The ZANDZ Technical Center has received a request to calculate the lightning protection for the surgery complex. Let's consider the solution offered by our specialists.
Calculation data:
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Facility: a surgery complex.
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Architectural drawings of the facility.
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Soil resistivity: 100 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 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 referred to as RD.
The facility is classified as category III in terms of lightning protection. The system's reliability should be not less than 0.9.
A set of measures to meet the necessary requirements to the lightning protection system and to the grounding arrangement of the surgery complex includes the following solutions:
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The facility lightning protection is made using lightning arresters on 2 m concrete foundations (GL-21131). Connection to current collectors is performed using holders included in the lightning arrester set.
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A steel copper-plated wire d8 mm (GL-11149) is used as a lightning arrester.
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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 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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3 m copper-plated steel electrodes in the locations of current collector downdrops as well as at the entrance edges are used as vertical grounding electrodes.
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The copper-plated steel strip with a cross-section of 30 x 4 mm, interconnecting all vertical electrodes, is used as a horizontal ground electrode. 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 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 1.27 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.
Results of the calculations performed by using the software developed by OAO Krzhizhanovsky Energy Institute (OAO ENIN):
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the density of lighting discharges into the ground is 4 strikes/sq. km per year;
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the total number of strikes into the system is 0.06 (once every 17 years);
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the total amount of breakthroughs (the strikes directly into the facility bypassing lightning arresters) is 0.0055 (once every 182 years);
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the system's reliability is 0.909.
Ground terminal resistance calculation:
Vertical electrode resistance:
Верт - Vert
Экв - Eq
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 deepening - is the distance from the ground surface to the ground electrode, 2 m;
where t is electrode top depth, 0.5 m.
Horizontal electrode resistance:
Гор - Hor
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, 208 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 1,27 Ohm.
The equipment layout and the protection zone are shown in Fig. 1.
Условные обозначения - Legend
- молниеприемник на бетонном основании высотой 2 м - 2 m lightning arrester on a concrete base
- проволока стальная омедненная диаметром 8 мм - steel copper-plated wire, diam. 8 mm
- полоса стальная омедненная сечением 30х4 мм - steel copper-plated strip, 30 x 4 mm
- зажим для подключения проводника - clamp for connecting conductor
- опуск токоотвода - downdrop
- вертикальный заземлитель длиной 3 м - 3 m vertical grounding electrode
Figure 1. Equipment layout.
The list of necessary materials is given in Table 1.
Table 1. List of needed materials.
| № | Part number | Name | Quantity, pcs. | Unit weight, kg | Note |
| 1. | GL-21131 | GALMAR Lightning arrester (2 meters; 1 m on a concrete foundation, zinc-plated steel; complete with the clamp for the stainless steel current collector) | 17 | ||
| 2. | GL-11149-50 | GALMAR Copper-plated wire (D 8 mm/S 50 mm²; 50-meter bundle) | 10 | 0.41 | Вес 1 м |
| 3. | GL-11551A | GALMAR Conductor connection clamp (painted zinc-plated steel) | 100 | 0.07 | |
| 4. | ZZ-202-015 | ZANDZ Holder for a circular conductor on a flat roof (D 8 mm; plastic + concrete) | 420 | 1.00 | |
| 5. | GL-11703A | GALMAR Current collector facade clamp providing 15 mm elevation of the collector over the clamp (painted zinc-plated steel) | 200 | 0.02 | |
| 6. | GL-11545A | GALMAR Main conductor rain water gutter terminal (painted zinc-plated steel) | 30 | 0.112 | |
| 7. | GL-11514N | GALMAR Ring clamp on rainwater pipe for current collector (tinned copper) | 20 | 0.076 | |
| 8. | GL-11075-50 | GALMAR Copper-clad strip (30*4 mm / S 120 mm²; 50-meter strip bundle) | 5 | 0.98 | Вес 1 м |
| 9. | ZZ-001-065 | ZANDZ Copper-plated threaded grounding rod (D14; 1,5 m) | 20 | 2.00 | |
| 10. | ZZ-002-061 | ZANDZ Threaded coupling | 11 | 0.08 | |
| 11. | ZZ-003-061 | ZANDZ Termination | 10 | 0.07 | |
| 12. | ZZ-004-060 | ZANDZ Guide head for jackhammer attachment | 4 | 0.09 | |
| 13. | ZZ-005-064 | ZANDZ Conductor connection terminal (up to 40 mm) | 26 | 0.312 | |
| 14. | ZZ-006-000 | ZANDZ Conductive grease | 2 | 0.10 | |
| 15. | ZZ-007-030 | ZANDZ Waterproofing tape | 9 | 0.40 | |
| 16. | ZZ-008-000 | ZANDZ Attachment to the hammer (SDS max) | 1 | 0.50 |
Do you have any questions regarding lightning protection and grounding for the surgery complex? Please contact the ZANDZ Technical Center!
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