Webinar «International electrotechnical standard IEC 62305. Protection of electrical and electronic systems», page 2

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

Webinar text. Page 2

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— More examples. If there is a transformer inside the building, very often in the country houses or even in the city buildings, there are transformers of low, high of medium voltage. If there is a line to be building between zones 0 and 1, it is necessary to install surge protection system. It is a very important requirement in Poland, when the building is connected directly. We are obliged to install surge protection system. In the second example we see when the transformer of low and medium voltage is placed inside the building. On the left picture, it was outside the building. It often happens so in large buildings, in some industrial facilities. If medium voltage line is used, we can apply zone 0 zoning, enlarge it into zone 1, but then it will be necessary to install surge protection system from the side of low voltage. On the third example we see the situation when we don't have a transformer, but we have electric or signal lines. And the equipment needs to be protected; two coordinated surge protection systems should be used. One at the border of LPZ 0 or 1 and second at the border of LPZ 1-2. And we will talk a bit later about the coordination of these zones.

— The next part of measures is magnet shielding and LEMP routing. What do we expect from magnet shielding? It should reduce the magnet field strength, which appears because of a lightning strike inside the building, inside lightning protection zone, because lightning flashes, when they strike directly into the building or near the building influence on the installations and on the equipment. We need to reduce the effect occurring because of them by using shielded wires or shielded cable conduits in order to reduce the possible damage. We also need to use correct lines routing, for example signal lines, telecommunication lines which come to the equipment.

— Here we see the idea of grounding and bonding which we created in a 3D form. This image contains grounding system and equipotential bonding system. Of course we need to keep in mind the equipment used inside the building, computers. And by using such a system we can reduce electromagnet field force. If there is a lightning strike, then such a cell system inside the building can seriously reduce the electromagnet force, appearing inside the building because of a lightning strike.

— Of course for buildings, when we have very sensitive equipment, for example, telecommunication systems, informational equipment, we should create lightning rod systems but using B type grounding electrodes. This is recommended. Electrode of B type - it is a grounding electrode or circular electrode, which performs the function of equipotential bonding. Typical cell system, the width of such a system should not be higher than 5 meters. Have a look at the picture, in the middle of № 1 there is this cell system is used with the fittings reinforcement. Under №2 you see a support for data transmission. This support is very sensitive. Of course, it is connected by cell configuration. №3 is free-standing equipment, for example, video surveillance camera, lighting equipment, different kinds of free-standing equipment which is often used in different buildings. They are also included into the electric and electronic system of the whole building. They will be all connected by this cell system, the cell grounding system. It is a recommended solution of protecting equipment which is strongly subject to lightning strikes.

— How do we create this grounding and bonding network? There can be different structures, but there is one point of grounding system, when the equipotential bonding system is created with the use of metal structures. We have different possibilities for the configuration of bonding system inside the building. This is the so-called configuration in the form of S star or M. Configuration M is a cell configuration. The main configuration. In case of a cell system we can use natural components of lightning protection system of metal structures or some other metal elements, if they are connected by the lightning protection system.

— I hope there will be more questions, but we will now talk about creation of magnet shielding. Of course, it must be used for al metal or armour structures of the building. If we have metal elements in the building: armour or some frames, metal casings of conductive surface or even roof, we need to use natural components of magnet shielding. It is necessary to keep in mind the sizes of cross-section of metal parts in order to minimize the influence of electromagnet field from a lightning strike. It is very interesting - the use of spatial shielding. If we have a building made of bricks without conductive elements and we install lightning rod system outside the building and connect it into the system, we will get spatial shielding, created by natural or artificial components of lightning protection system. Here you can read information what spatial shielding means. These spatial shields determine protection zones which may cover the whole building, part of the building or some certain room or premise with the equipment inside. They can create cell configuration or spatial area around the equipment inside the building and it is recommended to use these shields because they can easily limit lightning protection zones.

— It is a cube of a certain size. The distance between the external shield and the protected volume. And in accordance with it, we can understand when and how we can install sensitive electronic equipment. Safe distance it is value ds/1. If we have Wm - it is the cell of grid shielding system and SF - shielding factors or a factor suppressing electromagnet impulses. And this way we can distance in meters using these formulas on the base of network width size. In this case we can define if we can use natural components of the building as a shield. We can define if there is safe room for sensitive equipment inside the building which is not subject to electromagnet pulses.

— We can count the value of magnet field force for such measures. On the two diagrams you see the values of distances from the shields to the objects. We see that the reduction is very important. On the second example we see how to count the magnet field force in two points inside the building, and on the first one, the magnet field force was calculated along the line.

— Now another method which we mentioned before - routing of electromagnet lines and their shielding. On the first picture you see the protection system image. Here we see connections of two units of equipment. For example, these are computers; there is a power line, signal line between them. №2 is a single line, № 3 - power cable. They are interconnected into an induction loop - №4. In this case, magnet field may cause overvoltage. How can we prevent it? First of all, we can use shielded wires. In this case, we of course minimize the values by the induced effect. We can also install the shield outside the building, if we have an external system of lightning protection, as shown on the second picture on the top. Lightning protection system is used here, maybe it is some factory. Here the use of lightning protection zone can reduce electromagnet field. If we have a chance to change the place. If the wires create an induction loop.

— In the final part, which is very large we cover the choice and installation of surge protection system. Before talking about it, I would like to ask if you have questions, connected with the previous topics, for example, shielding, grounding or equipotential bonding. I see one question from Mr. Milyaev, let me read it. It is a very specific question how to connect safe zones using shielding method? Should we use galvanized steel and if I remember correctly, this question refers to the 3 part of our standards. What is the minimal distance is we use lightning rod systems? How long and how great should they be? If you use fittings, for example and how you use it in the system as a natural component, then each part should be connected by at least two elements. We should protect it from corrosion. There is another method, of course.

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