Item 3.3.1 of the Guidelines for Arrangement of Lightning Protection of Buildings, Structures, and Industrial Utilities SO 153-34.21.122-2003 prescribes using the software to calculate lightning protection:
...Generally, lightning arresters shall be chosen using the appropriate software capable of calculating the protection zones and the lightning breakthrough probability...
The ZANDZ Calculation Service is a convenient tool for designing lightning protection. Using this software, you can calculate essential parameters, such as the number of lightning strikes to the facility and the breakthrough probability as well as make the design of efficient and more economically feasible lightning protection system. The service was developed by the G.M. Krzhizhanovsky Energy Institute (AO ENIN) and it takes into account all effective regulatory documents in the lightning protection
This article compares the results of lightning protection calculations using two methods: the protection zone method and the ZANDZ calculation service.
Initial data:
- facility: vertical storage tank (VST) used to store fuel;
- diameter: 10.4 m;
- height: 9 m;
- lightning protection level: II (the lightning protection system's reliability should not be less than 0.95);
- the space of R = 5 m, H = 2.5 m above the VST breather should be additionally protected in accordance with RD 34.21.122-87, item 2.6.
To calculate using the protection zone, interception rods h = 20 m from the ground level will be used; the rods should be at least 13 m (11 m elevation above the facility +2 m for securing to the facade)
The results of calculation of protection zones according to SO 153-34.21.122-2003:
Cone height according to SO, Table 3.4:
Cone radius according to SO, Table 3.4:
To provide the protection zone with the required reliability, radius rx at the height hх = 9 m is determined as follows:
To provide the protection zone with the required reliability, radius rx at the height hх = 11.5 m is determined as follows:
The distance between interception rods (maximum): L = 10.4 m;
Limit distance between lightning rods according to SO, Table 3.6:
There is no sagging height.
For the protection zone with the required reliability, radius rcx at height h0 = 2 m is defined as follows:
The protection zones are shown in Fig. 1.
Figure 1. Layout of the lightning protection equipment.
Условные обозначения: Conventional representation:
- молниеприемник высотой 13 м - 13 m high lightning arrester
- проволока стальная омедненная диаметром 8 мм (ZZ-11149) - сopper-coated steel wire of 8 mm diameter (ZZ-11149)
- полоса стальная омедненная с сечением 30х4 мм (ZZ-11075) - сopper-coated steel strip of a 30x4 mm section (ZZ-11075)
- опуск токоотвода - down conductor lowering
- вертикальный заземлитель длиной 3 м - vertical ground electrode, 3 m. long
- защищаемая зона H=2,5 м, R=5 м - protected zone H=2.5 m, R=5 m
- зона защиты на H=9 м - protection zone at H=9 m
- зона защиты на H=11,5 м - protection zone at H=11.5 m
ЗАЩИЩЕНО И ЗАЗЕМЛЕНО GROUNDED AND PROTECTED
Now, let's perform calculations using the software according to SO 153-34.21.122-2003, item 3.3.1.
When calculating the lightning protection system's reliability using the calculation service, interception rods 16 m high from the ground level will be used; rods should be at least 8 m (7 m for the elevation above the facility, and 1 m for the attachment to the facade).
Results of the calculation performed using the ZANDZ software:
- intensity of lightning discharge into the ground is 4 strikes/square km/year;
- overall number of strikes into the system is 0.038 (once every 26 years);
- total number of breakthroughs is 0.00079 (once every 1,266 years);
- the system's reliability is 0.979;
- the probability of breakthroughs into all facilities of the system is 0.021;
- the layout of the equipment is shown in Fig. 2.
Figure 2. Layout of the lightning protection equipment.
Перевод картинки Рис. 2
Условные обозначения: Conventional representation:
- молниеприемник к фасаду высотой 8 м (ZZ-201-008-3) - lightning conductor for 8 m high facade (ZZ-201-008-3)
- проволока стальная омедненная диаметром 8 мм (ZZ-11149) - сopper-coated steel wire of 8 mm diameter (ZZ-11149)
- полоса стальная омедненная с сечением 30х4 мм (ZZ-11075) - сopper-coated steel strip of a 30x4 mm section (ZZ-11075)
- опуск токоотвода - down conductor lowering
- вертикальный заземлитель длиной 3 м - vertical ground electrode, 3 m. long
- защищаемая зона H=2,5 м, R=5 м - protected zone H=2.5 m, R=5 m
ЗАЩИЩЕНО И ЗАЗЕМЛЕНО GROUNDED AND PROTECTED
Comparison results
When you use the protection zone calculation method, the solution is based on higher rods, which increases the total cost of the lightning protection system. Using the ZANDZ Calculation Service, you can obtain the actual rated reliability of the lightning protection system. This provides for the opportunity to use lower interception rods to reduce the project budget. Moreover, you should consider negative effects of the interception rod's height on the lightning strike frequency: the higher the interception rod, the better it attracts the lightning.
The ZANDZ Calculation Service is free of charge and available here.
Do you need to calculate the facility's lightning protection system? Please contact the ZANDZ Technical Center!
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