Providing electrical safety for buildings where people live working on a rotational basis is no exception, because any force majeure can cause unpleasant consequences.
It will be about lightning protection of the building for shift teams in the Yamal-Nenets Autonomous Okrug, which was calculated by the employees of the ZANDZ Technical Center.
Initial data:
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architectural drawings;
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soil resistivity is 1000 Ohm*m.
Task:
- calculate the system of external lightning protection;
- calculate technological grounding with the resistance of 10 ohm max.
Solution:
Lightning protection and grounding of the building are made in accordance with:
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SO 153 34.21.122 2003 "INSTRUCTIONS FOR MOUNTING LIGHTING PROTECTIONS OF BUILDINGS, STRUCTURES AND INDUSTRIAL COMMUNICATIONS", hereinafter referred to as SO;
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RD 34.21.122 87 "INSTRUCTIONS FOR MOUNTING LIGHTING PROTECTION OF BUILDINGS AND STRUCTURES", hereinafter RD.
The object belongs to the “ordinary” from the SO point of view and to the III category of lightning protection in accordance with the RD. The reliability of the system shall be 0.9 min.
A set of measures to provide the necessary requirements for the grounding device and lightning protection of the building for shift teams is presented by the following solutions:
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Lightning protection of the object is made using ridge lightning rods. (GL 11521SS) that are fastened with GL 11525 holders.
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A copper-plated steel wire (copper coating thickness of 70 μm min.), d8 mm (GL 11149) is used as a down conductor.
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Down conductors are mounted using the GL 11747A clamp on the roof, GL 11703A on vertical surfaces. The clamp spacing is 0.8 to 1.0 m.
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The universal GL 11551A clamp is used to connect the rolled products over the length and in assemblies.
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All metal elements located on the roof shall be connected to the down conductor using GL 11545A clamps. Stairs, railings, are attached using the GL 11514N ring clamp.
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Horizontal electrolytic ground electrodes 3 m long (3 pcs.), as well as horizontal beam ground electrodes 3 m long, directed radially in the opposite direction from the object, made of copper-plated steel of 30х4 mm section are mounted in the places of down conductors lowering.
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A copper-plated steel strip of 30x4 mm section, which combines all electrolytic and horizontal beam electrodes, is used as a horizontal ground electrode. The distance to the object foundation is at least 1 m. Strip deepening is 0.5 to 0.7 m.
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According to EIC-7 issue, par.1.7.55 - Grounding devices for protective grounding of electrical installations for buildings and structures and the 2nd and 3rd categories lightning protection of these buildings and structures, as a rule, shall be common.
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Resistance design value of the grounding device is 8.76 Ohms.
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If there are concrete-steel constructions, they shall be connected to down conductors/grounding device.
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Connection to the grounding device is carried out using ZZ-005-064 clamps.
Calculation results carried out using software developed by the G.M. Krzhizhanovsky Energy Institute, JSC ENIN, OJSC
The occurrence of lightning strokes into the ground is 4 strokes/sq. km per year
The total number of strokes in the system is 0.017 (once every 59 years);
The total number of breakouts in the system is 0.00036 (once every 2778 years);
System reliability is 0.979;
The probability of breakout into all objects of the system is 0.021.
Ground terminal resistance calculation for the building of shift teams:
The resistance set ZZ-100-102:
where С is a dimensionless factor describing the electrolyte concentration in the surrounding soil, 0.125;
р is soil equivalent resistivity, 1000 Ohms m
L is vertical electrode length, 2.4 m;
d is vertical electrode diameter, 0.065 m;
T - deepening is the distance from the ground surface to the ground electrode, 0.6 m;
Horizontal electrode resistance:
where p is soil resistivity, 1000 Ohm m;
b - is horizontal electrode width, 0.03 m;
h - is horizontal electrode depth, 0.5 m;
Lгор - is horizontal electrode length,143 m.
Grounding impedance:
where n - is number of kits, 3 pcs. (electrolytic ground electrodes), 1 pcs. (strip);
Kисп is utilization factor, 0.99 (electrolytic ground electrodes), 0.7 (strip).
Rated resistance of the grounding device is 8,76 ohms, which is less than the required value of 10 ohms.
The location of the equipment is shown in Figure 1.
Figure 1 - location of lightning protection equipment and grounding of the building for shift teams
Условные обозначения - Conventional symbols
Молниеприёмник коньковый высотой 2 м (GL-11521SS) - Ridge lightning rod, 2 m. height (GL-11521SS)
Проволока стальная омедненная диаметром 8 мм (GL-11149) - Copper-coated steel wire of 8 mm diameter (GL-11149)
Полоса стальная омедненная сечением 30х4 мм (GL-11075) - Copper-coated steel strip of a 30x4 mm section (GL-11075)
Универсальный зажим-соединитель для проволоки (GL-11551A) - Universal Clamp Wire Connector (GL-11551A)
Зажим для подключения проводника (ZZ-005-064) - Main conductor connection terminal (ZZ-005-064)
Опуск токоотвода - Down conductor lowering
Комплект электролитического заземления (ZZ-100-102) - Electrolytic grounding kit (ZZ-100-102)
The list of necessary materials is given in Table 1.
Table 1 - List of needed materials.
Do you have questions or do you need to calculate grounding for a building of shift teams? Send a request to info@zandz.ru.
Refer also to: