ANALYSIS OF THE APPLICATION OF ACTIVE LIGHTNING RODS IN LIGHTNING PROTECTION OBJECTS

ANALYSIS OF THE APPLICATION OF ACTIVE LIGHTNING RODS IN LIGHTNING PROTECTION OBJECTS

Elshad  Safıyev

Candidate of Technical Sciences, Associate Professor, Azerbaijan State University of Oil and Industry,

Azerbaijan, Baku

Najiba Pirieva

Doctor of Philosophy in Engineering, Associate Professor, Azerbaijan State University Oil and Industry,

Azerbaijan, Baku

Goshgar Bagirov

master, Azerbaijan State University of Oil and Industry,

Azerbaijan, Baku

АНАЛИЗ ПРИМЕНЕНИЯ АКТИВНЫХ МОЛНИЕОТВОДОВ В МОЛНИЕЗАЩИТЕ ОБЪЕКТОВ

Сафиев Элшад Сулейман

канд. техн. наук, доц., Азербайджанский Государственный Университет Нефти и Промышленности,

Азербайджан, г. Баку

Пириева Наджиба Мелик

д-р философии по технике, доц., Азербайджанский Государственный Университет Нефти и Промышленности,

Азербайджан, г. Баку

Багиров Гошгар Тахмасиб

магистр, Азербайджанский Государственный Университет Нефти и Промышленности,

Азербайджан, г. Баку

ABSTRACT

Lightning is one of the interesting phenomena widespread in the atmosphere of our planet and constantly studied. About 2,000 lightning flashes simultaneously on our planet, and thunderclouds send about a hundred lightnings to the earth every second.

Lightning is more dangerous for strategic facilities - petrochemical complexes, nuclear power plants, high-voltage lines, substations, etc. The electromagnetic pulse generated by lightning strikes disrupts the operation of telecommunications equipment, computer networks and control systems. Therefore, high demands are placed on lightning protection.

Lightning protection is one of the most important issues in electrical engineering. Since the traditional lightning protection systems used are not at the required level, it becomes necessary to search for new methods to solve this problem.

АННОТАЦИЯ

Молнии — одно из интересных явлений, широко распространенных в атмосфере нашей планеты и постоянно изучаемых. На нашей планете одновременно вспыхивает около 2000 молний, ​​а грозовые облака ежесекундно посылают на землю около сотни молний.

Молнии более опасно для стратегических объектов нефтехимические комплексы, атомные электростанции, высоковольтные линии, подстанции и т.д. Электромагнитный импульс, генерируемый ударами молнии, нарушает работу телекоммуникационного оборудования, компьютерных сетей и систем управ­ле­ния. Поэтому к молниезащите предъявляются высокие требования.

Молниезащита является одним из важнейших вопросов в электротехнике. Поскольку используемые традиционные системы молниезащиты не находятся на необходимом уровне, возникает необходимость поиска новых методов решения этой проблемы.

Ключевые слова: Перенапряжение, молниезащита, заземление, активные молниеотводы

Keywords: Overvoltage, lightning protection, grounding, active lightning rods

Introduction

Lightning protection is one of the most important issues in electrical engineering. Since the effectiveness of the traditional lightning protection systems used is not at the required level, there is a need to search for new methods to solve this problem. The presented work is devoted to research of new methods.

Lightning is one of the widespread and constantly studied interesting phenomena of our planet's atmosphere. About 2000 lightning flashes on our planet at the same time, and storm clouds send about a hundred lightning bolts to the ground every second. In fact, lightning is a long spark carrying an electrical charge that occurs at a certain voltage between the storm cloud and the ground [1,2].

The discharge between the cloud and the ground begins with a weakly illu­mi­na­ted channel that moves from the cloud to the ground at a speed of 100–1000 km/s in a spur-like manner and is called a step leader. When the leader reaches the ground, the main discharge phase begins. It can be seen with the naked eye like lightning. A direct impact of lightning on an object or building can lead to electrocution of people and other living things, ignition and melting of various materials, splitting of trees, forma­tion of cracks in bricks and concrete, high potential in communication lines (electrical transmission wires, pipes, etc.). Even if "lightning" does not strike the object directly, the surge of voltage can spread over long distances through communication lines and destroy valuable equipment.

Lightning petrochemical complexes, nuclear power plants, high voltage lines, sub­stations, etc. more dangerous for strategic objects. The electromagnetic pulse gene­ra­ted during a lightning strike causes malfunction of telecommunication equipment, computer network, control systems. Therefore, high demands are placed on lightning protection [3].

Since the traditional lightning protection systems used in practice (rod, cable, grid-shaped lightning conductors) do not provide the necessary level of efficiency, there is a need to search for new methods to solve this problem.

The leading channel of lightning, formed in a storm cloud several kilometers abo­ve the Earth's surface, moves along a trajectory different from the electric field vector of the atmosphere at the beginning of its movement. This is due to the fact that the intensity of the electric field at the edges of the leader channel is at least 2 times greater than the external field. Observations show that the leader channel can move perpendicular to the external field and even in the opposite direction. For these reasons,  the trajectory of lightning towards the ground is also different

In hundreds of experiments carried out in laboratories under symmetrical con­di­tions, in large air gaps, it is possible to observe trajectories of electric discharge similar to the above-mentioned processes. Their average trajectory coincides with the vector of the external field (fiqure 1). When placing an electrode that plays the role of a ground object on a grounded surface, breaking the symmetry the mean trajectory of the discharge will be vertical up to a certain distance and then inclined to the surface object (Figure 2). As the height of the object h is large, the turning (orientation) height H₀ of the average trajectory is large.

