EP1575067A1 - Pivoting earthing switch with direct insertion and simple movement - Google Patents

Abstract

The switch has a fixed contact (4) with smaller dimension and electrically connected to a movable contact that has curved arms (2, 3) forming a branch. The contact (4) is engaged between a pair of fingers (21, 31), in closing position of the switch. A clevis and a spacer are connected to ends of the arms to permit lever effect that amplifies electro-dynamic pinch-off exerted on the contact (4) by the fingers.

Description

The invention relates to a disconnector comprising a pivoting movable contact assembly around an axis of rotation and an arranged fixed contact to be electrically connected to an end of said mobile contact set when this set is brought into the closed position of the disconnector.

The invention relates more particularly to a earthing switch intended for use in transmission and distribution facilities of high voltage electrical energy in the open air and even more particularly an earthing switch says to direct insertion and simple movement in which movement needed to connect the moving contact assembly with the fixed contact is done by a simple rotation of this set mobile. The mobile contact assembly is generally called "mobile contact", and for the sake of simplicity we will use this name in the description following.

The short circuit current value that a earthing switch is able to tolerate depends directly from overheating (the increase in temperature relative to the ambient temperature) in short circuit conditions and, in particular, overheating of the contact area between the contact fixed and moving contact. For example, it can be specified for a disconnector to be able to withstand a short-circuit current in the order of 50 kA for a second. The behavior of the disconnector of earth is all the better than the pressure of contact between the fixed and mobile contacts is high.

Another characteristic of this type of disconnectors is their behavior with respect to electromagnetic solicitations that tend usually to open the electrical circuit whose earthing switch is one of the components. If that occurs, the earthing switch contacts have tendency to melt.

In general, the best solutions pre-existing conditions concerning the arrangement of a disconnecting of earth use high contact pressures in the case of ground disconnectors with motion simple, or a mechanical separation between the mechanism rotation of the disconnector and the contact system, in the case of so-called dual earthing disconnectors movement. These two solutions are not really satisfactory because of their mechanical complexity and as a result of their high cost.

Until now, a good electrical contact between the contacts of a disconnector to simple movement is obtained using components very rigid elastics, for example springs, which achieve a high contact pressure but which induce high maneuvering torques even when the disconnector is not energized (these couples increasing proportionally to the nominal voltage of the disconnector). Good electrical contact between contacts of a dual-action earthing switch is obtained using complex mechanisms articulation of the movable contact.

US-4490595 discloses a disconnector of ground with direct insertion and simple movement in which has sought to minimize the impact of electromagnetic forces acting on the fixed contacts and mobile especially during the passage of a current of short circuit in the contacts. An insulating stop blocks rotation of the swivel knife of mobile contact, and prevents this knife from being able to go out in the direction beyond the slit spared between two parallel flexible arms ensuring the role fixed contact. This fixed contact is electrically connected to a metal shell to the potential of the Earth.

This configuration implies that the contact mobile is electrically connected to a phase of the line, which has drawbacks in particular for ensure control of the swivel knife and to ensure the arrangement of the knife in the open position without to pose problems of dielectric strength. On the other hand, the two flexible arms of the fixed contact must be sufficiently long and positioned to create when the disconnector is closed a loop current which allows to exercise on the knife a force which maintains support against the insulating stop. Such sizing of the fixed contact requires a distance of significant dielectric isolation in the space between the knife pivot and the fixed contact.

In addition, an electrodynamic pinch of the knife is created by the parallel currents that circulate in the two flexible arms of the fixed contact and that generate a force of mutual attraction between these two arms. It should be noted that with such configuration, the electrodynamic pinch force of the knife remains lower than the force of attraction which tends to bring the two arms closer together Flexible.

A first objective of the present invention is to realize a disconnecting earthing switch direct and simple movement in which the part mobile can be electrically connected to the earth, and in which the fixed part is of dimensions relatively small compared to the moving part to ensure a dielectric isolation distance relatively low between the fixed and mobile parts in the open position of the disconnector.

A second objective of the present invention is to exploit the electromagnetic forces that are exercised in a disconnecting earthing switch direct and simple movement when passing a short-circuit current in the contacts, for reinforce the maintenance of the earthing switch in its fully closed position, and to strengthen the mutual contact pressure between the fixed and mobile thanks to an electrodynamic pinch effect provided by the amplification by a leverage effect of the mutual force of attraction that tends to bring between them two parallel arms of the moving contact.

Another object of the present invention is to propose a direct insertion earthing switch and simple movement that can be put in motion using a low torque command, and which allows to do without springs to ensure the desired contact pressure between the elements of fixed and mobile contact.

