Complete protection against lightning for a single-family house involves the use of complex systems consisting of the elements of external lightning protection and surge protection devices. All this equipment must be properly designed and installed, then it will cope with the task. We present you an example of the calculation of lightning protection and surge protection for a single-family house.
Objective:
To calculate the system of external lightning protection and grounding for a two-storey residential house with an extension-bath house.
Solution:
Calculations are made in accordance with the following documents:
- Electrical Installation Code EIC 7th ed. (hereinafter - EIC);
- "Instructions for organization of lightning protection of buildings, structures and industrial communications"
Industry Standard 153-34.21.122-2003 (hereinafter IS); - "Instructions for lightning protection of buildings and structures" AD 34.21.122-87 (hereinafter - AD).
According to these documents, a single-family house refers to the type "ordinary" (according to IS) and the third category of lightning protection, lightning protection is carried out by the lightning rods installed on the roof (lightning rods). In case of a lightning strike into a lightning rod, lightning current, bypassing the protected object is drained into the ground. External lightning protection system also includes a down conductor and ground electrode.
*more about classification of objects
Detailed description of arrangement of lightning protection:
- Four lightning rods 4 m high are installed on the roof of a house. They are fixed on the edges of the roof ridge, taking into account that 0.5m of the rod length will be occupied by the fastening. Two air terminal masts for fixation to vertical surfaces 1,5 m high are installed on the bath house.
- Four down conductors made of copper-bonded wire D=8 mm are connected to the lightning rods. Two down conductors are installed on the house, and two - on the bath house. Lightning rods are also connected together for the organization of two electrodes from each lightning rod. Down conductors are located at the distance of not less than 3 meters from the entrances or in places inaccessible for people's touch. Fixation of down conductors to the roof ridge is made with the help of clamps GL-11564A. Fixation of down conductors on the roof is carried out by means of clamps GL-11737A.Fixation of down conductors to the well is carried out by means of clamps GL-11704A (0.6-1 m fixation step).
Connection and bifurcation of down conductors is carried out with the help of clamps GL-11551M. - Grounding device consisting of three vertical electrodes 3 m long is installed. The electrodes along the walls of the house are united in the ground by a copper-bonded tape 30x4 mm. A grounding device consisting of 2 vertical electrodes 3 m each is also installed for a bath house and these electrodes are united by a horizontal electrode - copper-bonded tape. In both cases, the distance between the vertical electrodes is at least 5 meters. The distance from the horizontal electrode to the walls of the building is 1 m, and the depth - 0.5 meters.
Connection of the down conductor with the output of the copper-bonded tape from the ground is carried out with the help of a control clamp GL-11562A.
Figure 1 - Protection zone and elements of lightning protection arrangement
Figure 2 - Construction of the grounding device
Choice of surge protection devices
Surge Protection Devices (SPD) are chosen according to the cable entry into the house and TN-S system (3 phases, separate zero protective earth and neutral conductors). Choosing the SPD class I+II+III PP BCD TNS 25/100, the installation of which is carried out on the main switchboard. If there are single-phase consumers in the house, to which the distance from the main switchboard along the electrical network is more than 10 meters, then it is reasonable to use SPD of Class III EP D TN 275, which is connected to the network directly before the protected device. Placement of the SPD inside the house and the connection circuit are shown in the figure below.
Питание кабельной линии- Cable line power supply
Ограждение- fencing
Дом - house
Защищаемое устройство – protected device
Главный распределительный щит – main distribution board
Ступень защиты – protection level
Кабельный ввод – cable entry
Конечные приемники –target reciever
Figure 3 - SPD arrangement and connection
List of required materials:
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Implementation of the described events will ensure the protection of the house from direct lightning strikes and its secondary effects.
Keep your home in safety; provide it with the system of internal and external lightning protection!
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