)
The gas discharge tube can be used under DC and AC conditions. The selected DC discharge voltage Udc is as follows: Use under DC conditions: Udc≥1.8U0 (U0 is the DC voltage for the line to work normally)
Use under AC conditions: U dc ≥ 1.44Un (Un is the rms value of the AC voltage for normal operation of the line)
It is a metal oxide semiconductor varistor with ZnO as its main component. When the voltage applied to both ends reaches a certain value, the resistance is very sensitive to voltage. Its working principle is equivalent to the series and parallel connection of multiple semiconductor P-N. The varistor is characterized by good nonlinear characteristics (I=CUα, α is a nonlinear coefficient), large flow capacity (~2KA/cm2), low of normal leakage current (10-7~10-6A), low residual voltage (depending on In the varistor operating voltage and flow capacity), the response time to the transient overvoltage is fast (~10-8s), no freewheeling.
The technical parameters of the varistor are varistor voltage (ie switching voltage) UN, reference voltage Ulma; residual voltage Ures; residual voltage ratio K (K=Ures/UN); maximum flow capacity Imax; leakage current; response time.
The varistor is used under the following conditions: varistor voltage: UN ≥ [(√ 2 × 1.2) / 0.7] U0 (U0 is the rated voltage of the power frequency power supply)
Minimum reference voltage: Ulma ≥ (1.8 ~ 2) Uac (used under DC conditions)
Ulma ≥ (2.2 ~ 2.5) Uac (used under AC conditions, Uac is AC operating voltage)
The maximum reference voltage of the varistor should be determined by the withstand voltage of the protected electronic device. The residual voltage of the varistor should be lower than the voltage level of the protected electronic device, ie (Ulma)max≤Ub/K. Where K is the residual voltage ratio and Ub is the damage voltage of the protected device.
4. Suppression diode:
The suppression diode has a clamp-limited function. It operates in the reverse breakdown region. Due to its low clamping voltage and fast response, it is especially suitable for use as the last-level protection components in multi-level protection circuits. The volt-ampere characteristic of the suppression diode in the breakdown region can be expressed by the following formula: I=CUα, where α is a nonlinear coefficient, for the Zener diode α=7～9, in the avalanche diode α=5～7.
Suppression diode technical parameters
(1) Breakdown voltage, which refers to the breakdown voltage at the specified reverse breakdown current (often 1ma), which is typically within the range of 2.9V to 4.7V for Zener diodes, and the rated breakdown of avalanche diodes. The wearing voltage is often in the range of 5.6V to 200V.
(2) Maximum clamp voltage: It refers to the highest voltage appearing at both ends of a tube when it passes a large current of a prescribed waveform.
(3) Pulse power: It refers to the product of the maximum clamp voltage at both ends of the tube and the current equivalent in the tube under a specified current waveform (eg, 10/1000 μs).
(4) Reverse displacement voltage: It refers to the maximum voltage that can be applied to both ends of the tube in the reverse leakage zone, at which the tube should not break down. This reverse displacement voltage should be significantly higher than the highest operating voltage peak of the protected electronic system, ie, it cannot be in a weak conduction state during normal operation of the system.
(5) Maximum leakage current: It refers to the maximum reverse current flowing through the tube under the reverse displacement voltage.
(6) Response time: 10-11s
5. Choke coil:
The choke coil is a common mode interference suppression device with ferrite as the core. It is symmetrically wound on the same ferrite toroidal core by two coils of the same size and the same number of turns. To form a four-terminal device, it is necessary to suppress the large inductance of the common mode signal, and it has little effect on the differential inductance of the differential mode signal. The choke coil can effectively suppress the common mode interference signal (such as lightning interference) in the balanced line but has no effect on the differential mode signal that the line normally transmits.
The choke coil should meet the following requirements when it is produced:
1) The wires wound on the coil core should be insulated from each other to ensure that no breakdown short occurs between turns of the coil under transient overvoltage.
2) When the coil flows through a large instantaneous current, the core does not appear to be saturated.
3) The core in the coil should be insulated from the coil to prevent breakdown between the two under transient overvoltage.
4) The coil should be wound as much as possible, which can reduce the parasitic capacitance of the coil and enhance the ability of the coil to instantaneous overvoltage.
