Parameters of surge protective device installation

2022-07-22
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Surge protector is an electronic device that can conduct shunt in a very short time when peak current or overvoltage is suddenly generated in the electrical circuit or communication line due to external interference, so as to avoid the damage of surge to other equipment in the circuit

the parameters of surge protective devices are an important basis for the selection of surge protective devices. Designers also need to consider the parameters of surge protective devices when selecting surge protective devices when designing electrical engineering drawings. Then, let's analyze the parameters of surge protector in detail

parameters of surge protective device

1. Maximum continuous operation voltage Uc

when SPD is selected in 220/380v three-phase system, its maximum continuous operation voltage Uc should be selected according to different grounding system forms

(1) when TN system is used for power supply, TN-S system must be used for distribution lines and branch lines from the main distribution board (box) in the building

(2) in the following places, the UC value specified above should be increased for zinc oxide varistor SPD according to the specific situation

① places where the power supply voltage deviation exceeds the specified 10%

② places where harmonics increase the voltage amplitude

2. The provisions of impulse current iimp

include amplitude current ipeak and charge q.

3, nominal discharge current in

flowing through SPD, 8/20μ The peak current of s current wave is used for level II Classification Test of SPD, and also for pretreatment of level I and level II Classification Test of SPD For class I classification test, in should not be less than 15ka, and for class II classification test, in should not be less than 5ka

4. Voltage protection level up

refers to the residual voltage under the nominal discharge current in, or the maximum clamp voltage of surge protector

in order to protect the protected equipment from overvoltage, the voltage protection level up of SPD should always be less than the impulse withstand voltage uchoc of the protected equipment, and should be greater than the maximum operating voltage usmax of the power grid based on the grounding type, that is, usmax< is required; Up< Uchoc. When the impulse withstand voltage of the equipment cannot be obtained, the equipment of 220/380v three-phase distribution system can be selected according to table 3

5. The maximum discharge current Imax

of class II Classification Test flows through SPD, 8/20μ Peak current of s current wave For class II classification test, imax> In.

installation method and requirements of surge protective device

1) determine the discharge current path

2) mark the wire of additional voltage drop caused by the equipment terminal

3) to avoid unnecessary induction circuit, PE conductor of each equipment should be marked

4) equipotential connection should be established between the equipment and hyc1

5) energy coordination of multi-level hyc1 should be carried out

surge protector is classified according to working principle

(1) switching type: its working principle is that when there is no instantaneous overvoltage, it presents high impedance, but once it responds to lightning instantaneous overvoltage, its impedance will suddenly change to low value, allowing lightning current to pass. When used as such devices, devices include: discharge gap, gas discharge tube, thyristor, etc

(2) voltage limiting type: its working principle is high resistance when there is no instantaneous overvoltage, but its impedance will continue to decrease with the increase of surge current and voltage, and its current voltage characteristics are strongly nonlinear. Devices used as such devices include: zinc oxide, varistor, suppression diode, avalanche diode, etc

(3) shunt type or choke type

shunt type: parallel with the protected equipment, it presents low impedance to lightning pulse and high impedance to normal working frequency

choke type: connected in series with the protected equipment, it presents high impedance to lightning pulse and low impedance to normal working frequency. Devices used as such devices include choke coils, high pass filters, low-pass filters, 1/4 wavelength circuit breakers, etc

summary: the above is the content of the parameters of surge protector introduced by the editor. I hope it can effectively help you. Please pay attention to more information

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