Lightning grounding is divided into two concepts, one is lightning protection, to prevent damage due to lightning strikes; the second is electrostatic grounding, to prevent electrostatic hazards. Then how to do lightning protection grounding system? Next by the decoration network I go together to learn it!
Lightning grounding categories
First, the factory lightning protection is divided into the overall structure of the lightning protection, that is, the main plant lightning protection, the main foundation to hit the grounding pole, grounding strap, forming a grounding network, grounding resistance is less than 10 ohms. And then connected to the main body of the steel or steel structure of the main plant. Cement concrete roof connected to the lightning belt or lightning rod, the ground outside the wall must also be left with a grounding test point, the steel structure should be galvanized flat iron as a direct lead to the roof.
Second, the power supply system grounding is divided into protective grounding and work point grounding, protective grounding is the shell of the charged equipment grounding. Work point grounding refers to the zero line grounding, grounding network practices and lightning grounding the same way, grounding resistance is less than 4 ohms. If the requirements are not met, the grounding pole should be added, the conditions are not good, electrolytes should be added and (or) replacement of soil. Work grounding and protective grounding in the distribution room independent lead, the system can be merged into one. Work, such as ground and zero line separate,
can also be combined into a lead to the electricity system (or equipment). Grounding system shall be repeated grounding. There are also separate ways to separate the TN-C system. Zero ground can not be combined into one.Third, instrumentation grounding system. The system grounding resistance is less than 1 ohm, can not be connected to the lightning ground.
Fourth, anti-static grounding, such as oil pipelines, etc., every (elbow) 35 meters there must be a reliable grounding (can be a system can also be independent), resistance less than 30 ohms. First, according to the national standard "Lightning Protection Design Code for Buildings" GB50057-94 (2000 edition), the external lightning protection devices, including flashover, lead wires and grounding devices.
(1) flashover: according to the characteristics of the building and the level of lightning protection selection of the sky network, lightning belt or lightning rod. Outstanding metal objects outside the scope of protection, such as metal equipment, metal pipes, metal railings, signboards, aviation lights, etc., should be welded with the lightning protection system or card, constituting a unified conductive system. Roof metal decorations such as metal flag poles or meet the code requirements of the wall thickness of the metal roof,
can be used as a flashover.(2) lead: try to use the building reinforced concrete columns within the diagonal reinforcement as a lead, the building's fire ladder, steel columns and other metal components can also be used as a lead, but the lightning protection components should be connected to the electrical path.
(3) grounding device: the design of grounding device, when the foundation using silicate cement and the moisture content of the surrounding soil is not less than 4%, the surface of the foundation information is not waterproof layer, you can use the foundation of the rebar as a grounding device (detailed later instructions), if the foundation is plastic, rubber, linoleum and other waterproof materials wrapped or coated with asphalt waterproofing layer, shall not be utilized as a grounding device, this time in the foundation groove, steel columns and other metal structures can also be used as a lead wire, but the various lightning protection components should be connected to the electrical pathway. Grounding device, this time in the foundation groove around the laying of ring-type grounding device, and with the foundation of the rebar to do a reliable connection.
Internal lightning protection measures and lightning electromagnetic pulse
1 to prevent side-strike lightning
If the protection range of the lightning rod according to the rolling ball method of calculation to determine the
lightning rod may accept the space above the falling lightning, but the side of the incoming lightning can still hit in the lightning range of the curve of the curve in the space under the points, that is, in the lower part of the lightning rod in this space Lightning rod protection rate is no longer 99%, but 50 ~ 80% or lower values, so we can not fully count on the lightning rod, but also to prevent side-strike lightning. For example:If the lightning protection level of the building is the second category, the larger metal objects such as railings, doors and windows on the external wall of 45 meters and above should be connected to the lightning protection device.2 equipotential connection
To do a good job of equipotential connection in the building, equipotential connection is aimed at reducing the need for lightning protection space, a variety of metal parts and a variety of systems between the potential difference. Building lightning protection against direct lightning introduced a strong lightning current through the lead line into the ground, in the vicinity of the space to produce a strong electromagnetic field changes will be induced in the adjacent wires (including power lines and signal lines) on the lightning over-voltage,
Therefore, the building lightning protection system is not only not able to protect the computer, but instead of the introduction of lightning may be. Computer network systems and other equipment such as cumulative circuit chip voltage resistance is very weak, usually below 100 volts, so it is necessary to establish equipotential connection, reduce the potential difference, to ensure that computers, especially computer network systems, such as the safety of the weak power system.The main practice of equipotential:
① with connecting wires or over-voltage protector, will be in need of lightning protection in the space of lightning protection devices, electrical equipment, metal doors and windows, elevator rails, cable trays, all kinds of metal piping, and the metal parts of the system of weak electricity (boxes, shells, racks), etc., welded or connected to each other to form a unified conductive system. Formation of the building's Faraday cage, thus avoiding the existence of potential difference between the grounding line to eliminate the induction overvoltage generated.
