Surge protector (surge protector), also known as surge arrester, referred to as (SPD) for AC 50/60HZ, rated voltage to 380V power supply system (or communication system), indirect lightning and direct lightning impact or other transient The surge surge protects the requirements of surge protection in the family home, tertiary industry and industrial fields, and has protection modes such as relative phase, relative phase, relative midline, midline to ground and combinations thereof.

The most primitive surge protector, the angular gap, appeared in the late 19th century and was used for overhead transmission lines to prevent lightning strikes from damaging equipment insulation and causing power outages. In the 1920s, aluminum surge protectors, oxide surge protectors and pill surge protectors emerged. A tubular surge protector appeared in the 1930s. Silicon carbide lightning arresters appeared in the 1950s. Metal oxide surge protectors appeared in the 1970s. Modern high-voltage surge protectors are not only used to limit overvoltages caused by lightning in power systems, but also to limit overvoltages caused by system operation.

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 impact.

1 Classified 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-circuited 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 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 by purpose

According to their use, SPD can be divided into power line SPD and signal line SPD.

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 strike 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-stage 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 that a second stage 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's withstand voltage level is low, it may require four levels or even More levels of protection.

To choose SPD, you first 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 at 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.

Signal line SPD

The signal line SPD is actually a signal lightning arrester, which is 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 equipments of 220/380V three-phase system cannot be obtained, it can be selected according to the given indicators of IEC 60664-1 and GB 50057-1994 (2000 version).

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 impulse 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, and they 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.

Fold edit this paragraph works

Surge protection device (Surge protection Device) is an indispensable device for lightning protection of electronic equipment. It used to be called "arrester" or "overvoltage protector". The English abbreviation is SPD. The role of surge protector is to put 窜The transient overvoltage into the power line and 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 varies from application to application, but it should contain at least one non-linear voltage limiting component. The basic components used in surge protectors are: discharge gap, gas-filled discharge tube, varistor, suppression diode and choke coil.

installation method

SPD general installation requirements

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 choice 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.

Surge protector installation wiring diagram

Surge protector installation wiring diagram

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. YD/T5098-1998.

Power line: 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; GB 500.54.2.9

Main parameters of the surge protector

1. Nominal voltage Un: The rated voltage of the protected system is consistent. In the information technology system, this parameter indicates the protection that should be selected.

Surge guarantee

Surge guarantee

The type of device that identifies the rms value of the AC or DC voltage.

2. Rated voltage Uc: can be applied to the specified end of the protector for a long time without causing a change in the characteristic of the protector and activating the maximum voltage effective value of the protective element.

3. 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.

4. Maximum discharge current Imax: The maximum inrush current peak that the protector is subjected to when the standard lightning wave with a waveform of 8/20 μs is applied to the protector.

5. Voltage protection level Up: The maximum value of the protector in the following tests: the flashover voltage of 1KV/μs slope; the residual voltage of the rated discharge current.

6. 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.

7. Data transmission rate Vs: It means 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. The data transmission rate of the lightning protection device depends on the transmission mode of the system.

8. Insertion loss Ae: The ratio of the voltage before and after the protector is inserted at a given frequency.

9. Return Loss Ar: The ratio of the leading edge wave reflected by the protection device (reflection point) is a parameter that directly measures whether the protection device is compatible with the system impedance.

10. 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 the ground.

11. Maximum lateral 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 between the line and the line.

12. 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."

13. Peak discharge current: There are two types: rated discharge current Isn and maximum discharge current Imax.

14. Leakage current: refers to the DC current flowing through the protector at a nominal voltage Un of 75 or 80.

classification

working principle

1. Switch type: Its working principle is to exhibit high impedance when there is no instantaneous overvoltage, but once it responds to 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.

2. Voltage-limiting type: Its working principle is high-impedance when there is no instantaneous over-voltage, but its impedance will decrease continuously with the increase of surge current and voltage, and its current-voltage characteristics are strongly nonlinear. Devices used as such devices are: zinc oxide, varistors, suppression diodes, avalanche diodes, and the like.

3. Split or turbulent type

Shunt type: In parallel with the protected device, it exhibits 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.

Folding purpose

(1) Power protector: AC power protector, DC power protector, switching power protector, etc.

· AC power lightning protection module is suitable for power supply protection in power distribution room, power distribution cabinet, switch cabinet, AC/DC power distribution panel, etc.

· There are outdoor input distribution boxes and building layer distribution boxes in the building;

Power surge protector

Power surge protector

· For low voltage (220/380VAC) industrial power grids and civil power grids;

· In the power system, it is mainly used for the three-phase power input or output in the power supply screen of the main 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.

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