WO2018214012A1

WO2018214012A1 - Circuit breaker with heat sink and shield element

Info

Publication number: WO2018214012A1
Application number: PCT/CN2017/085459
Authority: WO
Inventors: Fujian SU; Florian Brandl; Astrid Bauer; Daniel-Jun Cheng
Original assignee: Abb Schweiz Ag
Priority date: 2017-05-23
Filing date: 2017-05-23
Publication date: 2018-11-29

Abstract

A circuit breaker (10) comprises: a longitudinally extending inner conductor (20) and an outer conductor (30) surrounding the inner conductor (20) in a housing-like manner, which have a potential difference with respect to one another in operation, a heat sink (35) comprising cooling fins and being electrically conductively connected to the inner conductor (20) for dissipating a thermal load of the inner conductor (20), and an electrically conductive shield element (40) for reducing field peaks, which is mounted on a side of the heat sink (35) facing the outer conductor (30) and surrounds the heat sink (35) in an umbrella-like manner.

Description

CIRCUIT BREAKER WITH HEAT SINK AND SHIELD ELEMENT

TECHNICAL FIELD

The invention relates to a circuit breaker for medium and high voltage. In particular, it relates to a generator circuit breaker with housing, which is internally provided with a heat sink (German:

) , which has a shield element.

STATE OF THE ART

It is known to provide conductors for high currents with cooling fins at their surface, in order, for example, to improve the dissipation of heat and to increase the maximum current carrying capacity of the conductors. Due to their generally or principle-relatedly relatively sharp edges, also caused by the relatively small radius of curvature of the cooling fins, the use of such cooling fins, which are typically at the potential of the conductor, however leads to a partly considerable deterioration in the dielectric properties or the voltage strength of the respective system, in particular when the conductor is formed as an inner conductor which is surrounded by an electrically conductive housing at a different electrical potential. EP 2 747 226 A1 shows such a high-current arrangement with an inner conductor and an outer conductor enclosing the inner conductor, wherein cooling fin arrangements are mounted to the inner conductor.

This may for example require an enlargement of the respective housing, since the distances between respective poles or phases and the housing must be designed to be larger in order to ensure the required breakdown strength at a given nominal voltage. This is especially disadvantageous in the case of three-phase circuit breaker switches for generators (GCB systems) , since the distance between the poles is a critical parameter for the overall design.

Known approaches for solving the above problems are, for example, to use better and also more expensive conductor materials to reduce the resistance losses and thus the necessary cooling. In addition, the size of the housing can be increased； however, this causes the above mentioned problems. In addition, special field distribution-optimized designs for cooling fins were proposed, although they have a significant cost disadvantage compared to standard heat sinks.

In the context of the above mentioned and further problems, there is a need for circuit breakers with high current conductors having improved properties.

SUMMARY OF THE INVENTION

The above-mentioned problems will be at least partially solved by a circuit breaker according to claim 1. Preferred embodiments, further aspects and details arise from the dependent claims, the description and the figures.

According to a first aspect, acircuit breaker, in particular a generator circuit breaker, is proposed, which comprises: an elongated inner conductor and an outer conductor surrounding the inner conductor in a housing-like manner, which in operation have a potential difference with respect to one another, aheat sink comprising cooling fins, which heat sink is electrically conductively connected to the inner conductor, for dissipating a thermal load from the inner conductor, and an electrically conductive shield element for reducing field peaks, which is mounted on a side of the cooling element facing the outer conductor and surrounds the heat sink in an umbrella-like manner.

In general, all terms used in the claims are to be interpreted in the technical field according to their ordinary meaning unless otherwise expressly defined herein. All references to "a/an/the element, device, component, means, step, etc. " shall be interpreted openly to refer to at least one instance of the element, device, component, means, step, etc., unless expressly stated otherwise. The steps of any process disclosed herein need not be carried out in the exact order disclosed, unless expressly stated.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example, with reference to the accompanying drawings, wherein:

FIG. 1 shows a schematic top view of a cross-section of a circuit breaker according to embodiments,

FIG. 2 shows a schematic side view of a cross-section of the circuit breaker of FIG. 1,

FIG. 3 shows a shield element as used in the exemplary embodiments of FIG. 1 and FIG. 2.

DETAILED DESCRIPTION

The invention will now be described in more detail below with reference to the accompanying drawings, in which certain embodiments of the invention are shown. However, this invention can be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Instead, these embodiments are provided by way of example so that this disclosure will be thorough and complete and will completely convey the scope of the invention to those skilled in the art. Identical numbers refer to the same elements throughout the description.

FIG. 1 is a schematic illustration of a circuit breaker 10 according to exemplary embodiments. The circuit breaker 10 herein is implemented as a generator switch (also referred to as a generator circuit breaker, GCB) , can particularly be part of a typically three-pole generator switch system. The circuit breaker 10 comprises longitudinally extending inner conductor 20, which is surrounded by an outer conductor 30. The outer conductor 30 typically surrounds the inner conductor 20 in a housing-like manner. The two have a potential difference with respect to one another during operation. The case in which the outer conductor 30 or the housing is grounded is shown. For the sake of cooling the inner conductor 20, in the non-limiting example of FIG. 1, two individual heat sinks 35, each comprising a plurality of cooling fins, are fastened to the inner conductor 20. More heat sinks can also be arranged, e.g. four or six, which are typically symmetrically distributed around the circumference of the inner conductor 20. In the longitudinal direction of the inner conductor 20, several such arrangements can be arranged one after another, too. In this way, the inner conductor can be provided with heat sinks to a large extent and heat dissipation can be improved. The actual switching element, the switching chamber, which interrupts the current flow through the inner conductor 20, can be integrated approximately in the inner conductor and is not explicitly shown here.

