EP0678886A1 - Medium or high voltage circuit-breaker - Google Patents

Abstract

The medium or high tension circuit breaker comprises an envelope filled with dielectric gas, and a cut-off chamber (30) containing metal plates (14) for splitting up the electric arc into a number of smaller elementary arcs under the action of a magnetic field. The chamber includes a helicoidal insulating ramp (13) wound about a central generator axis (13a). This ramp is arranged around the internal edge of the chamber about a central conducting electrode (12). The metal plates are arranged along the length of the ramp, around and spaced from the central conducting electrode. <IMAGE>

Description

The invention relates to a medium or high voltage circuit breaker comprising, in an envelope filled with a dielectric gas, a breaking chamber in which are arranged metal plates for dividing an electric arc into a multitude of elementary arcs under the action of a magnetic field.

Such a circuit breaker is known from document FR-8900215. In this known circuit breaker, the metal fractionation plates are stacked in several compartments juxtaposed with each other. The electric arc is divided at the entrance of each compartment by electrodes and then fractionated on the metal plates inside each compartment under the action of magnetic fields.

This arrangement of the metal fractionation plates generates a large bulk of the breaking chamber which it is desirable to reduce.

Furthermore, in this known circuit breaker, it is necessary to create separate magnetic fields for the compartments, one for each compartment. Each magnetic field is created by conductors suitably arranged at the entrance to a compartment. These conductors are bent bars. It has been found that the strength of the magnetic field created by this kind of conductor remains insufficient to ensure effective extinction of the electric arc despite the fractionation of the latter on the metal fractionation plates.

In this document, it is well suggested to replace the conductors in the form of bent bars with electric coils. But practically, the insertion of such electric coils inside the breaking chamber having the arrangement described above is very difficult to implement due to the distribution of the metal plates inside compartments.

The object of the invention is therefore to propose a medium or high voltage circuit breaker, using the principle of splitting the arc into a large number of elementary arcs by means of metal splitting plates but which has better efficiency of cutoff that known from the aforementioned document and which is easier to achieve while having a more compact construction.

To this end, the invention relates to a medium or high voltage circuit breaker, characterized by a helical insulating ramp wound around a central generator, this ramp being arranged on the inner peripheral part of the chamber and around a conductive electrode and the metal plates being arranged along said ramp, around and at a distance from the conductive electrode.

The section of this helical ramp by a plane perpendicular to its generatrix is of any shape provided that the distance between the fractionation plates and the electrode does not vary in too great proportions.

In current constructions, it may take the form of a circle so that the size of the breaking chamber will be that of a cylinder. This section could also take the form of a regular polygon, for example a hexagon, or irregular if it is advantageous to favor a dimension of construction of the breaking chamber.

The magnetic field is directed in a direction substantially parallel to the central generator of the ramp. It is easy to create such a magnetic field using at least one electric coil disposed at one end of the ramp.

It is preferable that this coil is supplied by at least part of the alternating current at the input of the circuit breaker. In this way, the magnetic field created by this coil is always in phase with the direction of the current passing through the electric arc.

Such a coil arrangement makes it possible to obtain an intense magnetic field which is sufficient to effectively extinguish the electric arc. The strength of the magnetic field can be further increased if a second coil is provided at the other end of the ramp.

Furthermore, the long length of the ramp makes it possible to extend the arc over a large distance, of the order of 1.5 meters. This results in efficient cooling and rapid deionization of the middle of the interrupting chamber.

With such an arrangement, the electric arc rotates very rapidly around the conductive electrode under the action of the magnetic field. The arc takes the form of a solenoid as it enters the ramp. The forces created by the magnetic field push the arc between the fractionation plates. The forces created by the magnetic field tend to stabilize the arc in the middle of the plates, thus ensuring a high and stable arc voltage in a reduced space.

To avoid re-strikes of the electric arc inside the breaking chamber, the ramp comprises a plurality of turns between which the metal fractionation plates are inserted, these turns forming screens between the metal plates.

Such a circuit breaker can be used either to cut a current or to limit a sudden increase in it. In the second case, we speak of a current limiting circuit breaker.

In the first case, a current circuit is provided supplying the coil through a means intended to split an electric arc into several elementary arcs. The coil is therefore supplied by only part of the current to be cut. The strength of the magnetic field created by the coil depends on the intensity of the part of the current to cut which feeds this coil. The means for splitting the arc serves to increase the arc voltage to increase the strength of the magnetic field accordingly.

