WO2002047180A2

WO2002047180A2 - Current limiting device comprising current-carrying high-temperature superconductor tracks

Info

Publication number: WO2002047180A2
Application number: PCT/DE2001/004595
Authority: WO
Inventors: Stefan Fischer; Ralf-Reiner Volkmar; Hans-Peter Kraemer
Original assignee: Siemens Aktiengesellschaft
Priority date: 2000-12-05
Filing date: 2001-12-03
Publication date: 2002-06-13
Also published as: WO2002047180A3

Abstract

The invention relates to a current-limiting device comprising current-carrying high-temperature superconductor tracks (HTSL) arranged on a board (PL), which are particularly for use in medium voltage engineering, whereby the high-temperature superconductor tracks (HTSL) form a conductor track structure (LBS) with unbranched conductor tracks. The conductor track structure (LBS) of the high-temperature superconducting tracks (HTSL) is replaced by a line structure (LST), which is branched in series and in parallel, or is replaced by a closed network structure (GNW), whereby the line structure (LST) is realized by multiplying a line element (LE ..) with an identical basic structure, and the network structure (GWN) is realized by basic element recesses (GA).

Description

description

Current limiting device with current-carrying high-temperature superconductor tracks

The invention relates to a current limiting device with current-carrying high-temperature superconductor tracks arranged on a plate, in particular for medium-voltage technology, the high-temperature superconductor tracks forming a conductor track structure with unbranched conductor tracks.

A resistive superconducting current limiting device forms a superconducting switching path to be inserted serially into a circuit. The transition of a superconducting conductor structure from the practically resistance-free cold operating state below the transition temperature T _{c of} the superconductor material to the normally conducting state via T _c (so-called phase transition or "quench") is used, the electrical resistance R _{n of} the conductor structure now present limits the current to an acceptable level I = U / R _n . The heating above the transition temperature T _c takes place through Joule 'see heat in the superconductor material itself, if after a short circuit the current density j rises above the critical value j _{c of} the superconductor material, whereby the material can already assume a finite electrical resistance even below the transition temperature T _c . In the limiting state above the transition temperature T _c , only a residual current then continues to flow in the circuit containing the current limiting device until an additional mechanical disconnector completely interrupts the circuit ht.

With such a superconducting current limiting device of the 'resistive type', a current rise after a short circuit can be limited to a value of a few multiples of a nominal current - moreover, such a limiting device is ready for operation again shortly after being switched on. So it acts like a quick, self-healing fuse. In addition, it ensures a high level of operational safety because it acts passively, ie it works autonomously without prior detection of the short circuit and without active triggering by a switching signal.

Metal oxide high-T _c superconductor material (HTS material) is preferably planned for the conductor track structure of known current limiting devices, the transition temperature T _{c of which is} so high that it can be kept in the superconducting operating state with liquid nitrogen of 77 K. This material shows a rapid increase in electrical resistance when the critical current density j _{c is} exceeded. The heating to the normally conductive state and thus the current limitation takes place in a relatively short time, so that the peak value of the short-circuit current can be limited to a fraction of the unlimited current, for example 3 to 10 times the nominal current. The superconducting current path of the conductor track structure is in contact with the coolant, which is able to return it to the superconducting operating state in a relatively short time after the critical current density j _{c has been} exceeded.

A current limiting device of the type defined at the outset is known, for example, from WO 00/04589. The current limiting device contains insulating support bodies in

Form of plates on which high-temperature superconductor tracks are arranged. The high-temperature superconductor tracks themselves are linear and interconnected. The high-temperature superconductor tracks accordingly have straight and curved conductor track sections.

In order to optimize the maximum switching capacity, it is proposed here to design the curved conductor track sections of the current limiting device with respect to one another in terms of their outer and inner radii.

The ratio of the radii to the track width itself must also be kept within certain limits, otherwise it would be too desires high heat development on the inside of the radii of the superconducting layers. Excessive thermal loads can cause the conductor tracks to burn through and damage them and their supporting bodies, so that the superconductor structure is unusable and the current limiter is no longer functional. The reason for this is, due to inhomogeneities or flaws within the structure of the high-temperature superconductor tracks, undesired locally occurring quench processes, in which the entire applied voltage drops at the local high-resistance areas and thus the entire electrical power conducted over the track is converted there into heat becomes. The local points are thus overheated, melted, if necessary, and completely destroyed by the resulting arc.

