Patent Application
20180261406
The invention relates to the field of medium-, high-, or very high-voltage circuit breakers. It relates more particularly to the problem of the arc-control chamber heating by the Joule effect while it is in the closed position, and also to managing the discharging of hot gas that results from blasting the electric arc during an operation of opening the circuit breaker.
From the prior art, numerous circuit breaker designs are known, such as for example, the design described in document DE 10 2011 083593. Such a circuit breaker incorporates a discharge cap with openings made therein to allow gas to be evacuated.
In the closed position, the circuit breaker has current passing therethrough that, by the Joule effect, releases energy in the form of heat at the electrical interfaces, into the arc-control chamber. The openings in the discharge cap must therefore be large enough to enable the hot gas to be evacuated towards the volume of gas defined by the outer casing of the tank without damaging the electrical interfaces.
However, during opening of the circuit breaker, the hot gas that results from blasting the electric arc passes through said openings so as to be extracted into the arc-control chamber towards the outer casing of the circuit breaker.
This outer casing is thus subjected to risks of attack from the hot gas and from the microparticles entrained by said gas. In addition, for shielded circuit breakers of the gas-insulated switchgear (GIS) or “dead tank” type, an electrical insulation fault may form via the hot gas and give rise to electric arcing between a portion of the chamber that is electrically charged (at a non-zero potential) and the metal outer casing of the circuit breaker that is at zero potential. In order to limit this risk, in this situation the openings through the discharge cap must not be too large, so as to reduce the stream of hot gas flowing towards the outer casing.
Consequently, there exists a need to optimize the design of such circuit breakers, in such a manner as to provide a satisfactory response to the problem of the circuit breaker heating in the closed position, as well as to the problem of discharging the hot gas that results from blasting the electric arc during an operation of opening the circuit breaker.
In order to meet this need, the invention provides a medium-, high-, or very high-voltage circuit breaker, comprising at least one arc-control chamber and an outer casing defining a space in which the arc-control chamber is arranged, said arc-control chamber comprising:
According to the invention, the circuit breaker includes sealing means for sealing said opening, said sealing means being movable between a sealing position in which they prevent the gas from passing through the opening, and a retracted position in which they allow passage therethrough, the circuit breaker being configured in such a manner that in its closed position, said sealing means are in their retracted position, and in such a manner that passage from the retracted position to the sealing position takes place during an operation of opening the circuit breaker.
The invention initially presents the advantage of reducing the temperature in the arc-control chamber in normal operation, when the circuit breaker is in the closed position. Removing the sealing means from the opening enables natural convection to take place towards the inside space defined by the casing. Also, the effects of heating the arc-control chamber that are caused by current passing when the circuit breaker is in the closed position, may be considerably lessened.
In addition, the invention provides sealing of the opening during an operation of opening the circuit breaker. Consequently, as soon as said opening is sealed, the hot gas resulting from blasting the arc remains confined in the chamber, and that limits the risk of attack on the outer casing of the circuit breaker by said hot gas and by the microparticles that it entrains, and also the risk of arcing between the arc-control chamber of the circuit breaker and the outer casing.
The invention further provides at least one of the following optional characteristics, alone or in combination.
The circuit breaker is configured in such a manner that the sealing position is maintained until the end of the operation of opening the circuit breaker, and passage from the sealing position to the retracted position takes place during the following operation of closing the circuit breaker. By maintaining the sealing position until the end of the operation of opening the circuit breaker, the risk of the outer casing of the circuit breaker being attacked is further reduced. The sealing means may be returned to the retracted position at the start or at the end of the operation of closing the circuit breaker or at any instant between these two moments. In addition, it should be observed that the passage from the sealing position to the retracted position may be sudden or gradual, as a function of the design selected.
The circuit breaker is configured in such a manner that passage from the retracted position to the sealing position takes place after the operation of opening the circuit breaker has been initiated. This makes it possible to evacuate all or some of the high-pressure cold gas that is present in the arc-control chamber just after the operation of opening the circuit breaker has been initiated. As a result of this cold initial front being evacuated, the pressure in the chamber diminishes, and the mechanical forces required for moving the electrical contacts are advantageously reduced. In addition, during the remainder of the opening operation, this preliminary evacuation makes it possible to increase the pressure difference between the core of the chamber and the discharge that has been emptied of its high-pressure cold gas stream. Advantageously, this results in gas flowing better between the nozzle and the gas-flow chamber, i.e. in better arc blasting, and therefore in increased breaking capacity for the circuit breaker.