For this purpose, the subject of the invention is a earthing switch as defined in the preamble, characterized in that said moving contact assembly includes two electrically conductive arms substantially parallel which are bent to form each at least approximately one L, each arm elbow comprising at least one flexible finger extending at least on the shortest branch of the L, the contact stationary being so arranged as to be engaged between minus a pair of flexible fingers in the position of closing of the disconnector, and in that means of join are mechanically connected at both ends of the two arms bent on the branches shorter Ls to allow for leverage which amplifies the electrodynamic pinch exerted on the fixed contact by the flexible fingers when a short circuit current or fault current travels the arms bent.

   où l _c est la longueur totale de circuit d'un conducteur, l _i est la longueur d'un tronçon élémentaire rectiligne du circuit d'un conducteur, et f _i est la force d'attraction mutuelle de deux tronçons élémentaires parallèles (l _i et f _i correspondent respectivement à dl et df pour un tronçon élémentaire).The construction of an earthing switch according to the invention exploits the well-known electrotechnical principle of the elementary force which is exerted on a conductor when it is traversed by a current and when it is subjected to an induction field. On the basis of this principle, referring to FIG. 1, it is known that two parallel conductive elements d1 traversed in the same direction by a current I undergo a pulling force df which tends to bring them closer to one another. other, and that is proportional to the square of the current. Considering an electrical circuit consisting of two identical non-rectilinear conductors arranged substantially parallel to each other and traversed by the same current I, these two conductors attract each other with a force F _c which verifies the following relation:

where l _c is the total circuit length of a conductor, l _i is the length of a straight elementary section of the circuit of a conductor, and f _i is the force of mutual attraction of two parallel elementary segments ( l _i and f _i respectively correspond to dl and df for an elementary section).

We also know, referring to Figure 2, that each element of a loop circuit (like a coil) traversed by a current I undergoes a force df tending to separate the loop of the electric circuit.

When the earthing switch is closed and a short-circuit current passes through the fixed contact and the parallel arms in L of the moving contact, it is creates electromagnetic forces that tend to bring the two parts of the arm closer to one another L between which is arranged the fixed contact, which is used to get a pinch effect of fixed contact between the ends of the two arms of the mobile contact. At each L-arm of the mobile contact, forces are also created electromagnetic that tend to spread the loop partial circuit formed by this arm. Because the two L-shaped arms forming the moving contact are mounted to rotate integrally about the axis rotation of this contact, the resultant of these forces electromagnetic tends to rotate the contact mobile towards the side of the L that is opposed to the branches the shorter ones. This effect is used to maintain the fixed contact in support in the bottom of the slot formed by the spacer and the second parts of arm of the moving contact so that the disconnector of earth remains stuck in its closed position.

Pinch and blocking forces of the fixed contact in the slot of the moving contact, which are dynamic forces in that they do not occur in the presence of a short circuit, are all the more important that the circulating short circuit current in contacts is high. So we understand that after the closing of the disconnector according to the invention, the force maximum contact between the fixed contact and the contact mobile is only provided during a short circuit. This allows to use, for the current operations opening and closing of the disconnector, a low torque drive mechanism for the rotational drive of the movable contact.

• chaque bras coudé en L est fendu longitudinalement sur les deux branches du L pour former les doigts flexibles sur la majeure partie d'un bras, de façon à obtenir encore plus de souplesse dans l'écartement des extrémités des doigts et assurer un contact électrique optimal entre le contact fixe et le contact mobile du sectionneur ;
• les moyens de jointure mécaniquement reliés aux deux extrémités respectives des deux bras coudés comprennent une chape rigide assurant la fonction d'un noeud de charnière pour une pince électrodynamique dont les leviers sont constitués par les doigts flexibles des deux bras, cette chape comprenant une plaque rectangulaire dont une face présente deux épaulements parallèles sur deux bords opposés, chaque épaulement comportant au moins deux trous pénétrés chacun par une tige apte à assurer une liaison mécanique entre la chape et un doigt flexible ;
• un élément de butée électriquement isolant porté par le contact mobile est constitué par une barre en matériau isolant qui est fixée au milieu de la plaque de la chape parallèlement aux deux épaulements, cette barre étant prise en étau par les doigts flexibles des deux bras parallèles dans la position ouverte du sectionneur ;
• des plaques métalliques sont fixées aux doigts flexibles des deux bras parallèles, chaque plaque métallique présentant une extrémité biseautée ou arrondie du côté par lequel le contact fixe est apte à être engagé dans le contact mobile, et l'écartement entre deux plaques métalliques en vis à vis dans la position ouverte du sectionneur est inférieur à la largeur du contact fixe ;
• les deux bras parallèles sont prolongés axialement sur leurs branches les plus longues par une tige conductrice montée rotative autour de l'axe de rotation de l'ensemble de contact mobile pivotant. D'autres types ou modes de réalisation d'un sectionneur de terre selon l'invention sont décrits plus en détail dans la description qui suit. Un premier type de réalisation est décrit plus en détail et est illustré par les dessins des figures 3 à 5. Un second type de réalisation englobant le mode de réalisation avantageux résumé précédemment est aussi décrit plus en détail et est illustré par les dessins des figures 6 à 10.Les figures 1 et 2 illustrent le principe électrotechnique de la force élémentaire exploité par l'invention.
• La figure 3 montre une vue partielle en perspective d'un sectionneur de terre selon l'invention dans un premier type de réalisation.
• La figure 4 montre une vue en coupe longitudinale du sectionneur de terre de la figure 3, selon un plan parallèle à un bras en L du sectionneur.
• La figure 5 montre une vue partielle de dessus du sectionneur de terre de la figure 3.
• La figure 6 représente schématiquement une vue partielle de dessus d'un sectionneur de terre selon l'invention dans un second type de réalisation, et illustre le principe du pincement électrodynamique amplifié par un effet de levier.
• La figure 7 représente schématiquement une vue latérale du sectionneur de terre de la figure 6.
• La figure 7a représente très schématiquement une vue de dessus d'un élément visible latéralement sur la figure 7.
• La figure 8 montre une vue partielle en perspective d'un sectionneur de terre selon l'invention dans un mode de réalisation avantageux du second type.
• La figure 9 montre une vue partielle de dessus du sectionneur de terre de la figure 8.
• La figure 10 représente schématiquement un détail d'une variante au sectionneur de terre de la figure 9.

