FR2618018A1 - SELF-PNEUMATIC COMPRESSED GAS CIRCUIT BREAKER - Google Patents

Abstract

Self-pneumatic compressed gas circuit breaker characterized in that a cylinder forming a screen 21 completely separates, during the breaking of short circuits, the space 19 outside the external contacts 4, 5 from the space of the arcing contacts 12 , 13 interior, and in that the cylinder forming the screen 21 is located outside the breaking path for all other circuit breaker positions and breaking operations.

Description

The invention relates to an auto-pneumatic compressed gas circuit breaker

  comprising external contacts for service currents, comprising internal arcing contacts, delayed opening, an arc blowing device formed between the arcing contacts as well as a screen

  protection of the space of external contacts.

  In circuit breakers of this type, the blowing of the arc gives rise to an ionized plasma cloud during cutting. During breaking, large breaking currents occurring as a result of short circuits, this electrically conductive plasma cloud can propagate uncontrollably inside the circuit breaker and be responsible for discharges between the metal parts, which can damage fragile surfaces, for example greased contacts. This problem is particularly serious when it is the silver surfaces of the external contacts intended for service currents.

who are under attack.

  Solutions are known to overcome these problems which consist in giving a particular shape to the nozzle or in providing screens. However, a protection of this type of contacts intended for service currents is imperfect and presents

  disadvantages in different ways.

  EP-00 16 983 discloses, for example, a self-pneumatic compressed gas circuit breaker in which a cylindrical screen made of insulating material is integral with the nozzle intended for blowing the arc, and slides in a gas-tight manner in a second fixed cylinder - forming a screen. A total screen is thus obtained between the arcing contacts and the contacts of the operating currents, and the arcing plasma.

  is kept completely away from endangered areas.

  The drawback of this solution lies above all in the fact that in the open position of the contacts, the path of the gas between the metallic parts which conduct electricity, is bridged by a solid insulating body. The surface of such an insulating body is damaged by heat

  following short-circuit current cuts

  circuit. This can give rise to leakage currents or even bypass. The other disadvantages of this solution lie in the complex manufacture of the nozzle body with expensive material, in the large mass to be displaced from such a nozzle as well as in the forces transmitted on its fastening elements, and in the problems posed by the gas tight guide of the nozzle in the

screen cylinder.

  There seem to be conflicting demands on the solution to these problems. On the one hand, the path of the gas between the open contacts, conductors of electricity, must be free of insulating parts, on the other hand the space of the arcing contacts must be separated as gas tight as possible of the space of the contacts which conduct the operating voltage, when switching off

short circuit currents.

  The object of the invention is to propose an auto-pneumatic compressed gas circuit breaker in which the free path of the gas from the open circuit breaker does not include insulating elements, but in which the contacts of the service currents are completely protected from the plasma cloud which is form

  when breaking short-circuit currents.

  This object is achieved according to the invention in that a screen cylinder completely separates, during the breaking of short circuits, the external space of the external contacts from the space of the internal arcing contacts, and in that the screen cylinder is located outside the cutout path for all other circuit breaker positions and cutoff operations. Thanks to the solution according to the invention, the advantages of circuit breakers which have a gas path without an insulating element are combined with the advantages of the circuit breaker known by the state of the

technical.

  Various other features of the invention

  emerge from the detailed description which follows. A

  embodiment of the invention is shown in

  by way of nonlimiting example to the appended drawings.

  Figure 1 is a sectional view of the breaking chamber in the engaged position of the circuit breaker; Figure 2 is a sectional view of the breaking chamber in the cut position of the circuit breaker; Figure 3 is a sectional view of the chamber

  cut-off during the cut-off of a short- current.

  circuit; and Figure 3a shows a detail of a variant of the

  cylinder mechanism forming a screen.

  Figure 1 shows the section through the breaking chamber of a power circuit breaker which is surrounded by an external ceramic insulator. Circuit breakers with ceramic insulators of this type are

  generally used outdoors. This representation

  tation is given by way of example; it is understood that the configuration according to the invention of the cut-off path of the self-pneumatic compressed gas circuit breaker comprising a movable screen, can also be used for other construction solutions, for example in metal-shielded cut-off devices in which the cutting path is placed in an insulated metal enclosure, and which are generally installed in premises. Similarly, the horizontal mounting of the circuit breaker is given only as an example; vertical or oblique mounting is just as possible.- In the closed position of the circuit breaker, shown in Figure 1, the current flows almost exclusively through an external path which is formed by the following elements of the circuit breaker: a fixed support 1 which is electrically connected by one or more sliding contact (s) 2, to the outer wall of a mobile pump cylinder 3. This wall is fixedly assembled to a contact 4 which is also mobile. In the closed state of the circuit breaker, this movable contact 4 is engaged with a fixed contact 5 which is assembled to a fixed housing 6. An internal current path is formed by the following elements: the internal wall of the movable pump cylinder 3 which is integral with a movable arcing contact 12. In the closed state of the circuit breaker, the movable arcing contact 12 is engaged with a fixed arcing contact 13. This fixed arcing contact 13 is carried by a support 14 which is assembled to the fixed housing 6. When the circuit breaker is closed, the proportion of current flowing through the interior path is very small

  due to the known skin effect.

  When the operating currents and short-circuit currents are cut, a drive system, not shown, acts on a rod 7 and moves the movable pump cylinder 3 downwards at the same time as the movable contact 4, a nozzle. in insulating material 11, the movable arcing contact 12 and an arcing electrode, against a fixed piston 8. During this breaking movement, the external contacts 4 and 5 which carry most of the current by far, begin by separating one after the other, so that the current is displaced towards the internal path, and a little later the internal arcing contacts 12 and 13 separate. The arc formed between the movable U-shaped arcing contact 12 and the tip of the fixed arcing contact 13 switches due to blowing, after a short time, on the arcing electrode 15 disposed inside the movable arcing contact 12. This blowing is carried out by means of the fixed piston 8 and the pump cylinder 3 moving downwards, so that the insulating gas is compressed in the enclosure of the pump 9 and sent through the channels 10 of the nozzle. of insulating material 11. The high speed of flow of the insulating gas centers and cools the arc, so that it goes out for small currents, just after the separation of the contacts and for large currents, after reaching the

final position.

  FIG. 2 represents the breaking chamber in the cut position. It can be seen that between the contacts 4 and 5 separated, under voltage, as well as between the arcing contacts 12 and 13, there are paths of insulating gas in which the parts of the nozzle

  insulating material 12 penetrates only slightly.

  FIG. 3 shows a breaking chamber during the breaking of a large current such as it occurs in the event of a short circuit. In the position shown of the circuit breaker, the external contacts 4 and 5 are already separated from each other, the arcing contacts 12 and 13 are no longer engaged and the switching of the arcing 16 on the arc electrode 15 occurred as a result of blowing. In the representation of FIG. 3, the cylinder forming

  screen 21 is in its screen position.

  The screen cylinder 21 which is made of an insulating material resistant to high temperatures, for example Teflon, is guided in the cylindrical interior space of the housing 6 by means of a guide ring 22 which is mounted in a shoulder, at the lower end of the cylindrical housing 6. The screen cylinder 21 is fixedly assembled to a soft iron ring 23, at its end remote from the nozzle of insulating material 11. This movable soft iron ring 23 faces axially a fixed soft iron ring 26, integral from the housing 6 the soft iron rings 23, 26 can be made of laminated sheets. A return spring 25 is mounted between the shoulder, at the lower end of the cylindrical interior space of the

  fixed housing 6, and the movable soft iron ring 23.

  The soft iron ring 23 with the screen cylinder 21 can take two positions: The first position is taken by the soft iron ring 23 and the screen cylinder 21 when no significant current crosses the internal current path comprising the arcing contacts 12 and 13. This is the case when the circuit breaker is closed, when, as a result of the film effect cited, only weak currents pass through the interior path (FIG. 1). In the event of a power failure in normal service, the switched current, following the opening of the external contacts 4 and 5, on the internal current path, is not enough either to produce a magnetic field strong enough for there is a repulsion effect between the two soft iron rings 25 and 26, an effect which must be sufficient to separate them against

spring force 25.

  The second position of the movable soft iron ring 23 and consequently of the screen cylinder 21 is taken during the breaking of currents which have the intensity of the short-circuit currents. During a cut of this type, the current switches completely from the external current path to the internal path, at the moment of the separation of the external contacts 4 and 5. The electromagnetic field which forms around this internal current path, causes a magnetic flux. in the same direction in the soft iron rings 23 and 26, which has the effect of separating them against the force of the return spring 25. The magnetic repulsion force is maintained even when the arcing contacts 12 and 13 separated, but the current flows through the arc

  16, from the arc electrode 15 to the fixed arc contact 13.

