lightning protective devices for Electrica power systems

The lightning protection of the power system includes the protection of direct lightning strikes and the protection of induction lightning. When selecting a surge protector for internal lightning protection, the following principles should be referred to:

Selection principle

1. Thunderstorm time in the area:

Less minefields are areas where the average annual number of thunderstorm days does not exceed 25 days;

Medium minefields are areas with an annual average number of thunderstorm days within 25 to 40 days;

A minefield is an area with an annual average number of thunderstorm days within 40 to 90 days;

Strong minefields are areas with an annual average number of thunderstorm days of more than 90 days

2. Power supply environment

Voltage fluctuations: involving cities, suburbs, mountains and remote areas (Uc/Vp)

3. Equipment pressure capacity:

Impulse overvoltage rating of various equipment in distribution lines

4. SPD connection

5. Graded protection

We design the lightning protection of building power and electrical system according to the four-level protection requirements:

(1) The first-level lightning protection of the power supply: M100B+C/4 (Techwin) AC power lightning surge protection device is used, which is installed in the main power distribution cabinet of the building.

(2) The second-level lightning protection of the power supply: M60B4 (Techwin) AC power lightning surge protector is used, which is installed at the distribution cabinet on each floor.

(3) The third-level lightning protection of the power supply:  M40B4 (Techwin) AC power surge protection device is used, which is installed in the indoor power distribution cabinets such as computer rooms, offices, and homes.

(4) The fourth-level lightning protection of the power supply: PDU10-220-6 (Techwin) power supply lightning protection PDU is used, which is installed in front of the terminal equipment such as the wall power outlet or the cabinet.

6. Grounding system

Whether it is to prevent direct lightning strikes or induction lightning, whether to use lightning rods or special lightning protection devices, there must be a good grounding device. Therefore, grounding technology is an important part of lightning protection. The grounding wire of power distribution should fully consider the requirements of lightning protection, anti-static, anti-electromagnetic and other requirements, and the shell of each equipment should be reliably grounded. At the same time, the safety requirements for personal safety and electrical equipment should be met, and the following principles must be followed:

1) AC work grounding, the grounding resistance should be less than 4Ω;

2) For safety protection grounding, the grounding resistance should be less than 4Ω;

3) DC work is grounded, and the grounding resistance should be determined according to the specific requirements of the system;

4) Lightning protection grounding, the grounding resistance should be less than 4Ω.

Lightning protection solution