EP0400523B1 - High tension gas blast circuit-breaker - Google Patents

Abstract

The invention relates to a high-tension circuit breaker insulated with dielectric self-blasting gas. <??>The circuit breaker comprising, inside a sealed insulating envelope filled with dielectric gas: - a fixed assembly comprising in particular a stationary main contact and a stationary arc contact, - a moving assembly driven by a manoeuvring linkage and comprising in particular a moving main contact and a moving arc contact, - a blasting volume prolonged by a blasting nozzle, - a blasting piston, - a pair of secondary contacts arranged in a first volume and intended to generate a secondary arc, is characterised in that it comprises first means of reducing the risks of untimely sparking due to the secondary arc and which consist of a jacket (25A) made of an insulating material and extending in line with the secondary contacts (41, 42) and in sliding contact with at least part of one (41) of the secondary contacts, the said jacket carrying longitudinal grooves (45) on the said secondary contact (41) side. <??>Application to high-tension circuit breakers. <IMAGE>

Description

The present invention relates to a high voltage circuit breaker according to the preamble of claim 1 in which the breaking chamber is filled with dielectric gas such as sulfur hexafluoride (SF₆), and in which the energy of the arc is used , thanks to the increase in pressure it gives the gas, on the one hand to blow the arc which is established when the circuit breaker opens and, on the other hand, to provide additional energy to the circuit breaker opening mechanism.

Document EP-A-302 390 describes a circuit breaker of the arc blowing type and comprising auxiliary contacts allowing the creation, during an opening operation of the circuit breaker (tripping), of a secondary arc being established by same time as the main arc.

It is mentioned in this document that the secondary arc produces, on closing of the circuit breaker (closing), an overpressure which opposes closing. Means are provided which allow this excess pressure to be released; these means increase the price of the device and require the use of a power control greater than that which would be necessary without this overpressure.

The document EP-A-367 072 constituting a state of the art within the meaning of art 54 (3) EPC describes a circuit breaker in which means are provided to avoid any secondary arc upon engagement.

An object of the present invention is to use the effects of the secondary arc which occurs during the closing of the circuit breaker to promote this closing and therefore to use a control whose power is not increased.

The object indicated above is achieved by the circuit breaker as defined in claim 1.

With regard to the characteristics of a preferred implementation of this circuit breaker, reference is made to the secondary claim.

• la figure 1 est une vue schématique partielle en demi-coupe axiale d'un disjoncteur selon l'invention, représenté en position enclenchée,
• la figure 2 est une vue en coupe selon la ligne II-II de la figure 1,
• la figure 3 est une vue du même disjoncteur au cours d'une manoeuvre de déclenchement pour la coupure d'un courant de faible intensité,
• la figure 4 est une vue du même disjoncteur au cours d'une manoeuvre de déclenchement pour la coupure d'un courant de forte intensité,
• la figure 5 est une vue du même disjoncteur au cours d'une manoeuvre de fermeture.
• la figure 6 est une vue schématique en demi-coupe axiale d'un disjoncteur selon une variante de réalisation de l'invention, représenté en position enclenchée,
• la figure 7 est une vue du même disjoncteur au début d'une manoeuvre de déclenchement,
• la figure 8 est une vue du même disjoncteur en fin de manoeuvre de déclenchement.

The invention will be better understood from the description given below of a preferred embodiment of the invention, with reference to the appended drawing in which:

• FIG. 1 is a partial schematic view in axial half-section of a circuit breaker according to the invention, shown in the engaged position,
• FIG. 2 is a sectional view along the line II-II of FIG. 1,
• FIG. 3 is a view of the same circuit breaker during a tripping operation for breaking a low current,
• FIG. 4 is a view of the same circuit breaker during a tripping operation for breaking a high current,
• Figure 5 is a view of the same circuit breaker during a closing operation.
• FIG. 6 is a schematic view in axial half-section of a circuit breaker according to an alternative embodiment of the invention, shown in the engaged position,
• FIG. 7 is a view of the same circuit breaker at the start of a tripping operation,
• Figure 8 is a view of the same circuit breaker at the end of tripping operation.