As a result of inhomogeneities in the layer of the high-temperature superconductor tracks, the so-called quenching process is not - as intended - initiated simultaneously over the entire length of the high-temperature superconductor tracks but only locally in the fault area of the layer.

Accordingly, the current limiting device is no longer fully functional or is no longer usable for the intended use.

The object on which the invention is based is to design a current limiting device with regard to its load in the event of a short circuit in such a way that impairments due to inhomogeneities in the layers of the high-temperature superconductor tracks are largely reduced, and furthermore the adaptation of the current limiting device to the different current and voltage loads in medium-voltage technology in a simple way.

According to the invention, this is due to the features 1.1 the conductor track structure LBS of the high temperature super conductor tracks HTSL is replaced by a series and parallel branched line structure LST,

1.2 the serial and parallel branched line structure LST is achieved by multiplying a line element LE ... with a geometrically identical basic structure.

The invention is based on the knowledge that, in order to overcome the known difficulties, the previously preferred unbranched line structures for the high-temperature superconductor tracks of the current limiting device have to be abandoned and the positive properties of a branched line structure have to be transferred to the design of the high-temperature superconductor tracks. The particular advantage of this branched line structure can be seen in the fact that the current carried is distributed over several conductor tracks instead of only one. The current is accordingly more evenly distributed over the entire plate surface of the current limiting device.

If there is an undesirable quenching process due to the inhomogeneity of the layer of high-temperature superconductor layers at a locally limited location, the voltage drop is divided proportionally to the number of parallel conductor tracks and the thermal energy introduced at the high-resistance quenching point is correspondingly lower. The possibility of local overheating and the associated destruction of the superconductor tracks and possibly also of the plates is thus considerably reduced.

A further increase in the number of conductor tracks lying in parallel is according to the invention due to the features

2.1 the conductor track structure of the high-temperature superconductor tracks is replaced by a closed network structure,

2.2 the network structure is provided with basic element recesses adapted to the power requirement, and 2.3 the basic element recesses are arranged distributed within the network structure in such a way that the high-temperature superconductor bars form parallel and serial branched lines with approximately the same size.

With the transfer of the unbranched conductor track structure into a completely closed network structure with the basic element recesses adapted to the power requirement, the degree of performance optimization for the conductor tracks with regard to their parallel arrangement and distribution over the entire board is further increased. If the current-carrying conductor tracks are designed so that short straight conductor track sections result in each node as connecting bridges to the adjacent conductor track sections and their nodes, then during a quenching process the temperature rise in a conductor track section is also transmitted directly to its adjacent connecting bars and also leads to a temperature increase there. The quenching process is initiated practically over the entire area by this avalanche effect.

If, on the other hand, the quenching process takes place in the closed network structure only in the area of a local conductor track with a faulty conductor track structure, only the proportional current and voltage value is converted into heat there, which can be dissipated well due to the surrounding free areas.

The quenching process is softer overall, i.e. stretched in time and distributed approximately evenly over the surface of the plate.

In addition, with the practically honeycomb closed network structure with the same outer dimensions of the plates, a variable configuration of the geometry of the conductor tracks and thus a flexible adaptation to the power requirements for the current limiting devices is achieved. According to advantageous embodiments of the invention, the features are alternatively

3.1 the basic element recesses have an angular circumferential structure, preferably a triangle, square, hexagon or octagon structure, and

4.1 the basic element recesses have any peripheral structure, provided.

The basic element recesses within the closed

Network structures thus enable an optimal adaptation to the power requirements for the current limiting devices, the heat loss resulting from the function being optimally distributed over the entire plate area of the respective current limiting devices.

It should also be emphasized as essential for the invention that the current limiting devices with their high-temperature superconductor tracks can be implemented both in thin-film layer technology on the carrier substrates and in so-called thick-film layer technology, for example between metal layers.

