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значительные по амплитуде импульсы напряжения, которые прикладываются к изоляции электротехнических устройств с подключенными радиально заземлителям кабельными или воздушными линиями, если корпуса устройств соединены с этими заземлителями, а защитные средства отсутствуют. Вместе с тем нелинейное поведение сопротивлений заземлений существенно облегчает работу защитных средств, позволяя выбирать их с меньшей величиной джоуле-ва интеграла и соответственно более дешёвые. Следовательно, молниезащитные за-землители фактически являются начальным каскадом систем грозозащиты и их следует рассматривать в единстве с остальными элементами этих систем.
Библиографический список
1. Методические указания по проектированию устройств автоматики, телемеханики и связи на железнодорожном транспорте И-247-97. Защита от перенапряжений устройств автоблокировки и электрической централизации / Институт ГТСС МПС. - СПб. : Институт ГТСС МПС, 1999. - С. 10-28.
2. Временные нормы «Требования к характеристикам испытательных импульсных воздействий на системы ЖАТ» / Департамент ТЩТ ОАО РЖД, ПКТБ ЦШ. - СПб. : Петербургский гос. ун-т путей сообщения, 2007. - С. 1-18.
3. Заземляющие устройства электроустановок / В. В. Бургсдорф, А. И. Якобс. - М. : Энер-гоатомиздат, 1987. - С. 300-309.
UDK 621.332 УДК 621.332
K. K. Kim, A. N. Abankin, I. M. Karpova K. K. ^м, A. Н. Абанькин, И. М. Карпова
Petersburg State Transport University
Петербургский государственный университет путей сообщения
ISOLATOR-ARRESTER FOR CATENARY ИЗОЛЯТОР-РАЗРЯДНИК ДЛЯ КОНТАКТНОЙ ПОДВЕСКИ
We propose an isolator-arrester as a principally new device to protect the catenary against direct lightning strokes. We describe the results of investigations on improving the arc-suppressing properties of an isolator-arrester with the help of the software package ELCUT of a field simulation and give the numerical values of the parameters influencing on the rate of the arc extinction in the proposed device at the running of a pulse current of lightning through it. We present the analysis of the influence of the new modification of an isolator-arrester on the voltage distribution along the insulator string.
Предложен изолятор-разрядник как принципиально новое средство для защиты контактной сети от прямых ударов молнии. Приводятся результаты исследований по улучшению дугогосящих свойств изолятор-разрядник с помощью пакета полевого моделирования ELCUT. Определены численные значения параметров, влияющих на скорость гашения дуги в предложенном устройстве при протекании по нему импульсного тока молнии. Проведен анализ влияния новой модификации изолятора-разрядника на распределение напряжения по гирлянде изоляторов.
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lightning stroke, isolator-arrester, spark discharge, electroconductive ring, electrodynamic force, heat generation, power arc.
удар молнии, изолятор-разрядник, искровой разряд, электропроводящее кольцо, электродинамическая сила, тепловыделения, дуга.
Introduction
One of the main sources, disturbing the normal operation of catenaries of electric railways in Russia, is direct lightning strokes to the catenary or a railway pole. The use of the overvoltage limiters can’t cope with a lightning protection problem in full, especially at high values of the overvoltage. To relieve the operation of the overvoltage limiters, i. e. «to clip» the overvoltage wave coming to the overvoltage limiter we offer to use the device developed on the basis of an isolator-arrester manufactured by OAO «№О Streamer» [1].
The isolator-arrester (Fig. 1) consists of a glass plate (1), the first (2) and second (3) units of the fitment, one of which is connected to a high-voltage wire, and the second unit is connected to a railway pole. The isolator-arrester is supplied with the interchamber system (IS) consisting of a great quantity of electrodes (6), built-in in the shape (4) made of silicone gum (5).The gum shape is rigidly fixed on the plate edge. The holes are made between the electrodes, which come out of the shape. These holes create miniature gas-discharge chambers 7. The ends of the upper (8) and
2
lower (9) leading-in electrodes are connected to the first and second units of the fitment, and their other ends are connected through the air gaps with the first (10) and second (11) ends of the IS. The ring (12) made of a current-conducting material is rigidly fixed on the plate from the interior of the IS.
Under the effect of overvoltage on the isolator-arrester, first, the spark air gaps are broken down and then the IS. The lightning surge current flows from the second unit of the fitment and its leading-in electrode through the spark channel of the lower sparking gap, then through the IS and after that through the spark channel of the upper sparking gap through the leading-in electrode to the first unit of the fitment. Owing to the fact that discharges between the intermediate electrodes in the IS take place in the chambers the volumes of which are rather small, at the expansion of the channel there appears high pressure under which its acting channels (13) of the spark discharges between the electrodes move to the plate surface forming a channel of discharge, and further on they are blown outside into the ambient air. Simultaneously with this the current is induced in the ring made of a current-conducting
Fig. 1. The isolator-arrester and the interchamber system (IS)
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material. The magnetic field of the current acts on the discharge channels, blowing them much stronger. The channels get cooled because of the blowing and lengthening of the channels taking place between the electrodes and t the total resistance of all the channels is increased,
i. e. the total resistance of the arrester increases, and there is a limitation of the pulse current of a lightning surge and quenching of the attendant current.