In an advantageous embodiment, a disconnector according to the invention has the following particularities:

• each L-shaped arm is split longitudinally on the two limbs of the L to form the flexible fingers over most of an arm, so as to obtain even more flexibility in the spacing of the ends of the fingers and to ensure optimum electrical contact between the fixed contact and the moving contact of the disconnector;
• the joining means mechanically connected to the two respective ends of the two bent arms comprise a rigid yoke providing the function of a hinge node for an electrodynamic clamp whose levers are constituted by the flexible fingers of the two arms, said yoke comprising a rectangular plate one face has two parallel shoulders on two opposite edges, each shoulder comprising at least two holes each penetrated by a rod adapted to provide a mechanical connection between the yoke and a flexible finger;
• an electrically insulating abutment element carried by the movable contact is constituted by a bar of insulating material which is fixed in the middle of the yoke plate parallel to the two shoulders, this bar being gripped by the flexible fingers of the two parallel arms in the open position of the disconnector;
• metal plates are attached to the flexible fingers of the two parallel arms, each metal plate having a beveled or rounded end on the side by which the fixed contact is adapted to be engaged in the moving contact, and the spacing between two metal plates screwed to screw in the open position of the disconnector is less than the width of the fixed contact;
• the two parallel arms are extended axially on their longest branches by a conductive rod rotatably mounted about the axis of rotation of the movable movable contact assembly. Other types or embodiments of an earthing switch according to the invention are described in more detail in the description which follows. A first embodiment is described in more detail and is illustrated by the drawings of Figures 3 to 5. A second embodiment including the previously summarized advantageous embodiment is also described in more detail and is illustrated by the drawings of Figs. Figures 1 and 2 illustrate the electrotechnical principle of the elementary force used by the invention.
• Figure 3 shows a partial perspective view of an earthing switch according to the invention in a first type of embodiment.
• Figure 4 shows a longitudinal sectional view of the earthing switch of Figure 3, in a plane parallel to an L-arm of the disconnector.
• FIG. 5 shows a partial view from above of the earthing switch of FIG. 3.
• FIG. 6 schematically represents a partial top view of an earthing switch according to the invention in a second type of embodiment, and illustrates the principle of electrodynamic clamping amplified by a lever effect.
• FIG. 7 schematically represents a side view of the earthing switch of FIG. 6.
• FIG. 7a schematically represents a view from above of a visible element laterally in FIG. 7.
• Figure 8 shows a partial perspective view of an earthing switch according to the invention in an advantageous embodiment of the second type.
• FIG. 9 shows a partial view from above of the earthing switch of FIG. 8.
• FIG. 10 schematically represents a detail of an alternative to the earthing switch of FIG. 9.

An earthing switch according to the invention for high voltage applications, is a disconnector said to direct insertion and simple movement. It is formed by a first part movable in rotation and by a second fixed part.

More particularly, as visible on FIGS. 3 to 5, the moving part of the earthing switch is a contact 1 mounted on a conductive rod pivoting about an axis of rotation (not shown) and connected to the potential of the earth. This mobile contact 1 includes two parallel metal arms 2,3 angled to each form an L, and is able to rotate about 90 ° around the axis of rotation that is located in the axial extension of the longest branch L-arms. The mobile contact 1 is connected electrically to the potential of the earth in its section lower and more precisely near the axis area rotation, while the upper section of the mobile contact (the shortest branch of the arms in L) makes the electrical contact with the fixed part of the switch. This fixed part of the disconnector is here a cylindrical contact 4 copper which is inserted between the two shorter branches of the L-arms of the movable contact 1 when the disconnector is moved from its open position to its position of closing. In FIGS. 3 to 5, the disconnector is shown in a fully closed position where the movable contact 1 is in electrical contact with the fixed contact 4.

