EP2256776B1 - Improved high-voltage circuit breaker with gas release - Google Patents

Description

TECHNICAL FIELD AND PRIOR ART

The invention relates to the field of high voltage circuit breakers under tank or metal shell, type GIS (Gas Insulated Switchgear) or Dead tank type. These circuit breakers can be part of a metal enclosure.

The invention relates more particularly to a method for evacuating the hot gases generated by a break in such a circuit breaker and the associated circuit breaker structure.

In this type of circuit breaker, for some short-circuit current values that correspond to a maximum fault current, the hot gases (i.e., plasma and exhaust gases) generated can promote reboots between the various live cut-off parts and the parts connected to the earth such as the metal tank.

In metal tank circuit breakers currently marketed, various types of exhaust or exhaust arrangements are provided.

A first type of arrangement, for example provided on Japanese type circuit breakers, such as that disclosed in the patent application JP2003217411 , comprises a short tube implanted at the outlet of the nozzle blowing hot gases and which also makes it possible to blow these directly inside the tank metallic. The dielectric insulation is obtained by maintaining great distances between the discharge ring formed with the tube and the metal tank.

A second type of arrangement, for example provided on the "Dead tank" as published in the patent application EP1806760 , allows to have a volume of dielectric gas present in the metal part of the exhaust sufficiently large to absorb all the hot gases generated during the longest arc period of the maximum short-circuit current. This exhaust arrangement includes lateral openings on the side through which the hot gases escape into the interior of the metal vessel.

The first type referred to above encloses volumes of insulating gas which are by construction less than the amount of hot gases blown during a break. Therefore, larger overall dimensions of the metal tank than the second type are provided because these hot gases are discharged in an uncontrolled manner, and therefore dimensional safety margins must be taken to ensure dielectric strength to the tank.

The closure provided in the arrangement of the second type involves a sufficient volume to keep the hot gases inside the metal part of the exhaust. Also, the dimensional safety margin between the outside of the exhaust and the metal tank can be reduced.

We can mention the patent EP 1 768 150 which provides, in its embodiment of the figure 2 , a mixture of a portion of the hot gases 11, 11a with insulating gas 111, such a mixture is in fact made by dividing the flow of hot gas at the outlet of the zone 6 blowing gases. In reality, only the initially divided radial portion 11a may be optionally mixed with the colder insulating gases 111 furthermore pushed by the other axial portion 11b of the hot gases.

The patent EP 1930929 discloses a so-called separation edge solution 21 at the exit of the exhaust gas 9 produced in the form of a narrow channel 22 between a portion of the fixed contact support 5 prolonged and an envelope 18 fixed to the bar conductor 13 for supplying current. The realization of the edge 21 in the form of a groove transverse to the channel 22 avoids the Coanda effect, that is to say, to take off the flow of exhaust gases 9 and thus to avoid that these they adhere to the convex surface 20 of the exhaust outlet and thus are guided to dielectrically charged areas.

The patent EP 1835520 discloses a particular construction of an annular exhaust channel 20 by a kind of cap 16 around the support casing 8 of the fixed contact A. The construction according to this patent is intended to avoid priming at the tank trying to orient the gas horizontally, that is to say substantially parallel to the walls of the tank, and to promote their cooling.

A problem that has so far not been highlighted is that of the risk of re-priming by direct projection of the metal particles or by displacement of metal particles resulting from opening maneuver (s) of the previous circuit breaker to sensitive areas, the displacement of said metal particles already present being caused by the discharge of the hot gases itself during a subsequent maneuver. Indeed, whatever the envisaged exhaust, during each opening maneuver there is friction between different parts that generate chips or metal particles. These metal particles created are projected by the exhaust gases and settle down the metal tank.

This problem can be all the more important as the space between the outside of the exhaust and the metal tank is reduced: in this case, the metal particles accumulated in the bottom of the tank are even closer to the exhaust and therefore likely to be displaced by the discharge of hot gases at the outlet of the exhaust to areas sensitive to reinforcement such as insulating cones.

It is specified here that, in the context of the invention, it is necessary to understand by "insulating cones", the elements shaped cones, made of electrically insulating material and whose function is to fix the exhaust casing to the metal tank .

