DE102017120002A1 - CURRENT LIMITATION DEVICE - Google Patents

Abstract

The present invention provides a variable impedance current limiting device (1) for current limiting in the case of a short circuit. The device (1) has at least one first component consisting of two coils (2, 3) and at least one second component consisting of an iron core, which has at least two iron core components (4, 5), wherein the first component and the second component a Coil-core pairing form. According to the invention, in such a coil-core pairing, one of the components is movably mounted relative to the other component such that in normal operation the coils (2, 3) are not penetrated by the iron core, and in a short circuit operation the coils (2, 3 ) are penetrated by at least one iron core component (4, 5).

Description

The invention relates to a current limiting device with variable impedance for current limiting in the case of a short circuit in a power grid.

Due to high magnetic forces and thermal effects occurring short-circuit currents threaten the stability of power grids and their power network components. Safety devices such as selective circuit breakers, IS switches or fuses disconnect the affected network segments from normally operating network segments in the event of a short circuit. This type of classic switching and security organs is out of the question for power grids with high operating voltages, since current-carrying network segments can not be disconnected from the grid by simply opening a switch. There may be arcing between the switching contacts, which have a thermal destruction of the switching elements result.

Currents in high and very high voltage grids can thus not be switched off by conventional galvanic isolation of the power supply branches. For this come z. B. inductive short-circuit current limiters for use, which are permanently connected in series with the loads of a network branch. The inductance of such a limiting reactor can limit a short-circuit current occurring in the event of a fault, but also acts as an inductive and resistive load during normal operation. The effectiveness of the short-circuit current limiting is proportional to the inductance of the applied choke. This inductance is also proportional to the reactive power losses occurring in the network.

One way to limit the current in such networks provide current-dependent variable inductance, such. B. in the DE 10 2010 007 087 A1 described. A current limiting device has a superconducting coil which is inserted inside a choke coil. The impedance can be reduced by inserting the superconducting coil because the magnetic field generated by the superconducting coil is opposite to the magnetic field of the reactor during normal operation. If a certain current value is exceeded, the superconducting coil is in the normal conducting state, whereby the inductance increases and the current is limited.

Current limiting inductors with fixed inductance have the disadvantage that even during normal operation large apparent power losses occur. The use of superconducting coils to compensate for the magnetic field of the choke coil in normal operation is expensive because the superconducting materials require energy-intensive cooling.

Based on this prior art, it is an object of the present invention to improve a current limiting device so that it is simple in construction and cost-effective provides a current-dependent variable inductance.

This object is achieved by a current limiting device having the features of claim 1.

Further developments of the current limiting device are set forth in the subclaims.

An embodiment of the device relates to a current-limiting device with variable impedance for current limitation in the case of a short circuit, wherein the device one or more first component (s), which consist of two coils, and one or more second component (s), which consists of a Iron core exist, has. This iron core has two or more iron core components, wherein the first component and the second component form a coil-core pairing. According to the invention, in one such coil-core pairing, one of the components is movably mounted relative to the other component such that in normal operation the coils are not penetrated by the iron core, and in short-circuit operation the coils are penetrated by one or more iron core component (s).

This provides a current-dependent inductive device for a power grid. The inductance of the device is low during normal operation and does not interfere with normal mains operation, nor does it cause significant normal operating losses. In the event of a short circuit, the short-circuit current, which in the normal case is many times higher than the operating current, causes a large increase in the inductance, which results in a reduction of the short-circuit current.

Advantageously, the components of the device are designed to be movable relative to one another: the first component can be fixed and the second component can be movably supported relative to the first component, so that the coil pair can be moved and the iron core components are fixed. In another embodiment, the second component may be fixed and the first component may be movably supported relative to the second component, so that the iron core or components thereof may be movable.

In an embodiment of the device in which the second component is movable relative to the first component, the second iron core component is movably mounted relative to the coils such that In normal operation, the coils are not penetrated by the second iron core component and in short-circuit operation, the coils are penetrated by the second iron core component.

For this purpose, the second iron core component can be spaced from the first iron core component by the length of the coils in normal operation. In normal operation, a small current flows through the coils and there is no iron inside the coils and also the iron circuit of this arrangement is not closed. Therefore, the inductance of the device is small in normal operation. Because the first iron core member is fixed and the second iron core member is movably supported, the second iron core member is attracted to transition from normal operation to short-circuit operation due to magnetic forces (reluctance forces) from the magnetic field in the coils and from the magnetic field in the first iron core member and is due to gravity when reversing the current conditions of short-circuit operation in the normal mode again movable in the reverse position. In normal operation, gravity is greater than the reluctance force between the iron core components and the coils, which is explained as follows:

If a short circuit occurs in the power grid, the current flowing through the device increases many times. The current increase results in an exponential increase in the reluctance forces acting on the moving part of the device. If the reluctance forces are greater than the gravitational force, the iron core component, as a moving part of the device, is drawn into the coils and the iron loop closes. The magnetic flux is then guided closed in this iron cycle. The device thus achieves a greater inductance than in normal operation. The large increase in the inductance then in turn results in a reduction of the flowing short-circuit current.

