What is Lightning? How does it occur?
Because the weather is insulating, the so-called ‘cumulus-nimbus’ lightning clouds charge as they move and generate high-voltage lightning clouds. During the loading, the ground surface is loaded with positive charges along the cloud and rarely there can be reverse loading (10%). A conductive channel is formed and discharge begins from the cloud to the soil or from the soil to the cloud.
The discharge between the clouds is called lightning and the discharge between the lightning and the cloud ground.
If we examine the formation of the lightning cloud in three stages;
Youth: Air flow increases from bottom to top and from the edge to the center, time is 10-15 minutes
Maturity: Approximately zero temperature, reduced buoyancy causes heavy rain. During this time, cold winds are seen from top to bottom. When they reach the ground, they cause a short, severe storm. This step is between 15-30 minutes.
Aging: Air currents end and last about 30 minutes.
In order for a lightning discharge to occur, the electric field strength must reach 2500kV / m. Cloud-cloud or cloud-earth discharge occurs when the electric field strength in the cloud increases sufficiently.
a) Lightning ascending: It is the pre-discharges starting from the positively charged pointy regions, the negatively charged region of the cloud. It starts at the peaks of high structures (GSM towers) or high mountainous areas on smooth terrain. At this time currents ranging from 1 to 10 kA are seen. current value is 10kA.
b) Lightning descending: When the energy in the lower part of the lightning cloud is sufficient, an electron beam moves towards the ground. The first beam traverses a distance of 10-15 meters at a speed of 50,000-60,000 km / sec. 30 to 100 microns of second, third, fourth electron beams move this distance 30 to 50 meters further than the previous one. Thus, each discharge allows the tip of the lightning to approach the earth. . As the pre-discharges approach the ground surface, the electric field is punctured by the insulator of the air, whereby a discharge moves upwards from a pointed point on the ground surface to the pre-discharges to form a conductive channel in the air and from this channel the high voltage (@ 100 million volts) flows to the ground with a current strength of 200,000 Amper. .
Effects of Lightning
a) Electrodynamic Effect: If a part of the lightning flow path is within the magnetic field of another part, great forces arise. This effect results in crushing of thin antenna pipes, short-circuit of parallel conductors, and damage of conductor clamps.
b) Pressure and sound effect: The pressure caused by the forces in the lightning channel expands in the form of explosion with the extinction of this current creates thunder. It is that it brings.
c) Electrochemical effect: At large current intensities, metals such as iron, zinc and lead are released by electrolyte disintegration.
d) Heat Effect: The temperature increases in the conductors where the lightning discharge current passes, but since the time is very short, there is no large heat increase in the conductors.
e) Light effect: Very bright light is formed around the conductive channel formed during lightning discharge. It causes glare or temporary visual disturbance in the near ones.
Lightning Protection Methods
Here we will talk about the methods used today to protect buildings from lightning.
1) Passive catch tips: It is the oldest of the lightning protection methods that do not have the lightning pull feature and the sharp pointers are used. The first application was made by Franklin in the 1760s. It is based on the connection of pointed rods to the earth by means of conductor by placing them on the structures to be protected. At that time, the length of the rod was calculated as the half diameter of the protection diameter, while today the length of the bar is considered as protection diameter. This method has been further developed and the method called FARADAY CAGE has emerged.
Faraday Cage cage the more frequent the eye gaps, the better results are obtained, this means an increase in costs.
Oxidation at the joint points of the horizontal and vertical laying conductors is an obstacle in providing the desired protection.
Maintenance is difficult, conductors and their current status are quite difficult to detect.
Implementing this method later in completed structures will increase costs and it is almost impossible to cage the lower part of the building.
It is almost impossible to detect the damage of the system as a result of tectonic movements in structures in earthquake-risk areas.
The most tragic example of a poorly established cage system is the Mont Black Observatory.
