In order to achieve the ideal lightning protection effect, attention should be paid to the reasonable installation of appropriate arresters in appropriate places. The selection of arresters is very important.
Lightning arrester manufacturer
1. The distribution of lightning current between various facilities entering the building is as follows: about 50% of the lightning current leaks to the ground through the external lightning protection device, and 50% of the lightning current will be distributed in the metal materials of the entire system. This *estimation mode is used to estimate the flow capacity of the arrester and the specifications of the metal conductors at the junction of the LPAOA zone, LPZOB zone and LPZ1 zone. The lightning current is a 10/35μs current waveform. In the case of the distribution of lightning current in each metallic material: the amplitude of the lightning current in each part depends on some impedance and inductive impedance of each distribution channel. Distribution channels refer to metal materials that may be distributed to lightning current, such as power lines, signal lines, water pipes, metal structures, etc. Generally speaking, only the respective ground resistance values can be roughly estimated. In case of uncertainty, the connection resistances can be considered to be equal, i.e. the currents distributed equally among the various metal pipes.
2. When the power line is introduced overhead and the power line may be struck by direct lightning, the lightning current entering the protected area in the building depends on the impedance and inductive reactance of the external lead, the arrester discharge branch and the user side line. If the impedances at both ends are the same, the power line will distribute half of the direct lightning current. In this case, a lightning arrester with direct lightning protection function must be used.
3. The subsequent estimation mode is used to estimate the lightning current distribution at the junction of the protected area behind the LPZ1 zone. Since the user-side insulation impedance is much greater than the impedance of the arrester discharge branch and external lead lines, the lightning current entering the subsequent lightning protection area will be reduced and no special estimation is required. The power arrester used in the subsequent lightning protection zone generally requires a current capacity of less than 20ka (8/20μs), and there is no need to use an arrester with a large current capacity.
The subsequent selection of arresters for lightning protection areas should consider the energy distribution and voltage coordination between various levels. When many factors are difficult to determine, using series and parallel power supply lightning protectors is a good choice. The series-parallel arrester is a concept proposed based on the many applications in modern lightning protection and the hierarchical differentiation of protection scopes (compared with traditional parallel arresters). Its essence is an effective combination of multi-stage discharger and filter technology for energy coordination and voltage distribution. Series lightning protection has the following characteristics: wide application. Not only can it be used routinely, but it is also suitable for use in places where protected areas are difficult to distinguish. To help achieve energy matching, inductive decoupling devices provide voltage division and delay under transient overvoltage. In order to slow down the rise rate of transient interference, low residual voltage, long life and fast response time are achieved.
Metal oxide arrester
4. The selection of other parameters of the arrester depends on the level of the lightning protection area where the protected object is located. Its working voltage is based on the rated voltage of all components installed in the lead circuit. Series and parallel lightning arresters should also pay attention to the rated current.
Other factors affecting lightning current distribution in electronic lines: Reducing the ground resistance at the transformer end increases the distribution current in the electronic line. The increase in the length of the power cable will reduce the distribution current in the power line and balance the current distribution among several wires. Too short cable length and too low neutral impedance can cause current imbalance, causing differential mode interference. Parallel supply cables for multiple users will reduce the effective impedance, resulting in increased distribution current. Under mesh power supply conditions, lightning temporary flows mainly flow into power lines, which is why most lightning damage occurs on power lines.
High voltage arrester