According to the invention, the current limiting device has end pieces for contacting the conductor track structure, the conductor track structure having at least one main current path which, viewed in the main direction of expansion of the conductor track structure, is subdivided into a plurality of identical parts arranged one behind the other, each of which forms two branches connected in parallel, the parallel connection of

Branches are made in the connection area between successive sections.

In the case of a further development in this regard, the shape of the sections is essentially racetrack-shaped or oval or arch-shaped. According to one variant, the sections have a greater extent transverse to the main direction of expansion of the conductor track structure than in this direction.

Furthermore, it is possible that in each branch the conductor track has two leg parts running transversely to the main direction of expansion of the conductor track structure, which merge into one another by a lateral arc part, and that the conductor track width in the arc part is at least equal to the conductor track width in the leg parts and preferably between the 1st 1 times and 1.2 times the track width in the leg parts.

The variants described above can also be combined with one another as desired within the scope of the invention.

The invention is explained in more detail by an exemplary embodiment shown in the figures, wherein

1 shows the unbranched line structure of the high-temperature superconductor tracks of the known

Current limiting device shows, Figure 2 shows the branched line structure of a possible

3 shows the closed network structure of a further possible embodiment of the invention, FIGS. 4, 5 represent combinations of unbranched conductor tracks with a branched line structure and a closed network structure.

FIG. 6 shows a basic form of the conductor track structure,

FIG. 7 shows a special embodiment of the conductor track from a conductor track structure and FIG. 8 shows a special further development from the basic shape according to FIG. 6. FIG. 1 shows a known current limiting device with a conductor track structure LBS arranged unbranched on a plate PL. The plate PL is realized by a so-called carrier substrate TS, on which the high-temperature superconductor HTSL is applied using thin-film DUS technology.

FIG. 2 essentially shows the serial and parallel branched line structure LST of the high-temperature superconductor tracks. The branched line structure LST is practically achieved by multiplying the line element LE with a geometrically identical basic structure on the plate PL.

The high-temperature superconductor track HTSL according to the invention according to FIG. 3 is also branched and has an overall closed network structure GNW, which essentially results from the symmetrical distribution of the basic element recesses GA over the entire plate PL of the current limiting device. With the basic element recesses GA, the high-temperature superconductor tracks HTSL are practically and directly linked in parallel and in series, as in a network, so that the partial flows indicated by the arrows are evenly distributed between the adjacent basic element recesses GA. This results in an approximately equally distributed current and voltage load over the entire area of the closed network structure GWN in the operating state of the current limiting device. This ensures that, due to inhomogeneities within the high-temperature superconductor layer, the harmful effects of the occasional quench process are limited to a minimum, because in contrast to the strictly linear line structures in the closed network structure GNW, local errors are caused by the division into partial currents - places are only correspondingly lightly loaded. The local heat load is therefore lower and, with regard to the larger error-free residual areas of the stress boundary device can be removed in a short time without significant difficulties.

The closed network structure GNW can be used for the current limiting devices both in thin film technology in connection with substrates and in thick film technology with and without substrates.

FIGS. 4 and 5 indicate that high-temperature superconductor tracks in the form of lines with a largely closed network structure would also be conceivable to implement the voltage limiting devices in conjunction with flexible adaptation to the different performance requirements.

FIG. 6 illustrates a current limiting device with a substrate 2 and a conductor track structure made of HTS material, the basic shape of which is generally designated by 3 in FIG. 6. According to the exemplary embodiment shown, this structure 3 has only a single current path SI between two end pieces 4a and 4b, on which the structure is to be contacted. In the main direction of expansion r of the conductor track structure 3 or of the current path SI, indicated by an arrowed line, the latter should be subdivided into several, identically designed sections 5j (with j = l .... n). Each of these sections 5j comprises two current branches ZI and Z2 illustrated by dashed lines. These current branches are connected in parallel in connection areas 6j between sections 5j arranged one behind the other. The structure 3 in this way forms two to a middle, between the

End pieces 4a and 4b connecting or center line or center axis A mirror-symmetrical meanders, which are connected to one another at the end pieces 4a and 4b and in the connecting areas 6j or merge there. One of the meanders is illustrated to some extent in the figure by a dotted line M. As can also be seen from FIG. 6, the shape of the sections 5j is essentially race track-shaped due to their branching into the branches ZI and Z2, the greater extent being transverse to the main direction of expansion r of the conductor track structures 3. If necessary, however, other shapes, for example an oval or arcuate shape, can also be selected. In each of the branches ZI and Z2, the conductor track labeled L consequently has two leg parts 7a and 7b which run transversely to the main direction of expansion r and which are connected to one another via a lateral arch part 8 or merge into one another there. In the area of the imaginary center line A, the leg parts 7a and 7b merge into the respective connecting area 6j of the sections 5j.

