FR2581476A1 - Limiter circuit-breaker apparatus for medium voltage network. - Google Patents

Abstract

A multiplicity of mobile contact levers 13 is thrust by the same contact pressure spring 21 against fixed contacts 24 placed at the end 72 of a contact rod 71 placed coaxially with the spring, and capable of moving axially in order to effect a controlled opening, whilst magnetisable means 31 associated with the levers assist in their automatic opening and an insulating case 79 is propelled rapidly between the contacts by virtue of the gas pressure developed in the presence of arcs, this case assuming, at the end of travel, a working position for which the required insulation is effected.

Description

CIRCUIT-BREAKER APPARATUS FOR
MEDIUM VOLTAGE NETWORK.

The invention relates to a circuit breaker or circuit breaker-limiter having a housing in which an insulating screen, which is propelled by the gas pressure developed as soon as an arc arises between contacts, movable one relative to the other and respectively connected to an input terminal and a current output terminal, is very quickly interposed between these contacts to destabilize the arc and limit the current.

Such switches, which are known in the context of a low voltage application, are for example known from French patent No. 2,540,666 to the Applicant.

The problem of limiting the currents that arise during the appearance of short circuits in medium voltage installations, that is to say in those where the voltage is in a voltage range from about 1 KV at 24 KV, to date there is no other solution than that of using fuses designed for this particular type of application.

The disadvantages of these fuses are, in addition to the need to replace the fuse after the appearance of such overloads, that of seeing the properties of this fuse change over time, for example due to the repeated appearance of overloads. close to the melting threshold.

It has also been proposed to use explosive charges to propel and separate contacts very quickly so as to produce a high arc voltage in a very short time interval; these devices therefore require the implementation of detection and monitoring means which will cause the ignition of this charge.

Here again, the appearance of a short-circuit current and the consumption of the load which results therefrom require special intervention in order to replace it.

Finally, it will be noted that the energy which this charge must develop at the appropriate time, as well as the constitution of the apparatus which must support it, must be studied to satisfy the cut-off conditions of an exceptional overload, for example of 40 KA , otherwise it would either be impossible to operate the desired limitation or be necessary to completely replace a damaged device. In other words, such a device does not have the ability to adapt its behavior to the level of energy which will appear during short circuits of different levels.

The invention proposes to provide a circuit breaker-limiting device for a medium-voltage network, which is capable of eliminating the drawbacks mentioned above, and whose size will be reduced.

According to the invention, the aim is achieved thanks to the fact that a - a multiplicity of respective carried mobile contacts
through a multiplicity of parallel levers to cross
seized by the current and regularly distributed around a
longitudinal axis concentric with a conductive rod
common supporting corresponding fixed contacts,
each pass through a side opening belonging to
an insulating movable tubular skirt which is suitable for
slide on this rod, and which plays the role of a screen
multiple between a rest position and a
job ; b - these levers being able to pivot simultaneously around
transverse axes to establish and interrupt a
multiplicity of parallel current paths due
of the appearance of attractive forces developed by
a multiplicity of magnetizable parts, placed
each around a lever in an isolated volume which
communicates with the cut-off zone and with a room
common expansion with variable volume, including a wall
movable transverse is integral with this skirt; c - while, for the working position of the skirt,
said opening is placed at such distances
of fixed contact and mobile contact as isolation
necessary for a medium voltage is established.

The quality of the limitations obtained thanks to the provisions which have just been mentioned, is due in particular to the high level which the arc voltage can take and to the fact that thanks to this limitation, the energy dissipated during the cut-off remains moderate.

The invention, as well as various embodiments to which it can lend itself, will be better understood on reading the description below and on examining the appended figures among which
Figures 1 and 2 show in two views in
elevation cut by the same axial plane, a first
embodiment of the device in states where
the shielding case is in the rest position, respec
tively in working position
Figure 3 and Figure 4 show two sectional views
of the device according to FIG. 1 by the trans planes
versals C and A respectively;
Figure 8 shows a localized axial section
a conductive rod of the device according to the figures
6 and 7 ;;
Figures 6 and 7 illustrate in two elevated views
tion cut by the same axial plane, a second mode of
realization in two rest states, respectively
working the skirt making the screen;
Figure 5 shows a sectional view through plane B
of the apparatus according to Figures 6 and 7; and
FIG. 9 illustrates means of load shedding of the
pressure from mobile contacts involved in particular
during a controlled opening of the device according to the
Figures 6 and 7.

