The ZANDZ Technical Center has received a request for the calculation of the lightning protection system for the plastics plant. Let us look further at what solution has been executed.
Initial data:
Dimensions of the protected facility: 78.15 х 17.4 х 10 m.
Soil resistivity: 45.1 ohm*m.
Task:
1. Calculate the lightning protection system.
2. Calculate the grounding arrangement.
The activities have been performed according to:
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EIC, 7th rev., SO 153 34.21.122 2003 Instructions for Mounting Lightning Protections of Buildings, Structures and Industrial Communications (hereinafter referred to as SO);
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RD 34.21.122 87 Instructions for Mounting Lightning Protection of Buildings and Structures (hereinafter referred to as RD).
The facility is classified as conventional according to SO and to the second category according to RD (explosion and fire hazard class is B-IIa).
A set of arrangements ensuring compliance with the lightning protection requirements is based on the following solutions:
1. Lightning protection for the facility is performed using the lightning masts with the height of 16 m (ZZ-201-016), which are installed at the distance of 3 m from the protected facility.
2. Metal structure of the facility is attached to the grounding circuit in the facility corners and every 15 to 20 m.
3. As vertical grounding arrangements, the copper-coated rods 3 m long are used, which are installed in the lightning arrester connections. 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.
5. According to the EIC, 7th rev., item 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 usually should be common.
6. If there are reinforced concrete structures, they should be connected to current collectors/grounding arrangement.
7. Connection to the grounding arrangement is made with clamps ZZ-005-064.
The results of calculation of protection zones according to SO:
Lightning arrester mast No. 1 - 6 (ZZ-201-016):
h = 16 m;
Cone height according to SO, Table 3.4:
h0 = 0.8h = 12.8 m;
Cone radius according to SO, Table 3.4:
r0 = 0.8h = 12.8 m;
Distance between lightning arresters (maximum):
L = 42.075 m;
Limit distance between lightning arresters according to SO, Table 3.6:
Sagging height:
For the protection zones with the required reliability, radius rcx at the height of h0 = 14.4 m is defined as:
Ground terminal resistance calculation:
Vertical electrode resistance:
where ρρeq – is soil equivalent resistivity, 45.1 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 deepening of the top of the electrode, 0.5 m;
Horizontal electrode resistance:
where ρ is soil resistivity, 45.1 ohm·m;
b is horizontal electrode width, 0.03 m;
h is horizontal electrode depth, 0.5 m;
Lhor is horizontal electrode length, 199 m.
Electrical impedance of the grounding arrangement:
where n is number of sets, vertical grounding arrangements 6 pcs, horizontal grounding arrangement 1 pc;
Kutil is utilization rate, 0.69;
The design resistance of the grounding arrangement is 0.67 ohm.
The equipment layout and the protection zone are shown in Fig. 1.
The list of equipment and necessary materials is provided in Table 1.
Figure 1. Equipment layout. Protection zone.
Молниеприемник-мачта высотой 16 м (ZZ-201-016) - Lightning arrester mast 16 m high (ZZ-201-016)
Электрод D = 14,2 мм, L = 3 м - Electrode D = 14.2 mm, L = 3 m
Полоса омедненная стальная сечением 30х4 мм (GL-11075) - Steel copper-plated strip having cross-section 30 x 4 mm (GL-11075)
Table 1. List of needed materials.
| № | Part number | Name | Quantity, pcs. |
| 1. | ZZ-201-016 | ZANDZ 16m vertical lightning arrester (galvanized steel; with parts embedded under the foundation) | 6 |
| 2. | ZZ-001-065 | ZANDZ Copper-plated threaded grounding rod (D14; 1,5 m) | 12 |
| 3. | ZZ-002-061 | ZANDZ Threaded coupling | 7 |
| 4. | ZZ-003-061 | ZANDZ Termination | 6 |
| 5. | ZZ-004-060 | ZANDZ guide head for jackhammer attachment | 3 |
| 6. | ZZ-006-000 | ZANDZ conductive grease | 1 |
| 7. | ZZ-008-000 | ZANDZ Attachment to the hammer (SDS max) | 1 |
| 8. | ZZ-005-064 | ZANDZ Conductor connection terminal (up to 40 mm) | 42 |
| 9. | ZZ-007-030 | ZANDZ Waterproofing tape | 14 |
| 10. | GL-11075-50 | Copper-clad strip GALMAR (30*4 mm / S 120 mm²; 50-meter strip bundle) | 5 |
Do you have any questions about grounding and lightning protection of the plastics plant? Please, contact the ZANDZ Technical Center!
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