As shown in Figures 3 and 4, each 2.3 L-shaped arm includes a first part of arm indicated by the references 2A, 3A which is formed by the longest branch of the L and stretching from the axis of rotation to a second part of arm 2B, 3B forming the shortest branch of L. second arm part indicated by the references 2B, 3B extends substantially transversely (perpendicularly) to the first arm part 2A, 3A.

In an earthing switch according to the invention, it is not essential that the two branches of an L be strictly rectilinear. In particular, it is possible to give the longest branch a slightly convex shape to accentuate curvature provided by the elbow of the L and possibly strengthen the electromagnetic forces of separation of the circuit, that is, the forces acting in the direction of the arrow F2 in FIG.

A hinge spacer E connects the free ends of the second arm portions 2B, 3B which are flexibly mounted in the sense that they can move independently. The spacer E defines with the second parts of arm 2B, 3B an open U-shaped slot indicated by 5 and more visible in Figure 5. This slot 5 Open U-shaped is the upper part of the mobile contact 1.

In the example of FIGS. 3 to 5, the seconds arm portions 2B, 3B are slotted longitudinally to define flexible contact fingers bringing even more flexibility in the elastic spacing. In particular, every second arm part is split to define two flexible fingers superimposed 2B1,2B2; 3B1,3B2 and the spacer E here comprises two bolts 6 crossing each of the two fingers juxtaposed, for example 2B1,3B1 or 2B2,3B2 and each blocked by a nut 7. There is left a weak game between each nut 7 and a flexible finger of a part 3B to allow a slight gap between the fingers of parts 2B and 3B when the fixed contact 4 is engaged between these fingers, to provide some contact pressure initial zero or low current. Once contact fixed end in abutment in the bottom of the slot 5, the spacer E provides a hinge function screws to screws fingertips flexible ends and allows the amplified electrodynamic pinch effect, when the second arm portions 2B, 3B tend to bring closer as explained later in this.

A cylindrical sleeve 8 made of electrically insulating surrounds the stem of each bolt 6 which ensures the independence of the structure bolt relative to a short-circuit current withstand.

In general, the minimum spacing allowed between the two arms 2,3 is set by a wedge 9 disposed between the two arms 2,3 of the movable contact 1 near the elbow. This wedge prevents both arms to get too close when the contact mobile is traversed by a current of short circuit.

Second arm parts (fingers flexible 2B1,2B2,3B1,3B2) are provided with plates of copper such as 10 promoting good contact electric with the fixed contact 4, and are also provided of skis made of insulating material such as 11 (more visible in Figures 4 and 5) extending longitudinally on the second arm parts and conferring a shape flared at the entrance to slot 5 to facilitate the insertion of the fixed contact 4 in the slot 5 when the closing of the earthing switch. Like this shown in FIGS. 4 and 5, each ski 11 extends in the extension of a copper plate 10 verses the back of the elbow of each L-shaped arm. Free spacing between two opposite plates 10 is slightly less than the contact diameter 4 cylindrical, so as to create the contact pressure initial mentioned above because of a slight elastic spacing of the second arm parts when the contact 4 is engaged between the plates 10.

Alternatively, the plates 10 may have a slightly larger thickness on the side of the spacer that on the ski side 11, so as to increase said elastic spacing and therefore also the contact pressure force in abutment and current no. It is also possible to dispense with the sleeve 8 insulation provided that plates 10 comprise they themselves on the side of the spacer elements stop, for example constituted on at least two plates opposite by two trapezoidal shoulders of each plate to stop the relative movement of the fixed contact 4 with respect to the slot 5. In this example, the two screw plates would form substantially a U-shaped slot, and the stop function for fixed contact would be provided by these plates. The air gap between the plates and the bolts of the spacer would allow the independence of the structure of the spacer in relation to a resistance to currents default. It must be understood from this example that stop element for the fixed contact is not necessarily electrically insulating in a earthing switch according to the invention.

It is not a priori indispensable, in a the earthing switch according to the invention, that the shortest branches of the cranked arms are slit longitudinally. For example, to increase the elasticity of these branches, it may be envisaged to locally reduce the thickness and / or height of metal plate of the arms in order to have only one finger or flexible part by arm.

Arm parts 2A, 3A of the movable contact are extended axially by a conductive rod 12 which is rotatably mounted at its free end around the axis of rotation of the movable contact 1. In position opening of the disconnector, the rod 12 is normally substantially horizontal. This rod is electrically connected to the earth via contacts sliders arranged at the axis of rotation of the mobile contact, or by wire ropes Flexible. The fixed contact 4, meanwhile, is fixed at the live bar which corresponds to the phase that can be grounded by the disconnector.

