Nowadays, satellite dishes are installed on the roofs of many houses, providing people with digital television and the Internet. Today it is simply a vital necessity for almost every person! However, not many people think about possible problems that may arise during a thunderstorm. At any time, a signal loss or equipment failure resulting from a lightning strike can occur.
В ZANDZ Technical Center received a request to protect satellite dishes on the roof of an office building. Let's have a look at the solution we offered.
object: office building;
type of roof: flat.
calculate the lightning protection system of satellite dishes;
calculate protective grounding device.
According to EIC-7, p. 1.7.103. The total speading 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 a three-phase power supply or 220 V of a single-phase power source.
1. Lightning protection of satellite antennas is made in accordance with IS 153-34.21.122-2003 "INSTRUCTIONS FOR THE INSTALLATION OF LIGHTING PROTECTIONS OF BUILDINGS, STRUCTURES AND INDUSTRIAL COMMUNICATIONS" and AD 34.21.122-87 "INSTRUCTIONS FOR INSTALLATION OF LIGHTNING PROTECTION FOR BUILDINGS AND STRUCTURES".
2. In accordance with the technical inquiry, the object must be protected according to the 2nd category of lightning protection. System reliability must be not less than 0,95.
3. Lightning protection of the object is made in the form of a lightning protection mesh with a pitch of not more than 10x10 m, using a copper-bonded copper wire with a diameter of 8 mm (GL-11149). All towering objects are protected by air terminals masts with the height of 10 and 4 m, fastening is carried out using holders to the vertical surface.
4. Copper-bonded steel wire is used as down conductor (thickness of the copper coating not less than 70 mcm), d8mm wire (GL-11149).
5. Installation of down conductors is carried out with the help of clamp GL-11711 - on a flat roof, GL-11703А - on vertical surfaces and parapets. Distance between the clamps- from 0.8 up to 1.0 meter.
6. To connect rolled metal over the length and in the nodes, a universal clamp GL-11551A is used.
7. All metal elements, placed on the roof must be connected to the down conductor with the help of clamps GL-11545А. Stairs and hand railings are connected with the help of a clamp-bridge GL-11514.
8. Copper-bonded steel electrodes 3 m long are used as a vertical grounding electrode. A copper-bonded steel tape with the cross-section of 30x4 mm (GL-11075), which unites all vertical electrodes, is used as a horizontal grounding electrode. The distance to the object foundation- not less than 1 m. Burial depth of the tape 0,5-0,7 m.
9. 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.
The calculated value of the grounding device resistance is 1.61 Ohms.
11. If there are metal reinforce concrete framings, they must be connected to down conductors/ grounding device.
12. Connection to the grounding device is carried out with the help of clamps ZZ-005-064.
Results of the calculation carried out with the software developed by the OJSC "Energy Institute to the name of G.M. Krzhizhanovsky (JSC "ENIN"):
Density of lightning strikes into the ground - 4 strikes / sq. km per year
The total number of strikes into the system in: 0.065 (once in 15 years);
The total number of breakthroughs is 0.0023 (every 435 years)
System reliability - 0,965
Probability of a breakthrough into all the system objects - 0.035
Grounding device resistance calculation:
The design resistance of the grounding device is 1,61 Ohms, which is less than the required resistance of 10 Ohm.
The location of the equipment is shown in Figure 1.
Figure 1 - Location of equipment for lightning protection and grounding of satellite dishes.
The list of required equipment and materials is given in table 1.
Table 1 - List of required equipment and materials.
Do you have questions or if you need to calculate a lightning protection system for satellite dishes? Send your request to email@example.com.