abstract：ConcernedSurge protection Device is an indispensable device for lightning protection of electronic equipment.

"Overvoltage protector" is abbreviated as SPD. The function of surge protector is to limit the transient overvoltage penetrating into the power line and signal transmission line to the voltage range that the equipment or system can bear, or to release strong lightning current to the ground to protect the protected equipment or system. Protect the system from damage.The type and structure of SPD are different for different applications, but it should include at least one nonlinear voltage limiting element. The basic components used in surge protectors are: discharge gap, gas-filled discharge tube, varistor, suppression diode and choke coil.VICFUSE: How to choose the right surge protector?Method/stepUnderstand the basic components of surge protectors:

 1. Discharge gap (also called protection gap): [ It usually consists of two metal rods, which are exposed to the air with a certain gap. One metal bar is connected to the power phase line L1 or neutral line (N) of the equipment to be protected, and the other metal bar is connected to the ground line (PE). When transient overvoltage occurs, the gap will be broken down, and some overvoltage charges will be introduced into the ground, thus preventing the voltage on the protected equipment from rising. The distance between the two metal rods in such a discharge gap can be adjusted as required, and the structure is relatively simple. Its disadvantage is poor fire extinguishing performance. The improved discharge gap is the angular gap. Its arc extinguishing function is superior to the former. It is offset by the electromotive force f of its circuit and the rise of hot air flow. 2. Gas discharge tube: It consists of a pair of cold cathode plates separated from each other and enclosed in a glass tube or ceramic tube filled with some inert gas (Ar). In order to increase the trigger probability of the discharge tube, a trigger is also provided in the discharge tube. There are two kinds of gas-filled discharge tubes, three-pole type. The technical parameters of gas discharge tube are: DC discharge voltage Udc；; The pulse discharge voltage Up (up ≈ (23) UDC under normal conditions); Power frequency withstand current in; Impulse withstand current IP; Insulation resistance R (> 109 Ω); Inter-electrode capacitance (1-5PF) [h] The DC discharge voltage Udc of gas discharge tube can be used in DC and AC conditions as follows: Under DC conditions, Udc≥1.8 U0(U0 is the DC voltage during normal line operation) Used under AC conditions: U dc≥1.44 Un(Un is

3. Varistor:Metal oxide semiconductor nonlinear resistor with ZnO as main component. When the voltage at both ends reaches a certain value, the resistor is very sensitive to the voltage. Its working principle is equivalent to the series-parallel connection of multiple semiconductors P-N.. The varistor has good nonlinear characteristics (I = nonlinear coefficient α in Cu α), large current capacity (2KA/cm2), small normal leakage current (10-710-6A) and low residual voltage (depending on the working voltage and current capacity of the varistor), and its response time to instantaneous overvoltage is very fast (about 10-8s), and there is no continuous current.Technical parameters of varistor mainly include: varistor voltage (i.e. switching voltage) UN, reference voltage Ulma；; Residual voltage Ures; The residual voltage ratio K(K = Ures/UN); Maximum current Imax; Leakage current; Response time.The application conditions of the varistor are: the varistor voltage: UN≥[(√2×1.2)/0.7] U0(U0 is the rated voltage of the power supply).Minimum reference voltage: Ulma≥(1.8 to 2)Uac (used under DC condition)Ulma≥(2.2 to 2.5)Uac (used under AC conditions, Uac is AC working voltage)The maximum reference voltage of the varistor should be determined by the withstand voltage of the protected electronic equipment. The residual voltage of the varistor should be lower than the damaged voltage level of the protected electronic equipment, that is, (Ulma)max≤Ub/K, where k in the above formula is the ratio of residual voltage and Ub is the loss voltage of the resistor. Protected equipment.⑷ Suppression diode:Suppression diode has the function of clamping voltage limitation, and it works in reverse breakdown region. Because it has the advantages of low clamping voltage and fast response speed, it is especially suitable to be used as the last protection elements in multilevel protection circuits. The volt-ampere characteristics of the suppression diode in the breakdown region can be expressed by the following formula: I =CUα, where α is the nonlinear coefficient, α= 7-9 for zener diode and α= 5 -7 for avalanche diode. [H]VICFUSE: How to choose the right surge protector?Technical parameters of suppression diode:Breakdown voltage refers to the breakdown voltage at the specified reverse breakdown current (usually lma), and the unit is Zener. The rated breakdown voltage of the diode is usually 2.9V to 4.7V, while the rated breakdown voltage of avalanche diode is usually 5.6V to 200V.Clamping maximum clamping voltage: refers to the highest voltage appearing at both ends of the pipe when the pipe passes through a large current with a specified waveform.