When closing the disconnector, the rod 12 with the L-shaped arms 2,3 are driven in rotation on an angle of about 90 ° to a substantially vertical position. When moving from mobile contact 1 during closing of the disconnector, the fixed contact 4 fits into the slot 5 while passing first at the elbows of the arms 2,3 between the skis 11 and finally comes to a stop against the spacer E formed. The cylindrical fixed contact 4 which extends axially towards the axis of rotation is then moderately pinched between the plates of copper 10 which are attached to the flexible fingers 2B1.3B1 and 2B2.3B2.

In the fully closed position of the disconnector, the conductive rod 12 with the first arm portions 2A, 3A is inclined with respect to a vertical position of no balance while the cylindrical fixed contact is arranged in the bottom of the open U-shaped slot, resting against the spacer; so even when it is not traveled by a short-circuit current, the disconnector earth is kept in its closed position without that it is necessary for the control mechanism of the disconnector to exert a couple in the direction of the closing on the mobile contact 1 pivoting.

In the foregoing, electromagnetic forces have been ignored to consider only a static mechanical pinch of the fixed contact under the effect of the elastic forces which tend to bring the second arm parts closer together because of their flexibility. But if we consider a closed state of the disconnector with passage of a short-circuit current or fault current, we must take into account the electrodynamic pinch effect provided by the electromagnetic forces. The pinching of the fixed contact by the flexible fingers then becomes much more important. By fault current is meant a current greater than the nominal current that may pass through the line conductor that supports the fixed contact 4. The spacer E, and in particular the bolts 6 associated with the nut 7, prevents any further separation of the ends of the flexible fingers once the fixed contact 4 positioned in abutment, and has a hinge role for an electrodynamic clamp whose two opposite levers are formed by the second arm portions 2B, 3B. This makes it possible to amplify at the fixed contact the force of mutual attraction as defined by the preceding relation (1) and which tends to bring the opposite levers of the clamp, in particular at the level of the flexible fingers. It is recalled that the mutual attraction force F _c is proportional to the square of the current flowing through the electrical circuit of the earthing switch.

This results in a pressure force of the flexible fingers against the fixed contact which is much greater than the force F _c due to the electrodynamic effect exerted on the second arm portions 2B, 3B. The fixed contact 4 being in abutment against the spacer, the pressure zones of the plates 10 against this contact are indeed closer to the axis of the spacer, that is to say the hinge of the clamp. This effect of amplification of the nip is particularly advantageous compared to a conventional device as shown in the document US-4490595, in which the parallel flexible arms do not act as levers of a "nut crack" type of pliers. made of the absence of hinge element at the end of the arms.

The line of axial alignment of the cylindrical fixed contact 4 with the axis of rotation of the moving contact is represented by the substantially vertical line lv in FIG. 3, and it can be seen in this figure that the rod 12 with the arm portions 2A , 3A extend in a longitudinal direction which is inclined relative to the line lv of a non-zero angle α of a few degrees. The fixed contact is then in abutment against the spacer E of the movable contact 1, ensuring the latter a stable closed position. When an electrical fault current flows through the arms 2,3, while the disconnector is in its closed position, electromagnetic attraction forces tend to bring together the second arm portions 2B, 3B which bear the opposing flexible fingers 2B1 , 3B1,2B2,3B2, resulting in an electrodynamic pinch of the fixed contact 4 between the two arms of the upper part of the movable contact. In this way, an optimal electrical contact is ensured between the fixed and mobile contacts 1.4 since the clamping force exerted is amplified relative to the electromagnetic attraction force F _c resulting on the two arms. The electrodynamic pinch effect is illustrated later in FIG. 6 in connection with another embodiment of an earthing switch according to the invention.

Since the spacer is electrically insulated relative to the fixed contact 4 by the sleeve 8, it it does not have to be thermally dimensioned to withstand short-circuit currents, which makes it independent of the amplitude of the short circuit current from a structural point of view and thermal. In addition, electromagnetic forces exerted in the direction of arrow F2 on the arms 2,3 cubits, which tend to bring the fixed contact 4 closer together of the spacer E with the effect of blocking the contact fixed 4 in the bottom of the slot 5 and so a accentuation of the maintenance of the disconnector in its closing position. It should be noted that this is possible because in the closed position the disconnector, the state of the rod carrying the contact mobile is inclined with respect to the position of the lv line, and the electrodynamic effect that tends to open the L-shaped circuit allows you to push the rod even further 12 with the arms bent in the direction of the closing of the switch. As noted above, these forces electromagnetic are dynamic and all the more strong that the short circuit current is high.