6. 1/4 wavelength short circuited
The 1/4 wavelength crowbar is a microwave signal surge protector based on the spectral analysis of lightning waves and the standing wave theory of the antenna feeder. The length of the metal shorting bar in this protector is based on the operating signal frequency (eg 900 MHz or 1800 MHz). The size of the 1/4 wavelength is determined. The parallel shorting bar length has an infinite impedance for the working signal frequency, which is equivalent to an open circuit and does not affect the transmission of the signal. However, for lightning waves, since the lightning energy is mainly distributed below n+KHZ, the shorting bar For the lightning wave impedance is small, equivalent to a short circuit, the lightning energy level is discharged into the ground.
Since the diameter of the 1/4 wavelength shorting bar is generally a few millimeters, the impact current resistance is good, and it can reach 30KA (8/20μs) or more, and the residual voltage is small. This residual voltage is mainly caused by the self-inductance of the shorting bar. The shortcoming is that the power band is narrow and the bandwidth is about 2% to 20%. Another disadvantage is that DC bias cannot be applied to the antenna feeder, which limits some applications.
The circuit of the surge protector has different forms according to different needs. The basic components are the above-mentioned several types. A technically well-known lightning protection product researcher can design a variety of circuits, just like a box of blocks can be used. Different structural patterns. It is the responsibility of lightning protection workers to develop products that are both effective and cost-effective.
The surge protector’s first-stage lightning arrester can bleed for direct lightning current or bleed when the power transmission line is subjected to direct lightning strike. For places where direct lightning strikes may occur, CLASS-I must be performed. Lightning protection. The second-stage lightning arrester is a protective device for the residual voltage of the front-end lightning protection device and the lightning-induced lightning strike in the area. When there is a large lightning energy absorption in the front stage, there is still a part of the equipment or the third-level lightning protection device. It is quite a huge amount of energy that will be transmitted and requires a second-stage arrester for further absorption. At the same time, the transmission line of the first-stage lightning arrester will also induce lightning impulse electromagnetic radiation LEMP. When the line is long enough, the energy of the induced lightning becomes large enough, and the second-level lightning protection device is needed to further discharge the lightning energy. The third-stage lightning arrester protects the LEMP and residual lightning energy through the second-stage lightning arrester.
First level protection
The purpose of the surge protector is to prevent the surge voltage from being conducted directly from the LPZ0 area into the LPZ1 area, limiting the surge voltage of tens of thousands to hundreds of thousands of volts to 2500-3000V.
The surge protector installed on the low-voltage side of the power transformer is a three-phase voltage switch type power supply lightning arrester. The lightning flux should not be lower than 60KA. The power supply lightning arrester of this class shall be a large-capacity power supply lightning arrester connected between the phases of the inlet of the user’s power supply system and the earth. It is generally required that the power surge protector of this class has a maximum impact capacity of more than 100KA per phase, and the required limit voltage is less than 1500V, which is called a CLASS I power surge protector and a surge protector. Designed to withstand the high currents of lightning and inductive lightning strikes, and to attract high-energy surges, these electromagnetic surge arresters shunt large amounts of inrush current to the ground. They only provide a limiting voltage (the maximum voltage that appears on the line when the inrush current flows through the power supply arrester is called a limiting voltage). The CLASS Class I protector is mainly used to absorb large inrush currents, only They cannot fully protect sensitive electrical equipment inside the power supply system.
The first-level power surge protector can protect against 10/350μs and 100KA lightning waves and meet the highest protection standards stipulated by IEC. The technical reference is as follows: the lightning flux is greater than or equal to 100KA (10/350μs); the residual voltage is not greater than 2.5KV; the response time is less than or equal to 100ns.
Second level protection
The purpose of the surge protector is to further limit the residual surge voltage through the first-stage lightning arrester to 1500-2000V and to equipotentially connect the LPZ1-LPZ2.
The power supply lightning arrester outputted by the distribution cabinet line shall be a voltage-limiting power supply lightning protection device as the second-level protection. The lightning current capacity shall not be lower than 20KA. It shall be installed in the power supply to important or sensitive electrical equipment. Road distribution station. These power surge arresters provide a better absorption of the residual surge energy through the surge arrester at the customer’s power supply inlet and have excellent suppression of transient overvoltages. The power surge arrester used in this area requires a maximum impact capacity of 45kA or more per phase, and the required limit voltage should be less than 1200V, which is called a CLASS II power supply lightning arrester. The general user power supply system can achieve the second-level protection to meet the requirements of the operation of the electrical equipment.
