EP2997587B1 - Circuit breaker - Google Patents

Description

The invention relates to the field of electrical power generation and transmission. It relates to a circuit breaker according to the preamble of the independent claim, which in particular in power plants, substations and other facilities of the electric power supply for switching on and off of operating and overcurrents, in particular in the range of medium or high voltage, is used.

TECHNOLOGICAL BACKGROUND

Such a switch is for example from the European patent applications EP 0 696 040 A1 and EP 0 951 039 A1 known.

When switching high currents, as they occur in particular in the case of short circuit, usually arise in such switches in an insulating gas in a pressure chamber and a return channel high pressures in the range of 10 to 100 bar and temperatures above 2300K. At very high currents, especially in one Range above 250kA, and / or compact switches can also temperatures up to 3000K or more occur. This can lead to plastic deformation occurring on a shut-off valve designed as a metal ring of a check valve, which is installed in a mouth of the return channel in a heating volume for the insulating gas, which cause the check valve can no longer fulfill its function satisfactorily.

As tests have shown, such plastic deformations can indeed be avoided or at least largely reduced by a more solid design of the shut-off body; However, at the same time lead to an increased inertia of the check valve, so that it closes the return channel too fast if necessary, whereby undesirable amount of insulating gas can flow out of the heating volume.

Out DE 29 604 500 U1 a blow piston switch is known in which the blow piston is coated with a layer of heat-resistant plastic such as PTFE or polyamide to serve as electrical shield against the contact piece, or to prevent the formation of bases of the switching arc on the blow piston.

It is therefore an object of the invention to provide a circuit breaker, by means of which the disadvantages described above can be avoided.

DESCRIPTION OF THE INVENTION

These and other objects are achieved by a circuit breaker having the features of the independent claim. Further advantageous embodiments of the invention are specified in the dependent claims.

A circuit breaker according to the invention, which can be switched between a closed position and an open position, so that in the open position, an interruption path is formed, which comprises an arcing space; comprises a standing with the arc chamber storage volume for an extinguishing gas, which storage volume has an inlet for the quenching gas, further comprising a valve is provided at the inlet, which comprises a shut-off device, by means of which the inlet is closable. The shut-off body has a heat-insulating coating. The heat-insulating coating serves to avoid plastic deformation of the shut-off.

In an alternative embodiment of the circuit breaker according to the invention, which can be switched between a closed position and an open position, comprising a first power connection and a second power connection, wherein in the closed position between the first power connection and the second power connection an electrically conductive connection is formed, in the off position between the first power connection and the second power connection an interruption path is formed, wherein the interruption path comprises an arc space, which is formed between a first, electrically conductively connected to the first power terminal contact element and a second, electrically conductively connected to the second power terminal contact element, standing with the arc chamber in gas exchange storage volume for a quenching gas, which storage volume comprises an inlet for the quenching gas, and wherein at the inlet a valve is provided which comprises a shut-off body, by means of which the inlet is closable, the shut-off body has a heat-insulating coating. Again, the heat-insulating coating serves to prevent plastic deformation of the shut-off.

In a preferred development of the circuit breaker according to the invention, a plastic, preferably a polymer, is used as the heat-insulating coating. Particularly preferably, a thermoset is used because this remains rigid up to a decomposition temperature and thus in particular a drop formation is prevented. Such droplet formation occurs partly in elastomeric and in particular in thermoplastic plastics, and often leads to flame formation at temperatures in the range or above the decomposition temperature of the corresponding plastic, in particular by igniting droplets or droplets formed. Particularly preferably, an epoxy resin or epoxy resin system is used as the plastic.

In a further preferred embodiment of the inventive circuit breaker, a plastic, in particular an epoxy resin or epoxy resin system is used for the heat-insulating coating, which is provided with one or more fillers, which are in particular at least substantially uniformly distributed in the plastic volume. In particular ceramic powders, such as, for example, aluminum oxide, can be used as the filler; but also with molybdenum sulfide in powder form, good results were achieved in experiments. The filler increases on the one hand, a burn-off resistance of the plastic, on the other hand, a mechanical stability both the heat-insulating coating as well as the coated shut-off body as a whole.

