Patent Application
20080083704
The characteristics and advantages of the invention can be better understood on reading the following description and on examining the accompanying drawing which is given merely by way of non-limiting illustration, and in which:
A high-voltage or medium-voltage circuit-breaker includes an interrupting chamber 10 which can be filled with a dielectric gas of the SF6 type. The interrupting chamber 10 contains a moving first contact 12 made up of an arcing contact 12a and of a main contact 12b, and an oppositely moving second contact 14 made up of an arcing contact 14a and of a main contact 14b. These two elements co-operate between an open position (
During the breaking procedure, the two contacts 12, 14 move in opposite directions; the two main contacts 12b, 14b separate, and then the arcing contacts 12a, 14a separate, after a latency period, if any, generated by the length of their plug-in, forming an electric arc that is extinguished by the contacts 12, 14 subsequently being moved further apart.
The first contact 12 (even though, in particular in the claims, it could be the second contact 14) is usually secured to a nozzle 16 which is made of an insulating material and which itself extends a gas compression volume. This dielectric nozzle 16 serves as a blast nozzle for blasting the gas coming from the compression volume towards the electric arc.
In order to optimize the dielectric gas content while current is being broken, and in order to prevent arcs from re-striking, the two main contacts 12b, 14b are located in an insulating tube 18, which surrounds them regardless of whether they are in the open position or in the closed position. Advantageously, the walls of said tube 18 are uniform and solid; the tube 18 is preferably a hollow circularly symmetrical cylinder, but it could also be conical or even polygonal in shape.
In particular, the tube 18 can be a hollow cylinder made of a thermoplastic or thermosetting polymer. Among thermosetting polymers, mention can be made, in particular, of the families of unsaturated polyesters, or of phenolic resins, or of epoxy resins in reaction with acid anhydride setting agents, or of polybismaleides, or of vinylester resins; among thermoplastic polymers, mention can be made, in particular, of the families of thermoplastic polyesters, or of polyamides, or of polycarbonates, or of phenylene polyoxides, or of polysulfones, or sulfur polyphenylenes, or polyetherketones, or liquid-crystal polymers, or polyimides, or fluorine-containing polymers of the polytetrafluoroethylene (PTFE) type. It is also possible to use a blend or alloy of these materials.
The tube 18 can also be made of an arrangement of fibers, in particular inorganic fibers such as glass fibers or polyester fibers or aramid fibers of the Kevlar™ type, each of which fibers can be in the form of continuous filaments, long fibers (>3 millimeters (mm), short fibers (<3 mm), mats or woven fabrics. Alternatively or additionally, the tube can, locally or throughout, contain particular reinforcement (alumina Al2O3, alumina trihydrate ATH, calcium oxide CaO, magnesium oxide MgO, silica SiO2, wollastonite, calcium carbonate CaCO3, titanium oxide TiO2, compounds based on silicate such as montmorillonites, vermiculites, and kaolin) that are organic or inorganic.
In another embodiment, the hollow cylinder 18 is made up of filamentary windings, in which the angle given to the winding can be in the range 0° to 90° uniformly over the entire cylinder 18 or varying thereover (in which case it is possible to modify the mechanical properties of the cylinder locally). The fibers are pre-impregnated or post-impregnated with resins (the impregnation being performed in a vacuum or otherwise), e.g. with an epoxy resin of the following types: bisphenol A, bisphenol F, or cycloaliphatic. Various reinforcing materials can also be used, such as inorganic fibers such as glass fibers, or polyester fibers or aramid fibbers of the Kevlar™ type, each of which fibers can be in the form of continuous filaments, long fibers (>3 mm), short fibers (<3 mm), mats, or woven fabrics.
In order to protect the fibers from the polluted SF6 and from the decomposition products of SF6, a protective varnish can be deposited, e.g. in a coat that is about 30 micrometers (μm) thick, such as an aliphatic polyurethane or a polyester film.
In both cases (polymer cylinder or arrangement of fibers), the insulating cylinder 18 can be of varying geometrical shape (with local extra thickness). It can also be manufactured with localized injections of fillers, at its surface or in its thickness: in addition to its functions of transmitting movement and of providing protection from hot gases, the insulating cylinder 18 can also be used to provide an additional function of electric field distribution. Thus, the cylinder 18 can include bisphenol A, bisphenol F, or cycloaliphatic epoxy resins with local injection of a filler of the zinc oxide ZnO or titanium oxide TiO2 type, optimizing its electric field distribution function.
In addition, another material can be overmolded onto the inside diameter and/or onto the outside diameter of the cylinder 18, or deposited in a thin layer on its inside diameter and/or on its outside diameter. The layer can be made of a mixture of polymers (thermoplastic or thermosetting) with incorporation of a filler (material that can have a high relative permittivity) of the following types: ZnO, TiO2, or carbon black, the filler content by weight lying in the range 0.1% to 300%, over a thickness lying the range 10 μm to 5 mm.
The two contacts 12, 14 and the nozzle 16 move along the main axis AA of the interrupting chamber 10 of the circuit-breaker. Preferably, the interrupting chamber 10, the nozzle 16, the first and second contacts 12, 14, and the insulating tube 18 are symmetrical around the axis AA.
Each of the contacts 12, 14 is actuated to move away from or towards the other contact via a single actuation system 20; the moving contact 12 being moved during triggering of the circuit-breaker drives the actuation system 20 which moves the oppositely moving contact 14.