  This configuration has the particular advantage of allowing, thanks to the geometric configuration, to precisely adapt the materials and the force of the return spring 25 to the intensity for which the screen cylinder 21 must assume its screen position. As a general rule, these will be currents whose intensities lie in the field of short-circuit currents since for these intensities only it is necessary to have a screen between the external zone of the contacts and the internal enclosure. The repulsion force between the soft iron rings 23 and 26 in the event of a short circuit must be adjusted in such a way that the soft iron ring 23 movable with the screen cylinder is accelerated strong enough to follow the nozzle of insulating material 11 which moves away, pass over it and strike an elastic pad 27 which is placed on a

  shoulder of the insulating material nozzle 11.

2 6 18 01 8

  The space filled with arc plasma is thus surrounded by the screen cylinder 21 and separated from the space 19

  outside by cold gas, clean.

  After the arc 16 has extinguished, the electromagnetic field disappears and the movable soft iron ring 23 is pushed back into the rest position by the

return spring 25.

  Advantageously, this movement of

  recall is delayed by a braking device.

  This is justified by the strong overpressure of hot gases, containing impurities, which prevails in the arc extinction journey as well as in enclosure 18. The aim is to prevent these ionized gases from propagating in the entire volume of the circuit breaker after the cut. This return delay should advantageously take sufficient time to allow the overpressure to disappear following the cooling of the gas, or

  by flow through the inner enclosure 18.

  This delay of the return movement can be obtained by means of a pneumatic braking device. Figures 1 to 3 show such a device. The pneumatic braking device encloses a space 32 which is formed by the fixed housing 6 with the shoulder containing the guide ring 22 and delimiting the space 32, as well as the screen cylinder 21 with the movable soft iron ring 23 serving movable delimitation space 32. The movable part is slidingly guided in a gas-tight manner in the fixed part. The space 32 included between them increases as a result of the return movement, so that a depression is established with respect to the external space 19. Small ventilation holes, not shown, made in the lower part of the space 32, lead to the external space 19 and have dimensions such that the desired delay occurs in the return movement, due to the slow suppression of depression. During the return movement, the movable soft iron ring 23 passes over another series of bores 30. A rapid ventilation takes place which is accompanied by an acceleration of the return movement. In order not to hinder the movement of the screen cylinder 21 in the screen position, a series of radial bores 28 with non-return valves 29 is provided in the lower part of the space 32. These provide a air purge in case

  overpressure and are closed in the event of depression.

  The following specific variants are still possible: For circuit breakers mounted vertically and obliquely, the return spring 25 must be reduced according to the self-weight of the cylinder

forming a screen 21.

  In their simplest embodiment, the soft iron rings 23 and 26 are rectangular. A slowly decreasing repulsive force during movement can be obtained by giving the soft iron rings 23 and 26 a roughly triangular cross section, the hypotheses of these triangles being superimposed in the rest position of the screen cylinder 21. The Figure 3 shows this configuration. The most advantageous shape is that of an elongated triangle so that when the soft iron rings 23 and 26 are superimposed, they form in cross section an elongated rectangle whose diagonals are represented by the hypothenuses. On the periphery of the nozzle of insulating material 11, there is advantageously disposed a gasket 31 which ensures gas tightness between the nozzle of insulating material 11 and the cylinder forming a screen 21 in its screen position. Given the low friction, it is advantageous for the seal 31 to be a labyrinth seal. At the lower end of the space 32, another elastic end stop 24 can be arranged, in order to prevent the movable soft iron ring 23 from coming hard against the shoulder of the space

  cylindrical interior of the fixed housing 6.

  The non-return valves 29 of the radial orifices 28 can be produced in a simple elastic plastic ring which is of a cost

advantageous and effective.

  The hot gas containing impurities, discharged from the external enclosure 18 can pass through a

  filter before being sent to the outdoor area 19.

Claims (16)