According to an embodiment which is simple to implement, the means for dividing the electric arc comprises an insulating support arranged between a fixed arcing contact and an arcing insertion contact in the breaking chamber, the contact d insert being electrically connected to the coil and in which there is provided a series of conductive elements carried by the insulating support and distributed on the insulating support between the fixed arcing contact and the insertion contact.

If the coil is placed between the insertion contact and the insulating ramp, an electrically insulating means is provided to conduct the arc of the insertion contact to the metal fractionating plates.

In a simple embodiment, the insertion contact is carried by a conductive ring on which is arranged the insulating means for conducting the arc.

To improve the rise of the electric arc from the insertion contact towards the ramp and therefore towards the fractionation plates, an insulating means is provided for conducting the arc which has a helical shape.

It is also advantageous, for reasons of space, to provide that the coil is placed on the periphery of the crown.

In the case where the circuit breaker is intended for use as a current limiter, the coil is supplied with all of the current at the input of the circuit breaker through the electrode which is movably mounted on a conductive element cooperating electromagnetically with the coil , the construction of the ramp remaining identical.

According to a simple construction method to implement, the conductive element is a metal ring mounted on an axis of rotation close to the coil so that the ring approaches the coil under the action of a elastic return element and moves away from the coil under the effect of electromagnetic forces created by an increase in the current at the input of the circuit breaker.

Such an arrangement ensures that the circuit breaker opens sufficiently in a very short time immediately after the appearance of the short-circuit current. The opening system draws its energy from the short-circuit current. It is simpler to implement and less expensive than an opening system based on a mechanical control external to the circuit breaker. The development of the arc in the breaking chamber and its fractionation on the metal fractionation plates are carried out quickly because the coil, supplied with all of the current at the input of the circuit breaker, constantly generates an intense magnetic field.

Other characteristics and advantages of the invention will become apparent on reading the following description of exemplary embodiments of the invention.

Figure 1 is a schematic sectional view of the circuit breaker according to a first embodiment, this non-limiting circuit breaker being in the closed position.

Figure 2 shows the circuit breaker of Figure 1 in a first semi-open position.

Figures 3 and 4 show the circuit breaker of Figure 1 in a second semi-open position.

Figure 5 is a schematic sectional view of the circuit breaker according to a second embodiment, this current limiting circuit breaker being in the closed position.

Figure 6 shows the circuit breaker of Figure 5 in a semi-open position.

Figure 7 shows the circuit breaker of Figure 5 in an open position.

In Figure 1, we can see the inside of a medium or high voltage circuit breaker which is used to cut a current, the inside being seen in schematic section. Such circuit breaker can be used for single-phase or polyphase current.

It includes an enclosure, not shown, which is filled with a dielectric gas such as sulfur hexafluoride (SF6), under pressure of a few bars.

The circuit breaker comprises, inside the enclosure and for a phase of the current, a fixed arcing contact represented diagrammatically by the element 1. This fixed arcing contact is, if necessary, protected by an element with high melting point to resist an electric arc.

Contact 1 is connected to a terminal, not shown, bringing the current indicated by I inside the enclosure.

The circuit breaker also includes a movable arcing contact represented diagrammatically by the element 2. This contact 2 is also protected, if necessary, by a high melting point element 2a to resist an electric arc.

The arcing contact 2 is therefore mounted mobile around an axis 4 on a terminal 3 bringing the current inside the enclosure.

The movable contact 2 is moved around the axis 4 by means of a connecting rod 5 of insulating material which is rotatably mounted around an axis 6 connected to one end of the contact 2. The connecting rod 5 is itself connected mechanically to an operating device, not shown, conventional in itself.

In the closed position of the circuit breaker, the contact 2 is electrically connected to the contact 1. In the open position of the circuit breaker, the contact 1 and the contact 2 are separated and an electric arc is then established between these two contacts when the terminals d 'current input are supplied by a current to be cut.

The arrangement of the fixed 1 and movable 2 contacts generally takes the form of series of knives as shown and described in the document FR-8900215.

The circuit breaker also includes a breaking chamber indicated by 30 and disposed near the contacts 1 and 2.

