MXPA99001447A - Half or high tension circuiter that carries a better dielectric retention cutting chamber - Google Patents

Abstract

The present invention relates to a medium or high voltage circuit breaker, comprising a cutting chamber containing a dielectric gas, in which the displacement of a moving contact (2) with respect to a fixed contact (3) to open the circuit breaker gives rise to an electric arc that is quickly established between the mobile contact (2) and an external electrode (6) that is electrically connected to the fixed contact (3), and in which a coil (7) mounted in series with the electrode external (6) is fed by the electric arc to generate a magnetic field that displaces the electric arc with respect to the dielectric gas that is at rest. A central electrode (9) is electrically connected to the moving contact (2) and passes through the external electrode (6) so that the electric arc is caused during the displacement if it is established between the two electrodes (6,9). The electric field created between the two electrodes is substantially uniform, which minimizes the risk of restarting the electric arc.

Description

HALF OR HIGH VOLTAGE CIRCUITER THAT CARRIES AN IMPROVED DIELECTRIC CUTTING CUTTING CHAMBER Field of the Invention The present invention relates to a medium or high voltage circuit breaker in which an electric arc generated in the opening of the circuit breaker is displaced under the action of a magnetic field into the interior of a cutting chamber intended to contain a dielectric gas and which it comprises a cylindrical external electrode and a central electrode extending substantially following an axial direction of the external electrode.

Background of the Invention A circuit breaker of this type is especially known from the European patent application EP 0 058 007 published June 4, 1986. In this document, a mobile contact performs both the electrical contact role of the central electrode. During the opening of the circuit breaker. The electric arc that is initially formed between the movable contact and a fixed contact is quickly established between the moving contact and the REF .: 29515 external electrode and a coil supply current is created mounted in series with the external electrode. The magnetic field created by the coil causes the electric arc to move with respect to the dielectric gas at rest under the action of the electromagnetic forces acting on the molecules of the dielectric gas, ionized by the electric arc. At the end of the opening, the movable contact is placed approximatively following an axial direction of the first electrode, its free end being located in front of one of the faces of this first electrode. This disposition of the movable contact at the end of the opening does not seem sufficient, insofar as its free extremity locally creates a gradient of a relatively important electric field. This localized gradient may favor the restoration of the electric arc after the zero current of the electric current to be cut, retarding the regeneration speed of the ionized dielectric gas with respect to the speed of rise of the electrical voltage imposed by the network on which is branched the circuit breaker. The gradient can also favor the restoration of the arc after a certain effective cutting time.

Under these conditions, the dielectric retention between the mobile contact and the external electrode does not seem to be ensured except by an increase in the pressure of the dielectric gas contained in the cutting chamber during the cutting phase and also the prolonged periods in which the circuit breaker is open. The object of the invention is to improve the dielectric retention between the electrodes of a cutting chamber of a circuit breaker such as that described above. The basic idea of the invention is to make the mobile contact play the role of electrical contact, and that of assigning to a central electrode not confused with this contact, the cutting electrode paper. For this purpose, the invention has as its object a medium or high voltage circuit breaker in which an electric arc generated in the opening of the circuit breaker is displaced under the action of a magnetic field into the interior of a cutting chamber intended to contain a gas dielectric and comprising a cylindrical external electrode and a central electrode extending substantially following an axial direction of the external electrode, characterized in that the central electrode passes through the external electrode.

The central electrode passes through the external electrode to create a substantially uniform electric field between the two electrodes. Due to the zero crossing of the current to be cut, the risk of restarting the electric arc is minimized, resulting in an increase in the dielectric retention of the cut-off chamber of the circuit breaker. Other features and advantages of the invention will become apparent upon reading the description of the embodiments of the invention, illustrated by the drawings. Figure 1 shows a circuit breaker according to the invention, comprising a cutting chamber in which a central electrode passes through an external electrode, being fixed to a connecting piece by the intermediation of a conductor. Figure 2 shows a central electrode according to Figure 1, the first part of which is partially covered with an insulating thickness. Figure 3 shows a circuit breaker according to the invention, comprising a cutting chamber in which a central electrode passes through an external electrode which is fixed to a fixed support with respect to a connection piece by the intermediation of an elbowed conductor.

