Lightning protection grounding working principle - Solutions - Huaqiang Electronic Network

Lightning protection and grounding systems are essential components in modern electronic and communication infrastructure, especially in intelligent buildings and monitoring systems. These systems help ensure the safety of equipment, reduce the risk of damage from electrical surges, and maintain stable operation under various environmental conditions.

1. Lightning Protection Grounding

Lightning protection grounding is designed to safely direct lightning currents into the earth, preventing potential damage to structures and equipment. When combined with the working ground of telecommunication devices, the grounding resistance must meet specific minimum standards to ensure effective dissipation of energy. This type of grounding is crucial for protecting sensitive equipment from high-voltage surges caused by lightning strikes.

2. AC Working Ground

AC working grounding involves connecting a point in the power system directly or through specialized equipment to the earth. Typically, this refers to the neutral point of a transformer or the neutral line (N line). The N wire should be insulated with copper core cables to prevent electrical hazards. Additional equipotential terminals are often installed within power distribution units to maintain uniform voltage levels across the system. It's important that these terminals remain isolated from other grounding systems like DC grounding, shielded grounding, or static grounding to avoid interference.

3. Safety Protection Grounding

Safety protection grounding ensures that non-current-carrying metal parts of electrical equipment are properly connected to a grounding body. This is usually done using PE wires, which link building structures and nearby metal components to the ground. However, it's strictly prohibited to connect PE wires to N wires, as this could create dangerous voltage differences and pose a risk to personnel and equipment.

4. DC Grounding

DC grounding is necessary to provide a stable reference potential for electronic devices, ensuring their accuracy and reliability. A thick insulated copper cable is typically used as the lead wire, with one end connected to a reference potential point and the other to the device’s DC grounding point. This helps maintain consistent performance in low-noise environments where stability is critical.

5. Shield Grounding and Anti-Static Grounding

Shield grounding protects against electromagnetic interference by grounding the outer casing of electronic devices or shielding cables. Anti-static grounding, on the other hand, prevents static electricity buildup in dry environments, such as those found in computer rooms. Both types of grounding are essential in intelligent buildings to safeguard sensitive equipment from external disturbances.

6. Power Grounding System

A power grounding system is used to prevent interference voltages from entering the system through AC/DC power lines. Filters are often installed to isolate these signals, and the grounding of the filters is an integral part of this process. Proper grounding helps maintain signal integrity and reduces the risk of data corruption or equipment failure.

Grounding Requirements

- Independent lightning protection grounding resistance: ≤ 10 ohms - Independent safety protection grounding resistance: ≤ 4 ohms - Independent AC working grounding resistance: ≤ 4 ohms - Independent DC working grounding resistance: ≤ 4 ohms - Anti-static grounding resistance: ≤ 100 ohms

Design of Intelligent Building Grounding Systems

1. For lightning protection, the grounding body is usually integrated with the building's pile foundation. Reinforcing bars connect the upper ends of the piles, while steel bars inside columns serve as down conductors. Lightning rods and receptors are strategically placed to form a voltage equalizing ring at regular intervals, especially in buildings over 30 meters tall. The grounding resistance must be less than 1 ohm for optimal performance.

2. The working grounding system uses the N line in the power network. This line is critical for maintaining balanced voltage levels and ensuring safe operation of electrical devices.

3. Safety grounding involves installing a main equipotential copper bar in the power distribution room. From there, PE trunk lines are routed to each floor, where auxiliary equipotential bars are also placed. These bars connect to equipment casings and metal pipes, helping to equalize potentials and reduce the risk of electrical shocks.

4. DC grounding is derived from the main equipotential bar using 35 mm² copper-insulated cables. These cables are directly connected to the device’s grounding point to ensure a stable reference potential.

5. In the power grounding system, the neutral line (N) is used alongside phase conductors. This setup is common in TN-S systems and helps maintain clean power delivery to sensitive equipment.

6. Shield and anti-static grounding use weak electric main lines drawn from the equipotential bus. Each floor has its own auxiliary equipotential copper bar, which connects to equipment casings, shielding, and static grounding points to minimize interference and protect against static discharge.

While standard practices exist, the implementation of lightning protection systems can vary depending on industry needs, budget constraints, and security requirements. Key considerations include:

1. Transmission Lines

Signal transmission lines, including control and alarm lines, are typically made of copper-core shielded cables. Direct burial offers the best protection against lightning, while overhead lines are more vulnerable. To reduce risks, overhead lines should be grounded at each pole, and signal sources and power supplies should be protected with surge arresters.

2. Front-End Equipment

Front-end equipment, whether installed indoors or outdoors, requires different protection strategies. Indoor equipment is not directly exposed to lightning but still needs protection from overvoltage. Outdoor equipment, however, must be shielded and positioned within the coverage of lightning rods to prevent direct strikes. Signal cables should be enclosed in metal conduits to reduce electromagnetic induction and protect against induced lightning currents.

3. Terminal Equipment

The monitoring room is the most critical area for lightning protection. It should include direct lightning protection, wave intrusion prevention, equipotential bonding, and surge protection. Since most lightning strikes enter via power lines, a three-level lightning protection system is recommended for general power supplies. Surge protectors should be installed before video transmission lines, control signals, and alarm lines enter the equipment or central console.

In conclusion, proper grounding and lightning protection are essential for the reliable and safe operation of any modern electronic or monitoring system. Whether indoor or outdoor, no system is immune to lightning threats, making the installation of appropriate protective measures a necessity.