The circuit breaker includes first drive means for driving the first and/or second sets of electrical contacts, and second drive means ensuring passage of the sealing means from their retracted position to their sealing position, and said second drive means comprise at least one movable part of the circuit breaker, which part is set into movement during the operation of opening said circuit breaker. In other words, the setting into movement of the parts for opening/closing the circuit breaker is judiciously used to advantage in order to move the means for sealing the opening between its two positions. By way of example, the first and second drive means may have one or more parts in common. In another example, the electrical contacts and/or the parts secured thereto, such as the blast nozzle, could form an integral part of these second drive means. Advantageously, that makes it possible to obtain good synchronization between the opening/closing operations, and the operations for driving the sealing means. Alternatively, separate means for driving the contacts and for driving the means for sealing the opening could be provided.
In any event, it is possible to implement various contrivances such as a spring, a lever system, or similar, in order to speed up/slow down one or both operations of the sealing means. In addition, as mentioned above, a non-linear drive train may be provided, e.g. in such a manner as to cause the circuit breaker to open and the sealing means to close at different instants.
In a first preferred embodiment of the invention, the sealing means comprise a sealing gasket that is mounted on the same axis as the side wall of the discharge cap, and that is movable axially relative thereto. Preferably, this gasket seals a single annular opening, or a plurality of openings distributed angularly about the axis of the side wall of the discharge cap.
In a second preferred embodiment of the invention, the sealing means comprise a shutter covering one or more openings in the sealing position, the shutter being mounted to pivot relative to the discharge cap. This shutter may be mounted on the side wall of the cap or equally on its end wall.
In a third preferred embodiment of the invention, the sealing means comprise at least one check valve, capable of passing from its retracted position to its sealing position under the effect of the gas pressure inside the gas-flow chamber, the circuit breaker being configured in such a manner that after the value reaches its sealing position, said position is maintained by additional maintaining means, independent of the gas pressure being exerted on the valve. These additional means are preferably mechanical means for maintaining the valve in the sealing position, designed to be released during the following operation of closing the circuit breaker, again in mechanical manner. Nevertheless, the use of other technologies may be envisaged, such as electromagnetic maintaining means. In this example also, it should be observed that the valve may be provided on the side wall of the discharge cap or on its end wall.
In addition, it should be observed that the arc-control chamber is preferably of the double-motion type, but could be of the single-motion type, without going beyond the ambit of the invention.
Finally, the invention provides a method of controlling a medium-, high-, or very high-voltage circuit breaker as described above, the method being characterized in that it comprises the following steps:
Other advantages and characteristics of the invention appear in the non-limiting detailed description given below.
The description is made with reference to the accompanying drawings in which:
With reference initially to
The circuit breaker 10 comprises an arc-control chamber 12. The arc-control chamber 12 is arranged inside a casing 14. The arc-control chamber 12 is thus placed in a space 13 that is internally defined by the outer casing 14. This space 13 is usually filled with an insulating gas, e.g. of the SF6 type.
The chamber 12 includes a first set of electrical contacts 18a, 20a, and a second set of contacts 18b, 20b. More precisely, the first set comprises a first permanent contact 20a co-operating with a second permanent contact 20b of the second set, when the circuit breaker is in a closed position such as that shown in
However, the invention is not limited to this embodiment. The invention may in particular be applied to double-motion circuit breakers. In order to perform such movement, any design deemed appropriate by the person skilled in the art may be used, e.g. the design described in French patent document No. FR 2 976 085. In such an example, the two sets are thus movable in sliding along the main axis A of the arc-control chamber 12, in opposite directions.
The second arcing contact 18b is surrounded by two volumes 21 and 21′ separated axially from each other by a wall, and enabling the electric arc to be extinguished by blasting, so as to interrupt the current. The blast nozzle 19 makes it possible to channel the gas stream during said blasting.