In Figure 6, the pinch principle electrodynamic amplified by leverage is illustrated for a second type of realization of a earthing switch according to the invention. The disconnector is shown schematically in partial view by the above. The conductive rod in the extension of the two parallel arms 2,3 and the wedge between arm in the vicinity of the elbow are not shown. The difference with the first type of embodiment in relationship with Figures 3 to 5 focuses on the joining means that are mechanically connected at the two respective ends of the two bent arms on the shortest branches of L. These means of join do not include in this case a spacer itself, in the sense that the rigid piece 13 is not interposed between the fingers flexible of the two parallel arms. But this piece 13 forms a kind of stirrup that presents a section substantially in C and which limits the spacing flexible fingers. This piece ensures the same function that the spacer E in the first type of production. In general, the joining means of these two types of realization ensure the function a hinge knot for an electrodynamic clamp whose levers are constituted by the fingers flexible of the two parallel arms. In the following, the piece 13 is called a screed.

In the closed position of the disconnector shown in FIG. 6, the fixed cylindrical contact 4 is engaged in abutment in the bottom of the U-shaped slot 5 which is defined by the yoke 13 and by the shorter branches of the two parallel bent arms. . For the sake of simplicity of the commentary of FIG. 6, only the parallel flexible fingers 21 and 31 will be considered for the explanation of the electrodynamic pinch, but the same explanation is valid for the other pairs of flexible fingers facing each other. When a current of short-circuit or fault current traverses the parallel flexible fingers 21 and 31, it results on the two fingers an electromagnetic attraction force F1 can be determined in the same way as the force F _c in the relation (1 ). This force of attraction F1 resulting from the summation of the elementary forces along the length of the flexible fingers returns to a unique force of attraction whose point of application on each finger is approximately half of the length of the finger. Thus, given the relatively long length of the flexible fingers in this second embodiment, the distance L1 between the point of application of F1 and the hinge node provided by the joining means is approximately equal to the length of the branch. shorter bent arms. This distance L1 is in any case much greater than the distance L2 between one or the other of the two points of application of the clamping force F3 of the fingers 21 and 31 on the fixed contact 4 and the hinge node.

As with any type of mechanical clamp "Nutcracker", here we have the relation F1 · L1 = F3 · L2, F3 = F1 · L1 / L2, which implies that an effect of lever amplifies with a coefficient equal to L1 / L2 the electromagnetic attraction force F1 exerted on the levers that are made up of flexible fingers parallel 21 and 31, to obtain the pinch force F3 exerted on the fixed contact 4.

The distance L2 can be modified to a certain extent by modifying the height of the insulating bar 19 which serves as a stop means for the fixed contact 4 and which is fixed inside the yoke 13 by a bolt associated with a nut 15 On the other hand, as explained further in the commentary of Figure 9, it should be understood that this bar 19 also serves as a stop means for limiting the approach of the flexible fingers facing in the open position of the disconnector. More specifically, in this open position, there is provided a prestressing force which tends to bring together the two parallel arms 2 and 3, and the bar 19 is clamped by the metal plates of each pair of flexible fingers screw to screw. This allows an increase in the static nip exerted on the fixed contact 4 in the absence of fault current in the disconnector. The width l ₂ of the fixed contact, in this case the diameter of the cylinder forming this contact, is therefore necessarily greater than the width of the bar 19.

In Figure 7, the earthing switch of the FIG. 6 is diagrammatically represented by a view lateral perpendicular to the plane formed by the arm elbow 3 of the disconnector. We can see a additional difference with the first type of in connection with FIGS. 3 to 5: shorter branches of each bent arm 2 or 3 are split longitudinally along their entire length to form flexible fingers, and the slots become extend beyond the elbow over much of the branch the longest of each arm. Fingers Flexible hoses are thus bent with the same shape in L that arms, which allows to increase the elasticity of each finger and increase the length effective leverage for amplification of the Electrodynamic pinching by a lever effect. This allows to obtain an electrodynamic clamp producing a contact pressure on the fixed contact 4 which is greater than that obtained in the first type of production.

The choice of one-piece type joining means such as clevis 13 makes it possible to make a knot of hinge more solid and a manufacturing cost less than the completion of a spacer E with bolts. In addition, it is advantageous in this mode of particular achievement of having three flexible fingers such as 31, 32 and 33 on each bent arm, so to further increase the elasticity of each finger, and to have a finger length that increases by closer to the inside of the elbow.

Wedge 9, located behind the bent arm 3 in this side view, is crossed by two bolts 16 and is free to slide between the two crank arms parallel with a little play along the stems of bolts. In Figure 7a, we can see that this little game is twice the spacing j. Function of this hold 9 has been explained previously for the first type of realization.

In Figure 8, an earthing switch of the second type according to the invention is shown in a view partial perspective. This embodiment advantageous is almost identical to the one with Figures 6 and 7, and corresponds exactly to one or other of the achievements represented respectively in Figures 9 and 10. There is shown here the bar 20 forming the single-phase driver of line that supports the fixed contact 4. The disconnector earth is in an intermediate open position, and the mobile contact assembly 1 is in the process of rotate to operate for example closing the switch.