In this case, the horizontal surface of the observatory sitting on the ground should also be caged, but this was not done and the conductivity of the soil was trusted for the closure of the cage there. When the conductivity of the soil was insufficient, there were accidents at the observatory due to lightning strikes.
Active catches (lightning rods)
Active trapping leads to an ionizing path to lightning clouds or by sending ions, disrupting the insulation of air for the discharge of lightning, causing a conductive channel to be opened in the air.
Active Lightning Rods (ESE-TYPE)
The latest point in lightning protection is the electrostatic active lightning rods. Lightning discharges are realized at the highest and pointed places of the lightning rods. capacitor system.
ESE (Early Streamer Emission), called Early Flow Warning Lightning Rods, has also entered the standards in France and USA.
The principle of operation is very simple. It works only in cases where the risk of lightning may occur in the air, it does not cause unnecessary discharges at other times. Using this type of lightning rods, it is a system that will cause the same effect instead of planting catch bars at the height of meters.
Airborne electrostatic charge generation in Turkey has made active SAT-ESE lightning rod for national and international quality and testing necessary documents and certificates. In our country, these lightning rods are manufactured with stainless steel body so that they are not affected by meteorological conditions and impacts and are resistant to the effects of weather conditions and lightning discharges in terms of insulation and sealing. They do not require maintenance or arc. It is easily possible to test that they are working with the test device at the sales points.
Technical Specification for Lightning Protection and Grounding
1) Customer Address
2) Address of the Construction Project
3) Available Documents
4) General Information
5) Concept Definition of Lightning Protection System
6) Lightning Impulse and Surge Protection (Surge Arrester) Measures
7) Grounding System
8) Lightning Current Parameters
1. Customer Address
2. Address of project
3. Available Documents
Drawings DWG / PDF
4. General Information
Lightning, a natural phenomenon, cannot be controlled. It is therefore necessary to take measures to protect structures against:
– Threats to human life
– Destruction of security systems (eg fire alarm systems, burglar alarm systems, etc.)
– Accidental activation of fire extinguishing systems
– Damage to electronic devices
– Destruction or dysfunction of measuring and control systems
– Electronically stored change or loss The contents of parts 1 to 4 of IEC 62305 standard are general concepts.
4. 4.1 Lightning Protection System
Damage to electronic devices
The lightning protection system is a whole system and is applied to reduce the physical damage caused by direct lightning strikes in the building. It has an external lightning protection system and an internal lightning protection system.
External lightning protection system:
a) Directs the lightning strokes to the capture terminals.
b) Ensures the safe transmission of lightning current to earth by means of down-conductors.
c) Provides the distribution of lightning current to the ground by means of grounding system.
Fig. 4.1 – Lightning protection system
The internal lightning protection system shall be constructed by means of the equipotential bonding between the electrically conductive parts and the external lightning protection parts or by the separation distance method (safe electrical separation method).
4.2 Separation distance
Electrical isolation between external lightning protection and conductors (means the isolation between the catches, down conductors and parts of the natural lightning protection system and the metal and electrical installation to be protected inside the building) is provided by the separation distance “s ((fig. 4.2).
Fig. 4.2 – Separation distance
Calculation formula for separation distance: s = ki * kc / km * l [m]
Function of two selected lightning protection classes (induction factor; fig. 4.3) function of geometric arrangement kc (current division coefficient) material function of the proximity point (material multiplier; fig. 4.3) l Separation distance from the next equipotential point of the catch end system or the downstream conductor system distance to the point of problem
fig. 4.3 – ki ve km katsayıları
5. Conceptual description of external lightning protection system to be made:
5.1. In the XXXXX project, the Lightning Protection System specified in the latest IEC 62305 standard shall be made. Implementation shall be made according to the measures specified in risk management.
5.2. Risk management is a whole and failure to take the specified measures in risk management invalidates the practice.
5.3. All construction steel in building reinforced concrete, IEC 62305-3 E4.3.3. All the interconnected reinforced concrete steel of the building shall be considered as natural descent conductor.
