Designing lightning protection of a covered berth!

Covered berths are buildings that are used for the repair and storage of the shells of boats, yachts and other watercrafts. Most often covered berths are built on the banks of reservoirs where there are no other high objects. In such cases, structures are at increased risk of a direct lightning strike.

Recently, the ZANDZ Technical Center received a request for the development of lightning protection system for a covered berth. Let's consider what solution our experts offered.

 

Initial data:

• object: covered berth located in the Leningrad region;

• dimensions: 30x19 m;

• wall and roof materials: wall and roof sandwich panels;

• Specific resistance of the soil used for calculations – 300 Ohm * m.

 

Task: to develop lightning protection system for a covered berth.

 

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

 

Solution for covered berth lightning protection:

1. Lightning protection and grounding of the covered berth are made in accordance with EIC-7 ed. "Rules for electrical installations", IS 153-34.21.122-2003 "INSTRUCTIONS ON THE ARRANGEMENT OF LIGHTNING PROTECTION OF BUILDINGS, CONSTRUCTIONS AND INDUSTRIAL COMMUNICATIONS" and AD 34.21.122-87 "INSTRUCTION ON THE ARRANGEMENT OF LIGHTNING PROTECTION OF BUILDINGS AND STRUCTURES.

2. The object refers to the III category of lightning protection.

3. According to IS 153-34.21.122-2003, paragraph 3.2.1.2, the metal roof of the object (roofing sandwich panel) is used as an air terminal.

4. Wall sandwich panels are used as down conductors.

5. Transient resistance between all metal sheets and panels should be no more than 0.05 ohms with a mandatory annual monitoring of the latter before the beginning of a thunderstorm season in accordance with AD 34.21.122-87, p. 3.4.

6. All metal elements placed on the roof must be attached to the metalwork of the object.

7. All reinforced concrete foundations, plinths should be used as natural ground electrodes and be attached to the artificial grounding device.

8. Copper-coated steel electrodes 3 m long in places of downdrops are used as a vertical ground electrodes. Copper-bonded steel tape with the cross-section of 30x4 mm uniting all vertical electrodes in the form of a contour is used as a horizontal ground electrode. The distance to the object foundation- not less than 1 m. Deepening of the tape 0,5-0,7 m.

8. Connection to the grounding device is carried out with the help of clamps ZZ-005-064.

11. In accordance with the EIC-7 ed., P.1.7.55 - Grounding devices for protective grounding of electrical installations of buildings and structures and lightning protection of the 2nd and 3rd categories of these buildings and structures, as a rule, should be common.

 

Calculation of the grounding device resistance:

 

The design resistance of a grounding device is 6,43 Ohms, which is less than the required resistance of 10 Ohm.

 

Location of equipment is shown in the figure below.

Figure 1 - Location of equipment.

Полоса стальная омедненная сечением 30 на 4 – copper-bonded tape with the cross-section of 30 to 4 mm
Зажим для подключения проводника – conductor connection clamp
Точка подключения к заземлению – point of connection to the ground electrode
Вертикальный заземлитель длиной 3 м – vertical rod 3 m long

 

Location of equipment is shown in the figure below.

 

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