11.11.16
Vacations are widely popular at any time of year, so there are tourist camps in almost all parts of the world. Normally, they are located quite a distance from populated localities. Such facilities must be protected against external hazards, in particular, a direct lightning strike. Otherwise, that could result in serious consequences.
One of our partners asked the ZANDZ technical center, "How can we set up lightning protection for a tourist camp? What solution can you offer?"
The ZANDZ technical center responded promptly and suggested the following solution for the problem:
Object:
Specific resistance of the soil used for calculations – 150 Ohm * m.
Tourist camps are referred to as "ordinary" according to the JI and are in the 3rd category as per RD. Required reliability - 0.9.
As per EIC 7, article 1.7.103. The total spreading resistance of the earthing 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 a line voltage of 380 V for a three-phase power supply or 220 V for a single-phase power source.
Required arrangements for lightning protection
The action plan to ensure compliance with the necessary requirements for a lightning protection system is as follows:
- Setting up a conductor cable around the perimeter of the roof and its ridge, as well as making 1m high vertical elevations using copper-coated copper wire of D8 mm on the corners of the facility (see Fig.1).
- Installation of an earthing device consisting of 3 vertical electrodes of 3 m in length linked by a horizontal electrode (a copper-plated band of 30x4 mm). The distance from the horizontal electrode to the facility shall not be less than 1 m, embedded 0.5 - 0.7 meters deep.
- All metal objects on the roof shall be connected to conductor cables.
Calculation of resistance of the earthing device:
The design resistance of the grounding device is 9.24 Ohm, which is less than the permitted resistance of 10 Ohm.
Results of calculations performed with software developed by the G. M. Krzhizhanovsky Energy Institute:
The density of lightning discharges into the ground – 6 strikes / sq. km per year;
The total number of strikes into the system is 0.023 (one every 261 years).
Total number of breakthroughs is 0.00091.
System reliability is 0.96.
The probability of a breakthrough into all the system's objects – 0.004 (one every 1055 years).
Figure 1. Equipment layout.
Table 1. List of equipment and required materials.
See also:
- How does an SPD help?
- How to fix a conductor cable on the roof?
- We design earthing and lightning protection correctly!