This breaking chamber comprises a conductive electrode 7, for example in the form of a crown. The crown 7 is provided with an insertion contact 7a or priming horn which is intended to cooperate electrically with the movable arcing contact 2. The contact 7a is protected, if necessary, by a high-point element of fusion 7b to resist an electric arc.

The crown-shaped electrode 7 comprises an insulating element 7c produced by a recess in the wall of the crown, this obviously having preferably a helical shape. This obviously is therefore filled with dielectric gas which gives it its insulating quality. As a variant, the recess 7c is replaced by a deposit of insulating substance on the inner wall of the crown, this substance exhibiting good resistance to high temperatures such as for example ceramic.

The outer periphery of the crown 7 is surrounded by the windings of an electric coil 8 which serves to create a magnetic field.

The coil 8 is electrically connected to the crown 7 by a connection 7d and to the fixed arcing contact 1 by a connection 9.

Contact 1 is separated from contact 7a by an insulating part 11 carrying metal bars 10 spaced apart and electrically isolated from each other. The role of these bars 10 is to split the electric arc which is established between the contacts 1 and 7a into a large number of elementary electric arcs so as to increase the supply voltage of the coil 8.

The interrupting chamber also comprises a conductive electrode 12 having one end 12a protected, if necessary, by a high melting point element to resist an electric arc. This electrode is intended to cooperate electrically with the movable arcing contact 2.

The electrode 12 ends at its other end with a disc-shaped support plate 12b, the plate 12b preferably being part of the same part as the electrode 12.

In the example shown in Figure 1, the interrupting chamber has the shape of a cylinder and the electrode 12 extends along the axis of revolution of the cylinder.

The interrupting chamber further comprises an insulating ramp 13 of helical shape which is wound around a central generator 13a, here merged with the axis of revolution of the cylinder.

This insulating ramp 13 is disposed on the outer periphery of the breaking chamber, therefore on the inner surface of revolution of the cylinder.

In the arrangement shown in Figure 1, the insulating ramp 13 is covered at its upper part by the plate 12b, the electrode itself plunging inside the part 13 so that the ramp 13a is also wound around of electrode 12.

A large number of metal plates 14 are arranged along the ramp 13a, preferably at regular intervals of 1 to 1.5 millimeters, and are used for splitting the electric arc. The plates 14 can be pre-assembled in packages to facilitate their positioning along the ramp 13a. These metal plates are therefore arranged around the electrode 12 and at a distance from it.

Preferably, locations not shown are arranged in the ramp 13a to receive each plate 14 and immobilize it in place.

These metal fractionation plates 14 are arranged on edge between two turns of the ramp 13 and are preferably oriented radially in the direction of the electrode 12 without being in contact with the latter. Their end part closest to the electrode 12 is cut into a V to increase the speed of the arc's rise inside the ramp 13. They are made of a magnetic material with a thickness between 0.8 and 2mm.

The ramp 13 is made of an insulating material having a high resistance to temperature and to electric arc, such as for example ceramic or a thermoplastic or thermosetting material.

The turns of the ramp extend sufficiently towards the electrode 12 so as to define screens 13b which isolate the fractionation plates 14 inserted between two consecutive turns.

An insulating sheath 15 of cylindrical shape surrounds the ramp 13.

The part 12b and the sheath 15 have orifices 12c and 15a forming passages for the expulsion of the dielectric gas.

The operation of the circuit breaker of Figure 1 is now described.

By actuation of the operating device, the movable contact 2 is moved in the direction indicated by the arrow O visible in FIG. 1 between the fixed contact 1 and the contact 7a, the contacts 1 and 2 being supplied by the current to be cut.

An electric arc A1 is established between the contact 1 and the contacts 2 and 7a as visible in FIG. 2. Under the action of the electromagnetic forces created by the contacts 1,2 and 3, the electric arc A1 breaks up on the metal bars 10 in several elementary arcs, thus creating a significant potential difference.

A part I2 of the current to be cut I passes through the crown 7, the connection 7d, the coil 8, the connection 9 and returns to the contact 1. The other part I1 of the current I passes through the electric arc A1 established between contacts 1 and 2.7a.

Current I2 in coil 8 creates a strong magnetic field (indicated by arrow B) in the chamber that is directed in a direction parallel to the generator 13a of the ramp 13.

The contact 2 is then moved from the contact 7a to the electrode 12 as visible in FIG. 3. A second electric arc A2 traversed by all of the current I is established between the electrode 7 and the electrode 12.