In FIG. 1, the reference 1 designates a cylindrical envelope, of axis xx, of insulating material such as ceramic, delimiting an interior volume 2 filled a gas with good dielectric properties such as sulfur hexafluoride (SF6).

The circuit breaker comprises a fixed main contact 3 consisting of contact fingers arranged in a tulip; this contact is surrounded by a corona hood 4. The main contact 3 is associated with a fixed arcing contact consisting of a metal tube 5 terminated by a part 5A resistant to the effects of the arcing and produced for example by pure or alloyed tungsten. The two aforementioned fixed contacts are connected to a first outlet not shown.

The moving element of the circuit breaker comprises a metal tube 6, terminated by a wearing part 6A, constituting the moving arcing contact. This tube is connected, by a metal piece 7, to an axial rod 8 of insulating material, used for the opening and closing operations of the circuit breaker.

The moving assembly further comprises a part 9 having the form of two cylinders 9A and 9B, adjacent, coaxial and of unequal diameter: the cylinder 9A of smaller diameter serves as a permanent mobile contact and cooperates for this purpose with the contact fingers 3; the cylinder 9B, of larger diameter, defines, with the tube 6, a blowing volume 10. The parts 9 and 6 are secured by an annular piece of insulating material 11, pierced with passages 11A. The tube 9A carries a blowing nozzle 12 made of insulating material.

The fixed assembly comprises, at its opposite end with respect to the blowing zone situated at the end of the nozzle, a fixed metal block 15 electrically connected to a second outlet not shown. The block 15 carries a ring of contact fingers 15A cooperating with the tube 9 to ensure the continuity of the flow of current between the tube 9 and the block 15. The block 15 also carries a metallic tubular part 16, defining with the tube 6 an annular volume 20. This volume is closed at one end by an insulating annular part 21 provided with openings 22 which can be closed by one-way valves 23 preventing the passage of gas from the interior to the exterior of the volume 20. The part 21 is integral with the movable tube 6 and slides along the tube 16 in a leaktight manner thanks to a dynamic seal 24. The other end of the volume 20 is closed by a part 25, made of insulating material, which acts as a blowing piston while cooperating with the cylinder 9. This part 25 is fixed to the tube 16. It carries a dynamic seal 26 cooperating with the tube 9B and a sliding joint 27 cooperating with the tube 6. The part 25 has a generally tubular shape, with a thickness sufficient to allow on the one hand to have first conduits 28 and second conduits 29, parallel to the axis x x and each bringing the volumes 10 and 20 into communication. The conduits 28 can be closed by a piston 30 sliding in a volume 31 formed in the part 25 on the side of the volume 20; the piston 30 is pushed, in a direction tending to close the conduits 28, by a spring 32 resting on a fixed part of the circuit breaker which will be specified below. The conduits 29 can be closed, on the side of the volume 10, by a differential valve 35 constituted by a simple annular washer whose stroke is limited by a stop 36. The conduits 29 extend beyond the area of overlap of the part 25 and tube 16; holes 37 in the latter allow communication between the conduits 29 and the interior of the volume 20.

The tube 16 carries a first contact 41 of the pair of secondary contacts. This contact 41 serves as a stop for the spring 32. This contact 41, terminated by a wearing part 41A, is of tubular shape.

The tube 6 carries the second contact 42 of the pair of secondary contacts. This contact 42, also tubular and terminated by a wearing part 42 A, is coaxial with the contact 41. When the circuit breaker is in the closed position (case of FIG. 1), the contacts 41 and 42 have a large facing portion. opposite.

The part 25 has channels 44 connecting, when the piston 30 does not close the channels 28, the volume 10 and the volume 20. The major part 44A of these channels 44 is parallel to the axis xx; they have a radial part 44B opening out in the vicinity of the outlet of the channels 28.