The conductor track structure 3 is characterized by the number N _m and the track width B _m and the leg length L _{s of} the two meanders. The number N _m and the leg length L _s are linked to one another in that their product must be smaller than the usable width b of the substrate 2.

The conductor track width B _b in the arch part 8 of each meander M must be at least equal to the track width B _ra in the leg part 7a or 7b. In addition, the web width B _v in the connection area 6j of the meanders or the sections 5j should be at least twice B _m . The following are advantageously chosen:

B _b = 1, 1 1, 2 x B _m , ^■

B _v = 2.2 .... 2.4 x B _m (with "x" = multiplication symbol). This ensures that the leg parts 7a and 7b in front of the arch parts 8 and the connecting areas 6j become normally conductive. This is advantageous a reduction in the temperature increases at the arch parts and the connection areas.

By varying the web width B _m and the leg length L _{s of} the meanders M or sections 5j used, any desired ratio l _e ff / b _e ff> 1 / b of the effective length l can be obtained on rectangular substrates 2 of length 1 and width b _e ff set to the effective width b _{eff of} the conductor track structure 3. The effective length l _e ff of the conductor track structure is the entire length of the current path along a meander M. It determines the maximum voltage at which the switching conductor track structure can be used. Analogously, the effective width b _e ff is the total conductor cross-section available to the current to be switched (that is to say N _ra x B _m , where N _{m is} the number of meanders and is equal to 2 according to FIG. 6). It determines the critical current I _c and thus the nominal current in the switching conductor structure. By selecting a structure with a suitable effective length l _eff and / or effective width b _e ff, a switching conductor track structure can be adapted to a desired nominal voltage and / or a desired nominal current.

A ratio l _ef f / b _ef f ~ 5 x 1 / b results if, as a borderline case, one assumes a meander which no longer contains straight conductor track parts, i.e. which only consists of 180 ° bends. Such a meander M ^{x is} indicated in FIG. 7 as a detailed image of a conductor track L ^{Λ of} a current limiting device designed according to the invention. If you assume size 3 for the ratio of the outside to the inside radius of the arcs of the conductor track L ^λ , you get the aforementioned ratio of l _eff / bef - you can of course also imagine a meander that does not extend from 180 ° - Arches, but is composed of arches with smaller angles. In a corresponding embodiment, a straight conductor path would result as a limit case and thus l _e ff / b _e f _f = 1 / b. If the above-mentioned inequality is observed, all of the above criteria are met at the same time and a land use of significantly more

50% reached. It is advantageous to provide relatively small web widths B _m, in particular approximately 1 mm or less, and also small meandering radii, since the substrate 2 is then heated more evenly.

A conductor track structure of a current limiting device according to the invention advantageously has several preferably at least three main current paths according to FIG. 6. These current paths are then connected in parallel between the end pieces 4a and 4b. It is to be regarded as particularly advantageous if adjacent main current paths in the lateral transition areas between adjacent branches ZI and Z2 are electrically connected to one another or merge there. FIG. 8 shows a corresponding exemplary embodiment with three main current paths S _j (with N _m = j = 1 ... 3), although the number j can also be selected to be significantly larger. The common transition areas between the main current paths on the lateral arc parts 8 and 8 of adjacent branches ZI and Z2 are denoted in the figure by IIj.

Claims

claims

1.Current limiting device with current-carrying high-temperature superconductor tracks (HTSL) arranged on a plate (PL), in particular for medium-voltage technology, the high-temperature superconductor tracks (HTSL) forming a track structure (LBS) with unbranched tracks, the characteristics

1.1 the conductor track structure (LBS) of the high-temperature superconductor tracks (HTSL) is replaced by a serial and parallel branched line structure (LST),

1.2 the serial and parallel branched line structure (LST) is achieved by multiplying a line element (LE ...) with a geometrically identical basic structure.