The switch device 1 visible in Figure 1, comprises a metal part 2 which can serve as a support and which constitutes a current supply. This part maintains an insulating body 3 having a shape of revolution around the axis XX 'which is crossed by a channel 4 receiving a conductive rod 5 movable axially between a commanded closed position F and a commanded open position O.

The insulating body has means of association with the part 2, for example through an opening 6, and has a portion 7 limited by a cylindrical surface 8 with a diameter greater than that of the region 9, see also FIG. 3.

This portion 7 has radial grooves such as 10, 11, 12, see FIG. 3, which are intended each to receive a movable contact lever such as 13, respectively 13at 13b, 13c, see FIG. 4; each of these levers, which extends substantially parallel to the axis XX ′, is pivoted around a pivot such as 14, the axis of which is transversely placed at a groove end remote from the part 2; one end 15 of this lever which is placed between the pivot and said part 2 is electrically connected to the latter by a flexible conductive part or braid 16.

A spout 17 of each of the levers also adjacent to the pivot, but directed in the opposite direction of the axis XX ', is placed opposite a circular edge 18 belonging to a pusher 115 having a ring 19 which is integral with a skirt tubular 20 and which can slide on the surface 8, see also FIG. 3.

A helical compression spring 21 or other suitable elastic means which is placed around this skirt and between the part 2 and the ring 19, develops a coaxial force M and communicates to each of the levers a torque K which tends to direct their free ends such as 22 towards the axis XX '; in the illustrated embodiment, this spring bears directly or indirectly on the part 2.

For the closed position F, movable contacts such as 23 carried by these ends elastically meet fixed contacts such as 24 which are arranged around the end 25 of the conductive rod 5 thereby closing a multiplicity of elementary switches 26 connected parallel to the part 2 and to an opposite end 27 of the rod 5.

This connection end 27 which constitutes, for example, the current outlet, is itself in relation either with a sliding contact, or with a flexible braid so as to allow the axial movement of the rod 5.

A controlled opening and closing of the switching device can therefore be effected by the axial movement of the rod 5 between positions O and F, in particular by means of the end 27.

This switch has by nature the property of opening automatically when very large currents flow between parts 2 and 5 due to the appearance of electro-dynamic forces which develop between the rod 5 and the levers 13 and raise these the latter in directions opposite the axis XX '.

During such movements, the spouts 17 push the ring 19 and the skirt 20 by compressing the common pressure spring 21. In order for the contact pressure to be well distributed, it is necessary that the bearing surfaces 17a of all the nozzles 17 each receive the same force communicated by the edge 18 simultaneously; the choice of a number of levers such as 13 equal to three, accompanied by a rigorous positioning of the bearing surfaces of the spouts such as 17 relative to the pivots 14, and a judicious sliding clearance to prevent jamming of the skirt 20 on the surface 8, constitute measures capable of ensuring not only this balanced distribution, but also a correct transmission of the repulsive movement of the levers to the sleeve 20 to then cause a concentric displacement of this.

Additional measures are taken below to exploit forces capable of favoring the lifting of the contact levers, to operate a very effective limitation of the currents and to establish an excellent isolation during an operating process in automatic opening, when these currents reach short circuit intensities.

A tubular insulating envelope 30 is placed around the switch device which has just been described to operate an external protection and to maintain around each of the levers such as 13 magnetizable parts in the form of
U, such as 31. These parts which each have a bottom 32 and two parallel branches 33, 34 surrounding a contact lever arm 13, develop during the circulation of a current in the lever of the magnetic fields which communicate forces to it radials directed towards this bottom, see Figures 3 and 4, thanks to the orientation of the branches towards the axis XX.

Between each of the housings such as 35, 36, 37 receiving each of these magnetizable parts, there are disposed insulating partitions 38, 39, 40, respectively 38 ′, 39 ′, 40 ′ which are substantially radial, which start either from the periphery of 'envelope and join a tubular region 41 of the body 3 placed opposite the contact levers, that is to say of this region 41 to reach the envelope, see FIG. 4.

This envelope is extended, on the side opposite to the part 2 on which it rests, by an insulating sheath 42 held by a transverse partition 43, which is close to the ends 22 of the levers and which receives the radial roots of the isolation partitions .

