EP0789928B1 - High-voltage circuit breaker with automatic arc extinction - Google Patents

Abstract

A high-voltage insulating gas circuit breaker with an automatic extinction device (9, 10) for extinguishing the arc (17) generated between the stationary arcing contact (2) and the moving arcing contact (7) when power is cut off. A cooling tube (1) downstream from the blow nozzle (5) is provided with a plurality of gas through-holes (19) in the flow path of the hot gas (18) generated by the arc. As the gas flows through the cooling tube (1), the gas pressure differential at the through-holes (19) causes fresh gas (20) to be sucked into the tube (1) and mixes the hot and fresh gases together. The gas (21) discharged from the cooling tube (1) is sufficiently cooled to maintain the dielectric properties of the circuit breaker.

Description

State of the art

The invention relates to a high-voltage circuit breaker with isolation gas, comprising a fixed arcing contact, a movable arcing contact capable of being coupled to a control mechanism to be actuated between a position of closing, and an open position, a self-blowing piston device cylinder associated with a blowing nozzle intended to send a gas jet pressurized towards the cut-off interval to extinguish the arc drawn between the contacts separated, and means for cooling the hot gas coming from the cut-off interval and arranged downstream of the blowing nozzle in the track gas flow allowing the exhaust to the outside of the circuit breaker, the cooling means comprising a cooling tube serving support in fixed arc contact, said tube being provided with holes for the gas hot is cooled by a first thermal conduction effect of the tube, and by a second mixing effect with the cold gas.

For the interruption of a high intensity current the problem to be solved remains in the hot gas sweep outside the cut-off interval between the circuit breaker contacts. The hot gas generated in the cut-off interval during the interruption of the current escapes in the tank to the earth potential in case a shielded circuit breaker. The expansion of this hot gas in the tank risks reduce the dielectric strength between the active part of the circuit breaker and the earth / earth, or between the active parts of the circuit breaker phases.

To solve this problem, it has already been proposed to provide a cooling tube in which the hot exhaust gas downstream of the cut-off interval is cooled by the effect of thermal conduction. The gas discharged to the tank is sufficiently cooled so that the insulation of the shielded circuit breaker remains correct.
In the case of a self-blowing circuit breaker, if the pistonable volume of the cylinder is large, the blowing pressure generates a large amount of blowing gas. This results in a significant gas cooling effect which promotes the dielectric strength of the circuit breaker. In this case, the cooling of the gas by conduction in said cooling tube is secondary, but to the detriment of the bulk and the energy required for the self-blowing device.

In document EP-A-75668, a circuit breaker includes a device with self-blowing piston cylinder, and means for cooling the hot gas by thermal conduction, and by mixing with cold gas. A tube serving as support for fixed arcing contact, has holes for gas evacuation cooled to the outside of the switching chamber. Such a circuit breaker requires a large volume of blowing gas from the self-blowing device.

The recent development trend of the circuit breaker towards miniaturization and the decrease in the operating energy results in the decrease in the diameter of the blowing cylinder. This results in more efficient use of arc energy increasing the blowing pressure to obtain a better blowing effect arc. The disadvantage of such a system results in a decrease in the volume of the gas blowing cold, affecting the cooling effect of hot gas. Under the effect hot gas, the dielectric strength in the tank of the circuit breaker becomes critical even in the presence of the cooling tube downstream of the blowing.

Summary of the invention

The object of the invention is to improve the dielectric strength of a circuit breaker high voltage, and self-blowing.

The circuit breaker according to the invention is characterized in that the holes in said tube cooling are arranged to allow the suction of cold gas to the track internal flow of the circuit breaker, so that the hot gas is cooled by the second mixing effect with the cold gas passing through the holes.

At the gas passage holes arranged in the cooling tube, fresh gas at low temperature is drawn into the interior of the tube through of said gas passage holes by the effect of the difference in internal pressures and external of the tube. The fresh gas thus introduced into said cooling tube mixes with hot gas by cooling said hot gas. The gas exhaust to the outside of the circuit breaker is sufficiently cooled to re-establish its isolation clothing.

According to a characteristic of the invention, the holes of the cooling tube are arranged in the vicinity of a support member of the fixed main contact, said support member comprising a conductive tube coaxially surrounding the fixed arcing contact. The mobile cylinder of the self-blowing device has a outer diameter less than the inner diameter of the insulating jacket on which is mounted the conductive tube.

Brief description of the drawings

• la figure 1 est une vue en coupe du disjoncteur selon l'invention, lors de la phase de coupure du courant;
• la figure 2 est une vue identique à celle de la figure 1, en position fermée du disjoncteur.

Other advantages and characteristics will emerge more clearly from the description which follows of an embodiment of the invention, given by way of nonlimiting example, and represented in the appended drawings, in which:

• Figure 1 is a sectional view of the circuit breaker according to the invention, during the power cut phase;
• Figure 2 is a view identical to that of Figure 1, in the closed position of the circuit breaker.

