The ZANDZ Technical Centre has received a request to calculate the lightning protection system for the administration building. Let's consider the solution proposed by our engineers.
Calculation data:
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facility: an administration building in the Leningrad Region;
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roof plan;
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soil resistivity 150 Ohm*m.
Task:
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calculate the lightning protection system;
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calculate the grounding device.
Solution:
Lightning protection and grounding for the bakery and confectionery complex are made in accordance with:-
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 referred to as RD.
The facility is classified as “conventional” in terms of SO and to Category III of lightning protection according to RD. The required reliability of the lightning protection system should be at least 0.9.
According to the EIC Rev. 7, item 1.7.103. total dissipation resistance of grounding electrodes (including natural) of all repeated groundings of the PEN wire of each high-voltage line in any season of the year should not be more than 10 Ohm, respectively, with linear voltages 380 V of a three-phase source or 220 V of a single-phase source.
A set of measures to provide necessary requirements to the lightning protection and grounding system for the administration building includes the following solutions:
1. Lightning protection of the facility was made using vertical lightning arresters and lightning rods on three concrete supports. The rods are interconnected using a wire. Wire type is copper-plated steel with diam. 8 mm, plating thickness 70 mcm (GL-11149).
2. Current collectors are installed on flat surfaces using clamp GL-11711, and on vertical surfaces using GL-11703A. The clamp spacing is 0.8 to 1.0 m.
3. The multi-purpose GL-11551A clamp is used to connect the rolled products over the length and in assemblies.
4. Lightning arresters GL-21105G are installed on vertical surfaces. Lightning arresters GL-21125 are installed on three concrete supports complete with the clamps to connect the conductor. Current collectors are connected to the lightning rods using clamp GL-20023.
5. All metal elements located on the roof must be connected to the current collector using clamps GL-11545A.
6. An artificial grounding arrangement is used as a grounding device: copper-plated steel electrode D - 14 mm, L = 3 m, combined using a steel copper-plated bar GL-11075, cross-section 30 x 4 mm.
Results of the calculations performed by using the software developed by OAO Krzhizhanovsky Energy Institute (OAO ENIN):
The density of lighting discharges into the ground is 4 strikes/sq. km per year;
the total number of strikes into the system is 0.24 (once every 12 years);
the total number of breakthroughs (the strikes directly into the facility bypassing lightning arresters) is 0.072 (once every 39 years).
The system's reliability is 0.928..
Ground terminal resistance calculation:
Vertical electrode resistance:
Верт - Vert
Экв - Eq
Ом - Ohm
where ρρeq – is equivalent soil resistivity, 150 Ohm·m;
L is vertical electrode length, 3 m;
d is vertical electrode diameter, 0,014 m;
T is depth, i.e. the distance from the ground surface to the ground electrode, 2 m;
where t is deepening of the top of the electrode, 0.5 m
Horizontal electrode resistance:
Гор - Hor
Ом - Ohm
where ρ – is soil resistivity, 150 Ohm·m;
b is horizontal electrode width, 0.03 m;
h is horizontal electrode depth, 0.5 m;
Lhor is horizontal electrode length, 200 m.
Electrical impedance of the grounding arrangement:
ЗУ - GA
Ом - Ohm
where n is a number of sets, vertical grounding arrangements - 10 pcs, horizontal grounding arrangement - 1 pc;
Kutil is utilization rate, 0.69.
The calculated resistance of the grounding arrangement is 1,97 Ohm.
- Молниеприемник вертикальный (5,7 метра) - Vertical lightning arrester (5.7 meters)
- Молниеприемник-мачта на трех бетонных основаниях (6 метра) - Lightning rod installed on three concrete supports (6 meters)
- Проволока стальная омедненная диаметром 8 мм - Steel copper-plated wire diam. 8 mm
- Полоса стальная омедненная сечением 30х4 мм - Steel copper-plated bar 30 x 4 mm
- Фальцевая клемма для крепления к металлическим конструкциям - Flange terminal for securing to metal structures
- Универсальный зажим-соединитель для проволоки - Multipurpose coupling clamp for wire
- Зажим контрольный для крепления проволоки к полосе - Control clamp for securing wire to bar
- Электрод стальной омедненный D=14 мм, L = 3 м - Steel copper-plated electrode D = 14 mm, L = 3 m
- Держатель на плоской кровле - Holder for a flat roof
- Зажим к фасаду - Façade clamp
Figure 1. Equipment layout.
The list of necessary materials is given in Table 1.
Table 1. List of needed materials.
Do you have any questions regarding lightning protection and grounding for an administration building? Please contact the ZANDZ Technical Center!
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