Lightning protection grounding working principle - Solutions - Huaqiang Electronic Network

First, type 1: Lightning protection grounding

Lightning protection grounding is designed to quickly channel lightning into the earth, preventing damage caused by lightning strikes. When a lightning protection system shares a grounding grid with the working ground of telecommunication equipment, the grounding resistance must meet minimum standards for safety and efficiency.

2, AC Working Ground

AC working ground involves connecting a point in the power system directly or through specific equipment to the earth. This primarily refers to the transformer’s neutral point or the N line grounding. The N wire should be insulated with copper core wiring. Power distribution systems often include auxiliary equipotential terminals located within cabinets. These terminals must not be exposed and should not be mixed with other grounding systems such as DC grounding, shield grounding, or anti-static grounding.

3, Safety Protection Grounding

Safety protection grounding ensures a good metal connection between non-charged parts of electrical equipment and the grounding body. In buildings, PE wires are used to connect metal components near the equipment, but it is strictly prohibited to connect PE wires to N wires.

4, DC Grounding

To ensure the accuracy and stability of electronic devices, a stable reference potential is essential. A thick insulated copper wire can be used as a lead wire, one end connected to the reference potential, and the other end grounded for DC grounding of the device.

5, Shield Grounding and Anti-Static Grounding

Anti-static grounding prevents static electricity generated in dry environments from interfering with electronic equipment. Shield grounding protects against electromagnetic interference by grounding the outer casing of devices, shielding cables, or metal pipes that encase them.

6, Power Grounding System

In electronic equipment, to prevent interference voltages from entering through power lines, an AC/DC filter is installed, and the filter is grounded to ensure stable operation of low-level signals.

Second, Requirements

1. Independent lightning protection grounding resistance should be ≤10 ohms.

2. Independent safety protection grounding resistance should be ≤4 ohms.

3. Independent AC working grounding resistance should be ≤4 ohms.

4. Independent DC working grounding resistance should be ≤4 ohms.

5. Anti-static grounding resistance is generally required to be ≤100 ohms.

Third, Design of Intelligent Building Grounding System

1. The lightning protection grounding system typically uses the building's pile foundation. The upper part is connected via reinforcing bars, and the down conductor is usually made of steel bars inside the column. Lightning rods and receptors are combined, forming a voltage equalizing ring every three floors if the building is over 30 meters high. The grounding resistance must be less than 1 ohm.

2. The working grounding system uses the N line in the power system.

3. For protection grounding, a main equipotential copper bar is placed in the power distribution room, and a PE trunk line is led from it. Each floor has an auxiliary equipotential copper bar, connected to equipment casings and metal pipes.

4. The DC grounding system draws its reference potential from the main equipotential copper bar. A 35 mm² insulated copper wire is used, directly connected to the equipment for DC grounding.

5. Power grounding involves using a copper core wire with the same cross-section as the phase conductor, laid together with the phase wire in the TN-S system as the N line.

6. Shield and anti-static grounding: The PE weak electric main line is drawn from the main equipotential copper bus. Each floor has a weak electric auxiliary equipotential copper bar, used for grounding the equipment casing, shielding, and anti-static purposes.

However, due to varying economic conditions and security requirements across industries, the integration of lightning protection systems differs. Key factors to consider include:

1. Transmission lines for monitoring systems mainly use signal lines. Control and alarm lines typically use copper-shielded cables, installed between the front-end and terminal. Direct burial offers the best protection, while overhead lines are most vulnerable to lightning strikes. To reduce damage, overhead lines should be grounded at each pole, and cable hanging wires and metal pipes should also be grounded. Surge arresters should be installed at the input of intermediate amplifiers.

2. Front-end equipment, whether installed indoors or outdoors, requires different considerations. Indoor equipment is less likely to be struck directly but still needs protection against overvoltage. Outdoor equipment must be protected from both direct lightning and electromagnetic induction. Cameras should be within the protection range of lightning rods, and signal and power lines should be shielded through metal conduits. Signal lines, being long and low-voltage, are prone to induced lightning current, so quick-acting signal overvoltage protectors are essential.

3. Terminal equipment protection is critical in monitoring systems. Since 80% of lightning strikes come from power lines, three-level surge protection is recommended on general power supplies. Surge protection devices should be installed before video lines, control lines, and alarm signals enter the front-end equipment or the central console.

In conclusion, proper lightning protection is essential for both indoor and outdoor monitoring systems. It involves comprehensive strategies including direct lightning protection, wave intrusion prevention, equipotential bonding, and surge suppression to ensure system reliability and safety.