A partial view from above of the disconnector FIG. 8 is shown in FIG. in a position where the moving contact assembly is about to come connect with the fixed contact 4. Shim 9 is not shown in this view. To the difference in embodiment with respect to the Figures 6 and 7, the holes 18 of the shoulders of the clevis 13 do not have threads and are therefore not not intended for tightening a bolt. The screed 13 includes a rectangular 13C plate whose face inside the clevis has two shoulders 13A and 13B parallels on the two opposite edges that are intended to ensure a mechanical connection with the flexible fingers and their metal plates 10 '. Each shoulder 13A or 13B has three holes 18 each penetrated by a rod 14 able to ensure this mechanical connection between the clevis and a finger such as 21 or 31.

A sleeve of insulating material 24 is interposed between the wall of a hole 18 and the rod 14 which enters this hole. The portion of the rod that enters the hole 18 is not threaded and is constituted by the end of a bolt that allows the clamping of a plate 10 'against a finger such as 21 or 31 in combination with means The open U-shaped slot has a flared inlet which is formed by the metal plates 10 ', each plate having a tapered end at the entrance to the slot. Each plate has near its beveled end a threaded hole for fixing the plate on an arm 2 or 3 by means of a bolt 17. It is visible that the gap ₁ between two plates 10 'opposite, in the open position of the disconnector, is less than the width of the fixed contact 4.

The clamping means 25 have an abutment member arranged to limit to a predetermined distance d the sliding of the rod 14 in said insulating sleeve 24 when closing the disconnector in the presence of a strong current. This predetermined distance is close to the amplitude e of separation of a flexible finger defined as half of the difference between the spacing l ₁ and the width l ₂ of the fixed contact 4. It is indeed the following relation: e = 0.5 · (l ₁ - l ₂ ).

The width of the bar 19 determines the spacing l ₁ between two plates 10 'facing. The bar 19 is preferably made of the same electrically insulating material, and here has portions that have a substantially rectangular section to form a stop element 8 'for the fixed contact 4. However, an insulating bar only with a cross section. U is possible, provided to provide another insulating material in the inner space of the bar to cover the head of the bolt 15 and provide the stop function. The electrical insulation properties of the bar 19 and its stop element 8 'make it possible on the one hand to isolate, with respect to the joining means, each end of an arm 2 or 3, and on the other hand to isolate between them the two respective ends of the arms 2 and 3.

In FIG. 10, each rod 14 has a threaded first portion 14A which cooperates with the means clamping device 25 to assist in fixing a metal plate 10 'on a flexible finger, and a second portion 14B unthreaded slidable in the insulating sleeve 24. The assembly of the yoke 13 is facilitated in this embodiment, because the rod 14 can be introduced from the right of the sleeve 24 in the figure, contrary to the realization of the Figure 9. As for the previous realization, the stop member 26 of the clamping means 25 is arranged to limit to a predetermined distance d the sliding of the second portion 14B of the rod in sleeve 24. In comparison with the mode of embodiment in connection with FIGS. 6 and 7, it is possible to note that each rod 14 alone ensures times the mechanical connection function between the clevis 13 and a flexible finger and the fixing function of a 10 'metal plate on one finger, while these two functions are exerted by two separate bolts in the device of Figure 6. This construction allows also to reduce the height of the bar 19 in the plane of the figure, thus reducing the distance L2 shown in Figure 6, while ensuring that the contact area between the fixed contact 4 and the plates 10 'does not have a bolt hole. amplification by leveraging the electrodynamic pinch of the fixed contact is thus increased compared to device of Figure 6.

Alternatively, the clevis 13 could be replaced by a metal form frame rectangular, the amounts perpendicular to the fingers 21 and 31 would be pierced with holes having the function of the holes 18 of the shoulders 13A and 13B. A insulating material covering the upper and lower lower part of the frame could be sufficient to ensure insulating stop element function for contact fixed.

The construction of an earthing switch according to the invention allows the entire locking system in the closed position is provided by the contact mobile. In addition, in the open position of the disconnector, it is possible to easily maintain the desired dielectric distance in the interval between the fixed contact and the mobile contact since the contact fixed may be small. In other words, the axis of rotation of the movable contact can be arranged to a distance relatively close to the bar that supports the fixed contact. In this way, one can ensure with a small footprint the holding of high voltages in an open configuration of the earthing switch.