⑵ Pulse power: refers to the product of the maximum clamping voltage at both ends of the tube and the equivalent value of the current in the tube under the specified current waveform (e.g. 10/100μs).⑶ Reverse displacement voltage: refers to the maximum voltage that can be applied to both ends of the pipe in the reverse leakage area. Under this voltage, the lamp tube should not be damaged. This reverse displacement voltage should be significantly higher than the peak value of the highest working voltage of the protected electronic system, that is, it cannot be in a weak conduction state during normal system operation.5] Maximum leakage current: refers to the maximum reverse current flowing through the pipe under the reverse displacement voltage.[6] Response time: 10-11s

⑷ Choke: Choke is a common-mode interference suppression device with ferrite as the core. Coils with the same number of turns are symmetrically wound on the same ferrite toroidal core to form a four-terminal device. It must have a large inductance for common-mode signals and a small leakage for differential-mode signals. It almost doesn't work. Using chokes in balanced lines can effectively suppress common-mode interference signals (such as lightning interference) without affecting the differential signal transmission in normal mode.VICFUSE: How to choose the right surge protector?The choke coil shall meet the following requirements during manufacture:1) The wire wound on the coil core should be insulated to ensure that there is no breakdown short circuit between the coil turns under the action of transient overvoltage.2) When the coil passes through a large instantaneous current, the magnetic core should not be saturated.3) The magnetic core in the coil should be insulated from the coil to prevent the breakdown between the two due to transient overvoltage.4) The coil should be wound in single layer as much as possible. This will reduce the parasitic capacitance of the coil and enhance the ability of the coil to withstand transient overvoltage.[6] 1/4 wavelength short circuit1/4 wavelength short circuit is based on lightning wave, a microwave signal surge protector made by spectrum analysis of antenna feeder and standing wave theory. The length of the short metal bar of the protector depends on the 1/4 wavelength of the working signal frequency (for example, 900MHZ or 1800MHZ). . For the working signal frequency, the length of parallel shorting bar has infinite impedance, which is equivalent to open circuit and does not affect the signal transmission. However, for the lightning wave, because the lightning energy is mainly distributed below n+KHZ, the impedance of the short-circuit rod to the lightning wave is very small, which is equivalent to a short circuit, and the lightning energy level leaks to the ground.Because the diameter of the 1/4 wavelength short-circuit rod is usually several millimeters, it has good resistance to surge current, which can reach more than 30KA(8 /20μs), and has a small residual voltage, which is mainly caused by short circuit. The disadvantage of the self-inductance of the bar is that the industrial frequency band is very narrow, and the bandwidth is about 2% to 20%. Another disadvantage is that it can't add DC bias to antenna feeding equipment, which limits some applications.VICFUSE: How to choose the right surge protector?Classification protection of VICFUSE surge protector:The first-class lightning arrester can release DC lightning current, or directly strike lightning when the transmission line is protected, releasing huge energy. CLASS-I lightning protection measures must be implemented in places where direct lightning strikes may occur. The second lightning arrester is a protective device for the residual voltage of the previous lightning arrester and the induced lightning strike in this area. When large-scale lightning absorption occurred in the previous stage, there were still some equipment or third-level lightning arresters. A large amount of energy will be conducted, and this energy needs to be absorbed by the secondary lightning arrester. At the same time, the transmission line passing through the first-level arrester will also induce LEMP electromagnetic pulse radiation. When the line is long enough, the induced lightning energy will become large enough, and a secondary lightning arrester is needed to further release the lightning energy. The third level lightning arrester can protect LEMP and the remaining lightning energy passing through the second level lightning arrester.