The second-stage power surge protector adopts Class C protector for phase-to-phase, phase-ground and medium-ground full-mode protection. The main technical parameters are: lightning flow capacity greater than or equal to 40KA (8/20μs); residual voltage The peak value is not more than 1000V; the response time is no more than 25ns.
Third level protection
The purpose of the surge protector is to ultimately protect the equipment by reducing the residual surge voltage to less than 1000V so that the surge energy does not damage the equipment.
When the power supply lightning protection device installed at the incoming end of the AC power supply of the electronic information equipment is used as the third-level protection, it shall be a series-type voltage-limiting power supply lightning protection device, and its lightning current capacity shall not be lower than 10KA.
The final line of protection of the surge protector can be used with a built-in power surge protector in the internal power supply of the consumer to achieve a complete elimination of small transient overvoltages. The power surge arrester used here requires a maximum impact capacity of 20KA or less per phase, and the required limiting voltage should be less than 1000V. It is necessary to have a third level of protection for some particularly important or particularly sensitive electronic equipment, as well as to protect the electrical equipment from transient overvoltages generated within the system.
For the rectification power supply used in microwave communication equipment, mobile station communication equipment and radar equipment, it is necessary to select the DC power supply lightning protection device with the working voltage adaptation as the final stage protection according to the protection of its working voltage.
Level 4 and above
The surge protector according to the withstand voltage level of the protected equipment, if the two-level lightning protection can achieve the limit voltage below the withstand voltage level of the equipment, it only needs to do two levels of protection, if the equipment withstand voltage level is low, it may Need four or more levels of protection. The fourth-level protection of its lightning flow capacity should not be lower than 5KA.
1, SPD routine installation requirements
The surge protector is installed with 35mm standard rail
For fixed SPDs, the following steps should be followed for regular installation:
1) Determine the discharge current path
2) Mark the wire for the extra voltage drop caused at the device terminal.
3) To avoid unnecessary inductive loops, mark the PE conductor of each device.
4) Establish an equipotential bonding between the device and the SPD.
5) To coordinate energy coordination of multi-level SPD
In order to limit the inductive coupling between the installed protective part and the unprotected part of the device, certain measurements are required. The mutual inductance can be reduced by the separation of the sensing source from the sacrificial circuit, the selection of the loop angle, and the limitation of the closed loop region.
When the current carrying component conductor is part of a closed loop, the loop and induced voltage are reduced as the conductor approaches the circuit.
In general, it is better to separate the protected wire from the unprotected wire and it should be separated from the ground wire. At the same time, in order to avoid transient quadrature coupling between the power cable and the communication cable, the necessary measurements should be made.
2, SPD grounding wire diameter selection
Data line: The requirement is greater than 2.5mm2; when the length exceeds 0.5m, it is required to be greater than 4mm2.
Powerline: When the phase line cross-sectional area S≤16mm2, the ground line uses S; when the phase line cross-sectional area is 16mm2≤S≤35mm2, the ground line uses 16mm2; when the phase line cross-sectional area S≥35mm2, the ground line requires S/2.
The main parameters
- Nominal voltage Un: The rated voltage of the protected system is consistent. In the information technology system, this parameter indicates the type of protector that should be selected, which indicates the effective value of the AC or DC voltage.
- Rated voltage Uc: can be applied to the specified end of the protector for a long time without causing a change in the characteristics of the protector and activating the maximum voltage effective value of the protective element.
- Rated discharge current Isn: The maximum inrush current peak that the protector is tolerated when a standard lightning wave with a waveform of 8/20 μs is applied to the protector for 10 times.
- Maximum discharge current Imax: The maximum inrush current peak that the protector is tolerated when a standard lightning wave with a waveform of 8/20 μs is applied to the protector.
- Voltage protection level Up: The maximum value of the protector in the following tests: the flashover voltage of the slope of 1KV/μs; the residual voltage of the rated discharge current.