5.4. To check the connection accuracy of this reinforced concrete steel, see IEC 63250-3 E4.3.1. and the measured impedance value is below 0.2 Ohm. If this value is not reached, external HVI isolated conductors will be descended from the columns.
5.5. Since the isolated capture tip system will be placed with tripods and clamps as specified in the project, the population of any direct lightning stroke is not expected when the specific lightning current parameters are taken into consideration.
5.7. All metal building parts (façade, building reinforced concrete steel, metal conductors / pipes…) should be connected to each other with the capacity to carry lightning current. In this way, the different potential differences between the parts will be drawn to a single potential to prevent the formation of dangerous arcs.
5.8. The catch ends to be mounted on the tripods shall be fixed with insulated support pipes and HVI insulated conductor shall be passed through these insulated support posts.
5.9. The equipotentialization of the outer sheath of the HVI insulated conductor shall be carried out through the support post.
5:10. The external diameter of the HVI insulated conductor shall be 20 mm and the copper conductor therein shall be at least 19 mm2.
5:11. The HVI insulated conductor shall be capable of carrying a lightning current of 150kA 10 / 350us and the equivalent separation distance “s adaki in the air shall be 75cm. Since the insulated conductor is related to insulation, tests regarding separation distance shall be documented.
5:12. The dielectric strength of the insulated down conductor of the HVI insulated conductor and the creping discharge resistance test on the outer sheath insulation shall be documented. Thus, it shall be documented that no other dangerous current passes through the sheath of the conductor while providing a separation distance of 75 cm.
5:13. The HVI insulated conductor shall be easy to assemble with a minimum bending radius of 200 mm.
5:14. When connecting HVI insulated conductors to building reinforced steel, the internally tested accessories and clamps of the HVI insulated conductor shall be used.
5.15. As stated in the project, the length of the catch pole with support posts will be 4.2 m and 5.7 m at 14 and 2 points respectively.
5.16. Tripods will be fixed with necessary concretes to withstand 110km / h wind speed.
5:17. The tripod metal body shall be connected to the closest equipotential busbar to be formed on the building by means of aluminum if the surfaces to be contacted are not lime based and St / St stainless steel conductors if lime based.
5.18. The HVI insulated conductor must be placed on 1 m troughs with concrete feet to prevent dangerous displacement in the event of impact and the HVI insulated conductor will be connected to the reinforced concrete with a StSt stainless steel clamp, tested to IEC 62561 and carrying a lightning current of at least 150kA (10 / 350us) .
5.19. The total length of the insulated support pipes to be attached to the structures shall be 4.2 m together with the catch ends and the 50 cm portion of the support pipe shall be secured with clamps approved by the manufacturer and the metal part of the support pipe shall be connected to the closest equipotential busbar.
5.20. After the HVI insulated conductor support pipe to be installed in the structures, it must be fixed to the roof with plastic pedestal mounting parts approved by the related manufacturer every 1 meter and if there is a section from the ground to the ground point, the concrete feet should be placed on the ground with 1 meter spaces. The HVI insulated conductor is tested in accordance with IEC 62561 and will be connected to the reinforced concrete with a StSt stainless steel clamp that will carry at least 150kA (10 / 350us) lightning current
5.21. All products used must be tested in accordance with IEC 62561. The accessories and HVI insulated conductors must be of the same brand as the HVI insulated conductor and its attachments are tested together and the entire system is approved.
5:22. The HVI insulated conductor must be connected to the insulated support pipe internally and to the earth point with the StSt stainless termination parts of the insulated conductor.
6. Lightning Current and Impact Protection Measures (Surge Arrester)
6.1. In the XXXXX project, the Lightning Protection System specified in the latest IEC 62305 standard shall be constructed. Implementation shall be made according to the measures specified in the risk management report.
6.2. Risk management is a whole and failure to take the specified measures in risk management invalidates the practice.
6.3. Surge arresters specified below should be used where there is a low voltage power line and data / signal connections.