Primary protectionIs to prevent surge voltage from being directly conducted from LPZ0 area to LPZ1 area, and limit 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 household power transformer shall be a three-phase voltage switching type surge protector as the first protection, and its lightning flux shall not be less than or more than 60K A. This level of power arrester should be a large-capacity power arrester, which is connected between each phase of the input line of the user's power system and the ground. Generally, the maximum impact capacity of this kind of arrester is required to be 100KA per phase, and the required limit voltage should be less than 1500V, which is called CLASS I arrester. These electromagnetic lightning arresters are designed to withstand high-current lightning and induced lightning strikes, and attract high-energy surges, which may transfer a large amount of surge current to the ground. They only provide limited voltage (the maximum voltage on the line when the surge current flows through the power arrester is called limited voltage), which is intermediate protection. Because CLASS I protectors mainly absorb large surge current, they can only completely protect the sensitive electrical equipment inside the power supply system.Class I power arrester can prevent 10 /350μs and 100KA lightning waves, and meet the highest protection standard stipulated by IEC. The technical reference is: the lightning flux is greater than or equal to 100kA (10/350μ s); The residual voltage value is not more than 2.5KV；; The response time is less than or equal to 100ns.Secondary protectionThe purpose is to further limit the residual surge voltage through the first-stage arrester to 1500-2000V, and realize the equipotential connection with LPZ1-LPZ2.The power arrester that distributes the output of the distribution cabinet line as the second protection shall be a voltage-limited power arrester, and its lightning current capacity shall not be less than 20KA. It should be installed in important or sensitive areas. Branch distribution room powered by electrical equipment. These power surge arresters absorb the surplus surge energy passing through the surge arresters at the entrance of the user's power supply, and better suppress the transient overvoltage. The maximum surge capacity of the power arrester used here is greater than 45kA per phase, and the required limit voltage should be less than 1200V, which is called CLASS II power arrester. Ordinary users' power supply system can meet the requirements of electrical equipment operation through secondary protection. [H]Class C protectors are used for phase-to-phase, phase-to-ground and neutral-to-ground grounding of secondary power arrester. The main technical parameters are: the lightning current capacity is greater than or equal to 40KA(8 /20μs); The residual voltage peak value is not more than 1000V；; The response time is less than 25ns.Tertiary protectionThe purpose is to finally protect the equipment and reduce the value of the remaining surge voltage to less than 1000V so that the surge energy will not damage the equipment.When the lightning arrester installed at the input end of AC power supply of electronic information equipment is used as the third-level protection, it should be a series voltage-limiting type lightning arrester, and its lightning current capacity should not be less than 10KA.The last line of defense can use the built-in power arrester in the internal power supply part of electrical equipment to completely eliminate the tiny transient overvoltage. The maximum surge capacity required by the power arrester used here is 20KA or less per phase, and the required limit voltage should be less than 1000V. It is necessary to provide three-level protection for some particularly important or sensitive electronic equipment. At the same time, it can also protect electrical equipment from the transient overvoltage generated in the system.For rectifier power used in microwave communication equipment, mobile station communication equipment, radar equipment, etc., DC power arrester suitable for working voltage should be selected as the final protection according to the following conditions: protect its working voltage.Level 4 and aboveAccording to the withstand voltage level of the protected equipment, if two lightning protection levels can be used to limit the voltage lower than the withstand voltage level of the equipment, you only need to perform two levels of protection. If the withstand voltage level of the equipment is low, four or more protection levels may be required. The fourth level protection shall not be less than 5KA.