- Response time tA: The action sensitivity and breakdown time of the special protection component mainly reflecting in the protector, and the change in a certain time depends on the slope of du/dt or di/dt.
- Data transmission rate Vs: indicates how many bit values are transmitted in one second, the unit is: bps; it is the reference value of the lightning protection device correctly selected in the data transmission system, and the data transmission rate of the lightning protection device depends on the transmission mode of the system.
- Insertion loss Ae: The ratio of the voltage before and after the protector is inserted at a given frequency.
- Return Loss Ar: Indicates the ratio of the leading edge wave reflected by the protection device (reflection point), which is a parameter that directly measures whether the protection device is compatible with the system impedance.
- Maximum longitudinal discharge current: refers to the peak value of the maximum inrush current that the protector is subjected to when the standard lightning wave with a waveform of 8/20μs is applied to each ground.
- Maximum lateral discharge current: The maximum inrush current peak that the protector is subjected to when the standard lightning wave with a waveform of 8/20μs is applied between the line and the line.
- Online impedance: refers to the sum of the impedance and inductive reactance of the loop flowing through the protector under the nominal voltage Un. Often referred to as “system impedance.”
- Peak discharge current: There are two types: rated discharge current Isn and maximum discharge current Imax.
- Leakage current: refers to the DC current flowing through the protector at a nominal voltage Un of 75 or 80.
Classified by working principle
- Switch type: The working principle of the surge protector is high impedance when there is no instantaneous overvoltage, but once it responds to the lightning transient overvoltage, its impedance will suddenly change to a low value, allowing lightning current to pass. When used as such a device, the device has: a discharge gap, a gas discharge tube, a thyristor, and the like.
- Voltage limiting type: The working principle of the surge protector is high impedance when there is no transient overvoltage, but its impedance will decrease continuously with the increase of surge current and voltage, and its current and voltage characteristics are strongly nonlinear. Devices used as such devices are: zinc oxide, varistors, suppression diodes, avalanche diodes, and the like.
- Split or turbulent：
Shunt type: Parallel to the protected device, exhibiting a low impedance to the lightning pulse and a high impedance to the normal operating frequency.
Turbulent type: In series with the protected device, it exhibits a high impedance to the lightning pulse and a low impedance to the normal operating frequency.
Devices used as such devices are: choke coils, high pass filters, low pass filters, quarter wave shorts, and the like.
Usage of Surge Protection Device SPD
(1) Power protector: AC power protector, DC power protector, switching power protector, etc.
The AC power lightning protection module is suitable for power protection of power distribution rooms, power distribution cabinets, switch cabinets, AC/DC power distribution panels, etc.
There are outdoor input distribution boxes and building layer distribution boxes in the building;
For low voltage (220/380VAC) industrial power grids and civil power grids;
In the power system, it is mainly used for the input or output of the three-phase power in the power supply screen of the main control room of the automation machine room or substation.
Suitable for a variety of DC power systems, such as:
DC power distribution panel;
DC power supply equipment;
DC distribution box;
Electronic information system cabinet;
The output of the secondary power supply.
(2) Signal protector: low-frequency signal protector, high-frequency signal protector, antenna feeder protector, etc.
Network signal lightning protection device:
Inductive overvoltage protection caused by lightning strikes and lightning electromagnetic pulses for network equipment such as 10/100Mbps SWITCH, HUB, ROUTER; · Network room network switch protection; · Network room server protection; · Network room other network interface device protection;
The 24-port integrated lightning protection box is mainly used for centralized protection of multiple signal channels in integrated network cabinets and sub-switch cabinets.
Video signal lightning protection device:
The surge protector is mainly used for point-to-point protection of video signal equipment. It can protect various video transmission equipment from the inductive lightning strike and surge voltage from the signal transmission line. It is also applicable to RF transmission under the same working voltage. The integrated multi-port video lightning protection box is mainly used for centralized protection of control devices such as hard disk recorders and video cutters in the integrated control cabinet.
Surge Protector Brand
The most common arresters on the market are: China LSP surge protector, Germany OBO surge protector, DEHN surge protector, PHOENIX surge protector, US ECS surge protector, US PANAMAX surge protector, INNOVATIVE surge protector, US POLYPHASER Surge protector, France Soule surge protector, UK ESP Furse surge protector etc.