Apartment block grounding and lightning protection project

Task:

It is necessary to make calculations and make grounding and lighting protection project for the object.
Object: one section of an apartment block.
Soil: sand clay
Soil resisitivity: 100 Ohm*m
Than 10 Ohm will be used as a grounding device. All metal elements protruding over the roof of the building (ventilation shafts, metal ladders, etc.) must be connected to the building's metal structures

Download the layout of an apartment building (all sections) in PDF.
Download the layout of an apartment building (all sections) in DWG (AutoCAD).

Solution:

The calculations were performed in accordance with the EIC 7th ed., IS 153-34.21.122-2003 "Instructions for lightning protection of buildings, structures, and industrial communications" (hereinafter IS) and AD 34.21.122-87 "Instruction for lightning protection of buildings and structures" (hereinafter AD).

Apartment buildings refer to ordinary constructions in terms of lightning protection in accordance with the IS and to category 3 according to the AD. The required reliability of lightning protection system - 0.9.

According to EIC-7, p. 1.7.103 The total spreading resistance of the ground electrodes (including natural) of all repeated groundings of the PEN conductor of each overhead line at any time of the year should not exceed 10 ohms at line voltage of 380 V of the three-phase power supply or 220 V of a single-phase power source.

Lightning protection of the objest was performed by means of lightning protection mesh on the roof of the building with the installation of air-terminal masts for protection of shafts elevating over the roof level with the equipment installed inside. The size of the cell of the lightning protection mesh is not more than 10x10m. Type of mesh - copper-bonded steel with the diameter of 8 mm, thickness of the coating 70 micron (GL-11149).

Installation of mesh is carried out on flat surfaces with the help of GL-11711 clamp, on vertical surfaces - GL-11703A

The distance between the clamps - 0,8- 1,0 m. To connect the mesh over the length and in the mesh nodes, a universal clamp GL-11551A is used.

Air terminal mast are mounted on vertical surfaces with the help of holders GL-21201. Air terminal mast are mounted on vertical surfaces with the help of holders GL-21201.

All metal elements, placed on the roof (ventillation shafts, ladders, fencing etc) should be connected to lightning protection mesh with the help of clamps GL-11545A.

Copper-bonded wire 8 mm in diameter is used as down conductors (GL-11149).

The distance between the mesh and down conductors not more than 25 m. A horizontal electrode (GL-11149) should be laid every 20 m (height of the building) over the building's perimeter.

The grounding device is designed as a contour around the perimeter of the building. Horizontal conductor - copper-bonded steel tape 30x 4 mm (GL-11075). Copper bonded steel electrodes D=14 mm, L=3 m are used as vertical electrodes. Verical electrodes are installed in places of downdrop of down conductors. Distance from the building base not less than 1 m.

The results of the calculation performed by the software, developed by JSC "Energy Institute to the name of G. M. Krzizhanovsky" (JSC "ENIN"):

the density of lightning strikes into the ground - 6 strikes / sq. km per year;
the total number of strikes into the system in: 0.0066 (once in 910 years);
the total number of breakthroughs (strikes directly into the object passing lightning rods) - 0.00051 (once in 1810 years);
Protection reliability:0.923.

Calculation of grounding device resistance:

Resistance of a vertical electrode:

Resistance of a vertical electrode

where ρ_eq - equivalent soil resistivity, ohm · m;
L - length of the vertical electrode, m;
d - vertical electrode diameter, m;
T- deepening - distance from the ground surface to the ground electrode, m;

Resistance of a horizontal electrode:

Resistance of a horizontal electrode

ρ - soil resistivity, Ohm* m;
b - horizontal electrode tape width ,m;
L_гор - horizontal electrode length, m.

formula-1

where t - deepening of the electrode top, m

Impedance of the grounding device:

Impedance of the grounding device

where n - number of kits;
K_исп - utilization ratio;

formula-2

formula-3

formula-4

The design resistance of the grounding device is 0.74 ohms, which is less than the permissible resistance of 10 ohms.

The list of required materials:

№	Fig	Product item	Product	Q-ty	Weight (kg per unit)
1		GL-21103G	GALMAR Vertical lightning rod (air terminal- mast) (4 meters)	25	10
2		GL-21202	Holder for the air-terminal mast GL-21101G / GL-21102G/ GL-21103G to the chimney (stainless steel)	25	7,4
3		GL-20022	GALMAR Clamp to the air-terminal mast GL-21101G for down conductors (stainless steel)	25	0,2
4		GL-11149-10/20/50	GALMAR Copper-bonded wire (D 8mm / S 50 mm²; coil -10/20/50 meters)	3500 (in meters)	0,41
5		GL-11711	Clamp on a flat roof for the down conductor (plastic, concrete)	3000	1,00
6		GL-11551A	GALMAR Clamp for connecting down conductors (painted galvanized steel)	700	0,09
7		GL-11703A	Clamp to the facade for the down conductor with its elevation above the clamp to 15 mm (Painted galvanized steel)	400	0,02
8		GL-11545A	GALMAR Clamp on the gutter for the down conductor (painted galvanized steel)	500	0,11
9		GL-11563A	GALMAR Control clamp for connecting down conductors, wire + tape (painted galvanized steel)	60	0,13
10		ZZ-001-065	ZANDZ Copper-bonded threaded grounding rod (D14; 1,5 m)	74	1,9
11		ZZ-002-061	ZANDZ Threaded coupler	38	0,082
12		ZZ-003-061	ZANDZ Starting tip	37	0,074
13		ZZ-004-060	ZANDZ Driving head for a breaker hammer	15	0,088
14		ZZ-005-064	ZANDZ Clamp for connecting conductor (up to 40 mm)	48	0,312
15		ZZ-006-000	ZANDZ Conductive grease	4	0,152
16		ZZ-007-030	ZANDZ Water-proof tape	10	0,442
17		GL-11075-10/20/50	Copper bonded tape (30*4 mm / S 120 mm²; coil 10/20/50 meters)	600 (in meters)	0,98