# To have or not to have a lightning rod?

To have or not to have a lightning rod?

05.08.16 Tags: lightning protection, design, calculation example, technical consultation

Lightning discharge is a complex atmospheric phenomenon, the time and place of which is unpredictable. Today it is possible to calculate the probability of a lightning strike into an object, since it depends on many parameters of the building: height, size, location relative to the objects of larger and smaller height, intensity of storm activity and other factors. Every owner of a private house or villa, planning external lightning protection system, questions himself:  if the lightning rod placed on the house collect all the lightnings in the area? Also, whether it would bring more harm than good? We will get answers to these questions on the calculation example.

Here is an example of calculating the frequency of lightning strikes and reliability of a protection of a mid-sized single-family house 8x10 m and 7.5 m high. Rod lightning rods are fixed at the roof edges of the house.

Lightning protection is calculated using the software developed by JSC "Energy Institute to the name of G. M. Krzizhanovsky"(JSC "ENIN"):

Density of lightning strikes into the ground is 4 strikes / sq km per year - it is a typical value for many regions of Russia. At the same time the number of strikes into an unprotected object per is 0.0096, with the frequency of 1 every 104 years. Results of calculation performed in the software package are listed in the table for lightning rods of different height: 2, 3 and 4 m.

 Height of a lightning rod, m Frequency of strikes Period of breakthroughs, year Probability of a breakthrough into the object, passing lightning protection system Protection reliability 2 Once in 83 years Once in 1000 years 8.4 % 0.916 3 Once in 71 years Once in 3030 years 2,3 % 0.977 4 Once in 58 years Once in 8333 year 0,69% 0.9931

From the table results, you can see that during the installation of lightning rods there is some reduction in the frequency of lightning strikes into a house. It should be noted that compared with the value of the period of breakthroughs, which constitutes in the worst case, once in 1000 years for the lowest lightning rod 2 meters high, the possible increase in the number of lightning strikes looks insignificant.

We conclude that the lightning protection system is very effective, and the probability of a breakthrough is 8.4% and less. For you, this means that with the lightning protection system installed on a house, lightning strikes into the roof or any other point of the house will be almost eliminated.

When calculating each object, the ZANDZ Technical center takes into account all the factors given above and selects the optimal configuration of lightning protection systems. Learn more interesting from our groups in social networks: