EP3251140B1 - Circuit breaker equipped with an extensible exhaust cover - Google Patents

Description

TECHNICAL AREA

The invention relates to the field of medium current circuit breakers, high or very high voltage. It relates more particularly to the problem of dimensioning such a circuit breaker, in particular conditioned by the need for a minimum volume defined by the exhaust hood fitted to the breaking chamber, as well as by the minimum electrical insulation distance between this cover. exhaust and the outer casing of the circuit breaker in which is arranged the breaking chamber.

STATE OF THE PRIOR ART

From the prior art, it is known many circuit breaker designs, such as that described in the document DE 10 2011 083593 . Such a circuit breaker incorporates an interrupting chamber equipped with an exhaust hood defining a gas circulation chamber, also known as an exhaust chamber. The hot gases from an electric arc formed during the power failure in the circuit breaker are directed to the circulation chamber.

In order to limit the temperature and the pressure of the gas in the circulation chamber, this chamber must have a fairly large volume, in particular to cope with the breaking of strong currents. In this respect, it is noted that an exhaust volume that is too low can limit the flow of the hot gases out of the cutoff zone, and thus limit the breaking performance of the circuit breaker.

In addition, the interrupting chamber is placed in a space defined by an outer casing of the circuit breaker. For certain applications such as "GIS" or "Dead Tank" circuit breakers, a minimum electrical insulation distance is generally required between the outer casing of the circuit breaker and the exhaust hood forming the outer wall of the interrupting chamber. This minimum distance is set so as to limit the risks of dielectric ignition between a portion of the electrically charged chamber (at the non-zero potential), and the metal outer shell of the circuit breaker at zero potential.

These design constraints have a direct impact on the overall size, mass and cost of such circuit breakers.

There is therefore a need to optimize the design of such circuit breakers, so as to improve their performance in cut and reduce their size, while allowing them to respond correctly to the technical constraints mentioned above.

STATEMENT OF THE INVENTION

• un premier ensemble de contacts électriques ainsi qu'un second ensemble de contacts électriques, au moins de façon à permettre des opérations de fermeture et d'ouverture du disjoncteur ;
• une buse de soufflage d'arc électrique ;
• un capot d'échappement formant une partie de la paroi extérieure de la chambre de coupure, le capot d'échappement étant situé dans l'espace et définissant intérieurement une chambre de circulation de gaz située au moins en partie en aval de la buse de soufflage avec laquelle elle communique, ledit capot d'échappement comprenant une ou plusieurs ouvertures pour l'évacuation du gaz de la chambre de circulation de gaz vers ledit espace ;
• un support isolant électriquement et reliant mécaniquement la chambre de coupure à un fond de l'enveloppe extérieure du disjoncteur.

To meet this need, the subject of the invention is a medium, high or very high voltage current circuit breaker, comprising at least one breaking chamber and an outer envelope defining a space in which the breaking chamber is arranged, this one comprising:

• a first set of electrical contacts and a second set of electrical contacts, at least so as to allow operations of closing and opening the circuit breaker;
• an electric arc blow-out nozzle;
• an exhaust cowl forming a part of the outer wall of the breaking chamber, the exhaust cowl being located in the space and internally defining a gas flow chamber located at least partly downstream of the blow nozzle with which it communicates, said exhaust hood comprising one or more openings for evacuation of gas from the gas flow chamber to said space;
• an electrically insulating support and mechanically connecting the breaking chamber to a bottom of the outer casing of the circuit breaker.

According to the invention, the exhaust cowl comprises at least one movable portion under the effect of the pressure of the gases within the gas circulation chamber, so as to make the volume thereof expandable, in order to limit the pressure in this circulation chamber.

The invention is thus advantageous in that it provides an extensible exhaust hood, so as to allow the increase of the volume of the gas flow chamber in case of high currents failure. Also, in nominal configuration, that is to say in the closed position of the circuit breaker, or in the case of a low current cut producing little hot gas, the exhaust hood has a smaller dimension that allows to reduce the overall size of the circuit breaker. Moreover, in the case of "GIS" or "Dead Tank" type circuit-breakers, the invention is advantageous in that this reduction in size does not take place at the expense of the dielectric isolation of the chamber with respect to the outer casing of the circuit breaker. Indeed, the risk of dielectric ignition remains controlled even when the movable portion of the exhaust cowl moves in the direction of the outer casing of the circuit breaker, under the effect of the pressure of the gas in case of strong currents. This is explained by the fact that during a relative movement between the two elements considered, the spacing stress between these two elements is much lower than that required in a static situation, for example of the order of 40%.