② building structure of the whole building beams, slabs, columns, the foundation of the steel is part of the equipotential connection,
should be welded or tied into a unified conductive system, to the integrated **** with grounding device.③ from different directions, places into the building lighting, power and weak power system piping, should be connected to the nearest building grounding connection plate or ring-type master tape (indoor can use the foundation ring beam or bearing beam, or another do a number of equipotential connection master tape, outdoor for the circumferential grounding device).
Weak equipment mask
The mask should be used as a weak system to reduce the interference of the necessary measures, the main purpose of the mask is to prevent lightning EMP, electronic equipment and information equipment systems in more buildings, should be based on the requirements of the lightning protection zoning and equipment, will be built into a full mask (external mask), part of the mask, partial mask, or equipment and piping mask, so that the electromagnetic field layer by layer attenuation of the lightning strike. The electromagnetic field of the lightning strike is attenuated layer by layer. The outside of the building (facade) for full shielding to form a cage-type lightning protection is the most safe and reliable lightning protection design program. Therefore, the location of important microelectronic equipment, such as weak room should be placed in the center of the building, deep or lower floors.
About the surge protector SPD
1 SPD in the power system installation location
(1) in the LPZOA area and LPZOB area and LPZl area interface, in the line from the outdoor lead to the installation of the first level of SPD (generally voltage switching SPD). Suggested installation location: at the main power inlet, such as the low-voltage side of the transformer or in the main distribution cabinet.
(2) When the above installed SPD voltage protection level plus the induced voltage of the leads at both ends of the protection of the subsequent switchboard power supply equipment, should be installed in the level of the switchboard the second level of SPD (generally voltage-limiting type), and its location is generally located in the LPZl zone and the LPZ2 zone at the intersection of the interface. Suggested installation location: installed in the lower end with a large number of weak power, information system equipment or need to limit the transient overvoltage equipment in the distribution box, such as: floor distribution boxes, computer centers, telecommunication rooms, elevator control rooms, cable TV rooms, building automation room, security monitoring centers, fire control centers, industrial automation room, inverter equipment control room, hospital operating rooms, monitoring rooms and places equipped with electronic medical equipment. Inside the distribution box. In addition, all lead to the outdoor lighting or power lines of the distribution box, should be installed SPD, SPD in this role is mainly to prevent high potential tampering.
(3) for the need to limit transient overvoltage to a specific level of equipment (especially information systems equipment), it is appropriate to consider the installation of the equipment in front of the operating overvoltage and anti-induced lightning protection double function of the third level of the SPD (generally for the surge absorber), and its location is generally in the LPZ2 zone and its subsequent lightning protection zone at the interface. Recommended installation location: computer equipment, information equipment, electronic equipment and control equipment in front of or nearest outlet box.
Masking of weak power equipment
Masking should be used as a weak power system to reduce interference with the necessary measures, the main purpose of masking is to prevent lightning EMP, electronic equipment and information equipment systems more buildings, should be based on the requirements of the lightning protection zoning and equipment, the building is made into a full mask (external mask), part of the mask, partial masking or masking of the equipment and piping, so that the electromagnetic field layer by layer attenuation of lightning strikes. The electromagnetic field of the lightning strike is attenuated layer by layer. The outside of the building (facade) for full shielding to form a cage-type lightning protection is the most safe and reliable lightning protection design program. Therefore, the location of important microelectronic equipment, such as weak room should be placed in the center of the building, deep or lower floors.
About the surge protector SPD
1 SPD in the power system installation location
(1) in the LPZOA area and LPZOB area and LPZl area interface, in the line from the outdoor lead to the installation of the first level of SPD (generally voltage switching SPD). Suggested installation location: at the main power inlet, such as the low-voltage side of the transformer or in the main distribution cabinet.
(2) When the above installed SPD voltage protection level plus the induced voltage of the leads at both ends of the protection of the subsequent switchboard power supply equipment, should be installed in the level of the switchboard the second level of SPD (generally voltage-limiting type), and its location is generally located in the LPZl zone and the LPZ2 zone at the intersection of the interface. Suggested installation location: installed in the lower end with a large number of weak power, information system equipment or need to limit the transient overvoltage equipment in the distribution box, such as: floor distribution boxes, computer centers, telecommunication rooms, elevator control rooms, cable TV rooms, building automation room, security monitoring centers, fire control centers, industrial automation room, inverter equipment control room, hospital operating rooms, monitoring rooms and places equipped with electronic medical equipment. Inside the distribution box. In addition, all lead to the outdoor lighting or power lines of the distribution box, should be installed SPD, SPD in this role is mainly to prevent high potential tampering.
(3) for the need to limit transient overvoltage to a specific level of equipment (especially information systems equipment), it is appropriate to consider the installation of the equipment in front of the operating overvoltage and anti-induced lightning protection double function of the third level of the SPD (generally for the surge absorber), and its location is generally in the LPZ2 zone and its subsequent lightning protection zone at the interface. Suggested installation location: In front of computer equipment, information equipment, electronic equipment and control equipment or in the nearest outlet box.