On the IS segment between the leading-in electrodes there are no intermediate electrodes, and the discharge is developed along the IS occupying about three quarters of the perimeter of the plate edge, but not between the leading-in electrodes. The discharge quenching without the attendant current takes place due to the IS operation after the ending of a lightning surge and flowing off of its current through the railway pole into the ground, and the catenary operates on without disconnection.
From the economical point of view, we shouldn’t use isolator-arresters on all the objects that must be protected, they should be used only in certain places since the process of replacing ordinary isolators becomes very expensive in this case.
It’s necessary to place the isolator-arresters in every 2,5-3 kms if the distance between the traction substations is approximately 2025 kms with the posts of sectioning in the midpoint of the zone, thus it is necessary to have the overvoltage limiters in the places where they should be fitted according to the requirements of PUTEKS [2].
In this work we investigate the influence of the copper ring on the parameters and characteristics of the isolator-arrester.
The investigations were carried out by using the package ELCUT of a field simulation. The problem was considered in the simplified problem definition, the arc was replaced with a ring conductive unit in which the current runs by the desired time law.
The value of force acting on an arc of the IS, was determined as an average value in the area of the arc.
Influence of the ring on characteristics of an isolater-arrester at an idealized current pulse
The pulse parameters: Tf = 10 ns is the front duration; Т. = 10 mcs is the pulse duration; Im = 30 kA is the pick value (Fig. 2).
To estimate the character of changing the force in the process of blowing an arc from the IS we consider some variants of locating the arc (the displacing of the arc is made to the direction of the maximum action of the force). The draft of the rated area is shown in Fig. 3.
The initial relative position of the units and interval D are determined by the position of the ring and the IS on the plate.
The obtained patterns of a magnetic field show that the ring increases the field near the IS, thereby increasing force the effect on the arc.
The ring behaves as superconducting one (the magnetic field does not penetrate into the ring)
1 is the cross-section of the cooper ring;
2 is the cross-section of the channel arc
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since the time constant of the ring is equal to т = = L/R = 2,75 ms where L is the self inductivity of the ring and R is the resistance of the ring.
The value of resistance is estimated by the formula:
l
YS
2nR1 Y nr 2
1,5 • 10-4 Q,
where y = 5,6-10 7 S/m is the specific conductivity of copper, R1 = 105 mm is the ring radius, r = 5 mm is the radius of the cross section of the ring.
For the calculation of the self inductivity of the ring we use the formula
L = p0R1 (ln8^-2j= 0,413 -10-6 Н,
where p0 = 1, 26-10-8 H/m, [3].
To estimate the possibility of overheating the ring from eddy currents, we calculate the value of heat generation in the ring. As the most dangerous (most loaded) mode corresponds to the initial variant of the relative position of the ring and the IS, the time dependences of an induction of density on the eddy current and power of heat generation for the most loaded zone of the ring of the initial variant are shown in Fig. 4.
The character of changing and the values of the given magnitudes allow to judge about
Fig. 4. The distribution of density of the eddy currents in the ring and the distribution of the power of the heat generation on the ring surface
the safety of the ring operation because of the short-duration of effects.
The time dependences of force effects on the arc for various variants of the ring position are shown in Fig. 5.
Рис. 5. The force effect to the electric arc at various ring positions
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Position 1 is the initial variant that corresponds to the closest position of the ring and the IS (30 mms). We take a step equal to 10 mm for the subsequent positions.
Influence of the ring on characteristics of an isolater-arrester at an aperiodic current pulse
For the description of such a pulse shown in Fig. 6 we use the formula
.(t) = j(t/T1)10exp(- VT2) [4]
() h(1 + (t/ T1)10) , []
where I is the current peak; h is the coefficient correcting the value of the current peak; t is the time; т is the time constant for front; t2 is the time constant for a droop of pulse.
We use the following values: I = 100 kA; h = 0,955; т = 11 mcs; t2 = 480 mcs [5].
Qualitatively the magnetic field pattern at acting on such a pulse is the same as for the pulse shown in Fig. 2. However, the distribution of the current density in the ring changes since the time characteristics are closer now to the time constant of the ring and the magnetic field begins to penetrate into the ring. Accordingly, the power of heat generation in the ring changes too (Fig. 7).
We can note from Fig. 7 that the density of eddy currents is greater for the surface and
less in the middle. At the high frequency of a pulse of a lightning surge with increasing induction in the ring there is a sharp surface effect and a proximity effect. It leads to decreasing the effective cross-section of the ring that generates stronger heating up of the layers of the ring (Fig. 7).