This sheath has a bore 44 concentric with the axis XX ', the open side 45 of which and distant from the levers communicates with the atmosphere through baffles 46, 47 formed by a cap 48 having a shape of revolution and being fixed at the end of the sheath; an annular grid or filter 49 placed between the cap and the casing constitutes the last obstacle which gases developed by the arcs will have to pass through during a laden opening, in order to reach the atmosphere.

In a region 50 of the channel 4 starting from its end 51 there is between it and the rod 5 an annular gap 52 which is normally occupied by the skirt 53 of an insulating tubular case 54, of which a transverse bottom 55 covers the end 25 .

This case has as many openings 56 as there are levers to allow the movable contacts 23 to come to bear on the fixed contacts 24, see FIGS. 1 and 2.

When the case is in the rest position R illustrated in FIG. 1 for which the elementary switches are closed, each of the openings such as 56 communicates with an isolated space 57 placed between two partitions of the envelope 30, as well as with a volume or expansion chamber 58 which remains between the end 25 and the bottom 55.

When, due to the appearance of short-circuit currents passing through the switches and lifting the contact levers, arcs appear between the fixed and movable contacts, the gases caused or released and expanded by them exert on the bottom of the case a pressure which moves it instantaneously in direction G. During this displacement, which is made possible by the distance of the movable contacts, the elementary arcs are destabilized by shears intervening between the edges of the openings and the entry 28 of the bore 44 suitably adjusted with the external cylindrical surface 29 of the case.

When, at the end of the travel of the case, the latter reaches the working position T, visible in FIG. 2, for which the openings 56 communicate with the baffles, the gases can escape as has already been mentioned.

Damping means constituted here, and in a nonlimiting manner, by a conical stud 59 of the case and a conical housing 60 of the cap make it possible to avoid rebounding of the case.

For this position T, the skirt 53 completely closes and isolates the spaces such as 57 from the rod 5 thanks to an overlap -d- of the insulating surfaces. After their lifting, the movable contacts of the levers come to bear elastically on the outer surface 29 of the case 54; the medium voltage insulation distance is represented by the distance d1, figure 2.

The switch is reset by the intervention of thrust means applied axially to the case in the opposite direction to G, which fall under the direction and are not shown in the figures.

In a variant of switch 70 visible in FIGS. 6 and 7, measures have been taken to, on the one hand, increase the speed of movement of the case and, on the other hand, increase the isolation distances separating the current input and output parts.

According to this variant where the parts and components 2, 3, 4, 6, 9, 10, 11, 12, 12, 13, 14, 14, 15, 17, 18, 19, 20, 21, 22, 23, 24, 41 have the same structure and the same function, the conductive rod 71 extends in a region 111 which is not opposite the levers 13 and the elastic device 115, 21 is opposite to the previous one and carries at its end 72 of the fixed contact pads 24; an insulating rod 73 of substantially the same diameter extends this end to which it is integral through the external orifice 74 of the channel 4 and up to a point 75 possibly used for its operation.

The magnetizable parts 31at 31b, 31c associated with the levers are here carried by an insulating carcass 76 which is made integral with the region 41, see FIG. 5; this carcass bears longitudinally against a shoulder 77 of the body and extends axially beyond the movable contacts 23, to a transverse surface 87, see FIG. 7.

An insulating moving element 78 comprising an internal cylindrical skirt 79 threaded on the rods 71, 73 has, in addition, a transverse bottom 80 integral with this skirt, and a cylindrical external jacket 81 surrounding the cylindrical surface 112 of the carcass 76 on which it slips.

The internal skirt 79 has openings such as 82 for letting the movable contact pads 23 pass to the fixed pads 24; insulating partitions such as 83, 84, 85 radially connect the skirt and the jacket between two magnetizable parts.

The conductive rod 71 is, moreover, secured to a coaxial tubular casing 86 which surrounds the movable assembly 78 and terminates up to the part 2.

In the commanded closed position of the switch visible in FIG. 6, the rod 71 takes the position F, while in the commanded open position, this rod takes a position O for which the insulating rod 73 is opposite movable contact pads 23.

For position F, the bottom 80 rests against the transverse surface 87 of the carcass, limiting isolated volumes such as 102, and it can be seen that an annular space 88 then separates the mobile assembly 78 and the tubular casing 86 which can move axially with respect to each other, the transverse surface 87 can also be part of the body 3a if the latter fully supports the magnetizable parts and takes the corresponding shapes from the carcass 76.

