The commonly used lightning protection devices in electronic information systems mainly include signal lightning protection devices and power lightning protection devices. In special places (such as places with high explosion-proof requirements for petroleum and petrochemical industry), explosion-proof lightning protection devices should also be selected. Today, WPX Communication Technology Co., Ltd. shares the principles for selecting lightning protection devices in electronic information systems:
Firstly,the selection of signal lightning protection devices
By analyzing the main path of lightning surge invading electronic information equipment, it can be seen that the current waveform (10/350) has the greatest impact on the signal line μ s. A lightning surge with a current value of 2kA. Therefore, signal surge protectors for outdoor electronic information equipment and signal lines introduced into buildings should be equipped with the ability to protect against such lightning surges. In addition, it is necessary to set a single stage surge protector or a multi-stage surge protector based on the lightning overvoltage, overcurrent amplitude, and equipment port impulse voltage rating.
According to 5.4.4 of the "Technical Code for Lightning Protection of Building Electronic Information Systems" (GB 50343-2012) and the "Design Code for Lightning Protection of Buildings" (GB 50057-2010), "when metal wires are used for outdoor circuits of electronic systems, surge protectors of Class D1 high-energy test type should be introduced and installed.
The test type of D1 type signal surge protector is high energy, with an open circuit voltage greater than 1kV and a short circuit current of (0.5-2.5) kA [Current waveform: (10/350) μ s] ;
The test type of C1 class signal surge protector is fast rise rate, open circuit voltage (0.5-1) Kv [voltage waveform (1.2/50) μ s] Short circuit current is (0.25-1) kA [Current waveform: (8/20) μ s] ;
3. The test type of C2 type signal surge protector is fast rise rate, open circuit voltage (2-10) Kv [voltage waveform (1.2/50)] μ s] Short circuit current is (1-5) kA [Current waveform: (8/20) μ s] ;
The surge protector for electronic information system signals should not only consider discharge current, but also consider parameters such as signal interface form, rated voltage Un, load current, input power, working frequency, and transmission rate. Of course, there are many types of signal interfaces for electronic information equipment, and the parameters that need to be determined are also different. Overall, a surge protector with low insertion loss, small distributed capacitance, and compatibility with longitudinal balance and near-end crosstalk indicators should be selected. The maximum continuous voltage Uc should be greater than 1.2 times the rated voltage Un, and the voltage protection level Up should be lower than the rated impulse voltage Uw of the protected equipment.
Secondly, the selection of power lightning protection devices
The setting of power surge protectors for electronic information systems refers to Table 5.4.3 of the "Technical Code for Lightning Protection of Building Electronic Information Systems" (GB 50343-2012), and a selection table for surge protectors for power lines at the boundary of lightning protection zones is drawn according to the requirements of the "Design Code for Lightning Protection of Buildings" (GB 50057-2010) that "surge protectors for Class I testing should be installed at the point where power is introduced into the main distribution box".
In specific engineering examples, lightning protectors should be selectively installed according to the actual situation. Taking into account technical standards and engineering implementation plans, low-cost and efficient lightning strikes can be gradually achieved to minimize the probability, thus effectively avoiding economic losses or casualties caused by lightning.