Claims (18)

An earthing switch comprising a movable contact assembly (1) pivotable about an axis of rotation and a stationary contact (4) arranged to be electrically connected to an end of said movable contact assembly (1) when this assembly is brought into the closing position of the disconnector, characterized in that said movable contact assembly (1) comprises two substantially parallel electrically conductive arms (2, 3) which are bent to each form at least approximately one L, each bent arm (2, 3) comprising at least one flexible finger (2B1, 2B2, 3B1, 3B2; 21, 23, 31, 33) which extends at least on the shorter leg of the L, said fixed contact (4) being arranged to be engaged between at least one pair of flexible fingers in the closed position of the disconnector, and that joining means (E, 13) are mechanically connected to the two respective ends of the two bent arms (2, 3) on the branches shorter Ls to allow a lever effect that amplifies the electrodynamic pinch exerted on the fixed contact (4) by said flexible fingers when a short-circuit current or fault current flows through said arms (2, 3). Earthing switch according to claim 1, in which the fixed contact (4) and the set of contact (1) are arranged relative to each other the other such that in the closed position complete of the disconnector, the fixed contact is in support against a stop element (8, 8 ') electrically insulator carried by the movable contact assembly. Earthing switch according to one of the claims 1 and 2, wherein the fixed contact (4) in the form of a substantially cylindrical stud of which the axis defines a line (lv) substantially vertical, and wherein said line extends axially in direction of the axis of rotation of the contact assembly (1) mobile. Earthing switch according to one of the claims 1 to 3, wherein the most short (2B, 3B) of each bent arm (2, 3) shaped of L are split longitudinally to form flexible fingers (2B1, 2B2, 3B1, 3B2). Earthing switch according to claim 4, in which the longer branches of each angled arm (2, 3) L-shaped are also split longitudinally, so as to obtain fingers hoses (21, 23, 31, 33) bent in the shape of an L. Earthing switch according to one of the Claims 1 to 4, wherein said means for joint consist of a spacer (E) which comprises a sleeve (8) made of electrically insulation which surrounds a bolt (6) passing through two flexible fingers (2B1, 3B1; 2B2, 3B2) of both arms parallel (2, 3). Earthing switch according to claim 5, wherein said joining means comprises a rigid yoke (13) providing the function of a knot of hinge for an electrodynamic clamp whose levers are constituted by the flexible fingers of two parallel arms (2, 3). Earthing switch according to claim 7, wherein said yoke (13) comprises a plate (13C) rectangular one of which has two faces shoulders (13A, 13B) parallel on two edges opposite, each shoulder comprising at least two holes (18) each penetrated by a rod (14) adapted to ensure a mechanical connection between said screed and a flexible finger of an angled arm (2, 3). Earthing switch according to claim 8, wherein a sleeve of insulating material (24) is interposed between the wall of a hole (18) and the rod (14) who enters this hole. Earthing switch according to one of the preceding claims, wherein metal plates (10 ') are attached to the flexible fingers of the two parallel arms (2, 3), each metal plate having a beveled or rounded end on the side through which the contact fixed is able to be engaged in the movable contact assembly, and wherein the spacing (l ₁ ) between two metal plates (10 ') facing the open position of the disconnector is less than the width (12) fixed contact (4). Earthing switch according to claim Taken in combination with claim 9, in wherein said rod (14) has a first portion (14A) threaded which cooperates with clamping means (25) to contribute to the fixing of a plate (10 ') on a flexible finger (31) and a second portion (14B) unthreaded slidable in said insulating sleeve (24), and wherein said clamping means (25) have a stop member (26) arranged to limit to a predetermined distance (d) sliding said second portion (14B) in said insulating sleeve (24) when closing the disconnector in the presence of a strong current. The earthing switch according to claim 11, wherein said predetermined distance (d) is close to the amplitude (e) of spacing of a flexible finger (21, 31) defined as half of the difference between the gap ( ₁ ) between two metal plates (10 ') and the width (12) of the fixed contact (4). Earthing switch according to one of the claims 10 to 12 taken in combination with the claim 8, wherein the stop element (8 ') electrically insulating which is carried by the set of mobile contact is integral with an electrically insulator (19) having U-section portions and which is fixed in the middle of the plate (13C) of said clevis (13) parallel to the two shoulders (13A, 13B), and wherein said insulating bar is taken into vice by the flexible fingers of the two parallel arms (2, 3) in the open position of the disconnector. Earthing switch according to claim 13, wherein said stop element (8 ') is consisting of parts of said insulating bar (19) which have a substantially rectangular section. Earthing switch according to one of the preceding claims, wherein a shim (9) is arranged between the two parallel arms (2, 3) at neighborhood of their elbows and sets a spacing minimum allowed between the two arms when said mobile contact assembly (1) is traversed by a short circuit current. Earthing switch according to one of the preceding claims, wherein the two arms parallels (2,3) are axially extended on their longest branches by a conductive rod (12) rotative mounting around the axis of rotation of the pivoting contact assembly (1). Earthing switch according to claim 16, in which in the fully closed position of the disconnector, said conductive rod (12) is inclined compared to a vertical position of no balance. Earthing switch according to claim 5, wherein each L-shaped bent arm comprises three flexible fingers (31, 32, 33).

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