Webinar «International electro technical standard IEC 62305. Protection of structures against damage», page 2

The third webinar of a series "Grounding and lightning protection: IEC 62305 standard"

Webinar text. Page 2

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— Here we see an example of a spatial volume which is under protection in accordance with the mesh method and protection angle method.

— Let's continue our communication in the format of questions, please. If you want to ask or tell something on lightning protection, lighting rod systems, please write your questions in the chat in Russian, I will answer in Russian too. I, of course, can speak Russian, but for me it takes more time, Anastasia will interpret for you. I can see the first question. I'd like to being with the first question.

— "Why there is no mutual influence of lightning rods, that is protection zone of a double lightning rod is equal to the total of two single lightning rod protection zones?". Certainly, it is an important problem. We need to think about the efficiency of installing lightning rods in different places. I am very sorry, but we don't have a lot of time to discuss this big topic, but we can come back to the example I showed on this image. On this picture you see, if we change the minimal distance between two separate lightning rods, there will be overlapping of volumes. This means that in certain parts, some parts, some elements of the building will be overprotected. You need to consider that. I think you should study each individual case separately. I am not sure I can talk about this problem for a long time now, but if you are interested in something, you can send me an email without any problem. You can write in Russian. Write your questions in Russian, I understand, but I will answer you in English with great pleasure.

— Let's move on to the second question. "Is lightning protection grounding resistance normalized?". Yes, of course, it is. We will talk about it in a few minutes in the next part of the report.

— "Is it correct to consider that it is better to define a protection zone with the method of a protective angle much smaller, than the rolling sphere radius because of a possible error?". Well, it's a good question. This method is applied to small objects. It is not restricted by the minimal sizes of a lightning rod. We have a minimal radius. And of course, we need to view the minimal protection angle. But a direct lightning strike directly depends on the object sizes. And then, if the building is very small, we need to analyse the financial issues. It means there a need to protect such a small object from a direct lightning strike or not. If there is electronic equipment inside, then, of course it is necessary to use internal lightning protection systems.

—"Does the object influence a protection zone, for example, in Russia, lightning protection standard for the Ministry of Defence establishes the dependence of the protection zone on the square of the protected object?".

— Hello, Zhenya! This is my friend from the Ukraine. He is greeting me and asks a question. We met at some conference. He is a very good specialist. And the question is: «Can we protected people outside the buildings with the help of lightning protection systems or only inside?". Well, it's a good question, Eugenie. Of course, we can minimize direct lightning strike into a human being, who is within an immediate vicinity to the building or lightning protection system. But if the human is outside the building, outside the lightning protection zone, then of course the effect is reducing. We can be under a threat. It's an influence of electromagnetic field. And of course we can be subject to danger from step and touch voltage, being in these zones. There happened such situations, for example, in Poland, when a man was using a wired telephone and was sitting near some metal board and the building was hit by lightning. And the relation between the wire of this man and the lightning protection system worked out and he was hit by lightning. It's a big problem. We can minimize the possibility, the probability of a direct lightning strike, but we cannot minimize different effects of lightning strikes, which can affect health of human or living beings. Or, for example, if a man has some metal devices, like cardio stimulators or something like that, they are more subject to a lightning strike risk.

— Next question. Sorry, there is a big question about Bazelyan's work. We know that the publications of different scientists, which are intended to support other methods and lightning protection system standards. They exist and there are large discussions between different groups of scientists. There is even a forum for such discussions. I had a chance to talk to professor Bazelyan in Novosibirsk at the conference. And my question was. In fact I can't answer your question now, but if you want to apply that and come to a consensus on these standards, of course you need to discuss these methods with their representatives directly at the meetings of such committees or their representatives. We talked with professor Bazelyan and held some meetings at the conferences. And there are conferences, that in fact advertise using of such devices, but they are not introduced into IEC standards. There is a problem in the European committee on standardization. Some of my colleagues, they want to create new systems of standards, which are mainly based on the lightning protection sizes. But this is a big topic for discussion; today the disagreements between the scientists on this matter are great. There are various methods of lightning protection and everything is discussed at the conferences and group discussions.

— Vasiliy Kuryanov is asking where he could find a video recording. Alexey already answered where the webinar recordings are published.

— And the last question, I'd like to answer is from Dmitry Valkovich. "Is protection zone increasing at the height larger than the rolling sphere radius?".

— And the final thing, I see that Alexey wrote information about recording of the webinars. If you have any questions on them, send them to Alexey.

— I hope I have answered all questions. If you don't mind, we will continue our presentation. I forgot about very beautiful pictures. By the way, it refers to the question of professor Bazelyan. I showed you three examples of objects here. One of them is located in France, in Grenoble, where lightning rods were used. On the second picture, we see an image which was shot occasionally during a lightning strike. There were such examples in Poland at a private residence of one Warsaw citizen. The lightning hit the roof corner. You see it is marked with a red arrow. The length of the roof is about 7 meters and you see the use of a lightning rod was not effective in this case. There was also an example of a small chapel. There was a lightning rod on it and the lightning stroke the distance, about 6 meters from this chapel. In fact, there are much more registered pictures, which explain the efficiency, adequacy and determination of lightning protection sizes, it is very important.

— This table contains sizes and thicknesses of metal slabs and pipes, which will be used as parts of natural components in lightning protection systems. Different thicknesses must be used for different materials and different types of metal. These are minimal thicknesses, they are applied when it is important to prevent puncture in metal slabs and pipes. Later we will talk about systems of lightning rods. Before doing so, however, I would like to say that IEC 62305 system widely covers the questions given in the third part.

— If we have an insulated lightning protection system, then lightning rods will consist of lightning arresters on separate masts. There should be at least one mast. It means, every lightning rod must be grounded. There is also a possibility to create natural ground conductors and connected them by the grounding system. The use of reinforcing concrete is normal in Europe, but I have no information about Russia. If lightning protection system is inside the building. Sorry, if it is divided, is free-standing. That means it is the use of a free-standing mast. There should be at least one lightning rod. If we have a network of lightning rods, then there should be one lightning rod at each end of this network.

— I talked about separating distance. This means that there is a possibility that lightning rods may form themselves loops. But in fact, we need to avoid such a formation of loops. We need to pay more attention to the separation distance between lightning rods. We need to consider the height, sorry, length of conductor and three coefficients. Coefficients Ki, Km and Kc. They are given in the chart, you see, they depend on the lightning protection class, materials and lightning current, which goes through the lightning rod. How current is distributed, when we use lightning rods system. And of course, natural lightning rods, they can be used as the part of lightning protection system. But they should be, they should present themselves electrical continuity between different parts. They should be connected and their sizes, should at least be equal to the values declared in the standards. There are four types of materials. If we use reinforced concrete structures, then of course electrical continuity should exist here.

— It is preferable to use free-standing integrated grounding systems. It fits all purposes: lightning protection systems, power plants, supply systems, telecommunications. Thus, in some countries the designers should know that different types are used for different purposes. But sometimes, I don't want to discuss, but some designers define the parameters incorrectly.

— B type of electronic device includes circular conductors, which form themselves a closed loop. In such cases we cannot fail to say about the minimal length. We are comparing the radius of surface which covers these electrodes here. It is easily calculated, depending on the square to be protected and length of ground electrodes. If you see an equation, where re is higher than l1, then we need additional horizontal and vertical electrodes. They should be added, for example, horizontal - it is Lr, value r and vertical Lv.

Useful materials for designers:

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