In a further preferred embodiment of the circuit breaker according to the invention, a material is selected for the heat-insulating coating, in particular a plastic as described above, which has a low thermal conductivity λ with λ ≦ 10 W / (mK), preferably λ ≦ 1.0 W / ( mK), and more preferably λ ≤ 0.3 W / (mK). This allows a sufficient thermal insulation even with a relatively thin coating with thicknesses in the range of a few 10 .mu.m.

In a further preferred development of the circuit breaker according to the invention, a material is selected for the heat-insulating coating, in particular a plastic as described above, which has a modulus of elasticity E with E ≥ 5 GN / m ² , preferably E ≥ 10 GN / m ² , and especially preferably E ≥ 20 GN / m ² . In particular, in connection with a shut-off of a metal with a relatively low modulus of elasticity such as aluminum, magnesium, etc., this leads in conjunction with a solid, irreversible material compound, as formed between shut-off and heat-insulating coating, to increased rigidity, especially in annular shut-off, and thus to a reduction of plastic deformation of the shut-off during the turn-off.

In a further preferred development of the circuit breaker according to the invention, a material is selected for the heat-insulating coating, in particular a plastic as described above, which has a thermal coefficient of linear expansion α with α ≦ 20 × 10 ^-6 / K, preferably α ≦ 15 × 10 ^-6 / K, and more preferably α ≤ 10 · 10 ^-6 / K. In particular in connection with a shut-off of a metal with a relatively high coefficient of thermal expansion, in particular Aluminum, beryllium, magnesium, etc., this leads in conjunction with a solid, irreversible material compound, as formed between shut-off and heat-insulating coating, to a reduction of plastic deformation of the shut-off during the turn-off.

In a further preferred embodiment of the inventive circuit breaker, a plastic is selected for the heat-insulating coating, which has a glass transition temperature T _G with T _G ≥ 293K, preferably T _G ≥ 323K, and particularly preferably T _G ≥ 373K. The choice of a plastic with high glass transition temperature ensures a particularly high robustness at high temperatures and thus allows a particularly effective reduction of plastic deformation of the shut-off during the turn-off.

In a further preferred development of the circuit breaker according to the invention, a ceramic material or perfluorocarbons, in particular polytetrafluoroethylene (PTFE), are used for the heat-insulating coating.

BRIEF DESCRIPTION OF THE FIGURES

• Fig. 1 einen teilweisen axialen Längsschnitt durch einen erfindungsgemässen Leistungsschalter;
• Fig. 2 eine ausschnittsweise Vergrösserung entsprechend Bereich A aus Fig. 1 für einen erfindungsgemässen Leistungsschalter;
• Fig. 3 einen Querschnitt durch den ersten Absperrkörper für einen Leistungsschalter gemäss eines weiteren bevorzugten Ausführungsbeispiels der vorliegenden Erfindung.

It show schematically

• Fig. 1 a partial axial longitudinal section through a circuit breaker according to the invention;
• Fig. 2 a partial enlargement according to area A from Fig. 1 for a circuit breaker according to the invention;
• Fig. 3 a cross section through the first shut-off for a circuit breaker according to another preferred embodiment of the present invention.

Basically, like reference numerals designate like parts.

WAYS FOR CARRYING OUT THE INVENTION

Fig. 1 shows a partial axial longitudinal section through a circuit breaker according to the invention, in particular a generator switch, which is shown on the left in a closed position and on the right in an open position. The circuit breaker has a housing 1, which is constructed at least substantially rotationally symmetrical about a switching axis 2 extending in an axial direction. The housing 1 comprises an upper housing part 3 and a lower housing part 4, both made of metal, which are connected by a cylindrical central housing part 5 made of insulating material. The upper housing part 3 is connected to a first power connection, the lower housing part 4 to a second power connection of the circuit breaker. The entire housing 1 is filled with an insulating gas, preferably SF ₆ , which serves as an extinguishing gas.

