Illumination of the Working Principles of Lightning Protection

To avoid the damage that lightning might cause, the current needs to be rapidly directed to the ground. When the lightning protection device shares a common grounding grid with equipment, the grounding resistance must meet the minimum required values.

 

1. Types

 

â‘ Lightning Protection and Grounding: 

 

To avoid the damage that lightning might cause, the current needs to be rapidly directed to the ground. When the aluminum coil suppliers shares a common grounding grid with equipment, the grounding resistance must meet the minimum required values.

 

â‘¡AC Working Grounding:

 

This involves directly or through special equipment connecting a point in the power system to the earth with a metal connection. Working grounding mainly refers to the grounding of the transformer neutral point or neutral wire (N wire). The N wire must use copper-core insulated wire. In distribution, there are auxiliary equipotential terminals, which are generally located inside cabinets. It must be noted that these terminals cannot be exposed; they must not be mixed with other grounding systems, such as DC grounding, shielding grounding, or anti-static grounding; nor can they be connected to the PE line.

 

â‘¢Safety Protection Grounding:

 

Safety protection grounding involves making a good metal connection between the non-energized metal of electrical equipment and the grounding body. This means connecting the electrical devices within a building and some metal components nearby through a PE line, but it is strictly prohibited to connect the PE line to the N wire.

â‘£DC Grounding:

 

To ensure the accuracy and stability of electronic equipment, in addition to requiring a stable power supply, a stable reference potential is also necessary. A large cross-sectional area of insulated copper-core wire can be used as the lead, with one end directly connected to the reference potential and the other end used for DC grounding of electronic equipment.

 

⑤Shielding Grounding and Anti-Static Grounding:

 

Anti-static grounding is performed to prevent static electricity generated in the dry environment of computer rooms in intelligent buildings from interfering with electronic equipment. Shielding grounding is performed to prevent interference from external electromagnetic fields by grounding the electronic equipment enclosures and the shielding cable inside and outside the equipment or metal conduits,and this is called : Shielding Grounding.

 

â‘¥Power Grounding System

 

In electronic equipment, power grounding is used to prevent interference voltages of various frequencies from entering through AC and DC power lines, affecting the opponent which need low Signal Level environments so that electronic equipment is equipped with AC/DC filters. The grounding of these filters is referred to as power grounding.

 

 

2：Requirements

 

Independent lightning protection grounding resistance should be less than or equal to 10 ohms.

â‘ Independent Lightning Protection grounding systems’ resistance should be less than or equal to 10Ω

â‘¡The independent safety protection grounding systems’ resistance should be less than or equal to 4 Ω

â‘¢Independent DC working grounding systems’ resistance should be less than or equal to 4 Ω.

â‘£Anti-static grounding systems’ resistance generally should be less than or equal to 100 Ω.

 

3：Design of Grounding Systems for Intelligent Buildings

 

①：The grounding body of the lightning protection grounding system generally uses the pile foundation of the intelligent building.The upper ends of the pile foundation rebar connected through the rebar of bearing structure.The lightning protection grounding system down-conductor generally would make use of the rebar inside the columns. Lightning arresters use a combination of lightning belts and rods.

For buildings 30 meters or taller, every three floors use the rebar in the ring beams to connect with the column reinforcement to form a pressure-equalizing ring. The grounding resistance is required less than 1 Ω.

②：The working grounding system line is the N line in the power system.

③：The protection grounding system, Setting a main Equipotential copper bar in a suitable location within the substation or distribution substation. PE strong power conductors are drawn from the equipotential copper , and auxiliary equipotential copper are set on each floor in suitable positions. Grounding wires from the auxiliary equipotential copper are connected to equipment enclosures and metal pipelines.

â‘£The DC grounding system uses the reference potential drawn from the main equipotential copper busbar, with 35 mm² copper-core insulated wire protected by steel conduits directly leading to the equipment area for DC grounding.

⑤Power grounding uses insulated copper-core wire with the same cross-section as the phase conductor, drawn from the floor distribution box along with the phase conductor. In the TN-S system, this is the neutral line (N).

â‘¥Shielding and anti-static grounding are achieved by drawing PE low-voltage lines from the main equipotential copper. Auxiliary low-voltage equipotential copper are set on each floor in suitable positions. The shielding of Electronic devices and metal pipelines as well as the anti-static grounding are connected to these low-voltage auxiliary equipotential copper.