In other words, the invention advantageously reduces the size of the circuit breaker while greatly limiting the risk of gas overpressure within the flow chamber, and the risk of dielectric ignition between the exhaust hood and the outer casing of the circuit breaker.

Furthermore, the invention is remarkable in that the expansion of the volume of the gas flow chamber is performed automatically and reliably, by simple physical phenomenon of gas pressure on the movable portion of the hood. This extension also occurs only in the presence of high currents (usually 60% to 100% of the nominal short circuit current) rarely observed, which implies a movement infrequent, and therefore low risk of production of wear particles.

In addition, this also leads, during the opening operation of the circuit breaker, to see increase the pressure differential between the core of the chamber and the exhaust. This advantageously results in a better flow of gas and a better blowing of the electric arc, and therefore an increased capacity of cut for the circuit breaker. These benefits are significant, because the increase in the volume of the exhaust chamber can be high. This is explained by the fact that the movable portion, defining this volume, forms a portion of the outer wall of the exhaust hood, whose diameter is thus maximum.

In addition, with the solution specific to the invention, the hot gases resulting from the blowing of the arc remain at least partly confined in the chamber with extended volume, which limits the risks of aggression by these hot gases or dielectric priming in the outer casing of the circuit breaker.

Finally, the pressure in the exhaust chamber is thus reduced, the mechanical stresses in the various parts of the circuit breaker are advantageously reduced.

The invention preferably comprises at least one of the following optional features, taken singly or in combination.

Said movable portion of said exhaust hood is arranged around the support mechanically connecting the breaking chamber to the bottom of the outer casing.

Said movable portion of said exhaust cowl is slidably mounted on a fixed portion of said cowl, preferably along a longitudinal central axis of said cowl.

The circuit breaker comprises elastic return means reminding said movable portion of said exhaust hood in a rest position in which the volume of the gas flow chamber is minimal.

The exhaust hood is configured so that in the two extreme positions of its moving portion, it defines respectively minimum and maximum volumes of the gas flow chamber, the ratio between the minimum and maximum volumes being preferably between 0.9 and 0.5.

Finally, a fixed portion of this cover has a first inner surface of external delimitation of the gas circulation chamber, said movable portion of said exhaust hood has a second inner surface of external delimitation of the gas circulation chamber, and a maximum diameter of the second inner surface is greater than a maximum diameter of the first inner surface. This specificity makes it possible to further amplify the increase in the volume of the chamber, in case of displacement of the movable portion of the exhaust hood, under the effect of the pressure of the gases in this chamber.

Other advantages and features of the invention will become apparent in the detailed non-limiting description below.

BRIEF DESCRIPTION OF THE DRAWINGS

• les figures 1 et 2 représentent des vues schématiques en coupe longitudinale d'un disjoncteur haute tension selon l'invention, avec le disjoncteur se trouvant respectivement dans une position de fermeture, et dans une position occupée lors d'une opération d'ouverture de ce disjoncteur, visant à la coupure d'un courant fort ;
• les figures 3a et 3b représentent respectivement des vues similaires à celles des figures 1 et 2, avec le disjoncteur se présentant sous la forme d'un premier mode de réalisation préféré de l'invention ; et
• les figures 4a et 4b représentent respectivement des vues similaires à celles des figures 1 et 2, avec le disjoncteur se présentant sous la forme d'un second mode de réalisation préféré de l'invention.

This description will be made with reference to the appended drawings among which;

• the figures 1 and 2 are schematic views in longitudinal section of a high voltage circuit breaker according to the invention, with the circuit breaker being respectively in a closed position, and in a busy position during an opening operation of this circuit breaker, aimed at the breaking of a strong current;
• the Figures 3a and 3b respectively represent views similar to those of figures 1 and 2 with the circuit breaker in the form of a first preferred embodiment of the invention; and
• the Figures 4a and 4b respectively represent views similar to those of figures 1 and 2 , with the circuit breaker being in the form of a second preferred embodiment of the invention.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

With reference first to figures 1 and 2 , there is shown a high voltage circuit breaker 10 according to the invention. In these figures, the circuit breaker is shown schematically, in order to focus on the principle object of the present invention. In this respect, it is noted that this principle is applicable to all existing configurations of circuit breakers, in particular armored circuit breakers of "GIS" or "Dead Tank" type, which will be described later with reference to FIGS. Figures 3a to 4b .

