FR2846781A1 - Power circuit breaker having envelope with two spaced isolators and central metallic foot cooling channel support having upper part communicating radiator section - Google Patents

Abstract

The power circuit breaker (1) has a circuit break chamber (4) with an outer envelope and holding dielectric gas. The envelope has two spaced isolators (13,14) and a metallic foot cooling channel (11) supporting them. The circuit breaker communicates with the radiator (12) via the upper cooling channel section.

Description

The invention relates to a power circuit breaker comprising a

  cut-off delimited by an envelope containing a dielectric gas and arranged horizontally in a protective sheath, and a radiator arranged outside the protective sheath, and communicating with the interior of the cut-off chamber. The invention relates more particularly to an alternator circuit breaker, the breaking chamber of which extends horizontally. Such a circuit breaker is electrically connected to sets of busbars themselves surrounded by protective sheaths. These sheaths are generally made of aluminum in order to be able to be the seat of induced currents which have the effect of canceling around them the magnetic field produced by the flow of current in the bars and in the circuit breaker. In operation, the current passing through the circuit breaker and the bars has a nominal current of the order of 5 to 20 kA, which tends to overheat certain conductive aluminum parts of the circuit breaker. A cooling circuit is necessary to maintain the circuit breaker at a standardized temperature. The design of this cooling circuit presents difficulties linked to the need for electrical insulation between the two conductive bars, and between each conductive bar and the protective sheath. More particularly, the protective sheath which is at ground potential must remain electrically isolated from the busbars. This sheath is used not only to protect the circuit breaker from the outside environment, but also to protect the outside environment from magnetic disturbances caused by the circulation of a strong current in the circuit breaker. Insulating supports 25 generally keep the breaking chamber in position inside the sheath, ensuring electrical insulation between the sheath and the chamber

cutoff.

  There is a construction in which the interrupting chamber extends horizontally resting on two support insulators, and in which additional insulators are intended exclusively for the passage of dielectric gas from the interrupting chamber to the radiator arranged outside of the protective sheath. The additional isolators are mounted in the upper part of the circuit breaker between the breaking chamber and the sheath. However, the use of these additional insulators induces a surcharge and significantly complicates the adjustments to be made, which

increases the manufacturing cost.

  In a construction known from patent FR 2 800 905, the number of insulators is reduced by adopting an architecture in which the breaking chamber which is vertical is extended by a support insulator on which it rests. This hollow insulator serves to communicate the interior of the interrupting chamber with a radiator for cooling the dielectric gas. Another hollow insulator placed at the upper end of the breaking chamber makes it possible to establish a natural circulation of the dielectric gas. In this construction, the poles which are at each end of the breaking chamber are at different heights, and it is necessary to provide electrical connection pieces to connect

  these poles to conductive bars located at identical heights. These additional parts represent an overload and they lengthen the current path in the circuit breaker, which is detrimental for its performance.

  Patent US4378461 discloses a device for cooling a tubular electrical conductor in a gas-insulated line. A vertical insulating column is fixed to the conductor in which an insulating gas circulates, the hot gas being able to rise through the column towards a cooling casing which is fixed to the envelope of the line in a sealed manner with respect to the outside air. The gas cooled in the casing descends in line 20 towards the conductor, and a circulation of the gas by natural convection is

  thus established. This cooling device cannot be envisaged as such for an application to a conventional breaking chamber of a circuit breaker.

  In particular, the metal envelopes forming the end casings of a circuit breaker are not grounded, unlike the envelope of a gas-insulated line. According to the teachings of this patent, it is at most conceivable to fix a cooling casing on an end casing of the circuit breaker, on the condition of dispensing with the ventilation system mounted on the casing and of providing a compensation ventilation

  forced air into the circuit breaker's protective sheath. The object of the invention is to remedy these drawbacks.

  To this end, the subject of the invention is a power circuit breaker, comprising a breaking chamber delimited by an insulating envelope containing a dielectric gas and disposed horizontally in a protective sheath, further comprising a radiator arranged outside the 35 protective sheath and communicating with the interior of the interrupting chamber, characterized in that the insulating envelope is formed by two insulators arranged in the extension of one another, in that a metal leg supports the two tubular insulators in the sheath with at its end a crown interposed between the two tubular insulators, and in that the interrupting chamber communicates with the radiator through channels formed in the crown. With this construction, each insulator provides electrical insulation between a conductor bar and the crown, so that the metal leg with the crown can be brought to the potential of the protective sheath. In addition, thanks to the support provided by the metal foot 10, it is not necessary to provide support insulators for

  maintain the breaking chamber in the protective sheath, which significantly reduces the manufacturing cost of the circuit breaker. Finally, thanks to the channels made in the crown, it is not necessary to provide additional insulators for the cooling circuit, which further reduces the manufacturing cost of this circuit breaker.

