Surge protector parameters
1, the maximum continuous operating voltage Uc
In 220/380V three-phase system selection SPD, the maximum continuous operating voltage Uc should be based on the different grounding system form to choose.
(1) when the power supply using TN system, from the main distribution panel (box) in the building to start leading out of the distribution lines and branch lines must be used TN-S system;
(2) in the following places should be based on the specific circumstances of the zinc oxide varistor SPDs to increase the value of the above specified Uc;
①Power supply voltage deviation of more than 10% of the premises;
②Harmonics of the SPD should be selected according to the different forms of grounding system. p>
②Harmonics increase the voltage amplitude of the place.
2, the inrush current Iimp
Provisions including amplitude current Ipeak and charge Q.
3, nominal discharge current In
Flowing through the SPD, the peak current of the 8/20 μs current wave, used for SPD to do Ⅱ classified test, but also used for SPD to do the Ⅰ and Ⅱ classified test preprocessing. Classification test of Ⅰ In should not be less than 15kA, Ⅱ classification test In should not be less than 5kA.
4, the voltage protection level Up
That is, the residual voltage under the nominal discharge current In, or the maximum clamping voltage of the surge protector.
In order to protect the protected equipment from overvoltage, the voltage protection level Up of the SPD should always be less than the impact withstand voltage Uchoc of the protected equipment, and should be greater than the maximum operating voltage of the grid according to the type of grounding, that is, the maximum operating voltage of the grid, that is, the requirement of Usmax
5, the maximum discharge current of the II classification test Imax
Flowing through the SPD, 8/20μs current wave peak current. For class II classification test, Imax>In.
Surge protector installation and requirements
1) Determine the path of the discharge current
2) Mark the conductor of the additional voltage drop caused at the terminals of the equipment
3) In order to avoid unnecessary inductive loops, should be marked for each piece of equipment PE conductor
4) Equalization of the equipment with the HYC1 between the establishment of equipotential connection
5) to carry out multi-level HYC1 energy coordination
Surge protector classified according to the principle of operation
(1) switching type: its operating principle is that when there is no transient over-voltage is presented as a high impedance, but once responded to the lightning transient over-voltage, its impedance is suddenly changed to a low value to allow the passage of lightning current. Used as such devices when the device has: discharge gap, gas discharge tube, gate current transistor.
(2) voltage-limiting type: its working principle is that when there is no transient overvoltage for high interference, but with the increase in surge current and voltage impedance will continue to decrease, its current-voltage characteristics of a strong nonlinear. Devices used as such devices are: zinc oxide, varistors, suppression diodes, avalanche diodes and so on.
(3) shunt type or choke type
Shunt type: parallel connection with the protected equipment, the lightning pulse presents a low impedance, while the normal operating frequency presents a high impedance.
Choke type: connected in series with the protected equipment, it presents a high impedance to the lightning pulse and a low impedance to the normal operating frequency. Devices used for this type of device are: choke coils, high-pass filters, low-pass filters, 1/4 wavelength short circuit breakers and so on.