The gas from the electric arc and the volumes 21 and 21′ is evacuated axially on both sides by the nozzle 19 and the inside space 7 of the second arcing contact 18b. The gas escaping via the nozzle 19 penetrates into a gas-flow chamber 31, also known as a discharge chamber, which chamber is defined by a discharge cap 40 housed in the space 13. The chamber 31 is thus arranged at least in part downstream from the nozzle 19, the term “downstream” being considered along a main axial direction of the gas flow in the chamber 12, at the outlet of the nozzle 19.
In analogous manner, opposite from the arc-control chamber, the gas being discharged via the space 7 penetrates into another gas-flow chamber 32, defined by a discharge cap 41 that is also housed in the space 13.
Beside the first set of contacts 18a, 20a, the arc-control chamber 12 thus includes the discharge cap 40 forming an outer wall of the discharge volume 31. The discharge cap 40 includes an end wall 40a as well as a side wall 40b together defining, internally, the gas-flow chamber 31. In this embodiment, the side wall 40b includes an annular opening 50 for evacuating gas towards the space 13 defined by the tank 14. This opening 50 extends circumferentially over substantially 360° about the axis A, and extends axially along a considerable length of the cap, e.g. over 20% to 40% of the total length of the cap. The opening 50 is arranged near an upstream end of the cap 40, but naturally it may be arranged in some other way on the cap. The invention is also applicable whatever the configuration inside the chamber 31, and it is not limited to the particular embodiments described with reference to
In the invention, the cap 40 is fitted with means 52 for sealing the annular opening 50. These sealing means are movable between a sealing position that is shown in
First of all, it should be observed that the two sets 18a, 20a, 18b, 20b are driven simultaneously by a control mechanism comprising an operating rod 22 that is centered on the axis A of the arc-control chamber 12, and that is movable axially in sliding in the arc-control chamber. The operating rod 22 drives a drive member 24 that, in this example, consists of a return lever that is mounted to pivot on a stationary portion of the arc-control chamber 12 about an axis 25 that is perpendicular to the plane of
The lever 24 is connected to the operating rod 22 by means (not shown), in such a manner that sliding of the rod 22 causes the lever to pivot 24 in one direction or the other.
The sets of electrical contacts are connected to the return lever 24 in such a manner that the first contacts 18a, 20a and the second contacts 18b, 20b move simultaneously and in opposite directions during pivoting of the lever 24.
Moving the contacts in opposite directions has the main advantage of obtaining a high relative speed of movement, while maintaining a lower contact speed relative to the stationary portions of the arc-control chamber 12.
In this example, the lever 24 consists in an oblong element, having its longest length transverse relative to the main axis A of the arc-control chamber 12. The lever 24 is pivotally mounted at its center inside the arc-control chamber 12, and its ends are connected to the electrical contacts by means of links 26, that are possibly resilient.
A pivot member 28 that is mounted on the stationary portion of the arc-control chamber 12 serves to hinge the lever 24 about the axis 25. The pivot member 28 and the lever 24 are arranged in an inside portion 30 of the gas-flow chamber 31, defined internally by a tubular wall 33 that is centered on the axis A.
The inside portion 30 of the cylindrical gas-flow chamber 31 is defined at its upstream axial end by the nozzle 19, i.e. beyond a contact support 34 arranged substantially orthogonal to the axis A. The first set of contacts 18a, 20a is mounted to slide relative to the tubular wall 33, along the axis A. The movable support 34 is arranged inside this same wall 33 forming a tube in the discharge chamber 31.
In the upstream portion 36, the chamber 31 forms a blast chamber 36 that begins beside the nozzle 19. Also, the blast chamber 36 extends axially, from upstream to downstream, between the nozzle 19 and the support 34 of the first set of electrical contacts.
The support 34 causes the shape of the blast chamber 36 to vary when it moves axially during opening and closing operations and enables fluid communication to take place between both sides of said support. Suitable orifices are thus made through the support 34, so that gas may pass therethrough.
Beside the first set of contacts 18a, 20a, the arc-control chamber 12 comprises the discharge cap 40, having its side wall 40b surrounding the tubular wall 33. The end wall 40a of the gas-flow chamber 31 is located remote from the support 34. It extends laterally beyond the wall 33, to join the side wall 40b.