The heat sinks 35 are thermally and electrically conductively connected to the inner conductor 20 and are used to dissipate the thermal load from the inner conductor 20 to a medium surrounding the inner conductor, for example air. A top view is shown in FIG. 1, i.e. seen from top to the inner conductor 20. In order to reduce the field strength peaks between the heat sinks 35 and the grounded outer conductor 30, an electrically conductive shield element 40 is mounted on a side of the (herein for example: two) heat sinks 35 facing the outer conductor 30. The shield element 40 surrounds the heat sink in a umbrella-like manner so that the cooling fins are shielded from the outer conductor 30 by the shield element. Instead of conventionally relatively small radius of individual cooling fins, the field lines terminate on the always relatively large-designed radius of the surface of the shield element 40, as described further below, so that the field line distribution is influenced and thus a homogeneity of the electric field is achieved.

A side view of the circuit breaker of FIG. 1 is shown in FIG. 2. The arrows show the movement of the gas within the outer conductor 30, which moves in the direction of the heat sink 35 by convection.

A shield element 40 is shown in FIG. 3. It has the basic shape of a rectangular base surface 45 with

rounded side surfaces

50, 51. The shield element 40 can have at least one passage 60 for a fluid, typically air, in the base surface 45. Thus, the cooling is improved in comparison to a shield element with a closed base surface. For preventing that the passage or several passages does not lead to an increase of field peaks again, the circumferential edge 61 of the passage 60 is rounded or chamfered.

As shown in FIG. 3, the shield element 40 has side faces 50 which are extending downwardly. In the mounted state on the heat sinks 35, the side faces surround a portion of the heat sinks 35 laterally. Two side surfaces 51 located on opposite sides of the base surface 45 are extending further downwards than the side surfaces on the other two opposite sides of the base surface 45. The shield element 40 can be formed, for example, as a metal casting member, for example from cast aluminum.

The design of the shield element 40 comprises that the shield element on its side facing the outer conductor 30 is designed such that all radii of curvature are equal to or greater than about 10 mm, more preferably greater than about 15 mm. In order to achieve a sufficient shielding effect or a reduction of the field peaks, the downwardly extending side surfaces 50 surround the heat sink 35 laterally. Thus, the shield element 40 surrounds the sides of the heat sink at least about 10％of its total height, preferably more than 15％, as indicated in FIG. 2.

The shield element 40 has a further function due to the smooth/rounded configuration of its outer side. For example, it protects assemblers from contacting the normally at least partly extremely sharp-edged cooling fins. In the case of a correspondingly stable design, the shield element 40 can also provide a secure and safe tread surface for assemblers, which can be an advantage or safety benefit due to the cramped design of GCB systems in reality.

In order to achieve a stable fastening of the shield element 40 to the heat sink 35, a bore 65 may be provided in the center of the base surface. A screw (not shown) is inserted through that bore and screwed into a threaded bore provided in the heat sink. Alternatively, aplurality of openings can also be provided near the corners of the shield element 40 along with correspondingly mounted threaded holes in the heat sink.

Typical systems in which circuit breakers according to embodiments are used are in the voltage range from about 1 kV to about 60 kV, more typically from about 5 kV to about 40 kV.

By means of the design of the shield element 40 described in the exemplary embodiments, it can be used together with commercially available finned heat sinks and thus the negative influence of the cooling fins described above on the breakdown strength of the circuit breaker can be compensated.

Claims

A circuit breaker, in particular a generator circuit breaker, comprising:

-an longitudinally extending inner conductor (20) and an outer conductor (30) surrounding the inner conductor (20) in a housing-like manner, which have a potential difference with respect to one another in operation,

-a heat sink (35) comprising cooling fins, which is electrically conductively connected to the inner conductor (20) , for dissipating a thermal load of the inner conductor (20) ,

-an electrically conductive shield element (40) for reducing field peaks, which conductive shield element (40) is mounted on a side of the heat sink (35) facing the outer conductor (30) and surrounding the heat sink in an umbrella-like manner.
The circuit breaker according to claim 1, wherein the shield element (40) has a basic form of a rectangular base surface (45) with rounded side faces (50, 51) .
The circuit breaker according to one of the preceding claims, wherein the shield element (40) has at least one passage (60) for a fluid in the base surface (45) , the passage having at least one rounded or chamfered edge (61) .
The circuit breaker according to one of the preceding claims, wherein the shield element (40) has downwardly extending side surfaces, which laterally surround a portion of the heat sink (35) .
The circuit breaker according to claim 4, wherein two side surfaces (51) are located on opposite sides of the base surface (45) and are further extending downwarly than the side surfaces on the other two sides of the base surface (45) located opposite of one another.
The circuit breaker according to one of the preceding claims, wherein the shield element (40) is configured on its side facing the outer conductor (30) such that all radii of curvature are equal to or greater than about 10 mm.
The circuit breaker according to one of the preceding claims, wherein the side faces (50, 51) which are extending downwardly surround the heat sink (40) laterally to at least about 10％of its height.
The circuit breaker according to one of the preceding claims, wherein the circuit breaker is designed for voltages of about 1 kV to about 60 kV.