At the height of the central housing part 5, a nominal current path is formed on the outside, which in each case to the upper housing part 3 and the lower housing part 4, spaced apart in the axial direction, circumferential, fixed rated current contacts, an upper fixed rated current contact 6 and a lower fixed rated current contact 7 comprises such as a movable rated current contact 8 with circumferentially successive, each the distance between the fixed rated current contacts 6, 7 bridging contact fingers. The movable rated current contact 8 is connected to a switching drive, not shown, through which it bridges in the axial direction between a closed position of the circuit breaker, in which it bridges a distance between the upper fixed rated current contact 6 and the lower fixed rated current contact 7, and an open position of the circuit breaker, in which it is spaced from the upper fixed rated current contact 6, is displaceable.

The upper housing part 3 is closed by a horizontal first partition 9 down. It carries a fixed part of a Abbrandschaltanordnung 10. In a central opening of the first partition wall 9 is a contact tulip 11 is mounted as a first contact element with a plurality of circumferentially successive, obliquely downward and directed against the switching axis 2, separated by slots elastic contact fingers. The contact tulip 11 opposite a nozzle 12 surrounding the switching axis 2 is arranged made of electrically insulating material, which has the shape of an upwardly narrowing funnel. In a arranged in the lower housing part 4 sliding guide 13, which also produces a good electrically conductive connection is mounted as a second contact element by means of the switching drive axially movable switching pin 14 which projects in the closed position of the circuit breaker in the contact tulip 11 and touches the outside of the contact fingers becomes. The same are elastically deformed so that they exert a relatively high contact pressure on the switching pin 14. The sliding guide 13 is anchored to a second partition wall 15, which closes the lower housing part 4 upwards. In a central opening of the second partition wall 15, the nozzle 12 is fixed.

In the off position of the circuit breaker, the switching pin 14 is pulled down so that its tip is below the nozzle 12. If there is an arcing space 16 between the contact tulip 11 and the switching pin 14, a sufficiently large current flows between the first and second power connection at the beginning of a switching process in which the circuit breaker is transferred from the closed position to the open position formed an arc 17 in the arc chamber 16 said contact elements. The arc chamber 16 is surrounded by a continuous annular storage volume, which serves as a heating volume 18. The heating volume 18 is connected to the arc chamber 16 by a contact tulip 11 separating from the nozzle 12 gap forming a circumferential blow slot 19. The blow slot 19 thus forms an outlet and serves as directed against the arc chamber 16 blowing opening. Outside the heating volume 18 is completed by a circumferential third partition 20 made of thermally insulating material, which serves as a heating chamber insulator.

At the top of the arc chamber 16, separated therefrom by an opening formed by the ends of the contact fingers of the contact tulip 11, a pressure space 25 is defined by the contact tulip 11 flaring upwards and a subsequent annular cover 26 made of electrically insulating material and by a Cap 27 is limited from steel, the latter surrounds the cover 26 at a distance and abuts outside of the same to the first partition 9. The cover 26 and the cap 27 spaced from it form a rotationally symmetrical about the switching axis 2 return channel 28, which in all directions radially in a first region from the pressure chamber 25 on all sides leads outside, and then bent in a second area down and guided in the axial direction to the heating volume 18. An effective cross section of the return channel 28 thus widens steadily in the first area in the direction away from the indexing axis. An opening of the return channel 28 in the heating volume 18 forms an inlet for the insulating gas. In the mouth, a first check valve is installed, which has a first shut-off, which is designed as a circumferential, rigid, preferably made of spring steel, first metal ring 29. On a return channel 28 facing the rear side of the first metal ring 29, a heat-insulating coating 29a made of epoxy resin is provided. As an exhaust, which connects the pressure chamber 25 with the interior of the upper housing part 3, which serves as an exhaust volume 30, a central exhaust port 31 is provided in the cap 27. At the bottom, another exhaust volume 30 'in the lower housing part 4 adjoins the arc chamber 16.