An annular gas-discharge space 42 is then defined between the side wall 40b and the tubular wall 33, this space 42 forming an integral part of the gas-flow chamber 31, by constituting its external portion.
The gas streaming in the inside portion 30 of the chamber 31 may penetrate into said space 42 by means of holes 44 drilled in the wall 33. In addition, at its end situated opposite the end wall 40a, the cap 40 remains open and defines a discharge opening 46 of annular shape and of small section. This annular opening 46, defined internally by the wall 33, is directed axially in a direction away from the end wall of the circuit breaker. Nevertheless, a baffle-forming part 48 (shown in the following figures) makes it possible to redirect the gas stream towards the end wall of the circuit breaker, after its exit via the discharge opening 46. At the outlet of the baffle, the gas penetrates into the space 13 defined by the tank 14, outside the arc-control chamber 12.
Moreover, it should be observed that the end 15 of the tank, shown in
As mentioned above, the side wall 40b of the cap 40 is fitted in this example with an opening 50 for evacuating gas from the annular space 42, towards the space 13 defined by the tank 14. The means for sealing the opening 52 are in this example movable between a retracted position shown in
In the first preferred embodiment, the sealing means 52 take the shape of a sealing ring centered on the axis A, and movable relative to the wall 33 along said same axis. In the embodiment shown in
In the closed position of the circuit breaker 10, as shown in
When an operation of opening the circuit breaker is initiated, for interrupting current, the moving lever 24 causes the sealing ring 52 to move towards its sealing position shown in
The circuit breaker is designed so that the opening 50 is maintained sealed for the entire duration of the operation of opening the circuit breaker, and is released only during the following closing operation, still under the effect of the action of the lever 24.
As mentioned above, it could be arranged for the passage from the retracted position to the sealing position to take place after initiation of the operation of opening the circuit breaker, and not at the same instant as this initiation. That would make it possible to evacuate all or part of the high-pressure cold front that is present in the chamber 31, just after an operation of opening the circuit breaker has been initiated. As a result of evacuating the initial high-pressure cold front, the pressure in the chamber 31 is reduced, and the mechanical forces required for moving the electrical contacts are advantageously reduced. Arc blasting is also improved, because of the increase in the difference in pressure between the core of the nozzle 19 and the discharge.
A second preferred embodiment is described below in reference to
In the second embodiment, a plurality of openings 50 of small section are made in the side wall 40b of the discharge cap 40. These openings are grouped together, and cooperate with a shutter 52 that is operated in pivoting about the same axis 25 as that of the pivot member 28 that is used to drive the lever 24 or similar in pivoting. Here also, in a sealed position, the shutter 52 covers the openings as shown in
The shutter 52 is arranged externally on the wall 40b, but could be arranged internally, without going beyond the ambit of the invention.
Furthermore, another group of openings 50 may be made at the opposite end of the member 28, while still being associated with a shutter operated by this same member 28, that is used to perform opening and closing operations of the circuit breaker.
Reference is now made to
In both cases, the sealing means 52 take the form of a check valve associated with each opening 50. The valves 52 take the conventional form of spring valves, having particular operation that is described below.
In the neutral position at rest, the spring of each valve 52 leads said valve to release its associated opening, so that the valve adopts the retracted position making it possible for the chamber 31 and the space 13 to communicate via the associated opening 50. This retracted position, as shown for the valve 52 at the bottom of
During an opening operation, the above-mentioned cold front under pressure travels downstream towards the end wall 40a and, because of its high pressure, presses against each valve, which then moves into its sealing position. This position is shown for the valve 52 at the top of
Consequently, during the operation of opening the circuit breaker, the valves 52 can be maintained closed, and the risks of hot gas attacking the tank remain limited, as do the risks of arcing.
In addition, the additional means 56 are preferably designed to release the valves 52 mechanically during the following operation of closing the circuit breaker, e.g. during initiation thereof.
Finally, it should be observed that these means that are specific to the invention and that are described in association with the gas-flow chamber 31, can also be implemented in identical or analogous manner in association with the other gas-flow chamber 32, located on the opposite side of the nozzle.
Naturally, various modifications may be applied to the above-described invention by the person skilled in the art without going beyond the ambit of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 14 62907 | Dec 2014 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2015/080420 | 12/18/2015 | WO | 00 |