Description of a preferred embodiment

With reference to FIGS. 1 and 2, a gas circuit breaker, in particular with hexafluoride sulfur SF6, includes an upper conductive tube 14 serving to support the fixed main contact 3, and mounted between a cooling tube 1 and a 4 cylindrical insulating jacket. The cooling tube 1 supports the fixed arcing contact 2, which is arranged coaxially inside the contact fixed main 3. The insulating casing 4 is arranged on a conductive tube lower 11, itself supported by a support tube 13 made of insulating material.

An insulating rod 12 is connected to the control mechanism (not shown), by being pressed upwards when the circuit breaker closes, and downwards when opening. At the end of the insulating rod 12 is a rod movable conductor 15 of tubular shape, said rod 15 supporting the contact main mobile 6, the movable arcing contact 7 and a self-blowing device comprising a blowing nozzle 5 integral with the movable main contact 6. The movable conductive rod 15 is provided with the axial hole 16 constituting a channel exhaust gas.

The self-blowing device comprises a blowing cylinder 9 extending under the nozzle 5 and the movable main contact 6, and capable of sliding on a piston fixed 10 secured to the lower conductive tube 11. A sliding contact 8 cooperates with the movable conductive rod 15, and ensures the electrical connection between the movable contacts 6 and 7 and the lower conductive tube 11.

Holes 19 are provided between the cooling tube 1 and the conductive tube 14.

In the closed position of Figure 2, the main contacts 6 and 3 are located in engagement with each other and ensure the passage of current in the circuit formed by the upper conductive tube 14, the fixed main contact 3, the contact movable main 6, movable conductive rod 15, sliding contact 8, and tube lower conductor 11.

During the current interruption phase, the insulating rod 12 is biased towards the bottom by the mechanism, and causes the separation of the main contacts 6 and 3, then that of the arcing contacts 7 and 2. The birth of the arcing 17 between the contacts of arc 7 and 2 intervenes simultaneously with the intervention of the device to self-blowing.

Moving the blow cylinder 9 down causes compression gas in the pistonable space formed between the cylinder 9 and the piston 10. The gas thus pressurized escapes through the nozzle 5, and in the opposite direction through the hole 16 axial of the rod 15. The gas flow through the nozzle 5 is concentrated at nozzle neck level 5, and is directed towards the arc zone by exerting an effect of extinction on the arc 17, followed by the escape of the hot gas 18 generated by the arc towards the downstream side of the flow path.

The hot gas 18 passes through the cooling tube 1, and is cooled by the thermal conduction of the cooling tube 1. At the holes 19 of gas flow, the level of gas pressure inside the gas tube cooling 1 becomes lower than that of the static gas outside the tube 1 following the flow effect of the hot gas 18. This pressure difference generates a suction of cold gas 20 located outside the tube 1 towards inside the tube 1, passing through the holes 19. A mixture then occurs of cold gas 20 with hot gas 18 inside the cooling tube 1.

The hot gas 18 passing through the tube 1 is cooled not only by the effect of conduction of the tube 1, but also by the effect of mixing with the fresh gas 20, of which the temperature is lower than that of the hot gas 18.

The mixed gas 21 is then expelled to the outside of the circuit breaker ensuring the dielectric characteristics necessary for the insulation between phases or for phase-to-ground isolation.

The cooling effect of the hot gas 18 at the cooling tube 1 is increased even if the blowing gas from it decreases of the self-blowing device. The presence of the holes 19 thus makes it possible to reduce actuation energy for blowing the arc.

Claims (3)

1. A high voltage circuit breaker with isolating gas, comprising a stationary arcing contact (2), a movable arcing contact (7) designed to be coupled to an operating mechanism to be actuated between a closed position and an open position, a self-blast device with piston (10) and cylinder (9) associated to a blast nozzle (5) designed to send a pressurized gas blast to the breaking gap to extinguish the arc drawn between the separated contacts (2, 7), and means for cooling the hot gas coming from the breaking gap and arranged downstream from the blast nozzle (5) in the gas outlet channel enabling the latter to escape to outside the circuit breaker, the means for cooling comprising a cooling tube (1) acting as support for the stationary arcing contact (2), said tube (1) being equipped with holes (19) for the hot gas to be cooled by a first thermal conduction effect of the tube (1) and by a second effect of mixing with the cold gas, characterized in that the holes (19) of said cooling tube are arranged to allow the cold gas to be sucked into the internal outlet channel of the circuit breaker in such a way that the hot gas is cooled by the second effect of mixing with the cold gas passing through the holes (19).
2. The high voltage circuit breaker according to claim 1, characterized in that the holes (19) of the cooling tube (1) are arranged near to a support part of the stationary main contact (3), said support part comprising a conducting tube (14) coaxially surrounding the stationary arcing contact (2).
3. The high voltage circuit breaker according to claim 2, characterized in that the mobile cylinder (9) of the gas self-blast device presents an external diameter smaller than the internal diameter of the insulating enclosure (4) on which the conducting tube (14) is fitted.

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