At the second partition wall 15 are several, z. B. four distributed over the circumference of the blowing cylinder 21 arranged to be actuated by the switching drive blow piston 22, which are each connected via blow channels 23 to the heating volume 18. In mouths of the blowing channels 23 in the heating volume 18, a second check valve is installed, which has a second shut-off, which is designed as a circumferential, rigid, second metal ring 24.

In detail, a switch-off process runs as follows:

By the switching drive, not shown, starting from the on-position shown on the left, the movable rated current contact 8, the switching pin 14 and the blow piston 22 moves downward. Shortly after the beginning of this movement, the movable rated current contact 8 separates from the upper fixed rated current contact 6, whereby the rated current path is interrupted and the current commutated to the Abbrandschaltanordnung 10. Something later, the switching pin 14 is pulled out of the contact tulip 11. Between these contact elements, an arc 17 forms, which extends at the end of the switching movement through the arc chamber 16, which was opened by the movement of the switching pin 14 via the switching path. In this case, in the heating volume 18, a pressure build-up by the movement of the blow piston 22, which causes a Isoliergasströmung from the blow piston 21 via the blow channels 23 into the heating volume 18. If a pressure of the insulating gas in the heating volume 18, which is also built up by other actions, exceeds a blow pressure, a second check valve 24 closes and prevents gas from flowing out of the heating volume 18 into the blower channels 23.

By a radiated from the arc 17 through the blow slot 19 in the heating volume 18 heat the insulating gas is strongly heated in the same, so that the pressure in the heating volume 18 is further increased significantly.

Another, very significant contribution to the pressure build-up in the heating volume 18 is supplied by the pinch pressure of the arc 17, which is generated by a rapid contraction of the same in the region of the switching axis 2 and briefly a strong axial flow from the arc chamber 16 into the pressure chamber 25 and a strong Pressure increase causes in the same. This pressure is partly derived via the return channel 28 in the heating volume 18. It is favorable that the flow resistance in the return channel 28 thanks to the extension of the cross section of the same and its direct guidance and an installation-free training is very low. The first check valve at the mouth of the return channel 28 in the heating volume 18, in turn, prevents the gas from flowing out of the heating volume 18, when there the pressure exceeds that in the pressure chamber 25, which usually goes back relatively quickly.

At very high currents, such a high pinch pressure is generated that a complete return of the gas into the heating volume would lead to mechanical and thermal overloading of the burnup circuit arrangement 10. Excess pressure is therefore discharged via the exhaust port 31 directly into the exhaust volume 30. The central arrangement of the exhaust port 31 is advantageous because excessive Pinchdruck mainly produces a pressure surge in the axial direction, which can escape harmlessly through the exhaust port 31. In order to reduce a current dependence of a pressure build-up in the pressure chamber 25, preferably a pressure relief valve can be installed in the exhaust port. After building up a high pressure in the heating volume 18, the arc 17 is extinguished at the next zero crossing by the insulating gas from the heating volume 18 partly through the blow slot 19 and the contact tulip 11 in the pressure chamber 25, in which the pressure at this time already strong has fallen, and continues to flow through the exhaust port 31 into the exhaust volume 30. The blow slot 19 thus serves as an outlet for the insulating gas from the heating volume 18 in the arc chamber 16. When flowing a gas flow of the insulating gas inevitably crosses the arc gap and removed in the crossing region largely all ionized gases, so that after the zero crossing no arc can form more. On the other hand, the insulating gas flows parallel to the arc gap 16 through the nozzle 12 into the further exhaust volume 30 '.

Fig. 2 shows a schematic representation of a partial enlargement of area A. Fig. 1 ., In which on the return channel 28 facing the rear side of the first metal ring 29 provided heat insulating coating 29a made of epoxy resin is shown in detail.

In this case, a thickness of the heat-insulating coating 29a is preferably selected to be smaller than a cross-section of the metal ring 29 which is defined as the square root of a cross-sectional area of the metal ring 29, preferably smaller than a minimum longitudinal extent of the metal ring 29 cross-section.

The first metal ring 29 is held in position by an at least partially circumferential projection 9a, which is formed in the heating volume 18 leading to the mouth of the return channel 28 opposite to a provided on the first partition wall 9b 9b in position. Preferably, between the first metal ring 29 and projection 9a one or more, in Fig. 2 not shown springs, in particular spiral or leaf springs, be provided to press or bias the first metal ring 29 against the mouth.