  According to a preferred embodiment of the invention, the channels of the

  crown open into the cutting chamber at different heights. With this construction, each channel can be connected to the radiator to form a natural convection cooling circuit, which improves the reliability of this circuit breaker.

  According to another particular embodiment of the invention, the metal base and the radiator form a single piece, and the crown communicates with the radiator by a single channel in which a flow of hot dielectric gas and a flow of cold dielectric gas circulate. by 25 natural convection. The implementation of a single large channel makes it possible to simplify the manufacture of the part constituting the metal base and the radiator, which further reduces the manufacturing cost of the circuit breaker. The invention will now be described in more detail, and with reference to the accompanying drawings which illustrate an exemplary embodiment thereof.

not limiting.

  Figure 1 is a schematic view in longitudinal section of the circuit breaker according to the invention; Figure 2 is a schematic cross-sectional view of the circuit breaker according to the invention; Figure 3 is a schematic cross-sectional view of a variant of the circuit breaker according to the invention; Figure 4 is a schematic cross-sectional view of a

  variant of the circuit breaker according to the invention.

  In FIG. 1, an alternator circuit breaker 1 extends horizontally by resting on a chassis 2 to which it is fixed. This circuit breaker comprises a protective sheath 3 in which is mounted a breaking chamber 4 which encloses switching members which extend coaxially with this breaking chamber. These members include a moving element 5 and a fixed element 6 including respectively a moving contact 5 ′ and a fixed contact 6 ′. As known in this type of circuit breaker, the breaking chamber is delimited by a sealed envelope which contains a dielectric gas such as pressurized SF6. The envelope which is substantially cylindrical comprises a metal casing, 9 at each of its ends, each casing 8, 9 being electrically connected to a conductive bar not shown. Each metal casing contains a crew of fixed or mobile contacts. The casing 9 in which the movable element 5, 5 'slides is crossed in leaktight fashion by a control rod 10 made of insulating material, intended to move this contact assembly to actuate the circuit breaker 1. The envelope of the cut 4 is held horizontally in the protective sheath 3 by a central foot 11, preferably metallic, which positions it substantially in the center of the sheath so as to provide the best possible insulation. A cooling circuit connects the interior of the interrupting chamber 4 to a radiator 12

  which is external to the protective sheath 3, in order to maintain the interrupting chamber at a predetermined temperature by cooling the dielectric gas which it contains. In FIG. 1, the radiator 12 is shown in dotted lines because it is located behind the plane of the figure which is a section plane of the circuit breaker in a longitudinal direction.

  According to the invention, the insulating envelope delimiting the breaking chamber 4 comprises two insulators 13 and 14 arranged in the extension of one another, and it is fixed to the protective sheath 3 by a metal foot 11 including a crown 11 'to which the insulators 13 and 14 are fixed. These 35 insulators can be of tubular or frustoconical shape. More particularly, the crown 11 'is interposed between the insulators 13 and 14 so as to be midway between the poles 8 and 9. Each insulator 13, 14 thus provides electrical insulation between a casing and the crown 11', so that the foot 11 with the crown 1l ′ can be metallic and brought to the potential of the protective sheath 3, that is to say to the ground, without electrical risk. A metal foot 11 makes it possible to dispense with support insulators having a high cost, and to design this foot by giving it resistance

optimal mechanics.

  According to the invention, the crown 1l 'comprises channels communicating the interior of the interrupting chamber 4 with the radiator 12 which is located outside of the protective sheath 3. It is thus not necessary to resort to tubular insulators specific to the cooling circuit, which significantly reduces the manufacturing cost of this circuit breaker. More particularly, the two insulators 13 and 14 which surround the breaking chamber of the circuit breaker are fixed on either side of the metal base 11 which includes a communication orifice in the fixing zone. The connections between a pole casing and an insulator, and the fixing of each insulator to the crown 11 'of the metal leg are tight so that the breaking chamber can contain a dielectric gas such as SF6 under a pressure of a few bars. These tubular insulators 13 and 14 are made of porcelain, resin or composite materials. They comprise at each of their ends a fixing collar, not shown, with

  holes and intended for their attachment to the crown 11 and the poles 8, 9.

  Figure 2, which is a view in a section plane through the foot

  metallic 11 in a direction normal to the axis of the tubular insulators 13 25 and 14, shows more precisely the shape of the metallic leg 11.