Under the action of the electromagnetic forces (indicated by the arrow F) created by the contacts 1,2,3 and the crown 7 and the electrode 12 and under the action of the magnetic field B, the arc A2 is forced to penetrate inside the electrode 7 and inside the ramp 13, while turning and going up around the electrode 12.

The foot of the second electric arc A2 on the crown 7 is guided by the insulating element 7c and is directed towards the first fractionation plates 14. This arc then jumps from plate to plate following the helical ramp 13. The screens 13b act to avoid re-strikes of the second arc between the turns of the ramp 13.

Under the action of the magnetic field B, the arcs penetrate between the plates 14 to a position where the field B cancels and stabilizes at this location as visible in FIG. 4.

Due to the high arc voltage created by splitting the arc A2 on the plates 14, this results in a rapid reduction of the current I.

Because this electric arc develops over a long length along the ramp 13, this also results in very effective deionization of the dielectric gas and therefore very great possibilities of breaking the circuit breaker.

Continuing its travel, the contact 2 separates from the electrode 12. One obtains even more insulation between the contacts 1 and 3 and a fully open position of the circuit breaker.

As indicated previously, it is possible to produce according to the principle described above a current limiting circuit breaker. Such a circuit breaker is shown in section schematic in Figure 5 without its enclosure filled with a dielectric gas under pressure.

The movable arcing contact described above is replaced here by a repulsive type movable contact.

This circuit breaker comprises, for each phase, a first input terminal 101 of a current I, a second input terminal 112 of the current I, a movable contact of the repellant type which cooperates with the two terminals and an indicated breaking chamber by 130.

The repulsive type movable contact comprises a conductive part 113 articulated on the terminal 112 via a pin 115 but electrically isolated from the terminal 112 by an insulating part 114. It also includes a conductive electrode 108 carried by the part 113 In FIG. 5, this part 113 has the shape of a ring arranged on the top of the cylinder-shaped breaking chamber, the electrode 108 extending inside the chamber.

This repulsive type movable contact can be operated by an insulating rod 117 connected to an operating device, not shown. The insulating rod 117 is articulated on the part 113 by means of an axis 118. In this case, the operating device is arranged so that the rod is free to move under the effect of the movement of the part 113 as shown below.

The interrupting chamber 130 comprises, like that shown in FIG. 1, a helical insulating ramp 106 winding inside the chamber around a central generator 106a. Metal fractionation plates 107 are arranged along the insulating ramp 106, between the turns 106b thereof.

The current input terminal I 101 is connected to a first coil 103 by a conductive connection 102. The output of the coil 103 is electrically connected to an electrical contact pad 105 by a conductive connection 104.

The contact pad 105 and the coil 103 are arranged inside the chamber 130 and near a end of the ramp 106. The stud 105 is arranged to cooperate with the free end of the electrode 108. The coil 103 is used to create a magnetic field (indicated by B) directed in a direction parallel to the generator 106a of the ramp 106.

A magnetic piece such as 120 is provided inside the coil 103 to concentrate the magnetic field at the periphery of the breaking chamber.

A second coil 110 is arranged at the other end of the ramp 106. This coil 106 is intended to cooperate electromagnetically with the conductive ring 113.

The electrode 108 is connected by a flexible electrical connection 109 to the coil 110, itself connected to the terminal 112 by an electrical connection 111.

The coil 110 is arranged to create a magnetic field which is added to the magnetic field B. A magnetic element 119 is also provided for modulating the intensity of the magnetic field B inside the chamber 130.

As can be understood, the coils 110 and 103 are supplied by all of the current I at the input of the circuit breaker when the electrode 108 is in contact with the pad 105 so that they create a permanent magnetic field in the position of the electrode 108 shown in FIG. 5.

The ring 113 is also connected to the chamber 130 by a spring 116 which opposes the rotation of the ring around the axis 115 and which tends to keep the electrode 108 in contact with the stud 105.

Finally, an insulating sheath 121, for example made of ceramic, having orifices 121a for the passage of gas, encircles the ramp 106 between the coils 110 and 103.

The operation of such a current limiting circuit breaker is described below.

In FIG. 5, the current I at the input of the circuit breaker passes through the elements 101,102,103,104,105,108,109,110,111, 112. The coils 103 and 110 being supplied by the all of the current I, create inside the breaking chamber 130 a magnetic field B.

