Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H1/00—Contacts
  • H01H1/02—Contacts characterised by the material thereof
  • H01H1/021—Composite material
  • H01H1/027—Composite material containing carbon particles or fibres

Definitions

• the present invention relates to an arcing contact element for electrical medium or high voltage switchgear, a method of manufacturing such an element, a contact assembly comprising at least one such element, as well as an electrical apparatus for cutoff provided with such a contact assembly.
• an electrical switchgear for medium or high voltage is, for example, a circuit breaker, a disconnector, a contactor, or even a load switch.
• medium or high voltage is meant a voltage greater than about 1000 volts.
• such a switchgear comprises a contact assembly, which is provided with two fixed and movable members, each of which is equipped with a respective contact element. The movable element can thus be moved, relative to the fixed element, between a contact position and a separate position, or cut.
• the movable member is also provided with an insulating nozzle, which defines an annular channel through which, during the movement of the movable member, an insulating gas is directed towards the area where the electric arc occurs.
• FR-A-2 181 699 describes a high voltage circuit breaker, of the type explained above.
• the arcing contact elements are formed from graphite bodies enclosing, at the points of their contacts, an electrically conductive adduct, which consists of one or more metals.
• EP-A-0 665 565 has also proposed a contact assembly for switchgear, which is provided with an additional part, forming a wearing part, made of graphite.
• This second solution has drawbacks, however, linked to the insufficient mechanical strength of the material used. Thus, during mechanical shocks, particularly occurring during closing operations, small graphite particles are liable to detach from the contact assembly.
• the invention aims to propose an arcing contact element which can be produced in a simple and inexpensive manner, while having an overall resistance improved compared to the prior art, in particular mechanically and electric, so as to increase the service life of the switchgear fitted therewith.
• this element for medium or high voltage electrical cut-off equipment, in particular for a circuit breaker, this element being intended to be attached to a respectively fixed or mobile support belonging to a contact assembly. of this switchgear, this element being able to occupy, in service, a first position in which it is in contact with another contact element, as well as a second position in which it is separated from this other contact element in order allow the interruption of the current in the apparatus, this contact element comprising carbon fibers embedded in a matrix which comprises at least one electrically conductive material, characterized in that the matrix comprising at least one conductive material also comprises carbon , in the form of graphite.
• this electrically conductive material has an electrical resistivity of less than 200 ⁇ .cm.
• the presence of carbon fibers gives good mechanical strength, as well as satisfactory resilience, to the arcing contact element of the invention. Furthermore, the latter has a satisfactory electrical and thermal conductivity, thanks to the presence of the aforementioned matrix.
• the presence of the graphite matrix gives a low coefficient of friction to the contact element of the invention. Furthermore, this matrix provides a filling function, namely that it prevents an excessive quantity of conductive material from being present, which would entail risks of massive vaporization of the latter.
• This matrix thus makes it possible to retain the conductive material, within graphite cells. Thus, even though this material is in the liquid or vaporized state, it is retained within these cells, so that it has little tendency to be evacuated therefrom.
• these fibers are arranged in a tight braiding, with small gaps, in order to satisfactorily retain the conductive material, in the event of fusion thereof.
• the carbon fibers comprise long fibers arranged in a three-dimensional braiding.
• such long fibers have a ratio between their length and their diameter which is greater than 100, more particularly 1,000, even more particularly 10,000. This measure makes it possible to further improve the mechanical strength of the contact element, while imparting satisfactory homogeneity to the mechanical properties of the arcing contact element.
• the conductive material represents, by weight, between 10 and 50%, preferably between 20 and 40%, of the contact element.
• the particle size of the conductive material is between 0.1 and 200 micrometers, preferably between 1 and 50 micrometers.
• the fibers represent, by weight, between 1 and 90%, preferably between 30 and 80%, of the arcing contact element.
• the conductive material is copper.
• the diameter of these carbon fibers is between 0.1 and 50 micrometers, preferably between 2 and 15 micrometers.
• the arcing contact element is substantially made up of carbon fibers and of the matrix comprising at least one conductive material.
• the invention also relates to a method of manufacturing an arcing contact element as defined above, characterized in that it comprises the following stages:
• the carbon fibers are first partially impregnated with carbon, so as to form a primary carbon matrix having intermediate spaces, then these intermediate spaces are filled with the conductive material , so as to produce a secondary matrix formed of this conductive material.
