Thunderstorm and surge protection. Part 1

Recommendation points

• External lightning protection
• Lightning rod
• Catenary wire lightning rod
• Mesh lightning rod
• Active lightning protection
• Protection of houses and squares

Statistics say that a thunderstorm is one of the most dangerous natural phenomena for humans. In the city, housing and communal services are thinking about our protection. But in a country house, all responsibility falls on us. We will talk about how to properly defend yourself in this article..

The best protection for a person from a thunderstorm is the country house itself, of course, if such a house is properly protected. And without protection, it can become a source of additional danger. All the risks that a thunderstorm poses for a country house can be divided into two groups: external and internal. Everything that is associated with a direct lightning strike into the house belongs to external ones. Internal risks are associated with the consequences of lightning impact on intra-building networks. Unfortunately, there is no universal remedy. Each risk group will have to develop its own system. And only the simultaneous presence of such systems can provide real protection against the danger posed by a thunderstorm..

External lightning protection

The invention of the lightning rod is often credited to the American President Franklin. In fact, the president did not invent anything, and a very significant physics experiment was carried out on his instructions. During a thunderstorm, a kite was launched into the sky, to which a metal key was tied. Lightning struck the key and the rope on which the kite was attached burned out. Thus, the physical nature of lightning was established. And since this is an electrical discharge, it became clear how to deal with such a danger. And then the first lightning rods were developed. True, the goal was not to protect private homes. Still, the president was faced with state tasks. And the treasury suffered great damage from fires and explosions in ammunition warehouses, which often happened after lightning strikes them..

The electrical nature of lightning is now well known to any schoolchild. Therefore, we are more interested in another result of the president’s experiment. The rope has burnt out, which means that the current is high. Therefore, in order to divert the electrical energy that has entered the lightning rod (lightning rod), you will need a reliable down conductor that will not light up, like a rope.

Since childhood, we have become accustomed to the fact that a lightning rod is placed on the roof to protect against lightning. I must say that this term is outdated, and does not correspond to the functions assigned to it. Indeed, thunder is an acoustic signal. Therefore, a device called a lightning rod has nothing to do with it. The purpose of such devices is the same – to take on an electrical discharge. Therefore, it would be more correct to call such devices a lightning rod or a lightning rod. However, it is possible and more generalized – a thunderstorm. All of these terms are synonymous and describe devices that have the same functionality. We will consider the most popular types of lightning rods below..

Lightning rod

This is perhaps the oldest and most common design of a lightning rod. Just a rod of some length and thickness. The parameters of the bar are determined by the structure it protects. However, there may be rather fanciful designs. But this is only decoration, they do not affect the functionality. More precisely, they shouldn’t. In reality, such decorations can compromise the strength of the structure or have other undesirable consequences. For example, moisture can accumulate there, which accelerates corrosion, and therefore reduces the service life of the lightning rod..

Each rod lightning rod has parameters that are determined by the protected area. It is installed in such a way as to be higher than the protected object. It is clear that one rod lightning rod, installed in an arbitrary place, may not provide effective protection for the entire house, especially when the house is large and has a complex shape. The calculation methodology is described in the wonderful document RD 34.21.122–87 “Instructions for the device of lightning protection of buildings and structures.” It takes into account everything, and the frequency of thunderstorms in a given region, and the purpose of the building, its physical parameters, etc..

For the average country house in our mid-latitudes, a simple estimate can be made. Build a cone from the top of the lightning rod. The forming angle is usually taken at 45 degrees. If you calculate accurately, according to the above instructions, then it may differ by 1-5 degrees in one direction or another.

The question may arise, what to do if the rebuilt cone does not cover the entire structure? It is very simple here – you need to install additional lightning rods in such a way that all together they cover the protected structure. All of them can be reduced to one ground. But you need to remember that such a connection must be reliable and meet the requirements for the down conductor..

Catenary wire lightning rod

For elongated objects, you can use another type of lightning rod, which is called catenary wire. They consist of a sturdy metal cable that is attached to two or more supports. If we build cones around the two terminal supports according to the rules similar to rod lightning rods, and then impose two planes on them along the cable, then we will get a protection zone, which is provided by a catenary wire lightning rod. If we have a complex structure of the house, then there may be more supports, and the cable will be placed in accordance with its geometry. For example, along the roof visor.

In principle, such a lightning rod can protect not only a country house, but also the entire adjacent territory. This may be required, for example, if an advanced irrigation or lighting system is used that contains a sufficient number of expensive electronic components. Two strong masts are installed higher, and a cable is stretched between them, which is connected to the ground by a down conductor on one side.