When short-circuit currents appear, the influence of the magnetizable parts is preponderant here to cause the levers to be raised and the gases under pressure, which develop in their vicinity, exert on the bottom a force of direction G which takes off the bottom 80 from the surface 87, discovering between them an expansion chamber 100.

The moving part then moves in the same direction G with an even greater speed because of the extent of the surface which is now exposed to the pressure and this until the moment when this team meets the bottom 90 of the envelope.

The displacement of the movable assembly causes at the same time an elongation of the arc in the volume 88 and a rolling of the latter between the rod and the internal skirt, so that the limiting effect is excellent.

When the moving element 78 reaches a certain longitudinal position between the positions R and T, the space situated between the wall 99 of the envelope and the carcass 76 allows the gases to escape through an opening 101 of the first.

When the moving element 78 encounters and strikes the bottom 90, it communicates to the latter and to the rod 71 a displacement of the same direction which brings them together in the position indicated in FIG. 7; this position corresponds to the position
O of the rod 71. This percussion which results in a slowing down of the mobile assembly 1 must not preclude the use of additional damping means if necessary.

For each of the two embodiments, it is desirable to avoid metallization of the case 54, respectively of the internal skirt 79 or of the rod 73 which could result from the friction of the movable contact pads on their surface and compromise the quality medium voltage insulation, the distance of which is measured by -m- in Figure 7.

During a controlled opening, the insulation distance d2 between the contacts involves a parallel path on the previous one -m- along a baffle passing through the ends 108 and 51, see FIG. 7.

An arrangement applicable to the apparatus according to FIGS. 6 and 7, the principle of which is also applicable to the apparatus according to FIGS. 1 and 2, is shown in FIG. 9, where it is observed that a ball 95, placed in a through housing or opening 96 of the portion 41 of the body 3, transmits radially to the lever 13 a lifting movement which results from its cooperation with a groove 97 placed longitudinally on the rod 73; when this rod takes a position
F corresponding to the closure, the ball sinks into a notch 98 deeper than the groove to allow the application of the movable contact 23 on the fixed contact 42.

An improvement in the quality of the cut can also be obtained by the addition of materials favoring the extinction of the arcs (silica, PTFE, etc.) in a region 105 close to the fixed contacts 24. An improvement in the insulation after automatic opening - results from the coating of the rod 71 with an insulating layer 106, see FIG. 8.

Claims (18)