If the branch affected by the short circuit is now disconnected, the flowing current falls back to normal operating current and the reluctance forces decrease exponentially again. In comparison, when gravity is again greater than the reluctance forces, the iron core member may again fall down, thus returning the apparatus to the lower operating inductance normal operating condition.

Furthermore, the two iron core components may be U-shaped and have one or both of the two iron core components at its / its end faces a coating with low magnetic conductivity, such. B. a plastic film. "Low" within the meaning of the invention is not called ferromagnetic or non-diamagnetic. Furthermore, all paramagnetic substances with μ _r operate close to 1. The material or coating serves as a spacer to prevent a perfect closure of the iron circle and thus to prevent the magnetic flux density in the core from rising to the absolute maximum value. This allows for easier separation by gravity and prevents the core from remaining in the closed position due to remanent flow even after the current has dropped. Since for the above-described separation of the two iron core components, the natural gravity in transition to normal operation is in some cases not sufficient, such a coating acts as a reduction of the maximum flux density in the iron core and thus allows a simpler separation of the two components.

In a further embodiment, the two iron core components are arranged fixedly spaced from one another. The coils (one on top of the other, with opposite winding sense) may be movably supported by pairs of springs relative to the iron core components, with the coils repelling from normal operation to short-circuit operation and being forced toward the iron core components due to the Lorentz force (scaled square to the current) , Here, the Lorentz forces dominate between the coils and these are pressed apart against the spring forces. In this case, a first coil of the coil pair is pressed into the adjacent second iron core component and a second coil of the coil pair in the first iron core component. For this purpose, grooves may be provided in the iron core components which receive the coils. A section of the respective iron core component then penetrates the respective coil, which leads to an increase in the inductance since part of the magnetic flux is conducted in the iron of the partial core. From the short-circuit operation to normal operation, the coils can be moved again due to the spring force of the springs, as soon as these forces are greater than the Lorentz forces. In normal operation, the spring forces dominate over the Lorentz forces; The coils are held together and the magnetic fields of the coils can compensate in part, since the winding sense of the coils is opposite. The partial compensation of the magnetic fields in normal operation leads to a reduction of the inductance in normal operation compared to two spaced-apart coils. The Lorentz force is too low without the high short-circuit current to push apart the coils.

In this embodiment, the coils may be arranged between the iron core components, wherein the spring pairs are arranged crosswise, so that the first coil is held by a first spring pair and the second coil by a second spring pair.

For the second mentioned embodiment of the device according to the invention, it is provided that the coils each form coil pairs which are positioned tightly together in normal operation and thereby partially compensate for their magnetic fields. For this purpose, they must be wound in opposite directions relative to one another. Depending on the embodiment and application, the coils can be connected in series or in parallel.

The iron core may consist of several components that can be moved relative to each other or are fixedly arranged in relation to each other. For this purpose, the iron core may be a partial iron core. The first version with a movable iron core segment (U-shape) forms a virtually closed iron core (apart from the thin, non-ferromagnetic layers). The second embodiment with the two fixed iron core parts represents two partial cores for both coils. Here, in the case of a short circuit (coils in the iron), the magnetic circuit is not closed.

Other embodiments of the current limiting device, as well as some of the advantages associated with these and other embodiments, will become apparent and better understood from the following detailed description with reference to the accompanying drawings. The figures are merely a schematic representation of an embodiment of the invention.

• 1 eine schematische Schnittansicht einer ersten Ausführungsform der Erfindung im Normalbetrieb,
• 2 eine schematische Schnittansicht der ersten Ausführungsform im Kurzschlussbetrieb,
• 3 einen schematischen Teilschnitt durch eine zweite Ausführungsform der Erfindung im Normalbetrieb, und
• 4 einen schematischen Teilschnitt der zweiten Ausführungsform im Kurzschlussbetrieb.

Showing:

• 1 a schematic sectional view of a first embodiment of the invention in normal operation,
• 2 a schematic sectional view of the first embodiment in short-circuit operation,
• 3 a schematic partial section through a second embodiment of the invention in normal operation, and
• 4 a schematic partial section of the second embodiment in short circuit operation.

The device according to the invention relates to a current limiting device 1 with variable impedance for current limitation in case of a short circuit in a power grid.

In 1 and 2 is the current limiting device 1 composed of an iron core and a coil pair. The coil pair consists of a first coil 2 and a second coil 3 which are wound in opposite directions and via an electrical connection 9 connected to each other. The spools 2 . 3 have a coil length L and have an inner bore whose diameter is a diameter of the iron core components 4 . 5 matches, so the coils 2 . 3 from the iron core component 5 can be penetrated.