  This comprises a vertical portion provided with a lower base fixed to the protective sheath 3, or to the chassis 2, this vertical portion extending in its upper part in a substantially annular shape defining the crown 11 'to which the tubular insulators 13 30 and 14. This ring 11 'which is situated in a plane normal to the axis of the tubular insulators 13 and 14 has an inside diameter close to the inside diameter of the insulators. This internal diameter is chosen to be large enough to avoid the appearance of an electric arc between one of the contacts 5, 6 and the crown 11 '. It comprises radial channels 15, 16 connecting the interior of the interrupting chamber with the part of the cooling circuit which is external to the protective sheath 3, and intended to convey the dielectric gas to the radiators 12. In the example of FIGS. 1 and 2, the channels 15 and 16 are connected to the radiators 12 by means of aluminum tubes 15 ', 16' which are for example welded to the crown II 'so as to communicate respectively with the channels 5 15 and 16. As visible in FIG. 2, these tubes pass through the protective sheath

  3 by being for example welded to this sheath.

  The circulation of dielectric gas can be forced using a pump

  not shown. Advantageously, this pump is of the magnetic drive type so as to ensure the best possible seal between the interior of the cooling circuit and the environment of the circuit breaker.

  In a preferred embodiment, the circulation of the dielectric gas in the cooling circuit is ensured by natural convection, which simplifies the design and improves the reliability of the circuit breaker. To do this, the radial channels 15 and 16 located in the crown 11 'are produced so as to open out at different heights into the breaking chamber 4. In the example of FIG. 2, two radiators 12 each communicate with the interrupting chamber 4 via two channels 15 and 16. More particularly, each channel 15 opens into an upper zone of the ring to receive the hot gas and transmit it to the upper part of the corresponding radiator 12. After cooling in a radiator 12, the dielectric gas returns to the cutting chamber 4 through another channel 16 which opens into a lower zone of the crown 11 '. These channels 15 and 16 can be produced by drilling, or can be produced directly from the molding of the metal base. More generally, the metal base 11 including the crown 11 'can be produced

  in the form of a foundry piece, or else be made from boilermaking.

  In the example illustrated in the figures, the metal leg also includes another channel 17 connecting the interior of the interrupting chamber 4 to the lower part of the chassis 2. This channel 17 is here connected to a pressure gauge 18 30 for monitoring the dielectric gas pressure in the breaking chamber.

  This channel can also be used to fill the pressure chamber with dielectric gas during commissioning or during a maintenance operation. The radiator (s) 12 can for example be connected to the cooling circuit by means of tubes suitable for being placed in

  a ventilated area located at a certain distance from the protective sheath.

  In another embodiment which is shown in Figures 3 and 4, the radiator 12 is an integral part of the metal base 11, which reduces the manufacturing cost of the circuit breaker while facilitating its assembly. In this embodiment, the crown 11 of the metal foot 5 is extended upwards into a substantially parallelepipedal space with which the breaking chamber 4 communicates, this space defining the radiator 12. In the example of FIGS. 3 and 4 , the radiator 12 comprises a vertical duct 15 with an oblong section opening into an upper zone of the crown 11 '. This duct which is located above the crown 1i1 ', in a plane normal to the axis of the tubular insulators 13 and 14, comprises an upper end of round shape, the assembly constituting a relatively large heat exchange surface . As can be seen in FIG. 3, the crown 11a has here a greater thickness than in the example of FIGS. 1 and 2, so that the channel 15 which opens out inside this crown has a sufficiently large cross section to an upward and downward flow of gas flows there. In operation, a flow of hot dielectric gas rises in the central part of the conduit 15, to cool the upper part of the radiator, and it descends in a cold flow along the walls of the conduit 15 and of the radiator 12 to penetrate into the chamber. cut-off 4 at the

crown 1 1 '.

Claims (4)

  1 / Power circuit breaker (1), comprising a breaking chamber (4) delimited by an insulating envelope containing a dielectric gas and 5 disposed horizontally in a protective sheath (3), further comprising a radiator (12) disposed at the exterior of the protective sheath (3) and communicating with the breaking chamber, characterized in that the insulating envelope comprises two insulators (13, 14) arranged in the extension of one another, in that a metal leg (11) supports the two insulators (13, 14) in the sheath (3) with at its end a crown (11 ') interposed between the two insulators (13, 14), and in that the cut-off (4) communicates with the radiator (12) through channels formed in the crown (11 ').   2 / circuit breaker according to claim 1, wherein the radiator (12) is connected by tubes (15 ', 16') to the channels (15, 16) formed in the   crown (11 ') and which pass through the protective sheath (3).   3 / A circuit breaker according to claim 1 or 2, in which two channels (15, 20 16) open into the breaking chamber (4) at different heights,   to form a natural convection cooling circuit.   4 / circuit breaker according to claim 1, wherein the metal foot (11)   and the radiator (12) form a single piece from foundry or boiler making.   / A circuit breaker according to claim 4, in which the metal foot (11)   is connected to the radiator (12) by a single channel (15), in which flows both a flow of hot dielectric gas and a flow of cold dielectric gas by natural convection.