Although a decomposition temperature of epoxy resin, depending on the exact composition in the range of 200-400 ° C, and thus far below a maximum temperature T _{max of} the insulating gas in the return channel 28 with T _max ≥ 2300K, it has surprisingly been found in experiments that the coating 29 a the observed in known circuit breakers can effectively prevent deformations of the shut-off or even completely prevented, so that a back flow of insulating gas from the heating volume 18 in the return channel 28 is effectively prevented even after a variety of shutdown. On the one hand, this is due to the fact that due to a low thermal conductivity λ of the epoxy resin in the range 0.1 ≦ λ • mK / W ≦ 0.5, heating of the metal ring 29 is prevented or at least substantially reduced. On the other hand, due to a high modulus of elasticity E of the epoxy resin in the range of 15 GN / m ² ≥ E ≥ 20 GN / m ^2, a mechanical stabilization of the first metal ring 29 is achieved.

Although it has surprisingly been found in experiments, the coating 29a leads to a slightly deteriorated sealing behavior of the first check valve, which, however, remains without influence on a switch-off behavior of the circuit breaker in the context of conventional measurements and investigations.

As has also been shown, can be dispensed with a heat-insulating coating of the second metal ring 24 on the second check valve, as in the region of the second check valve significantly lower pressures and temperatures occur in the quenching gas than in the region of the first check valve. As described above, only cold extinguishing gas is pressed by the second check valve with a comparatively low pressure, preferably in a range between 1 and 10 bar, by means of the blowing cylinder 21 via the blowing channels 23 in the heating volume 18. A further, substantial increase in the pressure in the quenching gas, preferably to values between 10 and 100 bar, takes place only by a direct heating effect of the arc and an additional return of extinguishing gas via the return channel 28 into the heating volume 18.

Fig. 3 shows a schematic representation of a cross section through the first shut-off body for a circuit breaker according to another preferred embodiment of the present invention. The heat-insulating coating 29a of epoxy resin is applied so that it encloses the metal ring 29 on all sides. This allows a simpler and cheaper production on the one hand; on the other hand, a further increased reduction of the deformations. Here again, the thickness D of the heat insulating coating 29a preferably selected to be smaller than the cross section Q of the metal ring 29, which is defined as the square root of the cross-sectional area A of the metal ring 29, ie, Q = √ A; preferably smaller than the minimum longitudinal extent L _{min of} the metal ring 29 in cross section.

As has also surprisingly been found in experiments, for the thickness D of the heat-insulating coating 29a when using epoxy resin it is preferably already sufficient to have values of D < Q / 2 and / or D <L _min / 2, most preferably even values of D < Q / 10 and / or D <L _min / 10. The thickness D of the heat-insulating coating 29a of the coating is preferably in the range 0.01 mm ≦ D ≦ 1.0 mm, preferably 0.05 mm ≦ D ≦ 0.5 mm, most preferably 0.08 mm ≦ D ≦ 0.2 mm. Minimum longitudinal dimension L _min and / or cross-section Q are preferably in a range between 0.5 mm and 20.0 mm, most preferably between 1.0 mm and 5.0 mm.

Although the invention has been described and illustrated above with reference to specific embodiments, it is not limited to these embodiments. Rather, various modifications of detail may be made within the scope and equivalence of the claims without resulting in any departure from the invention.