Patent claims  1. A circuit breaker or circuit breaker-limiter having a housing in which an insulating screen, which is propelled by the gas pressure developed as soon as an arc arises between movable contacts with respect to each other, and respectively connected to an input terminal and a current output terminal, is very quickly interposed between these contacts to destabilize the arc and limit the current, characterized in that a - a multiplicity of mobile contacts (23) carried respec  by a multiplicity of parallel levers (13)  crossed by the current and regularly distributed  around a longitudinal axis XX 'concentric with a rod  common conductor (5, 71) supporting contacts  corresponding fixed (24), each through an open  lateral structure (56, 82) belonging to a tubular skirt  insulating mobile (53, 79) which is able to slide on  this rod, and which plays the role of a multiple screen  between a rest position R and a tra position  vail; b - these levers being able to pivot simultaneously around  of transverse YY 'axes to establish and interrupt a  multiplicity of parallel current paths due  of the appearance of attractive forces developed by  a multiplicity of magnetizable parts (31), placed  each around a lever in an isolated volume (57,  102) which communicates with the cut-off zone and with a  variable volume common expansion chamber (58, 100),  a movable transverse wall (55, 80) of which is integral  re of this skirt c - while, for the working position T of the skirt,  said opening is placed at distances -m  such as fixed contact (24) and movable contact (23)  that the insulation required for a medium voltage is  established.  2. Switching device according to claim 1, characterized in that the simultaneous pivoting of the levers (13) is ensured by a force accumulator means (21) coaxially exerting a force (M) which is transmitted by a tubular piece (19, 20), also coaxial, with bearing surfaces (17a) of three levers (13ar 13b, 13c), this part being able to slide on an external surface (8) of an insulating body (3) so that the lifting of a lever pushes this part coaxially against the force of this means.  3. Switching device according to claim 2, characterized in that each lever (13) is connected to a common conductive part (2), acting as a current input, by a braid or flexible conductor (16) circulating in the inside the tubular part (19, 20).  4. Switching device according to claim 3, characterized in that this conductive part (2) serves to support the body (3) of the device and to support a helical spring (21) which constitutes the force accumulator means.  5. Switching device according to one of claims 1 to 4, characterized in that U-shaped magnetizable parts (31) having their parallel branches (33, 34) towards the longitudinal axis XX 'are each held between two partitions longitudinal (38, 39, 40) participating in the formation of isolated volumes.  6. Switching device according to one of claims 1 to 5, characterized in that the conductive rod (5) passes through a channel (4) of the body which circulates between the current supply part (2) and the movable contacts ( 23), the case (54) having on the one hand a skirt (53) placed in an annular gap (52) between this body and this rod and a bottom (55) placed beyond the end ( 25) of the stem.  7. Switching device according to claim 6, characterized in that the case (54) is placed opposite an adjusted bore (44) of an insulating envelope (30), having a transverse partition (43) which limits the isolated volumes (57), and extends on one side around the magnetizable parts (31) and the force accumulator means (21), and on an opposite side around the bore, the latter opening on baffles (46 , 47) communicating with the openings (56) for the working position T of the case.  8. Switching device according to one of claims 1 to 7, characterized in that for the working position T of the case (54), the latter has with the end (51) of the channel (4, 50) an overlay -d- contributing to the insulation at medium voltage.  9. Switching device according to one of claims 1 to 8, characterized in that the conductive rod (5) is axially movable and can take an open position O for which its end (25) is distant from the movable contacts in direction reverse of the working position T of the case.  10. Switching device according to one of claims 1 to 5, characterized in that the conductive rod (71) is located in a region (111) opposite to that comprising the levers (13) and the force accumulator means (19, 21), while the skirt (79) is part of an insulating mobile assembly (78) which moves axially both on this rod and on an insulating extension (73) connected at its end (72) provided with fixed contacts, the expansion chamber (100) being comprised between, on the one hand, a front wall (87) which transversely limits the body (3 to respectively a carcass (76) which is integral therewith, on the other hand, a jacket (81 ) which slides on a cylindrical surface (112) of this body respectively of this carcass surrounding the magnetizable parts (31), and finally a partition (80) transversely connecting this skirt and this shirt.  11. Switching device according to claim 10, characterized in that a coaxial tubular casing (86) is fixed to the conductive rod (71) by a bottom (90) which is separated from the movable assembly (78) by a volume annular (88) traversed by this crew when the skirt moves between the rest positions R and working T, the external cylindrical wall (99) of this envelope having an opening (101) capable of connecting the expansion chamber (100 ) to the atmosphere for said working position.  12. Switching device according to one of claims 10 or 11, characterized in that the movable assembly (78) comprises longitudinal partitions (83) which contribute to the separation of the isolated volumes (102).  13. Switching device according to one of claims 11 or 12, characterized in that at the end of a stroke going from the rest position R to the working position T, the mobile assembly (78) strikes and moves l tubular casing (86) for bringing the conductive rod (71) from a closed position F to an open position O where the fixed and movable contacts (23, 24) are not opposite.  14. Switching device according to one of claims 10 to 13, characterized in that the conductive rod (71) has on its outer surface traversed by the movable assembly (78) an insulating coating (106).  15. Switching device according to one of claims 1 to 14, characterized in that the conductive rod (5) respectively (71) comprises in the vicinity of the fixed contact pads (24) a layer of a material (105) promoting l extinction of an electric arc.  16. Switching device according to one of claims 1 to 15, characterized in that the magnetizable parts (31) are indifferently fixed on the body (3, 3a) or on a carcass (76) which is integral therewith.  17. Switching device according to one of claims 1 to 16, characterized in that damping means contribute to stopping the case (54) respectively (79, 80) when the latter reaches the working position T.  18. Switching device according to one of claims 1 to 17, characterized in that the conductive rod (5), respectively the insulating rod (73) which extends the conductive rod (71) opposite the contact levers (13), comprise opposite each lever (13) a longitudinal groove (97) leading to a deeper notch (98) which are capable of causing an uplift of the movable contact lever (13) corresponding when these conductive rods are not in the position of closing F respectively to allow elastic application of the movable contacts against the fixed contacts when these rods are in the closed position.