Another problem is that the exhaust constructions provided to date, particularly in baffles, are not necessarily provided to optimize the speed of the hot gases in the exhaust. However, a hot gas velocity in the exhaust too low resulting in a risk of rebooting between arc contacts and a hot gas velocity in the exhaust too large result in a risk of rebooting between main contacts (permanent) .

The object of the invention is therefore to provide a solution for evacuation (exhaust) of the hot gases in baffles in a high-voltage circuit breaker which makes it possible to avoid, on the one hand, the risks of electrical rebooting by direct projection towards sensitive areas or by moving the metal particles already accumulated at the bottom of the metal tank towards said zones sensitive to reinforcement, such as insulating cones, and secondly, the risk of rebooting between arc contacts and between (permanent) main contacts.

The document WO 01/33594 describes a device according to the preamble of claim 1.

STATEMENT OF THE INVENTION

• des chicanes adaptées pour réaliser au moins deux changements d'orientation selon l'axe du vecteur vitesse des gaz chauds depuis leur entrée dans la chicane d'entrée ;
• un rapport de sections d'une chicane d'échappement donnée (Si) à la chicane d'échappement suivante (Si+1), située immédiatement en aval et dans la continuité de la chicane donnée, dans le sens d'échappement des gaz chauds, est tel que si :
  • Si>Si+1 alors 1 ≤ (Si/Si+1) ≤ 20 ;
  • Si<Si+1 alors 1 ≤ (Si+1/Si) ≤ 20
• le profil donné à la (aux) chicane(s) la(es) plus en aval tel que l'échappement des gaz chauds, à la sortie des chicanes, est dirigé à l'opposé de la zone de fixation entre l'enveloppe et la cuve au niveau du cône isolant.

To do this, the subject of the invention is a high voltage circuit breaker which extends along a longitudinal axis and comprises a metal tank filled with an insulating gas; a pair of arcing contacts, one fixed and one movable in translation which is integral with an insulating nozzle for blowing hot gases generated during the separation of the contacts; an envelope inside which the fixed contact is mounted, the envelope comprising, inside the gas exhaust baffles, an inlet baffle constituted by the casing and by a fixed tube surrounding the fixed contact, the envelope being attached to the metal vessel by an electrically insulating cone being arranged inside the metal vessel so as to communicate with it by the baffles to evacuate the hot gases. According to the invention, provision is made for:

• baffles adapted to perform at least two orientation changes along the axis of the velocity vector of the hot gases from their entry into the inlet baffle;
• a ratio of sections of a given exhaust baffle (Si) to the next exhaust baffle (Si + 1), located immediately downstream and in continuity with the given baffle, in the direction of escape of the hot gases , is such that if:
  • If> Si + 1 then 1 ≤ (Si / Si + 1) ≤ 20;
  • If <Si + 1 then 1 ≤ (Si + 1 / Si) ≤ 20
• the profile given to the baffle (es) the (s) further downstream such that the exhaust of the hot gases, at the exit of the baffles, is directed opposite the fixing zone between the envelope and the tank at the level of the insulating cone.

• ralentir les gaz chauds afin qu'ils atteignent une vitesse à la sortie des chicanes d'échappement tout à fait satisfaisantes étant donné le volume de gaz isolant délimité entre l'enveloppe et la cuve métallique ;
• limiter les turbulences à l'intérieur des chicanes, turbulences qui peuvent causer un bouchon (vortex) réduisant voire empêchant l'évacuation des gaz chauds des chicanes et avec comme conséquence possible le réamorçage au niveau des contacts d'arc ;
• éviter l'accumulation de particules métalliques au niveau des zones les plus sensibles au réamorçage électrique que sont les cônes isolants.

Thus defined, the invention allows in combination of:

• slowing down the hot gases so that they reach a velocity at the outlet of exhaust baffles quite satisfactory given the volume of insulating gas delimited between the envelope and the metal vessel;
• limit turbulence inside the baffles, turbulences that can cause a plug (vortex) reducing or preventing the evacuation of gases hot baffles and with the possible consequence of rebooting at the level of the arcing contacts;
• avoid the accumulation of metal particles in the areas most sensitive to electrical reboot insulating cones.

As a corollary, it avoids priming the metal tank on the inner wall of the tank because the hot gases blown are not directly discharged in their direction.