The part 25 is extended, on the side of the axis xx, by a tubular portion or jacket 25A of insulating material, in sliding contact with the tube 6. The jacket 25A carries, on the side of the contact 41, longitudinal grooves 45, c 'that is to say parallel to the axis xx, visible in Figure 2. In the example shown, the insulating part 25 and the jacket 25A constitute a single piece coming from machining.

The jacket 25A carries, at its end located closest to the operating rod, a metal block 47, cooperating electrically with the tube 6 by sliding electrical contacts 48. This block carries a crown 49 made of material resistant to the effects of arc, of diameter substantially equal to that of the tube 41 and turned on the side of the wear part of the latter.

The circuit breaker works as follows:
- in the engaged position (FIG. 1), the current flows through the fingers 3 of the main contact, the tube 9, the contact fingers 15A and the metal block 15.

Cut of low intensity currents.

These are currents with a value less than or equal to the nominal current of the line in which the circuit breaker is inserted.

At the time of release, the operating rod 8 is moved to the right of the figure and drives the moving assembly. The main contacts separate and the current is switched to the arcing contacts. It then passes through the tube 5, the tube 6, the tube 42, the tube 41, the tube 16 and the block 15.

When the arcing contacts 5 and 6 are separated, which coincides with the separation of the secondary contacts 41 and 42, an arc 51 arises between the contacts 5 and 6, and an arc 52 arises between the contacts 41 and 42. (See figure 3). As the current to be cut is low, the calorific power of the arc 52 is low. The valve 23 is open and allows the filling of the volume 20.
The increase in pressure in the blowing volume 10 is mainly due to the compression effect produced by the displacement of the piston 25 in the cylinder 10. This increase in pressure causes the arc 51 to be blown; the excess pressure is evacuated, via the conduits 28, 44B and 44A, to the volume 2; in fact, the increase in pressure in the volume 10 caused the piston 30 to move against the action of the spring 31 and despite the slight overpressure caused by the secondary arc 52. The valve 35 is also closed by the overpressure in the volume 10 during the opening operation of the circuit breaker. The overpressure inside the tube 6 can be evacuated by holes 53 made in the latter beyond the part 21.

At the end of the maneuver the tube 6 is brought to the potential of the block 15 by means of contact fingers 60.

Thanks to the presence of the metal block 47, the secondary arc 52 does not extend beyond a given length, equal to the distance separating the parts 41A and 49; this avoids the risk of priming on the surrounding metal walls. This avoids untimely priming thanks to the 25A folder. The friction with the contact piece 41 produces a certain wear and a slight carbonization of the insulating material which promotes the ionization of the near medium and, consequently, the routing of the arc and its channeling in the grooves 45.

Cut of high intensity currents

These are short-circuit currents.

The secondary arc 52 (FIG. 4) has a high calorific energy which causes a significant increase in the pressure P3 in the volume 20. The valve 23 closes. The hot gases of the volume 20 pass through the grooves 45 and cause the channels 30 to be closed by the piston 30. The differential valve 35 also closes because the action of the pressure P2 of the volume 10 on the total section S1 of the valve 35 is stronger than the action of the pressure P3 of the volume 20 on the section S2 of the conduits 29. The pressure in the blowing volume therefore becomes very important since the gas cannot escape from it. At the first zero crossing of the current, the gas in volume 10 expands and produces an extremely energetic blow of the arc 51 which extinguishes, which causes the extinction of the secondary arc 52. During the movement of the mobile equipment, the pressure P3 in the volume 20 is applied to the surface of the part 21, thus making an important contribution to the operating energy.

Circuit breaker closing

We will refer to figure 5.