LIST OF REFERENCE NUMBERS

1

casing

2

switching axis

3

Upper housing part

4

lower housing part

5

middle housing part

6

upper fixed rated current contact

7

lower fixed rated current contact

8th

movable rated current contact

9

first partition

9a

head Start

10

consumable

11

Contact tulip

12

jet

13

slide

14

switch Probe

15

second partition

16

Arcing area

17

Electric arc

18

heating volume

19

blow slot

20

third partition

21

puffer cylinder

22

puffer

23

blow

24

check valve

25

pressure chamber

26

cover

27

cap

28

Return channel

29

metal ring

29a

heat-insulating coating

30

exhaust volume

30 '

further exhaust volume

31

exhaust port

32

outer extinguishing chamber volume

Claims (18)

1. Circuit breaker, which can be switched between an on-position position and an off-position such that, in the off-position, an interruption path is formed, comprising an arcing space (16); wherein the circuit breaker

   a) comprises a storage volume for a quenching gas which is in gaseous communication with the arcing space (16), wherein said storage volume is provided with an inlet for the quenching gas, and wherein

   b) said inlet is also fitted with a valve comprising an obturator,
   characterized in that

   c) the obturator is provided with a heat-insulating coating (29a) for the prevention of plastic strain.
2. Circuit breaker according to Claim 1, characterized in that the heat-insulating coating (29a) is formed of a thermosetting plastic.
3. Circuit breaker according to one of the preceding claims, characterized in that the heat-insulating coating is formed of a material, specifically a plastic, having an elastic modulus E of E ≥ 5 GN/m², and preferably E > 20 GN/m².
4. Circuit breaker according to one of the preceding claims, characterized in that the heat-insulating coating is formed of a material, specifically a plastic, having a longtitudinal coefficient of thermal expansion α of α 0,1 ≤ 20•10^-6/K, and preferably α ≤ 10•10^-6/K.
5. Circuit breaker according to one of Claims 1 to 4, characterized in that the heat-insulating coating (29a) is formed of epoxy resin.
6. Circuit breaker according to Claim 1, characterized in that the heat-insulating coating (29a) is formed of a ceramic material.
7. Circuit breaker according to one of the preceding claims, characterized in that a permanent and irreversible material bond is formed between the obturator and the heat-insulating coating.
8. Circuit breaker according to one of the preceding claims, wherein the arcing space is formed between a first contact element and a second contact element, characterized in that a quenching gas which is heated by an arc generated between the contact elements during a breaking operation can be routed from the arcing space (16) via the inlet to the storage volume.
9. Circuit breaker according to one of the preceding claims, characterized in that the heat-insulating coating (29a) is applied to a surface of the obturator which, in the closed position thereof, faces away from the storage volume.
10. Circuit breaker according to one of the preceding claims, characterized in that the storage volume is configured as a heating chamber (18), in which the quenching gas can be heated by the heat energy radiated by an arc which is generated by a breaking operation.
11. Circuit breaker according to one of the preceding claims, characterized in that the obturator is formed of metal, preferably of aluminum or steel.
12. Circuit breaker according to one of the preceding claims, characterized in that the storage volume, for the exchange of gas with the arcing space (16), is provided with an outlet for the quenching gas, which is preferably configured as a puffer opening which is oriented in opposition to the arcing space (16).
13. Circuit breaker according to one of the preceding claims, characterized in that the circuit breaker comprises a pressure chamber (25) which communicates with the arcing space (16) in an axial direction, and which is in gaseous communication with the storage volume via the inlet.
14. Circuit breaker according to the preceding claim, characterized in that a return channel (28) for the quenching gas is arranged between the pressure chamber (25) and the inlet.
15. Circuit breaker according to one of the preceding claims, characterized in that the storage volume encloses the arcing space (16) in the radial direction, and is preferably configured in an at least essentially annular or toroidal form.
16. Circuit breaker according to one of the preceding claims, characterized in that the quenching gas is SF₆, CO₂, N₂, air, preferably dried air, or a mixture of said gases.
17. Circuit breaker according to one of Claims 9 to 16, insofar as said claims refer to claim 8, characterized in that the circuit breaker is a generator circuit breaker, and the contact elements between which an arc is generated during a breaking operation form part of an arcing contact arrangement, and the generator circuit breaker is also provided with rated current contacts (6, 7, 8).
18. Circuit breaker according to Claim 17, characterized in that the storage volume is enclosed in the radial direction by an external extinction chamber (32) in which the rated current contacts (6, 7, 8) are arranged, and wherein a circumferential third partition (20) of heat-insulating material separates the storage volume from the external extinction chamber (32).

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