2. Current limiting device with current-carrying high-temperature superconductor tracks (HTSL) arranged on a plate (PL), in particular for medium-voltage technology, the high-temperature superconductor tracks (HTSL) forming a conductor track structure (LBS) with unbranched conductor tracks,

g e k e n n z e i c h n e t d u r c h the features

2.1 the conductor track structure (LBS) of the high-temperature superconductor tracks (HTSL) is replaced by a closed network structure (GNW),

2.2 the network structure (GNW) is provided with basic element recesses (GA) that are adapted to performance requirements,

2.3 The basic element recesses (GA) are distributed within the network structure (GNW) in such a way that the high-temperature superconductor tracks (HTSL) form completely parallel and serially branched cable runs with approximately equal areas.

3. Current limiting device with current-carrying high-temperature superconductor tracks (HTSL) arranged on a plate (PL), according to claim 2, characterized by the feature

3.1 the basic element recesses (GA) have an angular peripheral structure, preferably a triangle, square, hexagon or octagon structure.

4. Current limiting device with current-carrying high-temperature superconductor tracks (HTSL) arranged on a plate (PL), according to claim 2, feature 4.1, the basic element recesses (GA) have an arbitrary circumferential structure.

5. Current limiting device with current-carrying high-temperature superconductor tracks (HTSL) arranged on a plate (PL), according to claim 1 or 2, g e k e n n z e i c h n e t d u r c h feature 5.1 the current-carrying high-temperature superconductor tracks (HTSL) are implemented in thin-film technology.

6. Current limiting device with current-carrying high-temperature superconductor tracks arranged on a plate (PL)

(HTSL), according to claim 1 or 2, g e k e n n z e i c h n e t d u r c h feature 6.1 the current-carrying high-temperature superconductor tracks (HTSL) are executed in thick film technology.

7. Resistive current limiting device

- with a substrate,

- With a conductor structure on the substrate with metal oxide

High-T _c superconductor material as well

- With end pieces for contacting the conductor track structure, the conductor track structure (3, 10) having at least one main current path (SI, Sj), which in the

The main direction of expansion (r) of the conductor track structure is subdivided into a number of successively arranged, identically shaped sections (5j), each of which forms two branches (ZI, Z2) connected in parallel, The parallel connection of the branches in the connecting area (6j) between the sections (5j) lying one behind the other is characterized in that the shape of the sections (5j) is essentially race track-shaped or oval or arch-shaped.

8. Resistive current limiting device

- with a substrate,

- With a conductor structure on the substrate with metal oxide

High-T _c superconductor material as well

- With end pieces for contacting the conductor track structure, the conductor track structure (3, 10) having at least one main current path (SI, Sj), which, viewed in the main direction of expansion (r) of the conductor track structure, is divided into a plurality of successively arranged, identically shaped sections (5j), which Each form two branches (ZI, Z2) connected in parallel, the branches being connected in parallel in the connection area (6j) between sections (5j) lying one behind the other, characterized in that the sections (5j) are transverse to the main direction of expansion (r) of the conductor track structure (3 ) have a greater extent than in this direction (r).

9. Resistive current limiting device

- with a substrate,

- With a conductor structure on the substrate with metal oxide high-T _c superconductor material and

- With end pieces for contacting the conductor track structure, the conductor track structure (3, 10) having at least one main current path (SI, Sj) which, seen in the main direction of expansion (r) of the conductor track structure, into several successively arranged, identically designed sections (5j) is subdivided, each of which forms two branches (ZI, Z2) connected in parallel, the branches being connected in parallel in the connecting region (6j) between sections (5j) located one behind the other, characterized in that in each branch (ZI, Z2) the conductor track (L, L ¹ ) two transverse to the main direction of expansion (r) of the conductor track structure

(3) has extending leg parts (7a, 7b) which merge into one another through a lateral arch part (8), and that the conductor track width (Bb) in the arch part (8) is at least equal to the conductor track width (B _m ) in the leg parts (7a, 7b) and is preferably between 1.1 times and 1.2 times the conductor track width (B _m ) in the leg parts (7a, 7b).