• the subject of the invention is also a contact assembly for electrical medium or high voltage cut-off equipment, in particular for circuit breaker, comprising a fixed contact member and a movable contact member, each member being provided with a contact element d respective arc, these two contact elements being able to present a first mutual contact position and a second mutual cut-off position, in which they are separated from each other, characterized in that at least one element of arcing contact is as described above.
• the invention finally relates to an electric switchgear for medium or high voltage, in particular a circuit breaker, comprising a breaking chamber provided with a contact assembly, characterized in that this contact assembly is as defined above above.
• FIG. 1 is a longitudinal sectional view illustrating a switching chamber belonging to an electrical switching device according to the invention
• - Figure 2 is a schematic view illustrating a first step in a method of manufacturing an arc contact element belonging to the switching device of Figure 1
• - Figures 3 and 4 are micrographic views illustrating the following two steps of this manufacturing process.
• FIG. 1 illustrates a switching chamber 2 belonging to an electrical switchgear for medium or high voltage, not shown, which is for example a circuit breaker.
• the arrangement of this breaking chamber is conventional, so that it will be described briefly in the following.
• This chamber 2 is delimited by an insulating cylindrical envelope 4 and is filled with an insulating gas such as, for example, SF6. It comprises first of all a fixed contact member, assigned as a whole by the reference 6. This member 6 comprises, in known manner, a support 8, on which an arcing contact element 10 is mounted.
• an insulating gas such as, for example, SF6.
• connection between the support 8 and the contact element 10 is provided for example by any mechanical means, such as screwing or pinning, or even any welding means with or without filler metal.
• the contact member 6, which is electrically connected to an electrical connection, not shown, is also provided with a permanent current contact 12.
• the breaking chamber 2 also contains a movable contact member, designated as a whole by the reference 14. This comprises a support 16, on which a movable contact element 18 is attached.
• connection between the support 16 and the contact element 18 is provided in a similar manner to the connection mentioned above, occurring between the support 8 and the element 10.
• This movable member 14, which is also connected to another electrical connection, not shown, is equipped with a permanent current contact 20.
• the latter supports an insulating nozzle or nozzle 22, delimiting an annular channel 24.
• the movable member 14 can be moved between a contact position, shown on the left in FIG. 1, in which the elements 10 and 18 are in mutual contact, as well as a cut-off position, represented on the right of this figure 1, in which these two elements 10 and 18 are mutually separated.
• FIGS. 2 to 4 illustrate three stages in the manufacture of an arcing contact element 10 or 18 fitted to the electrical equipment, the interrupting chamber 2 of which is shown in FIG. 1.
• the three-dimensional braiding 28 is produced from long carbon fibers within the meaning of the invention mentioned above, and it is inevitable that a non-negligible quantity of these long fibers is altered by breakage or separation of fibers during the formation of braiding. Consequently, the material obtained in braided carbon fibers consists on the one hand of long carbon fibers and on the other hand of carbon fibers which are no longer long fibers within the meaning of the invention.
• the braiding 28 is then a question of infiltrating the carbon fibers 26 which constitute it.
• the latter are impregnated with carbon, in the form of graphite, so as to form a primary matrix 30 extending mainly around the fibers 26.
• the primary matrix 30 defines intermediate spaces 32, forming free zones which are not filled with carbon.
• This second step, described with reference to FIG. 3, is also known as such. Thus, it is notably explained in the above work, which was previously mentioned with reference to the step of FIG. 2.
• an electrically conductive material such as copper. The latter then occupies the intermediate spaces 32, initially left free in the primary matrix 30.
• a secondary matrix 34 constituting, with the primary matrix 30, a main matrix in which the carbon fibers 26 are embedded.
• This third and last step of the process for manufacturing the contact element 10 or 18 is also known as such. It should be noted that, during the step of FIG. 3, the primary matrix 30 is formed so that the volume of the intermediate spaces 32 allows the copper matrix 34 to represent, for example, between 20 and 40% by weight of the contact element considered.
• This step is also carried out in a manner known per se, by any suitable machining means . These include turning, milling or electro-erosion.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Composite Materials (AREA)
• Materials Engineering (AREA)
• Contacts (AREA)
• Circuit Breakers (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 2002
  • 2002-07-05 FR FR0208498A patent/FR2842019B1/fr not_active Expired - Fee Related
• 2003
  • 2003-07-03 EP EP03762733A patent/EP1520282A2/de not_active Withdrawn
  • 2003-07-03 CA CA002491510A patent/CA2491510A1/en not_active Abandoned
  • 2003-07-03 US US10/520,645 patent/US20050236370A1/en not_active Abandoned
  • 2003-07-03 CN CNB038211432A patent/CN100367424C/zh not_active Expired - Fee Related
  • 2003-07-03 AU AU2003260652A patent/AU2003260652A1/en not_active Abandoned
  • 2003-07-03 WO PCT/FR2003/002069 patent/WO2004006275A2/fr not_active Ceased
  • 2003-07-03 JP JP2004518869A patent/JP2005532662A/ja active Pending

Non-Patent Citations (1)

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