  1. Self-pneumatic compressed gas circuit breaker comprising external contacts (4, 5) for service currents, comprising internal arcing contacts (12, 13), delayed opening, a device for blowing the arc formed between the arcing contacts (12, 13) as well as a shield for protecting the space of the outer contacts (4,), characterized in that a cylinder forming a shield   (21) completely separates, when cutting short-   circuits, the space (19) outside of the outside contacts (4,5) of the space of the airc contacts (12, 13) inside, and in that the screen cylinder (21) is located outside of the cutoff path for all other positions of the   circuit breaker and breaking operations.   2. Self-pneumatic compressed gas circuit breaker according to claim 1, characterized in that the screen cylinder (21) is mounted so as to be able to move outside the cutting path, and in that to cut the currents short-circuit, the screen cylinder (21) is brought by means of a mechanism into a position in which it concentrically surrounds the arc extinction path, closes it in a gas-tight manner by means of a nozzle of insulating material (11) and thus forms, with a fixed housing (6), an inner enclosure (18) through which the hot gas, containing impurities, is evacuated. 3. Self-pneumatic compressed gas circuit breaker   according to one of claims 1 or 2, characterized in   what a soft iron ring (26) fixes and a ring in 2 6I U 8   soft iron (23) movably assembled to the screen cylinder (21), are arranged concentrically around the internal path of the current, connected to the arcing contacts (12, 13), in that the current induces a magnetic field in the soft iron rings (23, 26), due to the switching on the internal current path of a short-circuit current greater than the operating current, following the opening of the external contacts (4, 5) , this magnetic field moving axially the soft iron ring (23) movable against the force of a return spring (25), at a speed greater than that at which the movable contact (4), the contact d the movable arc (12) and the isolation nozzle (11) are moved axially in their cut-off position by the circuit breaker mechanism.   4. Self-pneumatic compressed gas circuit breaker according to claim 3, characterized in that the soft iron rings (23, 26) have a roughly triangular cross section, the hypotheses of these triangles forming the diagonals of an elongated rectangle when the soft iron rings (23, 26) are superimposed in the retracted position of the screen cylinder (21).   5. Self-pneumatic compressed gas circuit breaker   according to one of claims 1 to 4, characterized in   what when breaking a short current   circuit, the screen cylinder (21) is pushed through a seal (31) disposed around the periphery of the insulating material nozzle (11), and is thus applied against a pad (27) elastic.   6. Self-pneumatic compressed gas circuit breaker according to claim 5, characterized in that the seal (31) disposed on the nozzle -2618018   insulating material (11) is a labyrinth seal. 7. Self-pneumatic compressed gas circuit breaker   according to one of claims 1 to 6, characterized in   that the return movement of the screen cylinder (21) in its initial position after the short-circuit current has been cut off, is effected by the action of a return spring (25) and in that this return movement is delayed by a braking device until the overpressure due to overheating of the   insulating gas under the effect of the arc, be removed.   8. Self-pneumatic compressed gas circuit breaker according to claim 7, characterized in that the device braking the return movement of the screen cylinder (21) is a device for pneumatic braking.   9. Self-pneumatic compressed gas circuit breaker comprising a pneumatic braking device according to claim 8, characterized in that the fixed cylindrical housing (6) comprising at its lower end a shoulder containing a guide ring (22), forms the part fixed of the braking device and in that the screen cylinder (21) with the movable soft iron ring (23) integral with the latter, forms the movable part of the braking device, the movable part being guided so as to slide in a gas-tight manner, in the fixed part, and the space (32) situated between them being enlarged due to the return movement and thus having a vacuum with respect to the external space (19), in that small ventilation holes lead to the lower part of the space (32) and have dimensions such that the desired delay in the return movement occurs, in that another series of holes (30) ensures a rapid ventilation in the middle part d e the space (32) after passage of the soft iron ring (23), and in that in the lower part of the space (32), are drilled (28) radial with non-return valves ( 29) which are open in the event of overpressure in the space (32), but closed in case of depression.   10. Self-pneumatic compressed gas circuit breaker comprising a pneumatic braking device according to claim 9, characterized in that the non-return valves (29) are formed by a ring elastic in plastic.   11. Self-pneumatic compressed gas circuit breaker comprising a pneumatic braking device according to claim 9 or 10, characterized in that a second elastic end stop (24) is   placed at the lower limit of the space (32).   12. Self-pneumatic compressed gas circuit breaker   according to one of claims 1 to 11, characterized in   that the hot, ionized gas evacuated from the interior enclosure (18) passes through a cooling device before being sent to the exterior space (19). 13. Self-pneumatic compressed gas circuit breaker   according to one of claims 1 to 12, characterized in   that the hot gas, containing impurities, evacuated from the interior enclosure (18), passes through a filter, before being sent to the exterior space (19). 14. Self-pneumatic compressed gas circuit breaker   according to one of claims 1 to 13, characterized in   that the screen cylinder (21) is made of an insulating material resistant to high temperatures. 15. Self-pneumatic compressed gas circuit breaker according to claim 14, characterized in that the   screen cylinder (21) is made of Teflon.   16. Self-compressed compressed gas circuit breaker   according to one of claims 1 to 15, characterized in   that the soft iron rings (23, 26) are laminated sheets.