CH626745A5 - High-voltage self-blasting circuit breaker - Google Patents

Description

The invention relates to a high-voltage self-blowing circuit breaker comprising:

- an interrupting chamber housed inside a sealed envelope filled with insulating gas with high dielectric strength,

- a self-blowing device with piston and gas compression cylinder defining a pistonable volume, capable of sending a flow of blowing gas and extinguishing an electric arc, drawn between separable contacts when the circuit breaker opens , towards a cutoff interval formed inside a nozzle coaxial with said contacts,

- a main collecting tank arranged in the lower zone of the envelope for storing the liquefied insulating gas at low ambient temperatures,

- And pumping means cooperating with said tank to discharge the liquefied gas towards the cutoff interval in which the high temperature of the arc causes the vaporization of said liquefied gas during the separation of the contacts.

Below the liquefaction temperature of the insulating gas contained in the enclosure, the breaking performance cannot be guaranteed given the drop in density of the gas in the breaking interval. In normal operation of the circuit breaker in cold regions, the contacts are in the closed position and the flow of permanent current through the switching chamber causes the gas contained in the device to heat up by Joule effect. A break after a long closing time will be less unfavorable than if the circuit breaker remains open for a very long time and is forced to suddenly carry out a closing - opening cycle. During such a prolonged opening of the circuit breaker, in periods of extreme cold, the gas condenses on the cold walls of the breaking chamber and is recovered in the liquid state in the collecting tank located at the lower part of the chamber. .

According to a known circuit breaker of the kind mentioned, during the precompression phase of the insulating gas, said means for pumping the liquefied gas consist of an injection pump separate from the self-blowing device, ensuring the admission of the liquefied gas into the cut-off interval when opening the circuit breaker. A determined dose of liquefied gas is thus injected during the precompression phase before the separation of the contacts, and the pump is formed by an auxiliary movable cylinder secured to the movable contact and mounted to slide on a fixed auxiliary piston located in the lower part of the tank. collector. The cylinder is extended by a tapered conduit, with a head pierced with orifices, housed inside the movable contact and ensuring the discharge of an axial jet of liquefied gas towards the cut-off interval when the movable contact is actuated towards the open position. After the precompression phase, the separation of the contacts generates the electric arc, and the self-blowing device then sends a radial jet of gas in the cut-off interval, the combined action of the two axial and radial jets causing the extinction of the arc at the end of a determined stroke of the movable contact. The difference in gas densities of the two separate jets is nevertheless harmful for a rapid cut-off of the electric arc, and obtaining the axial jet requires a special injection pump.

According to other known devices, an auxiliary electric heating controlled as a function of the outside temperature heats the envelope to avoid reaching the liquefaction temperature of the insulating gas.

The object of the invention is to avoid these drawbacks and to produce a simplified self-blowing circuit breaker devoid of a special injection pump for liquefied gas or of auxiliary electric heating, and having optimum reliability in very cold regions.

The circuit breaker according to the invention is characterized in that the said pumping means comprise communication conduits between the collecting tank and the pistonable volume of the self-blowing device such as the vacuum generated in the pistonable volume during actuation s

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from the circuit breaker to the closed position of the contacts causes automatic suction of the liquefied gas into said volume of the self-blowing device, causing an increase in the density of said insulating gas during the closing phase of the circuit breaker.

The injection of liquefied gas into the pistonable volume takes place simultaneously with the filling of the insulating gas sucked into the internal compartment of the casing when the circuit breaker is closed, and the vacuum in the pistonable volume of the self-blowing device is advantageously used. to suck both the liquefied gas contained in the collecting tank, and the insulating gas from the envelope. This arrangement eliminates the special injection pump and requires a simple piping between the collecting tank and the pistonable volume. In addition, the suction of the liquefied gas takes place exclusively during the closing phase of the circuit breaker and is stopped at the start of the opening of the circuit breaker during the precompression of the gas. When the contacts are separated, the self-blowing device sends a single jet of compressed gas towards the cut-off interval for rapid extinction of the electric arc.

According to one embodiment, baffles are arranged inside said communication conduits.

According to another embodiment, each communication conduit comprises a lower end which plunges into the liquefied gas collecting tank and an upper end which passes through the fixed element of the self-blowing device, constituted by the piston or the cylinder, for delimit an inlet orifice of said pistonable volume.