The mobile assembly is moved from right to left of the figure. When the main arcing contacts and the secondary arcing contacts approach beyond the insulation distance, pre-arcing arcs 61 and 62 appear. The valve 23 is closed. The pressure increase generated by the secondary arc 62 causes the piston 30 to close and the differential valve 35 to open. The pressure P4 of the volume 20 is therefore transmitted, through the conduits 29, to the part 11 and the portion connecting tubes 9A and 9B, and thus contributes to the closing energy.

The circuit breaker, an embodiment of which has just been described, has great operational safety thanks to the measures taken to avoid internal strikes; the arrangements made to use the effects of the secondary arc allow a significant contribution to the maneuvering energy necessary to cut off high intensity currents; priming is authorized on closing, but it also contributes to the operating energy.

Figures 6 to 8 illustrate an alternative embodiment of the invention, of simple construction. The elements common to these figures and to the preceding figures have been given the same reference numbers and will not be described again.

The movable arcing contact is a metal tube 106, extended by an insulating tube 107 itself extended by a metal tube 108 connected to the operating rod.

One of the secondary contacts, 141, is fixed to the piston 36 and is in electrical contact with the tube 106 by a sliding contact 143.

The other secondary contact, 142, is integral with the tube 16 and cooperates electrically with the tube 108 by a sliding electrical contact 144.

The openings of the piston 36 are closable by means of a valve made up of a ring 136.

According to a characteristic of this alternative embodiment, the ends of the secondary contacts are provided with horns 151 and 152 whose role is explained below.

In the circuit-breaker on position (Figure 6), the current flows through parts 3, 9 and 15A.

During tripping, and after separation of the arcing contacts, (FIG. 7) a main arc 51 and a secondary arc 52 develop. The secondary arc 52, under the action of electromagnetic forces, rises along the horns while elongating, which increases the heating of the surrounding gas and the rise in pressure in the volume. The energy provided by the secondary arc is thus increased and promotes triggering.

At the end of the tripping operation (FIG. 8), the secondary contacts 151 and 152 come into contact, by their rounded ends 141A and 142A, with the tube 106, so that they are placed at the same potential.

The variant which has just been described is of simple and robust construction and applies, like the previous variant, to high voltage circuit breakers.

The presence of the insulating tube 107 promotes the path of the secondary arc and avoids inadvertent strikes.

Claims (2)

1. A high voltage circuit breaker insulated by an arc blasting dielectric gas and comprising, inside a gas-tight insulating housing:

   - a fixed assembly comprising, in particular, a fixed main contact (3) and a fixed arcing contact (5, 5A);

   - a moving assembly driven by a drive rod (8) and including, in particular, a moving main contact (9A) and a moving arcing contact (6A) at the end of a metal tube (6) coupled to said drive rod;

   - a blast volume (10) of annular cross-section and delimited by a cylinder (9B) and said tube (6), the latter two parts being coaxial and being fixed to the moving assembly, the blast volume being further delimited by an annular insulating part (11) which is pierced by passages towards a blast nozzle (12);

   - a blast piston (25) having an annular cross-section and sliding in the blast volume, said piston being fixed to a second fixed tube (16),

   - a pair of secondary contacts (41, 42) disposed in a further volume (20) which is delimited by said second tube (16) and said blast piston and intended to generate a secondary arc, characterized in that it comprises first means for reducing the risks of unwanted arcs being struck due to the secondary arc, said means being constituted by a jacket (25A) of insulating material extending level with the secondary contacts (41, 42) when the arc strikes, and second means for supplying additional energy to contribute to closing by virtue of the secondary contacts prestriking, said means including a duct (29) between said further volume (20) and said blast volume (10) and being closeable by a differential valve (35) disposed in the blast volume, said blast piston separating said blast volume (10) and said further volume (20), said communication (29) taking place through said piston.
2. A circuit breaker according to claim 1, characterized in that said blast piston (25) includes a second duct (28, 44) which is closeable by a piston (30) urged by a spring (31), said communication being located between said blast volume (10) and a second volume (2) outside said further volume (20) and said blast volume (10), said piston being constrained to move only when the breaker is interrupting low value currents.

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