Advantageously, one of the baffles, downstream of the inlet baffle, comprises an inclined wall for deflecting the hot exhaust gases radially outwardly of the envelope, the inclination of the wall being included in an angle between ° and 80 ° with respect to the longitudinal axis. This avoids the risk of a turbulent flow as soon as the baffles enter, since the hot gases are accelerated by said inclined wall.

Advantageously, the envelope comprises, at the output of the exit baffle, a surplus of material in the form of a rounded. Due to the presence of this rounding, the characteristics of the envelope according to the invention are improved: in other words, the risk of dielectric breakdown is limited to the metal tank.

• une est constituée d'un fût cylindrique fermé, à l'une de ses extrémités, par un fond hémisphérique adapté pour ramener les gaz chauds évacués depuis la buse et entre le tube fixe et le contact fixe, vers le volume annulaire de la chicane d'entrée délimité d'une part, entre le tube fixe et le fût cylindrique et d'autre part, entre le tube fixe et un rétreint prévu, à l'autre des extrémités du fût cylindrique ;
• l'autre est constituée par un embout comprenant, à l'une de ses extrémités, une paroi cylindrique de diamètres et d'épaisseur compris entre le diamètre extérieur du rétreint et le diamètre intérieur de l'extrémité cylindrique du fût de l'enveloppe, et une paroi en forme de tronc de cône reliée à la paroi cylindrique et à laquelle est fixé intérieurement le tube. L'embout est emboîté dans le fût cylindrique, tel que la paroi cylindrique de l'embout est logée dans le volume compris entre la paroi cylindrique d'extrémité et le rétreint du fût en délimitant ainsi les deux chicanes les plus en aval, tandis qu'une chicane intermédiaire entre chicane(s) d'entrée et chicanes aval est délimitée entre la paroi en forme de tronc de cône de l'embout et le rétreint du fût. Les deux changements de vecteur vitesse des gaz chauds sont ainsi réalisés par ladite chicane intermédiaire et les deux chicanes les plus en aval.

According to an advantageous method of construction: the envelope consists of two parts including:

• one consists of a cylindrical barrel closed, at one of its ends, by a hemispherical bottom adapted to bring back the hot gases discharged from the nozzle and between the fixed tube and the fixed contact, towards the annular volume of the entry baffle delimited on the one hand, between the fixed tube and the cylindrical barrel and, on the other hand, between the fixed tube and a planned constriction, at the other end of the barrel cylindrical;
• the other consists of a tip comprising, at one of its ends, a cylindrical wall of diameters and thickness between the outside diameter of the necking and the inside diameter of the cylindrical end of the barrel of the envelope, and a truncated cone-shaped wall connected to the cylindrical wall and to which the tube is internally fixed. The tip is fitted into the cylindrical barrel, such that the cylindrical wall of the endpiece is housed in the volume between the end cylindrical wall and the narrowing of the barrel thus delimiting the two baffles furthest downstream, while an intermediate baffle between entry baffle (s) and downstream baffles is delimited between the truncated cone-shaped wall of the endpiece and the narrowing of the barrel. The two velocity vector changes of the hot gases are thus carried out by said intermediate baffle and the two baffles furthest downstream.

An application particularly targeted by the invention is that according to which the high-voltage circuit breaker is a "GIS" or "Dead tank".

BRIEF DESCRIPTION OF THE DRAWINGS

• la figure 1 est une vue schématique, en coupe longitudinale, d'un disjoncteur haute tension selon l'état de l'art, en fin de manoeuvre d'ouverture ;
• la figure 2 est une vue schématique, en coupe longitudinale, d'un disjoncteur haute tension selon un mode de réalisation avantageux de l'invention, également en fin de manoeuvre d'ouverture ;
• la figure 3 est une vue de détail partielle en perspective de la figure 2.

Other advantages and features will become more apparent when reading the description detailed with reference to the appended figures in which:

• the figure 1 is a schematic view, in longitudinal section, of a high-voltage circuit breaker according to the state of the art, at the end of the opening maneuver;
• the figure 2 is a schematic view, in longitudinal section, of a high-voltage circuit breaker according to an advantageous embodiment of the invention, also at the end of the opening maneuver;
• the figure 3 is a partial detail view in perspective of the figure 2 .

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

For the sake of clarity, the elements common to circuit breakers according to the state of the art ( figure 1 ) and according to the invention ( figures 2 and 3 ) bear the same numerical references.