VICFUSE: How to choose the right surge protector? VICFUSE: How to choose the right surge protector? Installation method: 1. routine installation requirements of SPD ] Install surge protector with 35MM standard guide rail. For fixed SPD, the routine installation should follow the following steps: 1) determining a discharge current path 2) Mark the wires that will cause extra voltage drop on the equipment terminals. 3) To avoid unnecessary inductance loop, the PE conductor of each device should be marked, and 4) Establish equipotential connection between equipment and SPD. 5) Energy coordination of multi-level SPD is required. In order to limit the inductive coupling between protected parts and unprotected equipment parts after installation, some measurements are required. The mutual inductance can be reduced by the separation of inductive and sacrificial circuits, the choice of loop angle and the limitation of closed loop area. [H] When the current-carrying component conductor is a part of a closed circuit, the circuit and induced voltage will decrease because the conductor is close to the circuit. Generally speaking, it is best to separate the protection line from the non-protection line and should be separated from the grounding line. At the same time, in order to avoid the transient orthogonal coupling between the power cable and the communication cable, necessary measurements should be made. [2] Installation wiring diagram of surge protector 2. Selection of SPD grounding wire diameter Data: it is required to be larger than 2.5mm2. When the length exceeds 0.5m, it is required to be more than 4mm2 YD/T5098-1998. Power line: when the cross-sectional area of phase line is S≤16mm2, the ground line is S; When the cross-sectional area of the phase line is 16mm2≤S≤35mm2, the ground line is 16mm2; S/2；; GB 50054 Article 2.2.9 VICFUSE: How to choose the right surge protector? Main parameters of surge protector: 1. Nominal voltage Un: the rated voltage of the protected system is consistent. In information technology systems, this parameter indicates the type of protection surge guarantee that should be used [3]. It indicates the RMS value of AC or DC voltage. 2. Rated voltage Uc: the maximum effective value of the voltage that can be applied to the designated terminal of the protector for a long time, without causing the change of the characteristics of the protector and the activation of the protection elements. 3. Rated discharge current Isn: the peak value of the maximum impulse current that the protector can bear when the standard lightning wave with the waveform of 8 /20μs is applied to the protector for 10 times. 4. Maximum discharge current Imax: when the standard lightning wave with 8 /20μs waveform is applied to the protector at one time, the peak value of the maximum pulse current that the protector can bear. 5. Voltage protection level Up: the maximum value of the protector in the following tests: the slope of flashover voltage is 1kV/μ s; Residual voltage of rated discharge current. 6. Response time tA: The action sensitivity and breakdown time of the special protection elements mainly reflected in the protector change according to the slope of du/dt or di/dt in a certain period of time. 7. Data transmission rate Vs: how many bit values are transmitted in seconds, unit: bps; It is a reference value for correctly selecting lightning protection equipment in data transmission system. The data transmission rate of lightning protection equipment depends on the transmission mode of the system. 8. Insertion loss Ae: the voltage ratio before and after inserting the protector at a given frequency. 9. Return loss Ar: indicates the proportion of the front wave reflected at the protective equipment (reflection point). This parameter directly measures whether the protection equipment is compatible with the system impedance. 10. Maximum vertical discharge current: refers to the peak value of the maximum surge current that the protector can bear when the standard lightning wave with 8 /20μs waveform is applied to each line at one time. 11. Maximum transverse discharge current: refers to the peak value of the maximum surge current that the protector can bear when the standard lightning wave with a waveform of 8 /20μs is applied between wires. 12. On-line impedance: refers to the sum of the loop impedance and inductive reactance flowing through the protector at the nominal voltage Un. Commonly referred to as "system impedance". 13. Peak discharge current: There are two types: rated discharge current Isn and maximum discharge current Imax. 14. Leakage current: DC current flowing through the protector at 75 or 80 nominal voltage Un.