Detailed description of the invention On Figure 1, the cutting chamber of a medium or high voltage circuit breaker has been represented. The cutting chamber contains under a pressure of a few bars a gas having high dielectric and thermal properties such as SF6 sulfur hexafluoride. An electrical connection piece 1 is connected by a cover 1A or IB to a first supply of the current. A movable contact 2 is mounted in rotation with respect to the electrical connection part 1 around an axis A. This movable contact 2 is constituted for example of a blade or of a plurality of blades placed parallel to each other and articulated in rotation around the same axis A, the number of these blades is chosen according to the intensity of the current to be cut. A fixed contact 3 is electrically connected to a second current supply by the intermediation of a junction zone 3A. When the circuit breaker is in the closed position, the mobile contact 2 exerts a contact pressure on the fixed contact 3. To open the circuit breaker, a mechanical command not shown rotates the mobile contact 2 by the intermediation of an insulated connecting rod 5. to a contact door 15. At the moment of the opening of the circuit breaker, the displacement in rotation of the movable contact 2 with respect to the fixed contact 3 gives rise to an electric arc that is quickly established between the mobile contact 2 and a cylindrical external electrode. 6 placed inside the cutting chamber. The external electrode 6 is electrically connected to the fixed contact 3 by the intermediation of a coil 7 mounted in series with this first electrode. In the example of Figure 1, the external electrode 6 is tubular in shape, with an external side wall serving as a winding support for a continuous ribbon forming the coil 7. The electric arc formed between the moving contact 2 and the electrode 6 external, comes to feed the coil 7 and thus creates a magnetic field. It should be noted that the current through the coil 7 is initiated by a transient current coming from an electric arc formed between the external electrode 6 and a priming horn 33 integral with the fixed contact 3. The priming horn 3B is made up of a high melting point material such as a tungsten alloy. Its tip shape directed towards the external electrode 6 favors the rapid establishment of an electric arc between the mobile contact 2 and the external electrode 6. An insulating plate 14 a few millimeters thick separates the priming horn 3B from the external electrode 6. This Plate 14 is made of an insulating material with high thermal content such as a refractory ceramic or fluorinated plastic of the PTFE type. The magnetic field created by the coil 7 causes the electric arc to move with respect to the dielectric gas that is at rest in the cutting chamber. The cutting chamber comprises a central electrode 9 extending substantially following an axial direction L of the external electrode 6. According to the invention, the central electrode 9 passes through the external electrode 6 to create a substantially uniform electric field between the two electrodes. Due to the zero crossing of the current to be cut, the risk of restarting the electric arc is thus minimized, as indicated above, resulting in an increase in the dielectric retention of the circuit breaker cut-off chamber. In the example of Figure 1, an insulating support 10 keeps in place the two electrodes 6 and 9 in the circuit breaker and allows an accurate regulation of its relative position to guarantee a good mechanical and electrical retention of the cutting chamber. A conductor 8 supports the central electrode 9 and ensures an electrical connection between this central electrode 9 and the mobile contact 2 through the intermediation of the electrical connection piece 1. The central electrode 9 is substantially cylindrical and its two extremities 9A and 9B greatly exceed the faces of the external electrode 6. According to an advantageous embodiment of the invention, the two protruding ends 9A and 9B of the central electrode 9 have round surfaces in the shape of a half-sphere or, preferably, of semi-ellipsoidal shape to locally weaken the gradient of the electric field and thus strengthen the dielectric retention of the cut-off chamber of the circuit breaker. On Figure 2, there is shown a circuit breaker according to Figure 1, in which the end 9A of the central electrode 9 that is opposite the conductor 8, is covered with an insulating thickness 11 to confine the electric arc between the two electrodes 6 and 9 and prevent the latter from escaping under the action of electromagnetic forces. It is also provided to cover the external electrode 6 of an insulating thickness 12 on a part with respect to the insulating thickness 11 of the central electrode 9 to reinforce the effect of confinement of the electric arc between the two electrodes 6 and 9. The insulating thicknesses 11 and 12 they are advantageously formed from a refractory ceramic tank or from a fluorinated plastic cap of the PTFE type. On Figure 3, another embodiment of the invention has been represented. A conductor 8 'supports the central electrode 9 which is bent with respect to the axial direction L to allow an angular displacement of the movable contact 2 around the axis of rotation A from a first contact position with the fixed contact 3 towards a second contact position with this elbowed conductor 8 'then to a third contact position with a grounding contact 13. The three closing, opening and grounding positions of the movable contact 2 confer on the circuit breaker of Figure 3 a Particular interest when the circuit breaker is used in the poles of secondary distribution of electricity. The insulating support 10 keeps the two electrodes in place in the circuit breaker and allows precise regulation of their relative position. The elbowed conductor B 'is integral with the insulating support 10 and is placed in a plane perpendicular to the axis of rotation A to escape displacement of the movable contact 2.

The free end 2A of the movable contact 2 has a width D greater than the distance separating the priming horn 3 from the cranked lead 8 'so that, at the moment of the displacement of the movable contact 2, the central electrode 9 is electrically connected to this mobile contact 2 before the latter does not move away from the fixed contact 3. It is foreseen to choose the distance between the cranked conductor 8 'and the grounding contact 13 in such a way that the mobile contact 2 is simultaneously in contact with this grounding contact and with this elbowed conductor 8 'to discharge the central electrode 9. In the two embodiments of the invention, the passage of the electric arc from the moving contact 2 to the central electrode 9 is very fast, which contributes to decrease the times of the electric arc and limit the wear of the electrodes.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it refers. Having described the invention as above, property is claimed as contained in the following

Claims (8)

1. A medium or high voltage circuit breaker in which an electric arc generated in the opening of the circuit breaker is displaced under the action of a magnetic field into a cutting chamber intended to contain a dielectric gas and comprising an external cylindrical electrode and a central electrode extending substantially following an axial direction of the external electrode, characterized in that the central electrode passes through the external electrode.

2. A circuit breaker according to claim 1, characterized in that the central electrode has a round surface at its two ends.

3. A circuit breaker according to claim 2, characterized in that the two ends of the central electrode are in the form of a hemisphere.

4. A circuit breaker according to claim 2, characterized in that the round surfaces are of a semi-ellipsoidal shape.

5. A circuit breaker according to one of claims 1 to 4, characterized in that the two electrodes are mounted fixed to the circuit breaker by the intermediation of an insulating part.

6. A circuit breaker according to one of claims 1 to 5, characterized in that the other or both electrodes are provided with a plastic or refractory ceramic material insulation to prevent the electric arc from escaping from the cutting chamber.

7. A circuit breaker according to one of claims 1 to 3, characterized in that the central electrode is mounted on a conductor that is angled to allow an angular displacement of a moving contact towards a grounding contact.

8. A circuit breaker according to claim 7, characterized in that the central electrode is connected to the grounding contact by the intermediation of the moving contact.