The circuit breaker 10 comprises a breaking chamber 12. The breaking chamber 12 is arranged at The interior of an envelope 14. The interrupting chamber 12 is thus housed in a space 13 defined internally by the outer envelope 14. This space 13 is usually filled with a pressurized insulating gas, for example of the SF6 type.

The chamber 12 comprises a first set of electrical contacts 18a, 20a and a second set of electrical contacts 18b, 20b. More specifically, the first assembly comprises a first permanent contact 20a cooperating with a second permanent contact 20b of the second assembly, when the circuit breaker occupies a closed position as shown in FIG. figure 1 . In addition, the first assembly comprises a first arcing contact 18a, cooperating with a second arcing contact 18b of the second set, when the circuit breaker is in its closed position. The first arcing contact 18a passes through a blow nozzle 19, made in a conventional manner.

However, the invention is not limited to this embodiment. The invention can in particular be applied to double movement circuit breakers. To perform such a double movement, any design deemed appropriate by those skilled in the art can be implemented, as for example that described in the document FR 2 976 085 . In such a case, the two sets are thus slidably movable along the main axis A of the breaking chamber 12, in opposite directions.

The second arcing contact 18b is surrounded by two volumes 21 and 22 separated axially from one of the other by a wall, and allowing the extinction by blowing the electric arc, in order to cut off the current. The blowing nozzle 19 makes it possible to channel the flow of gas during this blowing.

The gases from the electric arc and volumes 21 and 22 are discharged axially on either side by the nozzle 19 and the inner space 24 of the second arcing contact 18b. The gases escaping through the nozzle 19 penetrate into a gas circulation chamber 31, also known as an exhaust chamber, and delimited by an exhaust hood 40 housed in the space 13. The chamber 31 is thus arranged at least partly downstream of the nozzle 19, the term "downstream" being considered here in an axial main direction of gas flow in the chamber 12 at the outlet of the nozzle 19.

Similarly, opposite the breaking chamber, the gases escaping through the space 24 penetrate into another gas circulation chamber 32 delimited by an exhaust hood 41 also housed in the space 13. .

On the side of the first set of contacts 18a, 20a, the breaking chamber 12 therefore comprises the exhaust hood 40 delimiting the exhaust volume 31 and forming part of the outer wall of the breaking chamber 12. exhaust 40 preferably has several orifices 50 allowing the evacuation of gases to the space 13 defined by the tank 14. On the figures 1 and 2 these openings 50 are arranged near an upstream end of the cover 40, but they can of course be arranged differently on the cover 40. Moreover, the invention is applicable regardless of the configuration inside the chamber 31.

Likewise, on the side of the second set of contacts 18b, 20b, the exhaust hood 41, defining the exhaust volume 32, comprises several orifices 51 for the evacuation of the gases coming from the arc-breaking zone. , to space 13.

The exhaust hood 40 defines a substantially cylindrical chamber 31 of axis A corresponding to the longitudinal central axis of the cover 40, with a substantially circular section. This cover 40 has a bottom 40a substantially orthogonal to the axis A, and a side wall 40b surrounding this axis A. The bottom 40a and the side wall 40b of the cover thus form a part of the outer wall of the breaking chamber 12, located in the volume 13 away from the outer casing 14. In this regard, the casing 14 includes a bottom 14a also arranged substantially orthogonal to the axis A. There is provided a support 60 of axis A, mechanically connecting and electrically isolating the bottoms 14a, 40a. This support 60 preferably takes the form of a hollow cylinder, allowing internally the passage of the movable elements of a control mechanism 23.

One of the peculiarities of the invention lies in the fact that the exhaust cowl 40 has a movable portion 40 'slidably mounted on a fixed portion 40 ", the movable portion 40' corresponds to the bottom 40a, as well as to the a downstream end of the side wall 40b.The fixed portion 40 "corresponds to the remainder of the hood, being moreover said that these two portions 40 ', 40 "are both centered on the axis A and substantially cylindrical.

More specifically, the movable portion 40 'is pierced at the center of the bottom 40a of an opening 62 traversed by the support 60, on which it is mounted to slide along the axis A. The movable portion 40' is thus arranged around the support 60, being able to move along it, preferably in a sealed manner.