With increasing the duration of a pulse effect, the surface effect is weakened and the heat generation on the ring surface is decreased. The geometrical dimensions of the ring and distance from the ring to the IS play an important role in the heat generation.
In Figs. 8-9 there are shown time dependences of the density of eddy currents and the power of heat generation for the most loaded ring zone (from the side of the IS) in the initial position. The meltdown of the ring is not foreseen in this mode either.
From Fig. 9 we can see that the closer the ring is placed to the IS, the stronger the force effect on the arc is, and the rate of the arc quenching is increased.
The ring does not influence on the potential distribution along the insulator string. The potential distributions for the string from two ordinary isolators and the string from the isolator-arresters are shown in Fig. 10. The problem was solved within the limits of the electrostatic definition (the wavelength is equal to 6000 kms which corresponds to the frequency of 50 Hz).
Fig. 6. The calculated pulse of the lightning current
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Fig. 7. The density of eddy currents in the ring and the power of heat generation on the ring surface
Fig. 8. The density of eddy currents of the most loaded ring zone
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Fig. 9. The heat generation of the most loaded ring zone and the time dependences of the force effect on the arc at various ring positions
Fig. 10. The potential distributions for the string:
1 - ordinary isolators; 2 - isolator-arresters, n is the number of the isolators
Conclusion
The isolator-arrester successfully performs the function to protect the catenary against the direct lightning strokes. We can use an electro-conductive ring located on the tape of the isolator-arrester to increase the efficiency and rate of blowing off the arc. The ring does not influence on the potential distribution along the insulator string.
References
1. Patent RU 108206 U1 МРК H01B 17/00. Isolator-arrester / K. K. Kim, A. N. Abankin, 2011114763/07 ; Prefer 14.04.2011 ; published 10.09.2011.
2. Economics of Electrical Power Engineering / V. N. Fomina. - M. : IUE GUU, VIPKen-ergo, IPK-gossluzhba, 2005.
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3. Calculation of Inductance / P. L. Kalantarov,
L. A. Cheitlin - L. : Energoatomizdat, 1986. -488 pages.
4. Protection of a 6-35 kV Network Against Overvoltage / F. H. Halilov, G.A. Evdokunin, V. S. Polyakov et al. Edited by F. H. Halilov, G.A. Evdokunin, A. I. Tadzhibaev. - SPb., 2002. - 260 page.
5. Protection of 6-10 kV Network Against the Thunderstorm Overvoltage by Long Spark Arresters of Module Type / G. V. Podporkin, V. E. Pil-schikov, A. D. Sivaev. - SPb. : Energetik. - 2003. -№ 1. - PP. 27-29.
УДК 621.331:621.31 1
А. Н. Марикин, А. П. Самонин, В. Г. Жемчугов
Петербургский государственный университет путей сообщения
СПОСОБЫ УСИЛЕНИЯ ТЯГОВОГО ЭЛЕКТРОСНАБЖЕНИЯ ПОСТОЯННОГО ТОКА ПРИ ИНТЕНСИВНОМ ДВИЖЕНИИ ПОЕЗДОВ
При увеличении веса, скорости и интенсивности движения поездов требуется усиление действующих линий постоянного тока напряжением 3,3 кВ. Предпочтительным вариантом усиления является установка на тяговых подстанциях управляемых выпрямительных агрегатов с размещением между тяговыми подстанциями пунктов преобразования напряжения. Пункты преобразования напряжения служат для подпитки контактной сети от продольной линии постоянного тока повышенного напряжения.
система электроснабжения тяги поездов, постоянный ток, способы усиления, тяговые подстанции, уровень напряжения на токоприемнике, потери мощности в тяговой сети.
Введение
При организации скоростного и тяжеловесного движения на существующих линиях с централизованным электроснабжением тяги поездов, как правило, требуется усиление электротяговой сети [1].
На многих участках сечение проводов контактной сети приближается к 600 мм2 в медном эквиваленте, количество усиливающих проводов достигло предельных значений. В условиях повышенных электрических нагрузок лишь за счет подвески дополнительных проводов невозможно обеспечить термическую устойчивость контактной сети и требуемый уровень напряжения у токоприемников поездов.
1 Способы усиления тяговой сети постоянного тока
Провозную и пропускную способности электрифицированных участков можно увеличить только за счет строительства дополнительных тяговых подстанций и подключения их к системе внешнего электроснабжения, требующего значительных капитальных затрат. При этом расстояния между соседними подстанциями уменьшаются до 10.. .15 км, а в отдельных случаях, например на линии Санкт-Петербург - Москва, имеются меж-подстанционные зоны протяженностью 6.8 км.
В этих условиях традиционные системы питания тяговой сети оказываются неэф-
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