VICFUSE: How to choose the right surge protector? VICFUSE: How to choose the right surge protector? Installation method: 1. routine installation requirements of SPD ] Install surge protector with 35MM standard guide rail. For fixed SPD, the routine installation should follow the following steps: 1) determining a discharge current path 2) Mark the wires that will cause extra voltage drop on the equipment terminals. 3) To avoid unnecessary inductance loop, the PE conductor of each device should be marked, and 4) Establish equipotential connection between equipment and SPD. 5) Energy coordination of multi-level SPD is required. In order to limit the inductive coupling between protected parts and unprotected equipment parts after installation, some measurements are required. The mutual inductance can be reduced by the separation of inductive and sacrificial circuits, the choice of loop angle and the limitation of closed loop area. [H] When the current-carrying component conductor is a part of a closed circuit, the circuit and induced voltage will decrease because the conductor is close to the circuit. Generally speaking, it is best to separate the protection line from the non-protection line and should be separated from the grounding line. At the same time, in order to avoid the transient orthogonal coupling between the power cable and the communication cable, necessary measurements should be made. [2] Installation wiring diagram of surge protector 2. Selection of SPD grounding wire diameter Data: it is required to be larger than 2.5mm2. When the length exceeds 0.5m, it is required to be more than 4mm2 YD/T5098-1998. Power line: when the cross-sectional area of phase line is S≤16mm2, the ground line is S; When the cross-sectional area of the phase line is 16mm2≤S≤35mm2, the ground line is 16mm2; S/2；; GB 50054 Article 2.2.9 VICFUSE: How to choose the right surge protector? Main parameters of surge protector: 1. Nominal voltage Un: the rated voltage of the protected system is consistent. In information technology systems, this parameter indicates the type of protection surge guarantee that should be used [3]. It indicates the RMS value of AC or DC voltage. 2. Rated voltage Uc: the maximum effective value of the voltage that can be applied to the designated terminal of the protector for a long time, without causing the change of the characteristics of the protector and the activation of the protection elements. 3. Rated discharge current Isn: the peak value of the maximum impulse current that the protector can bear when the standard lightning wave with the waveform of 8 /20μs is applied to the protector for 10 times. 4. Maximum discharge current Imax: when the standard lightning wave with 8 /20μs waveform is applied to the protector at one time, the peak value of the maximum pulse current that the protector can bear. 5. Voltage protection level Up: the maximum value of the protector in the following tests: the slope of flashover voltage is 1kV/μ s; Residual voltage of rated discharge current. 6. Response time tA: The action sensitivity and breakdown time of the special protection elements mainly reflected in the protector change according to the slope of du/dt or di/dt in a certain period of time. 7. Data transmission rate Vs: how many bit values are transmitted in seconds, unit: bps; It is a reference value for correctly selecting lightning protection equipment in data transmission system. The data transmission rate of lightning protection equipment depends on the transmission mode of the system. 8. Insertion loss Ae: the voltage ratio before and after inserting the protector at a given frequency. 9. Return loss Ar: indicates the proportion of the front wave reflected at the protective equipment (reflection point). This parameter directly measures whether the protection equipment is compatible with the system impedance. 10. Maximum vertical discharge current: refers to the peak value of the maximum surge current that the protector can bear when the standard lightning wave with 8 /20μs waveform is applied to each line at one time. 11. Maximum transverse discharge current: refers to the peak value of the maximum surge current that the protector can bear when the standard lightning wave with a waveform of 8 /20μs is applied between wires. 12. On-line impedance: refers to the sum of the loop impedance and inductive reactance flowing through the protector at the nominal voltage Un. Commonly referred to as "system impedance". 13. Peak discharge current: There are two types: rated discharge current Isn and maximum discharge current Imax. 14. Leakage current: DC current flowing through the protector at 75 or 80 nominal voltage Un.