# Example Calculation of Lightning Protection System for a Chemical Analysis Laboratory

The ZANDZ Technical Center has received a request to calculate the lightning protection system for a chemical analysis laboratory located in the European part of Russia. Let's consider the solution offered by our specialists.

Calculation data:

1. Facility: chemical analysis laboratory.

2. Facility drawing.

3. Soil resistivity: 100 Ohm*m.

Задача:

• calculate the lightning protection system;

• calculate the grounding arrangement.

Solution:

Lightning protection and grounding of the building are made in accordance with:

The facility is "special, environmentally hazardous" from the viewpoint of SO and is classified as Category I of the lightning protection according to RD.

A set of measures to provide the necessary requirements to the lightning protection system and to the grounding arrangement for the chemical analysis laboratory includes the following solutions:

1. The lightning protection is made using 16 m lightning masts (ZZ-201-016-B7-Sn5-S9). The lightning arresters are installed on concrete foundations. The distance to the facility is at least 3 m.

2. The protection zone should include space over the valves, r = 5 m; h = 2.5 m.

3. Copper-plated steel electrodes 3 m long are used as a vertical grounding arrangement.

4. The copper-plated steel strip with a cross-section of 30 x 4 mm, combining all vertical electrodes, is used as a horizontal ground electrode. The distance to the mast foundation is at least 1 m. Strip deepening is 0.5 to 0.7 m.

5. Connection to the grounding arrangement is made through clamps ZZ-005-064.

The results of calculation of protection zones according to SO:

h = 16 m;

Cone height according to SO, Table 3.4:

м - m

Cone radius according to SO, Table 3.4:

м - m

The distance (maximum) between lightning arresters:

L = 22 m;

Limit distance between lightning arresters according to SO, Table 3.6:

м - m

There is not sagging height.

For the protection zone with the required reliability, radius rx at the height of h0 = 7.5 m is defined as:

м - m

Ground terminal resistance calculation:

Vertical electrode resistance:

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 is deepening, i.e. the distance from the ground surface to the ground electrode, 2 m;

where is deepening of the electrode top, 0.5 m.

Horizontal electrode resistance:

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, 79 m.

Electrical impedance of the grounding arrangement:

Ом - Ohm

where n is a number of sets, vertical grounding arrangements - 7 pcs, horizontal grounding arrangement - 1 pc;

Kutil is utilization rate, 0.69.

The rated resistance of the grounding arrangement is 2,51 Ohm.

The equipment layout and the protection zone are shown in Fig. 1.

Условные обозначения - Key
Молниеприемник-мачта высотой 16 м - Lightning arrester, 16 m high
Полоса стальная оцинкованная сечением 30х4 мм - Steel zinc-plated bar with cross-section 30 x 4 mm
Зажим для подключения проводов - Clamp for connecting wires
Вертикальный заземлитель длиной 3 м - Vertical grounding electrode, 3 m long
Зона защиты h = 7,5 м - Protection zone h = 7.5 m
Защищенное пространство над клапанами r=5 м; h=2,5 м - Protected space above valves, r = 5 m; h = 2.5 m

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 LIGHTNING PROTECTION: 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) 4 GROUNDING ARRANGEMENT: 2. GL-11075-50 GALMAR Copper-plated strip (30 * 4 mm / S 120 mm²; 50-meter strip bundle) 1 0,98 Вес за 1 м 3. GL-11075-20 GALMAR Copper-plated bar (30 * 4 mm / S 120 mm²; bundle 20 meters) 2 0,98 Вез за 1 м 4. ZZ-001-065 ZANDZ Copper-plated threaded grounding pin (D14; 1.5 m) 14 2,00 5. ZZ-002-061 ZANDZ Threaded coupling 8 0,08 6. ZZ-003-061 ZANDZ Takeoff tip 7 0,07 7. ZZ-004-060 ZANDZ Guide head for jackhammer attachment 3 0,09 8. ZZ-005-064 ZANDZ Conductor connection terminal (up to 40 mm) 15 0,312 9. ZZ-006-000 ZANDZ Conductive grease 1 0,10 10. ZZ-007-030 ZANDZ Waterproofing tape 5 0,40 11. 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 chemical analysis laboratory? Please contact the ZANDZ Technical Center!

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