In the event that the intensity of the current increases suddenly, there follows an immediate and significant increase in the magnetic field B created by the coils 103, 110.

This increase in the magnetic field B induces in the conductive ring 113 circulation currents of opposite direction to the current in the coil 110 which generates intense repulsive forces between these two elements. Under the action of these repulsive forces, the ring 113 moves away from the coil 110 by rotation around the axis 115 as visible in FIG. 6.

Furthermore, an electric arc A1 'is established between the electrode 108 and the stud 105 simultaneously with the movement of the ring 113 relative to the breaking chamber 130.

The magnetic field B induces on the arc A1 'an electromagnetic force represented by the arrow F which tends to rotate the arc A1' around the electrode 108 and to cause it to rise inside the ramp 106.

A foot of the arc A1 ′ follows the ramp 106 by catching in turn on the metal fractionation plates 107, the arc developing taking the form of a solenoid.

Still under the action of the magnetic field B, the arc penetrates inside the plates 107 and stabilizes in the region of the weak magnetic field, thus creating a high and stable arc voltage.

This arc voltage reduces the short-circuit current until it cancels its value. The very long length of the arc makes it possible to obtain very great deionization of the gaseous medium in the breaking chamber and the voltage withstand after the current has passed through zero.

The ring 113 is finally moved mechanically by the operating device which acts on the connecting rod 117 and therefore on the electrode 108 so that the electrode 108 is placed in a position substantially coaxial with the generator 106a of the ramp 106 as visible in FIG. 7. This electrode 108 stabilizes in this position ensuring full voltage withstand between the input terminals 101,112.

Claims (12)

1.) A medium or high voltage circuit breaker comprising, in an envelope filled with a dielectric gas, a breaking chamber (30; 130) in which are placed metal plates (14; 107) to split an electric arc into a multitude of elementary arcs under the action of a magnetic field, characterized by a helical insulating ramp (13; 106) winding around a central generator (13a, 106a), this ramp being arranged on the inner peripheral part from the chamber and around a conductive electrode (12; 108) and the metal plates being arranged along said ramp, around and at a distance from the conductive electrode. 2.) The circuit breaker according to claim 1, comprising means (8; 110,103) for creating the magnetic field and directing it in a direction substantially parallel to the central generator of the ramp. 3.) The circuit breaker according to claim 2, wherein the magnetic field is created by at least one electric coil (8; 110,103) disposed at one end of the ramp. 4.) The circuit breaker according to claim 1, in which the ramp (13; 106) comprises a plurality of turns (13b, 106b) between which are inserted the metal fractionation plates (14; 107), these turns forming insulating screens between the metal plates. 5.) The circuit breaker according to claim 3, comprising a current circuit (1,7,7a, 7d, 9) supplying the coil (8) through means (11,10) intended to split an electric arc into several elementary arcs. 6.) The circuit breaker according to claim 5, wherein the means for splitting the electric arc comprises an insulating support (11) disposed between a fixed arcing contact (1) and an insertion contact (7a) of the arc in the breaking chamber, the insertion contact being electrically connected to the coil (8) and in which there is provided a series of conductive elements (10) carried by the insulating support and distributed over the insulating support between the contact fixed arc and insertion contact. 7.) The circuit breaker according to claim 6, comprising an insulating means (7c) for conducting the arc from the insertion contact (7a) to the metal fractionation plates (14). 8.) The circuit breaker according to claim 7, wherein the insertion contact (7a) is carried by a conductive ring (7) on which is arranged the insulating means (7c) for conducting the arc. 9.) The circuit breaker according to claim 8, in which the insulating means (7c) for conducting the arc has a helical shape. 10.) The circuit breaker according to claim 8, wherein the coil (8) is placed on the periphery of the crown (7). 11.) The circuit breaker according to claim 3, in which the coil (110) is supplied with all of the current at the input of the circuit breaker through the electrode (108) which is movably mounted on a conductive element (113) cooperating electromagnetically with the coil. 12.) The circuit breaker according to claim 11, wherein the conductive element (113) is a metal ring mounted on an axis of rotation (110) close to the coil (110) so that the ring approaches the coil under the action of an elastic return element (116) and moves away from the coil under the effect of electromagnetic forces created by an increase in the current at the input of the circuit breaker.

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