The terms "downstream" and "upstream" are to be understood in relation to the direction of escape of hot gases GC evacuated during an arc failure by a high-voltage circuit breaker according to the invention. Thus, the baffle 74 furthest downstream is the exhaust baffle inside the casing 3 which is the last crossing by the hot gases G.C.

On the figure 1 , a longitudinal sectional view of a metal-enclosed circuit breaker (GIS) according to the state of the art arranged essentially horizontally and which extends along a longitudinal axis XX '. This high-voltage circuit breaker 1 comprises a metal tank 2 filled with an insulating gas GI electrically connected to the ground. An envelope 3 is arranged inside the metal tank 2 and is fixed to it by means of an insulating cone 4. This envelope 3 consists of two parts, one of which is essentially in the form of a closed cylindrical drum by a hemispherical bottom 300 and the other 31 which constitutes a mouthpiece.

More precisely, the barrel 30 closed at one of its ends by the hemispherical bottom 300 is cylindrical over a large part of its length and comprises a narrowing 301 at the other of its ends.

A tube 6 is fixed to the end piece 31 so as to extend inside the barrel 30 and the narrowing 301 of the casing 3. The attachment between the barrel 30 and the end piece 31 is made by means of tabs 60.

The relative arrangement between the tube 6, the cylindrical drum 30 and its necking 300, the tip 31 of the casing 3 delimits a volume with exhaust baffles 7 which constitute the escape route or exhaust gases hot according to the state of the art.

The circuit breaker 1 also comprises a pair of arcing contacts of which only the fixed contact 50 is represented and is fixed to the casing 3. The other movable contact in translation along the axis XX 'is integral with an insulating nozzle 51 intended to blow hot gases generated during the separation of the contacts.

Usually, the hot gases that result from an arc-breaking during which an opening operation of the arcing contacts is performed, follow the path schematized in solid lines (GC) in figure 1 : these gases pass through the tube 6 (from the left to the right on the figure 1 ) then change direction in contact with the hemispherical bottom 300 by passing through the volume of the cylindrical shaft 30 and then reach the inlet baffle 70 or in other words the annular volume between the tube 6 and the cylindrical shaft 30 and shrinks 300. The hot gases GC then follow the path delimited by the baffles 7 downstream of the entry baffle 7.

According to the state of the art and as represented in figure 1 , the hot GC gases which open at the outlet 71 of the exhaust baffles 7 necessarily contain metal particles which are therefore deposited on the bottom 20 of the tank 2.

However, there is still the risk of either directly projecting during a given opening maneuver the metal particles to areas sensitive to electric reboot or to move, during subsequent opening maneuvers, the metal particles already present at the bottom 20 tank 2 to said sensitive areas.

As represented in figure 1 , the zones most sensitive to electrical rebooting are those located Z between the insulating cone 4, which allows the fixing between the envelope 3 and the metal vessel 2, and the bottom 20 of the metal vessel 2.

Thus, as represented in figure 1 , the hot gases (GC) by the profile of the baffles 7 according to the state of the art are discharged in a direction directed towards the insulating cone 4, that is to say, potentially to the area sensitive to Z reboot.

In addition, there is always the risk that the speed of the hot gases in the baffles 7 according to the state of the art is not optimal. Thus, there is a risk that these hot gases are too slow with the adverse consequence of a reboot between arcing contacts or that these hot gases are not slow enough with the consequent detrimental effect of a reboot between permanent contacts.

• projection directe ou déplacement des particules métalliques issues des coupures d'arc vers les zones sensibles Z au réamorçage électrique, telles que les cônes isolants 4 ;
• vitesse non optimale de gaz chauds dans l'échappement en chicanes avec comme conséquence le réamorçage possible entre contacts d'arc et/ou entre en contacts permanents, les inventeurs ont alors défini des chicanes d'échappement 7 selon l'invention telles que représentées en figures 2 et 3.

To avoid the risks of:

• direct projection or displacement of the metal particles from the arc cuts to the sensitive zones Z to the electrical reboot, such as the insulating cones 4;
• non-optimal speed of hot gases in the baffled exhaust resulting in the possible rebooting between arc contacts and / or in permanent contacts, the inventors have then defined exhaust baffles 7 according to the invention as represented in FIG. figures 2 and 3 .

In the embodiment illustrated in figures 2 and 3 , the envelope (3) consists of two parts 30, 31.