Advantageously, said inlet orifice cooperates with a check valve arranged in the pistonable volume, said valve being respectively urged towards an intake position by the depression prevailing in the volume when the circuit breaker is closed, and towards a position of obturation to ensure compression of said gas when the circuit breaker opens.

Other advantages and particularities will emerge more clearly from the description which follows of an embodiment of the invention, given by way of example and shown in the appended drawing, in which:

FIG. 1 is a schematic view in axial section of a self-blowing circuit breaker equipped with means for pumping liquefied gas according to the invention, the position of the moving element being shown during the closing stroke of the circuit breaker;

Figure 2 is a view similar to Figure 1, and shows the moving assembly during the opening stroke of the circuit breaker.

In the figures, a high-voltage circuit breaker pole includes a breaking chamber 10 arranged inside a sealed casing 12, made of insulating material, filled with insulating gas of high dielectric strength, in particular sulfur hexafluoride under pressure . A conductive cover 14 for closing the casing 12 serves as an input terminal for the current, and supports the fixed hollow contact 16 cooperating with interlocking with the aligned movable contact 18 hollow in the closed position of the circuit breaker. The movable contact 18, slidably mounted in the chamber 10 in the direction of the axis XX ', crosses the bottom 20 of conductive material arranged in the lower zone of the casing 12 opposite the cover 14 and is extended by an insulating actuating rod 22 connected to the control mechanism (not shown) and extending axially inside a support insulator 24 of the pole.

A self-blowing device 26 comprises a cylinder 28 carried by the movable contact 18 and cooperating with a fixed piston 30 to confine a pistonable volume 32 of compression of the insulating gas capable of sending a flow of blowing gas towards the cut-off interval 34 in separate position of the contacts 16,18. The movable cylinder 28 is provided with a blowing nozzle 36 with diverging convergent, co-axially surrounding the contacts in the closed position and the convergent of which communicates through openings 38 formed in the cylinder 28 with the pistonable volume 32 for channeling the gas. of compressed air blowing towards the cut-out interval 34. The neck of the nozzle surrounds the fixed contact 16 in the closed position of the circuit breaker, and of the tap-off fingers 40, housed inside a conducting tube 42 support of the fixed piston 30, come into engagement with the movable contact 18 for the passage of the current, which circulates in the tube 42 towards the bottom 20 equipped with an output terminal 44.

A circuit breaker of the above type is well known and need not be described in detail. In the closed position, the current flows in through the input terminal 14 and flows through the contacts 16,18, the power outlet fingers 40, the tube 42, the bottom 20, towards the output terminal 44. The fixed contact 16 enters the end of the movable contact 18 in the form of a nozzle, and the convergent of the nozzle 36 is closed by the fixed contact 16. The opening of the circuit breaker is controlled by sliding down the actuating rod 22, which drives the movable contact 18. In a first phase of the movement, the fixed contact 16 remains fitted into the nozzle 36 and into the movable contact 18 preventing any escape of blowing gas which is precompressed by the cylinder 28 accompanying the movable contact 18 in its sliding stroke down. At the end of this first precompression phase, the movable contact 18 separates from the fixed contact 16 drawing an arc inside the nozzle 36 and freeing the exhaust path of the blowing gas. In the second phase, the continued sliding of the movable contact 18 causes the precompressed gas flow to escape towards the cut-off interval 34 and extinguish the arc.

The bottom 20 of the casing 12 and the tube 42 supporting the fixed piston 30 form a main collecting tank 48 for storing sulfur hexafluoride SFö liquefied at low ambient temperatures, and coaxially surrounding the hollow movable contact 18. Pumping means comprise communication conduits 50, the lower end of which dips into the collecting tank 48 of liquefied gas, and the upper end of which passes through the fixed piston 30 to delimit an inlet orifice 52 in the pistonable volume 32. This orifice inlet 52 cooperates with a valve 54 arranged in the pistonable volume 32 and urged respectively towards an intake position by the depression prevailing in the volume 32 when the circuit breaker closes, and towards a shutter position to ensure the compression of the SFö when opening the circuit breaker. The fixed piston 30 has a hollow cup-shaped head providing an additional tank 56 for recovering liquefied SF 6 in the pistonable volume 32. The fixed piston 30, the main 48 and auxiliary tanks 56, the conductive tube 42 and the bottom 20 constitute a single piece, and the communication conduits 50 extend parallel to the sliding axis XX 'of the movable contact 18. Other openings 58 associated with valves 60 ensure the admission of insulating gas sucked into the casing 12 when closing the circuit breaker.