In accordance with the invention, the oppositely moving contact 14 is driven via the tube 18: this option makes it possible to offer greater freedom in implementing the actuation means 20 in view of the particularly complex geometrical shapes of the contact members of a high-voltage or medium-voltage interrupting chamber; because of its diameter, the insulating tube 18, makes it possible to transmit a movement over a wide range of drive forces. The tube 18 can remain of small thickness: since it is a cylindrical tube with solid walls, the load is uniformly distributed, and moving the moving first contact 12 and driving the oppositely moving second cylinder 14 do not need the walls of the tube to be thick in order for them to be strong enough, e.g. the tube 18 can have walls of thickness in the range only a few millimeters to a few tens of millimeters.
To this end, the insulating tube 18 is fastened to the contact 12, e.g. via a link pin, and preferably at its end 22 opposite from the actuation device 20. This makes it possible to leave the other end free for connection to the actuation device 20, and optimizes the protection of the main contacts 12b, 14b with “clean” dielectric gas. The link between firstly the insulating tube 18 and the link pin 22 and secondly the rod 32 can be implemented in various manners: merely by a hole in the cylinder 18 and/or via a metal collar fastened to the cylinder 18 at the end in question, for example.
The actuation means 20 can take various forms known to the person skilled in the art. Advantageously, the actuation means 20 comprise a lever 24 having two arms 26, 28 mounted to pivot around an axis 30. The first arm 26 is connected to the insulating tube 18 (and thus indirectly to the first contact 12). It thus moves in the direction opposite to the direction in which the second arm 28 connected to the second contact 14 moves.
Preferably, the lever 24 is located on the same side as the oppositely moving contact 14, i.e. in the following order: lever 24—oppositely moving contact 14—nozzle 16—moving contact 12—end 22 of the tube 18.
The connection between the tube 18 and the first arm 26 is preferably implemented by a first rigid rod 32; advantageously the connection is achieved by inserting a pivot at an end portion of the arm 26, and by a rotary fastening at the end of the tube 18, e.g. by a pin.
Similarly, a link, or a second rigid rod 34 pivotally connects an end portion of the second arm 28 to the contact 14.
Depending on the desired movement and depending on the preferred speed ratio, the connection at the oppositely moving contact 14 can be situated at various distances from the axis AA of movement. Similarly, the arms 26, 28 of the lever 24 can be of identical length or of different lengths. In one embodiment, the combined length of the two arms 26, 28 is at its maximum, i.e. of the order of the diameter of the insulating tube 18, in order to optimize the forces.
It is possible to provide slots for connecting the connection rods 32, 34, in particular at the lever 24, if a latency time is recommended between starting to move each of the two contacts 12, 14: e.g. the second connection rod 34 of the oppositely moving contact 14 can move over a certain distance by sliding in a slot (not shown) in the second arm 28 before starting to move in translation along the axis AA.
Similarly, when the oppositely moving contact 14 comprises an arcing contact 14a and a main contact 14b, it is possible for these two elements 14a, 14b to be mounted to slide relative to each other, and thus for them to have different strokes and different speeds. The arcing contact 14a and the main contact 14b are then connected to the actuation system via another connecting rod and another lever (not shown).
In another embodiment, optionally in combination with the preceding embodiments, the axis 30 of the lever 24 is orthogonal to the axis AA of movement, so that the ends of the arms 26, 28 and thus the connection links 3234 move in a plane, thus making it possible for them to be subjected to less stress at their anchor points. Advantageously, for reasons of symmetry and of ease of assembly, the axis 30 of the lever intersects the axis AA of movement.
In order to improve the guiding of the moving cylinder 18, and in particular in order to reduce the radial forces to zero, in another embodiment, the actuation means 40 comprise two levers 42, 42′ whose pivot axes 44 coincide. The pivot axis 44 is normal to the axis AA of movement, and intersects it at a point B. Preferably, the system 40 is axially symmetrical: the two levers 42, 42′ are of identical shape and of identical type, and they are located at the same distance from the point B.
The first arm 46, 46′ of each lever 42, 42′ is connected via a first rod 32, 32′ to the tube 18, preferably at two diametrically opposite points. Similarly, two second rods 34, 34′ connect the second contact 14 to the second arms 48, 48′. The arms of the levers 42, 42′ are preferably not aligned along the axis 44.
In order to improve the guiding of the moving cylinder 18, in another alternative (and optionally in combination), the insulating tube 18 is advantageously guided in translation. For example, a mechanical guide system 52, 54 couples the tube 18 to at least one of the main contacts 12b, 14b. Preferably, the guiding 52, 54 is gastight: this makes it possible to prevent the hot gases that are generated from penetrating between the permanent contacts 12b, 14b. It is also preferred for the oppositely moving main contact 14b and the blast nozzle 16 to be guided, e.g. by a gastight system 56, so that a volume of clean dielectric gas is guaranteed around the main contacts 12b, 14b. Each guide system can be a continuous ring or a split ring, of small thickness, made of an insulating material having a low coefficient of friction (e.g., a PTFE filled or otherwise). Thus, the breaking performance is improved.
Other actuation or guide means can be devised. In accordance with the invention, by means of the presence of an insulating tube external to the contacts, design options are open and easier to implement. In addition, the overall radial size remains in the same proportions as in the state of the art, and the overall longitudinal size is not increased, while the protection of the contacts during breaking of high currents is increased.
| Number | Date | Country | Kind |
|---|---|---|---|
| 06 54163 | Oct 2006 | FR | national |