One of these parts consists of a cylindrical barrel 30 closed, at one of its ends 30a, by a hemispherical bottom 300 adapted to return the hot gases discharged from the blast nozzle 51 and between the fixed tube 6 and the contact fixed 50, towards the annular volume of the inlet baffles 70, 71. More exactly, the annular volume delimited between the fixed tube 6 and the cylindrical drum 30 defines a first inlet baffle 70 of the hot gases brought back from the Hemispherical bottom 300. The annular volume delimited between the fixed tube 6 and a constriction 301 provided at the end 30b of the opposite end of the shaft 300 defines a second inlet baffle 71.

The other of the parts of the envelope 30 is constituted by a tip 31. This tip 31 comprises, at one of its ends, a cylindrical wall 310 of diameters and thickness between the outer diameter of the necking 301 and the inner diameter of the cylindrical end 30b of the barrel 30 of the casing 3, and a truncated cone-shaped wall 311 connected to the cylindrical wall 310 and to which the tube 6 is internally fixed.

The exhaust baffles 72, 73, 74 in the continuity of the second inlet baffle 71 are thus formed by interlocking the end piece 31 in the cylindrical drum 30. The interlocking is such that the cylindrical wall 310 of the tip 31 is housed in the volume between the cylindrical end wall 30b and the shrinkage 301 of the barrel delimiting the two baffles 73, 74 further downstream. An intermediate baffle 72 between the second input baffle 71 is delimited between the truncated cone-shaped wall 311 of the nozzle 31 and the narrowing 301 of the barrel 30. The two changes in the velocity vector of the hot gases GC are accordingly made by said intermediate baffle 72 and the two most downstream baffles 73, 74.

• la section de passage des gaz chauds dans la deuxième chicane d'entrée 71 est définie par S1 ;
• la section de passage des gaz chauds dans la chicane 73 avant la chicane de sortie 74 est définie par S2 ;
• la section de passage des gaz chauds dans la chicane 74 de sortie, ou autrement dit la plus en aval, est définie par S3 ;
• la section de passage des gaz chauds à la jonction entre la chicane intermédiaire 72 et la chicane 73 avant la chicane de sortie 74 est définie par S4 ;
• la section de passage des gaz chauds à la jonction entre les deux chicanes les plus en aval 73, 74 est définie par S5.

As represented in figure 3 :

• the hot gas passage section in the second inlet baffle 71 is defined as S1;
• the hot gas passage section in the baffle 73 before the exit baffle 74 is defined as S2;
• the hot gas passage section in the exit baffle 74, or in other words the most downstream, is defined by S3;
• the hot gas passage section at the junction between intermediate baffle 72 and baffle 73 before outlet baffle 74 is defined as S4;
• the section of passage of the hot gases at the junction between the two most downstream baffles 73, 74 is defined by S5.

$$\mathrm{0}\mathrm{<}\mathrm{S}\mathrm{4}\mathrm{/}\mathrm{S}2\mathrm{\le }\mathrm{3}$$

$$\mathrm{0}\mathrm{<}\mathrm{S}5\mathrm{/}\mathrm{S}2\mathrm{\le }\mathrm{3}$$

$$\mathrm{0}\mathrm{<}\mathrm{S}5\mathrm{/}\mathrm{S}3\mathrm{\le }\mathrm{3}$$

In the illustrated embodiment, the following section report ranges have been determined: $$\mathrm{0}\mathrm{<}\mathrm{S}\mathrm{4}\mathrm{/}\mathrm{S}\mathrm{1}\mathrm{\le }\mathrm{3}$$

$$\mathrm{0}\mathrm{<}\mathrm{S}\mathrm{4}\mathrm{/}\mathrm{S}2\mathrm{\le }\mathrm{3}$$

$$\mathrm{0}\mathrm{<}\mathrm{S}5\mathrm{/}\mathrm{S}2\mathrm{\le }\mathrm{3}$$

$$\mathrm{0}\mathrm{<}\mathrm{S}5\mathrm{/}\mathrm{S}3\mathrm{\le }\mathrm{3}$$

With such ratios, it limits the turbulence that can cause a plug (vortex) preventing hot gases from escaping the baffles 7.

As shown, the walls 3010 and 3110 respectively of the shaft 30 and the tip 31 at the junction of the baffles 7 have a curved profile with a radius of curvature adapted to limit the pressure losses and thus promote the flow of gases.

