The ZANDZ Technical Center has received a request to calculate the lightning protection system and grounding arrangement for an arch framed and tent hangar. Let's consider the solution proposed by our engineers.
Facility: arch framed and tent hangar.
Protected facility dimensions: 40 x 24 x 10 m.
The soil resistivity accepted for calculations is 1000 Ohm * m.
1. Calculate the lightning protection system.
2. Calculate the grounding arrangement.
The activities have been performed according to:
- EIC, Rev. 7. Electrical Installations Code (hereinafter referred to as the EIC);
- SO 153-34.21.122-2003 Instructions for Mounting Lightning Protection for Buildings, Structures, and Industrial Utilities (hereinafter referred to as SO);
- RD 34.21.122-87 Instructions for Mounting Lightning Protection for Buildings and Structures (hereinafter referred to as RD).
The facility is classified as "conventional" according to SO and as Category 3 according to RD.
A set of arrangements ensuring compliance with the lightning protection requirements is based on the following solutions:
Lightning protection for the facility is made using the lightning arresters with the height 16 m (ZZ-201-016-В7-Сн5-С9), which are installed at the distance of 3 m from the protected facility.
Metal structures of the facility are attached to the grounding arrangement every 15 to 20 m.
As vertical electrodes, electrolytic grounding sets ZZ-100-102 are used, which are installed near lightning arresters at the distance of at least 3 m from foundations.
The copper-plated steel strip with a cross-section of 30 x 4 mm, connecting 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.
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.
If there are concrete-steel constructions, they shall be connected to down conductors/grounding device.
Connection to the grounding device is carried out using ZZ-005-064 clamps.
The results of calculation of protection zones according to SO:
h = 16 m;
Cone height according to SO, Table 3.4:
h0 = 0,85h = 13,6 m;
Cone radius according to SO, Table 3.4:
r0 = 1,2h = 19,2 m;
To provide the protection zone with the required reliability, radius rx at the height hх =10 m is determined as follows:
Distance between the lightning arresters (maximum):
L = 46 m;
Limit distance between lightning arresters according to SO, Table 3.6:
м - m
To provide protection with the required reliability, radius rcx at the height h0 10 m is determined as follows:
Ground terminal resistance calculation:
Vertical electrode resistance:
Ом - Ohm
where ρ – is equivalent soil resistivity, 1,000 Ohm·m;
С – is a non-dimensional factor describing the electrolyte content in the surrounding soil, 0.25;
L – is vertical electrode length, 2.4 m;
d – is vertical electrode diameter, 0.065 m;
T – is depth, i.e. the distance from the ground surface to the ground electrode, 0.6 m;
Horizontal electrode resistance:
Ом - Ohm
Гор - Hor
где ρ – 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, 66 m.
Electrical impedance of the grounding arrangement:
Ом - Ohm
PE - GA
where n – is a number of sets, vertical grounding arrangements - 2 pcs, horizontal grounding arrangement - 1 pc;
Kutil1 – is utilization rate, 0.99;
Kutil2 – is utilization rate, 0.7.
The calculated resistance of the grounding arrangement is 21,85 Ohm.
- Молниеприемник-мачта высотой 16 м - 16 m lightning arrester
- Комплект электролитического заземления - Electrolytic grounding set
- Полоса омедненная стальная сечением 30х4 мм - Steel copper-plated bar 30 x 4 mm
Figure 1. Equipment layout.
The list of necessary materials is provided in Table 1
Table 1. List of needed materials.
|№ п\п||Part number||Name||Quantity, pcs.|
|1.||ZZ-201-016-В7-Сн5-С9||ZANDZ Lightning arrester, vertical, 16 m (zinc-plated steel; with embedded elements for the foundation; 7th wind region; 5th snow region; 9th seismic region)||2|
|2.||ZZ-100-102||ZANDZ Electrolytic grounding set (horizontal; 3 meters long)||2|
|3.||ZZ-005-064||ZANDZ Conductor connection terminal (up to 40 mm)||7|
|4.||ZZ-007-030||ZANDZ Waterproofing tape||3|
|5.||GL-11075-10||GALMAR Copper-plated strip (30 x 4 mm/S 120 mm²; 10-meter strip bundle)||1|
|6.||GL-11075-50||GALMAR Copper-plated strip (30 x 4 mm / S 120 mm²; 50-meter strip bundle)||1|
Do you have any questions regarding grounding and lightning protection of the arch framed and tent hangar? Please contact the ZANDZ Technical Center!