Lightning protection grounding working principle - Solutions - Huaqiang Electronic Network

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First, type 1, lightning protection grounding:

Grounding for the purpose of quickly introducing lightning into the earth to prevent lightning.

When the lightning protection device uses a total grounding grid with the working ground of the telegraph equipment, the grounding resistance should meet the minimum requirements.

2, AC work ground

Connect a point in the power system directly or through special equipment to the earth.

The working ground mainly refers to the neutral point of the transformer or the neutral line (N line) grounding. The N wire must be insulated with a copper core. There are auxiliary equipotential terminals in the power distribution, and the equipotential terminals are generally in the cabinet. It must be noted that the terminal should not be exposed; it should not be mixed with other grounding systems, such as DC grounding, shielded grounding, anti-static grounding, etc.;

3, safety protection grounding

Safety protection grounding is a good metal connection between the metal part of the electrical equipment that is not charged and the grounding body. The electrical equipment in the building and some metal components in the vicinity of the equipment are connected by PE wires, but it is strictly forbidden to connect the PE wires to the N wires.

4, DC grounding

In order to make the accuracy and stability of each electronic device, in addition to a stable power supply, a stable reference potential must be provided. An insulated copper core wire with a larger cross-sectional area can be used as the lead wire, one end is directly connected to the reference potential, and the other end is used for DC grounding of the electronic device.

5, shield grounding and anti-static grounding

The grounding to prevent the static electricity generated by the dry environment of the computer room in the intelligent building from interfering with the electronic equipment is called anti-static grounding. In order to prevent external electromagnetic field interference, the grounding of the outer casing of the electronic device and the shielded wire inside or outside the device or the metal pipe worn by the device is called shield grounding.

6, power grounding system

In the electronic equipment, in order to prevent interference voltages of various frequencies from intruding through the AC/DC power line, affecting the operation of the low-level signal, an AC/DC filter is installed, and the grounding of the filter is grounded.

Second, the requirements

1. The independent lightning protection grounding resistance should be less than or equal to 10 ohms;

2. The independent safety protection grounding resistance should be less than or equal to 4 ohms;

3. The independent AC working grounding resistance should be less than or equal to 4 ohms;

4. The independent DC working grounding resistance should be less than or equal to 4 ohms;

5, anti-static grounding resistance is generally required to be less than or equal to 100 ohms.

Third, the design of the intelligent building grounding system

1. The grounding body of the lightning protection grounding system generally uses the intelligent building pile foundation. The upper end of the pile foundation is connected by the reinforcing bar of the bearing platform; the lightning protection grounding system leads the lowering line generally using the steel bar inside the column; the lightning protection lightning receptor is combined with the lightning rod and the lightning rod. The way, the intelligent building is 30 meters or more, and each of the three layers is connected with the column ribs to form a voltage equalizing ring; the grounding resistance is required to be less than 1 ohm.

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

3. Protect the grounding system, set the total equipotential copper bar at the appropriate position in the power distribution station, and lead the PE strong electric trunk from the equipotential copper bar. Each layer is provided with an auxiliary equipotential copper bar at the appropriate position, and is guided from the auxiliary equipotential copper. Ground wire to equipment casing and metal pipes.

4. DC grounding system. The reference potential of the DC grounding system is drawn from the total equipotential copper bar. It is made of 35 copper core insulated wire and is directly connected to the equipment for direct current grounding.

5. Power grounding. The insulated copper core wire with the cross section of the phase conductor is taken from the floor distribution box together with the phase conductor, which is the neutral line N in the TN-S system.

6. Shield grounding and anti-static grounding. The PE weak electric main line is drawn from the total equipotential copper bus. Each layer is provided with a weak electric auxiliary equipotential copper bar at the appropriate position. The outer casing of the electronic equipment, the shielding of the metal pipeline and the anti-static grounding are all caused. Weak electric auxiliary equipotential copper row

However, because each industry and even each unit has different economic conditions and different levels of security for monitoring requirements, the integration of lightning protection equipment varies from case to case. Generally, the following lightning protection factors should be considered:

1. The transmission line of the lightning protection monitoring system of the transmission line is mainly the power line for transmitting the signal line. The control signal transmission line and the alarm signal transmission line generally use a copper core shielding cord, and are erected (or laid) between the front end and the terminal. From the point of view of lightning protection, the direct burial method has the best protection effect, and the overhead line is most vulnerable to lightning strikes, and the damage is large and the range is wide. To avoid damage to the equipment at the end and end, the overhead line should be made on each pole. The grounding treatment, the hanging wire of the overhead cable and the metal pipe in the line should be grounded. The signal source and power supply at the input of the intermediate amplifier should be respectively connected to the appropriate arrester.

2. The lightning protection front-end equipment of the front-end equipment has two cases of outdoor and indoor installation. The equipment installed indoors generally does not suffer from direct lightning strikes, but it is necessary to consider the protection against lightning overvoltages on the equipment, while the outdoor equipment needs to be considered at the same time. To prevent direct lightning strikes, such as the front-end equipment camera should be placed within the effective protection range of the lightning receptor (lightning rod or other lightning conductor). To prevent electromagnetic induction, the power and signal wires that lead the camera along the rod should be shielded through the metal tube. The signal line has a long transmission distance and low withstand voltage. It is easy to induce lightning current and damage the equipment. In order to conduct lightning current from the signal transmission line to the ground, the signal overvoltage protector must respond quickly. The signal must be considered when designing the signal transmission line protection. Parameters such as transmission rate, signal level, startup voltage, and lightning flux.

3. Lightning protection of terminal equipment In the monitoring system, the lightning protection of the monitoring room is the most important, and should be carried out from direct lightning protection, lightning wave intrusion, equipotential bonding and surge protection. Since 80% of lightning strikes are intruded from the power line, in order to ensure the safety of the equipment, three-level lightning protection should be set on the general power supply. Before the video transmission line, signal control line, and intrusion alarm signal line enter the front-end equipment or before entering the center console, the corresponding lightning protection device should be installed.

Strictly speaking, the monitoring system needs to install lightning protection equipment, whether it is indoor monitoring or outdoor monitoring.