Elastic return means such as compression springs 64 are interposed between the two portions 40 ', 40 ", preferably being arranged inside the chamber 31. These springs 64 exert a return force forcing the movable portion 40 'to be positioned in a rest position, in which the volume of the gas circulation chamber 31 is a minimum volume Vmin.This configuration is shown in FIG. figure 1 . It is the one that is occupied in the closed position, or even during a cut of a weak current.

In this position, the movable portion 40 'occupying a first extreme position is indeed retracted to the maximum in the fixed portion 40 ", so that the distance between the two ends of the hood along the axis A corresponds to a minimum distance, referenced Lmin on the figure 1 . This makes it possible to obtain a satisfactory spacing distance De1 between the two bottoms 40a, 14a, with regard to the risk of dielectric primer between these two elements, in a static position.

In the case of an opening for the breaking of strong currents, the overpressure of the gases in the chamber 31 generates a pressure on the movable portion 40 'which leads the latter to be pushed towards the bottom 14a, against the forces Recall generated by the springs 64.

The figure 2 shows the second extreme position of the movable portion 40 ', after the latter has been displaced along the support 60, under the effect of the pressure of the gases in the chamber 31. In this second extreme position, the mobile portion 40 is at the maximum relative to the fixed portion 40 ", so that the distance between the two ends of the hood along the axis A corresponds to a maximum distance, referenced Lmax on the figure 2 . In this second extreme position, the volume of the gas circulation chamber 31 is a maximum volume Vmax, the ratio between the two volumes Vmin and Vmax may be between 0.9 and 0.5.

The supply of the movable portion 40 'in the second extreme position leads to obtain a reduced separation distance De2 between the two funds 40a, 14a. Nevertheless, even with this reduced spacing distance, the risk of dielectric ignition remains controlled. Indeed, the voltage between the breaking chamber 12 and the outer casing 14 of the circuit breaker when breaking strong currents is much lower than that required in a static situation. Respectively, the electrical isolation distance required during the breaking of strong currents is much lower than that required in a static situation, for example lower than 40%. Also, despite the small spacing distance, the risk of dielectric primer is advantageously very limited during the moving phase of the movable member 40 '.

The selected design thus makes it possible to obtain a small overall size of the circuit-breaker dictated by the first extreme position of the mobile portion 40 ', while limiting the risk of dielectric primer with the outer envelope 14.

It is also specified that during the breaking of a strong current, it is created in the chamber 12 a flow of gases from the zone between the contacts 18a and 18b, to the exhaust chambers 31, 32. Under the effect of the pressure exerted by the gases in the chamber 31, the movable portion 40 'of the exhaust hood 40 is pushed back to the bottom 14a, as explained above. The hot gases resulting from the blowing of the electric arc can pass through the orifices 50 before reaching the large space 13, when such orifices 50 are provided. Nevertheless, the expansion of the volume of the chamber 31 has the effect of reducing the pressure and temperature of the gases, and of confining an essential part thereof in the cover 30. The risk of aggression of the envelope 14 by these same gases and the microparticles they cause is therefore limited. It is the same for the risk of dielectric ignition related to the presence of these hot gases in the space 13.

In addition, since the pressure of the gases in the chamber 31 is reduced by the extension of its volume, the mechanical forces required for the displacement of the contacts electrical and the constraints in the mechanical interfaces of the circuit breaker are advantageously reduced.

Furthermore, the blowing of the electric arc is also improved, thus reinforcing the breaking performance of the circuit breaker, due to the increase in the pressure difference between the core of the nozzle 19 and the exhaust chamber 31.

It is finally noted that the principle of the invention is also applicable to the side of the second set of contacts 18b, 20b, on the hood 41. It is also applicable in the case of exhaust chambers 31, 32 closed, it is i.e. without orifice 50 and 51.

Referring now to Figures 3a and 3b , there is shown a shielded circuit breaker 10 of the "Dead Tank" type, according to a first preferred embodiment of the invention. In these figures, the control mechanism of the two assemblies 18a, 20a, 18b, 20b is represented, this mechanism being conventional and identified by the general reference numeral 23. In these figures, the elements bearing the same reference numerals as those attached to the elements of figures 1 and 2 , correspond to identical or similar elements.

In this first mode, the movable portion 40 'has a downstream end of wider section, so as to further increase the volume of the chamber 31 in case of abnormally strong currents. More specifically, the movable portion 40 'has an inner intermediate wall 70, substantially orthogonal to the axis A and pierced with an opening 74. This wall 70 delimits to upstream the widened end of the movable portion 40 ', and it is it that slides along the support 60. The bottom 40a is also arranged around the support 60, but at a radial distance from it for let the gases escape to the space 13, between the opening 62 and the support 60.