Figure 1. Average discharge trajectory (in symmetric conditions)

Figure 2. Average trajectory of the discharge with a grounded electrode (asymmetrically)

From a modern scientific point of view, it is  assumed that the lightning rotation mec­hanism is related to the mutual leader. The counter leader moves against the lig­ht­ning leader from above the object. The contact of leaders ends their development pro­cess. As the opposite leader becomes longer, it holds the lightning farther from the gro­und. Thus, in order to increase the effectiveness of the lightning rod, it is necessary to create a mutual leader in it as soon as possible and achieve its development at the maxi­mum speed. The working principle of modern active lightning arresters (ESE lightning arresters) is related to the physical processes shown. The abbreviation ESE is derived from the English words (early streamer emission).

In the middle of the last century, an attempt was made to create radioactive lightning rods in France. For this, a capsule with a radioactive substance was placed at the end of the lightning rod. The aim was to create an electrical charge by ionizing the air around the capsule as a result of the irradiation and obtain a long spark-preventer or mutual leader. However, the introduction of radioactive lightning rods did not last long, because the use of a strong radiation source creates a source of danger to human life, while the effectiveness of a weak radiation source is low. The air at the tip of the lightning conductor is ionized as a result of the corona discharge, even in the absence of a radiation source. Voltage on the lightning conductor when the height of the lightning conductor is h=10¸20m

happens.

here, Eo=10¸20 kV/m - is the field voltage at the earth's surface under lightning conditions. If the radius of the tip of the lightning conductor is r₀, then the field voltage there happens.

Will be Since the value of E is greater than the electric strength of air (E_d=3 kV/mm), a millimeter ionized layer is formed at the tip of the lightning rod, but a conductive plasma channel is not formed.

A circuit consisting of a two-turn inductive coil, a capacitor, a discharger and an air gap is  created in the upper part (head) of an active lightning rod that creates ioni­za­­tion and a mutual leader (streamer) and finds its application in practice. When a high mutual electric field is created between the cloud and the ground, an elec­tro­mo­tive for­ce (EMF) is created in the inductance and charges the capacitor. When the capacitor is fully charged, the discharger is pierced and the current flowing through the circuit creates an EHQ in the second loop of the coil. In turn, EHQ sends charged particles towards the cloud. The purpose of the process is to ionize the air directly at the tip of the lightning rod and facilitate the stretching of the mutual conductor (streamer). The scheme described is conventional, although manufacturers of active lightning arresters use different schemes, their working principle is the same.

Testing of active lightning arresters was  carried out in laboratory conditions. In ad­dition to the active lightning arrester, a common stick (passive) lightning arrester was also tested for comparison. Both lightning impulses are placed in the grounded plane of the voltage generator. In the experiment, the edges of the high voltage elec­tro­de, which was given a negative voltage, were in the form of a curved plane. The dis­­tance between them was 2 m. Both lightning conductors are  symmetrically placed at the required distance from the vertical axis of the gap to eliminate their mutual in­fluence. In the series of 20 discharges at the same value of the voltage, the number of discharges in the active and rod lightning conductors was recorded. The results were as follows: when the height of the lightning rods is 1 m, each of the 20 discharges was re­ceived by the active lightning rod, the height of the active lightning rod is im and when the height of the passive lightning rod is 1.02 m, 19 of the 20 impacts were re­cei­ved by the active lightning rod and 1 by the passive lightning rod, the height of the active lightning rod is 1 m, when the height of the passive lightning rod is 1.06 m, 16 out of 20 impacts were received by the active and 4 by the passive lightning rod [4]. Ac­ti­ve lightning protection can also be implemented using a laser beam. In this case, the air is optically pierced by the laser beam, a long laser spark is created, and the time of formation of the mutual leader is reduced. The leader captures part of the laser spark, thus increasing its speed.

One of the new methods of lightning protection is based on a water cannon fired from a laser. It is believed that with the help of a water cannon reaching a height of 300 m towards the hurricane clouds, the loads are transferred to the ground and thus safety is ensured. Activation of such protection occurs automatically when the intensity of the electric field is  registered, through the recorders, reaching a high value [5,6]. It is known that when using a traditional rod lightning arrester, the radius of its protection zone r_x is determined as follows (Figure 3):

Where h₀ is the height of the protection cone, r₀ is the radius of the protection cone. These parameters are calculated depending on the height of the lightning rod (h=0-150 m) and the reliability of the protection.

Fiqure 3. Lightning protection zone lightning rod

The calculation of the radius of the protection zone of active lightning rods based on ionization is somewhat complicated and is determined by the following expression:

where h₁- is the height of the lightning conductor above the protection object (h_ı<5m), ΔL = V×Δt - is the height of the mutual conductor, V (m/mksec) is the speed of the mutual conductor, Δt (mksec) is the activity time of the conductor. D=20; 45 or 60 m - depending on the protection level (I, II or III) is accepted [7,8].

Reports show that compared to a passive lightning arrester under the same conditions, the area of the object protected by an active lightning arrester based on ionization increases by 25%, and the volume of the protection space increases by 76%, which significantly increases the safety of the object.

CONCLUSION

Active lightning arresters are manufactured and used in many developed countries. At the same time, the investigation of active lightning arresters in the literature and scientific reports allows to come to the following positive conclusions:

1. It is economical to use active lightning arresters.

2. The aesthetic appearance of active lightning arresters gives beauty to the buildings where they are installed.

3. Active lightning arresters have a simple construction and are easy to install.

4. Active lightning arresters can work in extreme conditions. Active lightning arresters can work autonomously, without an external power source.

References:

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4. Michael J. Peterson et al. New WMO Certified Megaflash Lightning Extre­mes for Flash Distance (768 km) and Duration (17.01 seconds) Recorded from Space // Bulletin of the American Meteorological Society. — 2022.
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