An iron core is made of two components, a first iron core component 4 and a second iron core component 5 , constructed, the gem. 1 are arranged spaced from each other. The iron core thus consists of two U-shaped components 4 . 5 , The distance between the components 4 . 5 corresponds to the length L of the coils 2 . 3 , The second iron core component 5 , this in 2 is disposed below, is relative to the first component 4 movably mounted in the vertical direction. The U-shaped component 5 indicates at its end faces 5 ' . 5 '' a coating 8th with low magnetic conductivity on to the components 4 . 5 again easier to disconnect when the device 1 switches from the short circuit mode back to normal operation.

In the state of normal operation ( 1 ) are the iron core components 4 . 5 spaced apart. In short-circuit operation to 2 is the second iron core component 5 from the first iron core component 4 shown attracted. The legs of the second iron core component 5 penetrate the inner bore of the coils 2 . 3 , The magnetic circuit is thus closed as indicated by a ring arrow in FIG 2 is clarified.

In a further embodiment according to 3 and 4 are two iron cores in the form of iron core components 4 . 5 before that in relation to the coils 2 . 3 are fixed. The iron core components 4 . 5 each have an annular groove 10 on, which is dimensioned so that the coils 2 . 3 can be included in it.

The spools 2 . 3 are parallel to each other between the iron core components 4 . 5 arranged and are wound in opposite directions. They are made of paired springs 6 . 6 ' . 7 . 7 ' held, with the first coil 2 from a first spring pair 6 . 6 ' and the second coil 3 from a second spring pair 7 . 7 ' is held. The feathers 6 . 6 ' . 7 . 7 ' cross over to the oppositely wound coils 2 . 3 to keep in an equilibrium position. By opposing winding is the magnetic field of the coils 2 . 3 directed against each other, so that they repel in normal operation as well as in the event of a short circuit. The generated opposing magnetic fields reduce the normal operating inductance of the device while the two coils contact each other. The spring force of the springs 6 . 6 ' . 7 . 7 ' is chosen so that the coils 2 . 3 in the in 3 shown position in normal operation are set. The coils touch each other or lie against each other.

Shows a short circuit case 4 where the coils 2 . 3 due to the increased magnetic forces occurring due to the short circuit itself (Lorentz forces) and from the iron core components 4 . 5 have been attracted (reluctance forces 12 ) and in the grooves 10 are included. As a result, a portion of the magnetic flux is transported in the iron core, which increases the inductance of the entire arrangement. In this state, the arrangement can be considered as two independent coils with partial iron core.

LIST OF REFERENCE NUMBERS

1

Current limiting device

2

First coil

3

Second coil

4

First iron core component

4 ', 4' '

End faces first iron core component

5 ', 5' '

End faces second iron core component

5

Second iron core component

6, 6 '

Springs first coil

7, 7 '

Springs second coil

8th

coating

9

Electrical connection

10

groove

11

Iron core section

12

reluctance

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102010007087 A1 [0004]

Claims (9)

Current limiting device (1) with variable impedance for current limiting in the case of a short circuit, wherein the device (1) at least - a first component consisting of two coils (2, 3), and - a second component, consisting of an iron core, has at least two iron core components (4, 5), wherein the first component and the second component form a coil-core pairing, characterized in that one of the components is movably mounted relative to the other component in a coil-core pairing, that - in a normal operation, the coils (2, 3) are not penetrated by the iron core, and - in a short-circuit operation, the coils (2, 3) of at least one iron core component (4, 5) are penetrated. Device (1) according to Claim 1 , characterized in that - the first component is fixed and the second component is movably mounted to the first component, or - the second component is fixed and the first component is movably mounted to the second component. Device (1) according to Claim 1 or 2 characterized in that the second iron core member (5) are movably supported relative to the coils (2, 3) so that - in normal operation the coils (2, 3) are not penetrated by the second iron core member (5), and - In a short-circuit operation, the coils (2, 3) are penetrated by the second iron core component (5). Device (1) according to Claim 3 , characterized in that the second iron core component (5) in normal operation of the first iron core component (4) by the length (L) of the coils (2, 3) is spaced apart. Device (1) according to Claim 3 or 4 , characterized in that the two iron core components (4, 5) are U-shaped and at least one of the two iron core components (4, 5) at its end faces (4 ', 4'',5', 5 '') has a coating (8 ) having low magnetic conductivity. Device (1) according to Claim 1 or 2 , characterized in that the two iron core components (4, 5) are fixedly spaced from each other and the coils (2, 3) are movably mounted via spring pairs (6, 7) with respect to the iron core components (4, 5), the coils ( 2, 3) - from the normal operation to the short-circuit operation due to the Lorentz force and the reluctance force (12) of the iron core components (4, 5) are movable, and - from the short-circuit operation in the normal operation due to the spring force of the springs (6, 7 ) are movable. Device (1) according to Claim 6 , characterized in that the coils (2, 3) between the iron core components (4, 5) are arranged and the pairs of springs (6, 7) are crossed over, so that a first coil (2) of a first spring pair (6) and a second coil (3) is held by a second spring pair (7). Device (1) according to at least one of Claims 1 to 7 , characterized in that the coils (2, 3) form coil pairs and are wound opposite to each other. Device (1) according to at least one of Claims 1 to 8th , characterized in that the iron core is a partial iron core.

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