In the first extreme position of the movable portion 40 ', shown in the figure 3a , the intermediate wall 70 is pressed against an inner equipment 72 of the chamber 31. The volume defined by the hood 40 then corresponds to the minimum volume Vmin, not including the volume delimited internally by the enlarged downstream end. On the other hand, in case of displacement of the movable portion 40 'under the effect of the pressure of the gases in the chamber 31, the intermediate wall 70 moves away from the interior equipment 72. The two volumes located upstream and downstream of this wall 70 then accumulate to form together the volume Vmax of the chamber 31, as has been shown in FIG. figure 3b . Indeed, the gases can in this case enter the additional volume delimited internally by the enlarged downstream end of the portion 40 'in displacement. In this regard, it is noted that the substantially cylindrical fixed portion 40 "has a first inner surface of external delimitation of the chamber 31. Its maximum diameter D1max, which is here a substantially constant diameter, is smaller than the maximum diameter D2max of a second inner surface of outer delimitation of the chamber 31 defined by the downstream end of the movable portion 40 'The ratio between the two diameters D1max and D2max may for example be provided between 0.9 and 0.5.

Finally, with reference to Figures 4a and 4b , there is shown a shielded circuit breaker 10 of "GIS" type, according to a second preferred embodiment of the invention. Here again, elements bearing the same numerical references as those attached to the elements of figures 1 and 2 , correspond to identical or similar elements. Also, is it possible to note that the movable portion 40 'takes a shape similar to that shown in the schematic diagrams of figures 1 and 2 , ie integrating the bottom 40a and the downstream end of the side wall 40b. The inner diameters of the mobile and fixed portions 40 ', 40 "are here substantially identical.

Claims (6)

1. A medium-, high-, or very high-voltage circuit breaker (10), comprising at least one arc-control chamber (12) and an outer casing (14) defining a space (13) in which the arc-control chamber (12) is arranged, said arc-control chamber comprising:

   • a first set of electrical contacts (18a, 20a) and a second set of electrical contacts (18b, 20b), arranged at least in such a manner as to enable closing and opening operations of the circuit breaker;

   • an arc blast nozzle (19); and

   • a discharge cap (40) forming a portion of the outer wall of the arc-control chamber (12), the discharge cap being situated in the space (13) and internally defining a gas-flow chamber (31) situated at least in part downstream from the blast nozzle (19) with which it communicates, said discharge cap (40) including one or more openings (50) for discharging the gas from the gas-flow chamber towards said space (13); and

   • a support (60) that is electrically insulating and that mechanically connects the arc-control chamber (12) to an end wall (14a) of the outer casing (14) of the circuit breaker;

   the circuit breaker being characterized in that the discharge cap (40) comprises at least one portion (40') that is movable under the effect of the gas pressure in the gas-flow chamber (31), so that its volume is extensible.
2. A circuit breaker according to claim 1, characterized in that said movable portion (40') of said discharge cap (40) is arranged around the support (60) mechanically connecting the arc-control chamber (12) to the end wall (14a) of the outer casing (14).
3. A circuit breaker according to claim 1 or claim 2, characterized in that said movable portion (40') of said discharge cap (40) is mounted to move in sliding on a stationary portion (40") of this cap, preferably along a longitudinal central axis (A) of said cap.
4. A circuit breaker according to any preceding claim, characterized in that it includes resilient return means (64) for returning said movable portion (40') of said discharge cap to a rest position in which the volume (Vmin) of the gas-flow chamber (31) is at a minimum.
5. A circuit breaker according to any preceding claim, characterized in that the discharge cap (40) is configured so that in the two end positions of its movable portion (40'), it defines respective minimum and maximum volumes (Vmin, Vmax) for the gas-flow chamber (31), the ratio between the minimum and maximum volumes preferably lying in the range 0.9 to 0.5.
6. A circuit breaker according to any preceding claim, characterized in that a stationary portion (40") of the discharge cap (40) presents a first inside surface for externally defining the gas-flow chamber (31), in that said movable portion (40') of said discharge cap (40) presents a second inside surface for externally defining the gas-flow chamber (31), and in that a maximum diameter (D2max) of the second inside surface is greater than a maximum diameter (D1max) of the first inside surface.

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