Wireless monitoring system power lightning protection device how to choose?

The load current capacity of the power supply is relatively large. For the sake of safety and ease of use and maintenance, the multi-stage lightning protection of the data communication power supply system is, in principle, the parallel type power supply lightning protection device.

The protection mode of the power surge protector is common mode and differential mode. Common-mode protection refers to phase-to-ground (L-PE), neutral-ground (N-PE) protection; differential-mode protection refers to phase-neutral (LN), phase-phase (LL) Between the protection. For the second, third, and fourth-level protection on the low-voltage side, common-mode protection is usually selected.

The limiting voltage characteristic is the most important characteristic of the lightning protection device. The lower the limiting voltage, the better the protection effect. However, taking into account the fact that China's power grid voltage is generally unstable and has a large range of fluctuations, it is also necessary to select a lightning arrester with a low voltage limit as much as possible. It must also consider that the surge protector has a sufficiently high maximum continuous operating voltage. If the maximum continuous operating voltage is low, it is easy to cause the lightning arrester to self-destruct.

The power system has one, two and three different protection levels on the low-voltage side. It should be selected as the proper lightning protection device with rated discharge current (rated flow capacity) and voltage protection level according to the different protection levels, and the lightning protection device should be ensured. Sufficient lightning shock resistance. In principle, the level of connection between the AC power supply of each level should be more than 25m. Corresponding protection at this level should be done.

The power supply lightning protector for the protection of the low-voltage side of the power supply should be equipped with a lightning arrester that provides a failure warning indication and can provide the function of a telemetry port to facilitate monitoring, management, and future maintenance.

The power surge protector must have a flame-retardant function, and it cannot catch fire when it fails or self-destructs.

The lightning protection device of the power supply must have a failure separation device. When it fails, it can be automatically disconnected from the power supply system without affecting the normal power supply of the communication power supply system.

The connection terminal of the power surge protector must be able to adapt to at least 25mm2 wire connection. When avoiding the lightning protection device, the lead wire should adopt a multi-strand copper conductor with a cross-sectional area of ​​not less than 10mm2, and be as short as possible (the lead length should not exceed 1.0m). When the length of the lead exceeds 1.0m, the cross-sectional area of ​​the lead should be increased; the lead should be compactly arranged side by side or tied.

Grounding of the power surge protector: Connect as close as possible to the busbars of the AC protection ground, or the busbars and the grounding network. Grounding lines should use multiple copper conductors no smaller than 25mm2 to 35mm2.

Which three lines of defense are needed for lightning protection of the power supply system?

For low-voltage power supply systems, surge-induced transient over-voltage (TVS) protection is best done in a graded protection manner. From the entrance of the power supply system (such as the building's total power distribution room), the absorption of surge energy is gradually carried out, and the transient overvoltage is suppressed in stages.

First, it should be a large-capacity power surge protection device connected between each phase of the user's power supply system incoming line and the earth. General requirements This class of power protector has a maximum impact capacity of 100KA/phase or higher, and the required limit voltage should be less than 1500V. We call it CLASS I power surge protector. These power surge protection devices are designed to withstand high currents and high energy surge energy absorption due to lightning and induced lightning strikes. They can divert a large amount of inrush current to the earth. They only provide limited voltage (the maximum voltage appearing on the line when the inrush current flows through the SPD becomes the limiting voltage) for medium-level protection, because the CLASS I class of lightning arrester is mainly absorbed by large surge currents. They alone cannot completely protect the sensitive electrical equipment inside the power supply system.

Second, it should be a power surge protection device installed at a branch distribution equipment that supplies power to important or sensitive electrical equipment. These SPDs provide better absorption of residual surge energy that has passed through the customer's power supply inlet surge arresters, and have excellent suppression of transient overvoltages. The power surge protection device used here requires a maximum impact capacity of 45 kA/phase or more, and the required limit voltage should be less than 1200V. We call it CLASS II power surge protector. The general user power supply system can reach the second level of protection to meet the requirements for the operation of electrical equipment.

Third, a built-in power surge protector can be used in the internal power supply of the power consumer to achieve the goal of completely eliminating the transient transient overvoltage transients. The power surge protection device used here requires a maximum impact capacity of 20 kA/phase or lower, and the required limit voltage should be less than 1000V. For some particularly important or particularly sensitive electronic devices, it is necessary to have third-level protection. At the same time, it can also protect the power equipment from the transient overvoltage generated inside the system.