Mesh lightning rod

Many country houses have a metal roof. There is a temptation, why not use it as a lightning rod? In fact, this is quite possible, only you need to take into account some features. If you recall Franklin’s experience, then the rope burned out. Therefore, with a low metal thickness and poor connection between the sheets with a metal roof, the same can happen. If, for example, a reliable corrugated board is used, then everything will be fine. Of course, such a metal roof must be connected with a down conductor to ground.

In the event that the roof material is a dielectric, then there is another solution, which is called a mesh lightning rod. We place a metal mesh on top of the roof, which will act as a lightning rod. You can do the same when there is no confidence in the reliability of a metal roof.

For the organization of such lightning rods, steel mesh is usually used. The size of the cells is taken not very often, but there is a limitation – no more than 6×6 m.The thickness of the wire must be at least 5 mm.

The method of fastening the mesh is also important. Regardless of the material of the roof, it is better to fix such a mesh on special insulators. And, of course, it is necessary to ensure a reliable connection with the down conductor..

Active lightning protection

The designs of lightning rods, which are discussed above, have been in operation for many tens, or even hundreds of years. Their pros and cons are well known, their designs have been worked out. Nevertheless, we live in a time of all kinds of technical innovations. And they could not but appear in the field of protection against thunderstorms. The first successful developments date back to the eighties of the last century. Then a group of enthusiasts came up with the idea to make a fundamentally new device. Lightning rods usually catch random lightning. Protection could become more effective if you learn to attract lightning, that is, make the lightning protection active.

The principle of operation is described simply. The first thing such a device should be able to do is to identify a pre-storm situation. It is determined by the strength of the electric field between the cloud and the ground. Most importantly, the electric field strength can be measured, which means that the critical value can be determined. Second, when the danger is identified, that is, the critical value of the electric field strength is reached, the device must take the necessary action, that is, simply provoke lightning.

Structurally, such a device, and it is customary to call it a lightning rod, looks very simple. In fact, it is a rod lightning rod, to which one more contact is added, which is isolated from the rod. A gap is established between the contact and the rod, which corresponds to the critical stress value. When a critical value is reached, a breakdown or arc discharge occurs between the contact and the rod. This is the channel into which the lightning should discharge. After the discharge, the field strength decreases.

The main advantage of such a system is the area it protects. Typically, such a system is designed to protect an area with a radius of about one hundred meters around the air terminal, which is much larger than when using a standard lightning rod..

There is another advantage of such systems, which is often compared to reliability. Lightning by itself is not very predictable, like most natural phenomena. And the time of a lightning strike into a lightning protection system is all the more impossible to predict. Therefore, such an event can be expected for months or even years. It is clear that there can be no confidence in the serviceability of such a system, and at the most crucial moment it may simply not work. The system should be regularly serviced and checked. And if nothing happens, then such works are treated without due attention..

Active lightning protection systems are another matter. First, they have a built-in testing function. If you have any doubts about the system’s performance, just press a button and make sure everything is working properly. Secondly, the system has a discharge counter. It’s always nice to know how many times the system has protected a house, especially considering the cost of active lightning protection systems, which starts from 120 thousand rubles.

Protection of houses and squares

A country house is usually not built in an open field. One way or another, a whole household farm is being formed around it. This could be a garage, an inventory shed, or perhaps a greenhouse or even a small chicken coop. In addition, bushes and fruit trees can be planted on the site. If, in this case, only the country house itself is protected from a thunderstorm, then this is not enough for complete safety. If lightning strikes a tree or shed, it is also dangerous for your home. Distances are small, and the fire can spread to other buildings, including the house itself.

You can, of course, protect each building from a thunderstorm separately. But a rational solution would be an integrated approach. To do this, it is necessary to determine the area that requires protection from thunderstorms, and only then select lightning protection systems. A rational decision is always individual. In some cases, it will be appropriate to install an expensive active lightning protection system, in others it is quite enough to install several cheaper lightning rods. Moreover, at the same time, it is allowed to use different types of lightning rods, which will take into account both the geometric dimensions of the object and the materials from which they are made.

It may turn out that there will be no lightning rods at all in the country house itself. The lightning rod installed on a high tree or on a special mast will protect both the house and all yard buildings.

In this part of the article, we discussed protection in a situation where lightning strikes directly into the house. But if lightning strikes power lines somewhere a kilometer from the house, it will also not remain without consequences. How to protect the house from this danger, we will consider in the next part.