6.4. Fire alarm and automatic fire extinguishing equipment is a risk reducing factor in risk management and these systems are considered to exist in risk management when the energy and signal sides are protected with surge arrester.
6.5. For the air-conditioning and ventilation equipment to be installed in the building, necessary surge protection measures must be taken.
6.6. 3 + 1 surge arrester with a voltage protection of less than 1.5kV and a 10 / 350us Iimp value of 50kA should be used in the compact structure to the main panel entrance of the building with Tip1 + Tip2 sparkgap technology.
6.7. Type2 3 + 1 surge arrester with Imax value 120kA I nominal value 80kA should be used in sub-boards.
6.8. Type 3 3 + 1 surge arresters should be used in shops and offices.
6.9. Type 1P1 surge arresters suitable for 10kA 4-wire connection should be used in signal connections of fire alarm / extinguishing and air conditioning / ventilation systems.
6:10. The Ethernet connections found in the IT room should also be initialed against the direct and infectious effects of mobbing.
6:11. Surveillance cameras and connected Ethernet switches must be initialized.
7. Grounding system
7.1. In accordance with IEC 62305-3: 2010-12, type B ring ground electrode or basic ground electrode shall be used.
7.2. The base earth electrode tested and documented in accordance with IEC 62561-2 to be used must be a 30 × 3.5mm hot-dip galvanized steel strip with an average surface thickness of 70um (microns) or a V4A St / St 30 × 3.5mm stainless steel strip.
7.3. The total earthing resistance of the entire earthing system shall be ensured to be less than 2 ohms.
7.4. The basic earth electrode must be connected to the rebar every 2 meters with clamps approved by the manufacturer and in accordance with IEC 62561.
7.5. The basic earth electrode must be connected to equipotential busbars located at the appropriate locations within the building.
7.6. For the foundation grounding, hot dip galvanized steel strip with 30 × 3.5mm average 70um (micron) surface coating or V4A St / St 30 × 3.5mm stainless steel strip should be used in the bottom row of the iron to be left in the concrete inside the building.
7.7. The foundation earthing must be made in the form of a closed ring and placed on the foundations of the exterior walls of the building or within the foundation platform.
7.8. The basic earthing must be arranged in such a way that all sides are covered with concrete. The end points should be removed from the foundation and sufficiently fastened.
7.9. The connection shoots should be made of 50 × 5 mm galvanized strips to be connected to the equipotential busbars in the building, fixed to the foundation bars with vertical fixing pieces and min 2 mt. should be laid out.
7:10. If a white tank is to be applied with waterproof concrete, the earth electrode must be installed according to DIN 18014.
7.11. For this application, a 10mx10m mesh 10mm diameter V4A St / St stainless steel ring earth electrode2 will be placed under the gorebeton and the clamps4 will be removed at 10 meters with the clamp4 pictured below.
7:12. After the gorebeton, V4A St / St stainless steel ring earth electrode which is tested according to IEC 62561-2 with a diameter of 10mm with a 20mx20m mesh shall be placed into the reinforced concrete to be applied and connected to the construction iron with clamps specified in the following drawing every 2 meters.
7:13. At least every 20 meters and at least one section will have enough soil sprouts to drop 1 equipotential point and the soil sprouts must be connected to the waterproof wall bushings, which are based on a water pressure of 1 bar to form equipotential points.
8. Lightning Current Parameters
The design is based on the latest IEC 62305 Lightning Protection Standard.
The Lightning Protection Level (LPL) III is based on the following Lightning Current parameters.
Ipeak = 100 kA (10/350 s)
Qimpulse = 50 C
Specific energy = 2.5 MJ /
Rolling sphere = 45 m
Lowest peak current = 10 kA
Impacts greater than 10 kA = 91%
Since the lightning protection level is decided as LPL III, the lowest lightning current value is 10kA. with 91% of all possible lightning.