Webinar text. Page 3
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1. Lightning protection of large territories
2. Do we have to protect the large territories against lightnings?
3. Same old song: step voltage
4. Step voltage with the lightning current 100 kA
5. Lightning protection of forests and parks is pointless
6. Experience of lightning protection of extended territories is available
Crown’s shielding effect
Экранирующий эффект короны - Crown’s shielding effect Вероятность прорыва молнии - Lightning breakthrough probability Высота объекта, м - Object height, m 5 грозотросов на высоте 30 м - 5 ground wires at the height 30 m Объект 120x110 м - Object 120 x 110 m Без учета короны - Without crown Учет короны - With crown Если подавить встречные лидеры, не будет притяжения боковых молний - If we suppress the opposed leaders, there will be no attraction of the side lightnings
But the point is that almost the same effect may be achieved not with this umbrella but with a rather large number of wires that are hung up in the protected territory with the step of, e.g. 30 to 20 meters. And because the wires shield and create a volume charge cloud over this large territory, let it be, e.g. a substation territory or a plant territory. Then, as a result of this, the following point occurs that the number of strikes to this territory reduces dramatically and the protection reliability reduces significantly. This is what the protection probability would be without a shielding system (without considering the crown), and here, with the shielding system, it becomes more reliable almost by an order of magnitude . Such a multi-wire shielding system allows protecting large territories, first, with the reliability not less than 0.999. It means that about one lightning out of one thousand may reach this territory. But there is more.
Основные результаты Key results
Тросовая молниезащита больших территорий: - обеспечение защиты территории от прямых ударов молнии с надежностью свыше 0,999; Wire lightning protection of large territories: - providing the territory protection against direct lightning strikes with reliability more than 0.999;
- снижение числа ударов молнии в территорию (включая и сами грозотросы) примерно в 2,5 раза; - reducing the number of lightning strikes into the territory (including the ground wires) by approximately 2.5 times;
- полная ликвидация опасных импульсных воздействии на цепи вторичной коммутации при растекании токов молнии в грунте на защищаемой территории (в т.ч. напряжений шага); - complete elimination of dangerous pulse effects on the secondary switch circuits in the lightning current flowing in the soil in the protected territory (including the step voltages);
- существенное ослабление воздействия электромагнитных наводок на микропроцессорную технику от тока в канале молнии и в грозотросах; - significant reduction of the electromagnetic interference impact on the microprocessor equipment from the current in the lightning channel and in the ground wires;
The number of strikes into the shielding system is also decreased. It means that the number of strikes to the ground wires will be about twice of thrice lower than without shielding. As a result of this, the electromagnetic interference is also reduced. But there is one more point: you can place supports for these ground wires for 15–20 meters beyond the protected territory and install them. And then, your lightning currents will not flow in the territory and no interference in this territory will be provided. And it is also a very important and serious point. Such a multi-wire system with the shielding system is specifically aimed at its use for protection of large extended territories. What is the point that prevents its use? The point is as follows: our regulatory documents do not state anything about shielding lightning protection systems.
Can active lightning arresters be used?
Пригодны ли активные молниеотводы ? - Can active lightning arresters be used?
Принцип действия - Principle of action — - более раннее инициирования и ускоренное развитие встречного лидера за счет подачи высокого напряжения на вершину молниеотвода. - earlier triggering and accelerated development of the opposed leader due to supply of high voltage to the lightning arrester’s top.
Физически обоснован - Physically justified
Требуется - 400 - 500 кВ в течение ~ 0,5 мс - Required: 400–500 kV during ~0.5 ms
Реально формируется не более 250 кВ в течение 2-5 секунд - In reality, not more than 250 kV during 2–5 seconds are formed
Каковы последствия столь кратковременного воздействия? - What are the consequences of this short-term exposure?
And now, the question that would be asked anyway: why cannot we use active lightning arresters to protect large territories? There are many ads. And they say that if you install such an active tip shown here on the lightning arrester that is about 30 meters high, then the protection zone for this lightning arrester will be increased about 5- or 6-fold. It means that instead of the protection radius of 30 meters it will be about 220 meters. And you can protect an oil transfer station or the plant territory with using these active lightning arresters. And if you install several pieces of them, then it can protect even the golf field, where the New Russians can entertain. This is true if you believe the ad.
Эксперимент в ЭНИНе - ENIN experiment
Согласуется с полевыми наблюдениями Rison & Moore и с лабораторными измерениями Куприенко - Agrees with the field observations of Rison & Moore and with the laboratory measurements of Kuprienko
Активные молниеотводы менее эффективны, чем традиционные - Active lightning arresters are less efficient than the conventional ones
If you do not believe the ad, the situation is totally different. All the tests performed today have shown that the active lightning arrester is really active in the sense that it attracts the lightning much worse than the conventional one. This is due to the fact that the short-time impact of the voltage formed in the active lightning arrester of any type, I repeat that I mean among those we have today. They lead to a powerful ionization flash from the top of the lightning arrester that covers the top of the lightning arrester with the electric discharge and interrupts its formation from the channel that has to catch the lightning. For example, during the American trials of six active lightning arresters and six conventional lightning arresters of the same height, 13 lightning strikes were received.
Protection zones of the active lightning arrester
Зона защиты активного молниеотвода меньше, чем у традиционного той же высоты - The protection zone of the active lightning arrester is smaller than of the conventional arrester of the same height
Их применение для защиты больших территорий никак не оправдано - Their use to protect large territories is not justified
I repeat that if you buy an active tip and install it on the lightning arrester, then the protection zone of this lightning arrester will reduce rather than increase. And this fact has been proved experimentally. Before completing the webinar that is pretty short compared to the others, I would like to stop at the following thing.
Current transfer in the large territories
Транспортировка тока по большим территориям - Current transfer in the large territories
1000 Ом м - 1,000 Ohm m
500 Ом м - 500 Ohm m
Время, мкс - Time, mcs
We need to talk about large territories in the following context: imagine that you have a large territory and some metal utilities are laid in this large territory in the earth or on the earth. For example, this is a gas pipe or oil pipeline or some other utility that is laid in the earth. How will these events develop? The events will develop in the following way. Imagine a situation that you have got a forest land, and a way is made in the forest land, and the utility is installed along the way. What will happen next? And the following thing will be: the lightning will not strike the underground cable, the lightning will strike the trees in the margin. From the roots of these trees being the natural earthing device, the lightning current will flow, and a spark channel will be formed that can exist in the soil of any conductivity and may have the length of several dozens meters. And this channel will reach your metal utility. Then the current will flow along this utility progressively flowing into the earth. But if your soils are bad, if their resistivity is 1,000 Ohm*m to 2,000 Ohm*m, then look at what happens: when it passes 1,000 meters, about 25% lightning current will reach your object with the earthing resistance 10 Ohm. It means that if your lightning current was estimated as 100 kA for the third protection level, 25 kA of the current will reach your object. If it is 1,000 Ohm, then about 12% will reach, and if it has the soil resistivity of 500 Ohm*m, then about 8%.