The circuit breaker works as follows:

During the closing stroke shown in FIG. 1, the upward sliding of the actuating rod 22 causes an increase in the pistonable volume 32, and the resulting depression urges the valves 54 and 60 towards the intake position and ensures the automatic suction of liquefied gas stored in the reservoir 48, and of insulating gas contained in the internal compartment of the envelope 12. This results in a augs

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gas density before opening the circuit breaker.

When opening the circuit breaker, an initial precursor of sliding downwards of the movable contact 18 during the first phase of the movement causes the gas contained in the pistonable volume 32 to precompress after closing the orifice 52 and the openings 58 in position shutter valves 54 and 60. The suction of liquefied gas is stopped during this operating phase. During the second phase of the movement (FIG. 2), the continued sliding of the actuating rod 22 separates the fixed 16 and mobile 18 contacts between which an electric arc is drawn, the high temperature of which instantly vaporizes the liquid SF6 contained in the jet. of compressed gas injected by the self-blowing device 26 towards the cut-off interval 34 inside the nozzle 36.

s The high density of SFe before the precompression phase is suitable for rapid extinction of the arc arising in circuit breakers installed in regions with harsh climates.

The self-blowing device 26 associated with the contacts 16.18 io can be devoid of the initial phase of precompression of the insulating gas.

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1 sheet of drawings

Claims (8)

626745 2 1. High voltage self-blowing circuit breaker comprising: - an interrupting chamber housed inside a sealed envelope filled with insulating gas with high dielectric strength, - a self-blowing device with piston and gas compression cylinder defining a pistonable volume, capable of sending a flow of blowing gas and extinguishing an electric arc, drawn between separable contacts when the circuit breaker opens , towards a cutoff interval formed inside a nozzle coaxial with said contacts, - a main collecting tank arranged in the lower zone of the envelope for storing the liquefied insulating gas at low ambient temperatures, - and pumping means cooperating with said tank to discharge the liquefied gas in the direction of the cut-off interval in which the high temperature of the arc causes said liquefied gas to vaporize during contact separation, - characterized by the fact that said pumping means comprise communication conduits between the collecting tank and the pistonable volume of the self-blowing device such as the vacuum generated in the pistonable volume during actuation of the circuit breaker towards the closed position of the contacts causes automatic suction of the liquefied gas into said volume of the self-blowing device causing an increase in the density of said insulating gas during the closing phase of the circuit breaker. 2. Self-blowing circuit breaker according to claim 1, characterized in that baffles are arranged inside said communication conduits. 3. Self-blowing circuit breaker according to claim 1 or 2, characterized by the fact that each communication conduit comprises a lower end which plunges into the liquefied gas collecting tank and an upper end which passes through the fixed element of the self-blowing device, constituted by the piston or the cylinder, to delimit an inlet orifice of said pistonable volume. 4. Self-blowing circuit breaker according to claim 3, characterized in that said inlet orifice cooperates with a check valve arranged in the pistonable volume, said valve being respectively urged towards an intake position by the depression prevailing in the volume during closing the circuit breaker, and towards a closed position to ensure the compression of said gas when opening the circuit breaker. 5. Self-blowing circuit breaker according to one of claims 1,2,3 or 4, characterized in that an additional tank for recovering liquefied gas is formed in the bottom of the pistonable volume arranged in the form of a bowl. 6. Self-blowing circuit breaker according to one of the preceding claims, characterized in that said insulating gas is sulfur hexafluoride. 7. Self-blowing circuit breaker according to claim 5, characterized in that the fixed element of the self-blowing device and the main and additional collecting tanks for liquefied gas form a single piece coaxially surrounding the hollow movable contact, slidably mounted in said breaking chamber. 8. Self-blowing circuit breaker according to claim 7, characterized in that said communication conduits arranged between the one-piece part and the inner wall of the envelope, extend parallel to the sliding axis of the movable contact.