Lightning arrester manufacturers tell you how to choose a lightning arrester! According to the lightning protection device, in order to achieve the lightning protection effect, we should focus on "reasonably installing appropriate lightning protection devices in appropriate areas", and the selection is very important.
1. The distribution of lightning current between different equipment entering the building is as follows: About 50% of the lightning is discharged to the ground through external lightning protection equipment, and another 50% of the lightning current is distributed in the metal materials of the entire system. This estimation table is used as the standard for the current flow capacity of the lightning arrester and the metal conductor of the equipotential connection at the junction of the LPAOA zone, LPZOB zone, LPZOB zone and LPZ1 zone. Lightning current is a 10/35 microsecond current waveform. Distribution of lightning current in each section: The amplitude of lightning current in each section depends on the impedance and inductive reactance of each distribution channel, metal materials that can distribute lightning, such as wires, signal lines, water pipes, metal brackets, etc., and others that can be grounded. Under normal circumstances, it can be estimated based only on their respective ground resistances. If you can't tell, you can make the on-resistances equal, that is, distribute the current equally to each metal line.
High voltage arrester
2. When power lines are introduced from the air and can be struck by lightning, the lightning current in the maintenance area of the building depends on the impedance and inductive reactance of the external leads, the discharge branch of the lightning arrester, and the user-side lines. For example, if both ends have a common impedance, then the power line is assigned half of the direct lightning current. Therefore, a lightning protection device with resistance to direct lightning strikes should be selected.
3. Follow-up assessment will be used to evaluate the lightning distribution at the junction of future protected areas in LPZ1. Since the user-side insulation impedance is much greater than the impedance between the discharge branch of the lightning arrester and the external lead, the lightning current entering the subsequent lightning protection zone will be reduced, and no special calculation is necessary in terms of value. It is generally required that the flow rate of the power supply lightning arrester shall not exceed 20kA (8/20μs), and it is not necessary to choose a lightning arrester with a large flow capacity.
The selection of lightning protection devices should consider the energy distribution and voltage coordination between various levels of the lightning protection device. When many factors are difficult to determine, choosing a series-parallel power supply lightning protector is a good choice. The series-parallel type is proposed based on the characteristics of many modern lightning protection applications and the hierarchical maintenance of scale (compared with traditional parallel lightning protectors). Its essence is a useful link between energy cooperation and filtering techniques for voltage distribution in multi-stage dischargers. Series and parallel lightning arresters have the following characteristics: wide range of uses. Not only can it be used regularly, but it is also suitable for other places in the maintenance area. When transient overvoltage occurs, the voltage division and delay effects of the decoupling device are induced to assist in the completion of energy coordination. Slows the rise of transient disturbances to achieve low residual pressure, long life and fast response time.
Metal oxide arrester
4. The selection of other parameters of the lightning arrester depends on the lightning protection zone level of each maintenance point, and the operating voltage of the lightning arrester is determined based on the additional voltage installed on all components in the lead circuit. Series and parallel lightning protection devices should also pay attention to additional current.
5. Other factors that affect the distribution of lightning current in wires: The reduction of ground resistance at the transformer end will lead to an increase in the distribution current of electronic lines. Increasing the length of the supply cable reduces the horizontal distribution of current across power lines while reducing the number of conductors needed to equalize current distribution. If the cable length is too small and the impedance of the neutral line is too small, it will cause current imbalance and result in differential frequency interference. When power supply and distribution cables are connected to multiple users in parallel, the effective impedance will decrease, causing the distribution current to increase. When the mesh power supply is connected, lightning temporary currents mainly flow into the power lines, which is the main reason why lightning damage occurs on the power lines.
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