The ZANDZ Technical Center has received a request to calculate the lightning protection and grounding system for the hatchery located in the Ryazan Region. Let us consider the proposed solution.
Initial data:
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Facility: a hatchery device.
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Facility dimensions: 76 m x 26 m x 7.7 m.
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The soil resistivity accepted for calculations is 100 Ohm * m.
Task:
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Calculate the external lightning protection system.
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Calculate the grounding device.
Solution:
The facility is classified as "conventional" according to SO and as Category 3 according to RD. The required system reliability is at least 0.9.
A set of arrangements to ensure compliance with the requirements of the lightning protection system for the hatchery is based on the following solutions:
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The lightning protection of the facility is made using 2 m lightning arresters (GL-21131) secured with concrete holders.
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A copper-plated steel wire (copper coating thickness of at least 70 μm), d8 mm (GL 11149), is used as a current collector.
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Current collectors are installed using clamp ZZ-202-015 on the roof and GL-11703A on vertical surfaces. The clamp installation step is 0.8 to 1.0 m.
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The multipurpose GL 11551A clamp is used to connect the rolled products over the length and in assemblies.
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3 m steel copper-plated electrodes in the locations of the current collector downdrops are used as vertical grounding electrodes.
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30 x 4 mm steel copper-plated bar combining all vertical electrodes is used as a horizontal grounding device. The distance to the facility foundation is at least 1 m. Strip deepening is 0.5 to 0.7 m.
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According to the EIC, Rev. 7, item 1.7.55, grounding devices for protective grounding of electrical installations for buildings and structures and Categories 2 and 3 of the lightning protection for these buildings and structures usually should be common.
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If there are reinforced concrete structures, they should be connected to current collectors/to the grounding device.
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Connection to the grounding device (external and internal) is made by clamps ZZ-005-064.
Results of the calculation performed using the software developed by Krzhizhanovsky Energy Institute (OAO ENIN):
Intensity of lightning discharge into the ground is 4 strikes/square km/year;
The total number of strikes into the system is 0.04 (once every 25 years).
The total number of breakouts into the system is 0.0027 (once every 370 years).
System reliability is 0.933.
The probability of breakout into all facilities of the system is 0.067.
Ground terminal resistance calculation:
Vertical electrode resistance:
Ом - Ohm
where ρeq is equivalent soil resistivity, 100 Ohm·m;
L is vertical electrode length, 3 m;
d is diameter of the vertical electrode, 0,014 m;
T is depth, i.e. the distance from the ground surface to the ground electrode, 2 m;
where t is electrode top depth, 0.5 m
Horizontal electrode resistance:
Ом - Ohm
where ρ is soil resistivity, 100 Ohm·m;
b is horizontal electrode width, 0.03 m;
h is horizontal electrode depth, 0.7 m;
Lhor is horizontal electrode length, 212 m.
Electrical impedance of the grounding arrangement:
Ом - Ohm
where n is a number of sets, vertical grounding arrangements - 10 pcs, horizontal grounding arrangement - 1 pc;
Kutil is utilization rate, 0.63.
The calculated resistance of the grounding arrangement is 1.37 Ohms.
The layout of the equipment is shown in Figure 1.
Молниеприемник-мачта высотой 2 м (GL-21131) - 2 m lightning arrester (GL-21131)
Проволока омедненная стальная диаметром 8 мм (GL-11149) - Steel copper-plated wire diam. 8 mm (GL-11149)
Полоса омедненная стальная сечением 30х4 мм (GL-11075) - Steel copper-plated bar 30 x 4 mm (GL-11075)
Электрод D=14 мм, L=3 м - Electrode D = 14 mm, L = 3 m
Figure 1. Equipment layout.
The list of equipment and necessary materials is provided in Table 1..
Table 1. List of needed materials.
Do you need to design the lightning protection and grounding system for the hatchery? Please contact the ZANDZ Technical Center.
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