The inclined wall in the form of a truncated cone 311 delimiting a portion of the intermediate baffle is inclined at an angle α of between 5 and 80 ° with respect to the longitudinal axis XX '.

Thanks to the defined invention, an effective escape of the hot gases in a high-voltage circuit breaker is obtained by avoiding the risk of rebooting at the sensitive areas, such as the insulating cones 4 at the arcing contacts or at the contacts permanent.

As represented in figure 2 , the metal particles produced during an arc failure according to the invention are accumulated in a zone remote from the cone 4.

Claims (5)

1. A high-voltage circuit-breaker (1) that extends along a longitudinal axis (XX') and that comprises: a metal tank (2) filled with an insulating gas (IG); a pair of arcing contacts (5), namely a stationary arcing contact (50) and a moving arcing contact that is mounted to move in translation and that is secured to an insulating nozzle (51) for blowing hot gases generated on separation of the contacts; a casing (3) inside which the stationary contact (50) is mounted, characterized in that:

   - the casing being provided internally with gas exhaust baffles (7) including an inlet baffle (70) constituted by the casing and by a stationary tube (6) surrounding the stationary contact (50), the casing being fastened to the metal tank via an electrically insulating cone (4) while being arranged inside the metal tank so as to communicate therewith via the baffles for removing the hot gases (HG);

   - the baffles (7) are adapted to cause the hot gases to change direction at least twice along the axis (XX') of the speed vector from entering the inlet baffle (70);

   - the ratio of flow section (S_i) of a given exhaust baffle (7) to the flow section (S_i+1) of the next exhaust baffle situated immediately downstream from and following continuously on from the given baffle, in the hot gas exhaust direction, is such that if:

   S_i > S_i+1 then 1 ≤ (S_i/S_i+1) < 20; and if

   S_i > S_i+1 then 1 ≤ (S_i+1/S_i) ≤ 20;
   the profile given to the farthest-downstream baffle(s) (73, 74) is such that the hot gas exhaust (HG) at the outlet of the baffles is directed away from the fastening zone between the casing (3) and the tank (2) at the insulating cone.
2. A high-voltage circuit-breaker (1) according to claim 1, wherein one of the baffles downstream from the inlet baffle (70) has an inclined wall (310) for deflecting the exhaust hot gases radially towards the outside of the casing (3), the inclination of the wall (311) being at an angle α lying in the range 5° relative to the longitudinal axis (XX') to 80° relative thereto.
3. A high-voltage circuit-breaker (1) according to claim 1 or claim 2, wherein, at the outlet of the outlet baffle (74), the casing (3) has surplus material in the form of a rounded portion (302).
4. A high-voltage circuit-breaker (1) according to any preceding claim, wherein the casing (3) is made up of two parts, namely:

   • a part that is constituted by a cylindrical drum (30) that is closed at one of its ends (30a) by a hemispherical end-wall (300) adapted to bring the hot gases removed from the nozzle and between the stationary tube (6) and the stationary contact (50), back towards the annular volume of the inlet baffle, which annular volume is defined firstly between the stationary tube (6) and the cylindrical drum (30) and secondly between the stationary tube (6) and a neck segment (301) provided at the other of the ends (30b) of the cylindrical drum; and

   • another part that is constituted by an end-piece (31) that, at one of its ends, has a cylindrical wall (310) of diameters and of thickness lying between the outside diameter of the neck segment (301) and the inside diameter of the cylindrical end (30b) of the drum of the casing, and a frustoconical wall (311) connected to the cylindrical wall (310) and to which the tube (6) is fastened internally;
   wherein the end-piece (31) is fitted into the cylindrical drum (30) such that the cylindrical wall (31-0) of the end-piece (31) is received inside the volume lying between the end cylindrical wall (30b) and the neck segment (301) of the drum (30), thereby defining the two farthest-downstream baffles (73, 74), while an intermediate baffle (72) between inlet baffle(s) (71) and downstream baffles (73, 74) is defined between the frustoconical wall (311) of the end-piece (31) and the neck segment (301) of the drum (30), the two changes in speed vector of the hot gases (HG) being achieved by said intermediate baffle (72) and by the two farthest-downstream baffles (73, 74).
5. A circuit-breaker of the GIS type or of the dead-tank type according to any preceding claim.

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