EP2510530B1 - High-voltage circuit breaker with a removable screen for improving the field gradient - Google Patents

Description

TECHNICAL AREA

The invention relates to electrical switchgear which must improve the performance vis-à-vis the electric field that appears during switching. It relates in particular to circuit breakers which it is desired to improve the coordination of the various parts provided vis-à-vis the electric field during an opening operation of the circuit breaker.

PRIOR ART AND PROBLEM POSE

High-voltage circuit breakers used to interrupt large short-circuit currents require a relatively large piston to create the overpressure required to blow the arc when opening the circuit breaker. This imposes an extremely wide radial space between the central contact, the rod and the corresponding permanent contact. As a result, electric field values become extremely important at the end of the rod. Thus, the performance of the high-voltage circuit breakers are depreciated, particularly the resistance to the inherent transient recovery voltage due to the power cut of the lines, cables or capacitor banks.

To counteract this disadvantage, another geometry must be proposed to improve the field values at the end of the rod. This consists in using a metal screen or a screen made of a material with a high dielectric constant and with a suitable shape. This screen can slide between the rod and the permanent contact. In this way, the shape of the equipotential lines changes and, as a result, the electric field can decrease significantly in other words for acceptable values.

To fulfill its role, the display must remain stationary at least until the separation of the contacts or until the contacts of the circuit breaker travel a certain distance. At the end of this run, the position they arrived at is considered to be the starting point where the values of the electric field on the ends of the contacts start to be critical. At this determined moment, the screen must begin to move with one of the contacts until the end of the race of the latter. Pre-compressed springs define the initial position of the screen.

Moreover, by patent documents US 5,478,980 , US5,585,610 and US 6,462,295 such circuits are known using a simple movement. The removable screen is attached to the end of the nozzle. When opening the circuit breaker, the screen is hidden by the permanent contact for almost all its movement. It is then obvious that the screen will influence the distribution of the electric field only in the open position of the circuit breaker, which does not improve only the dielectric performance of the circuit breaker.

The device described in the documents US 6,410,873 and US4,378,477 use a double touch movement. In these two cases, the screen is moved through the nozzle but it is not connected directly to its ends. As the insulating nozzle always surrounds the contact which is directly connected to the control mechanism (clip-shaped contact), the screen moves in the same direction, but in the opposite direction of the rod which is supposed to be protected. Thus, the effectiveness of the screen is reduced during the opening maneuvers as well as during the closing maneuvers.

The document US Patent 6,410,873 uses a very complicated mechanism composed of levers systems. The document US Patent 4,132,876 ( figure 1 ) implements a simple movement of contact with a screen operated by insulating rods. These very complicated mechanisms are unreliable for metal-enclosed circuit breakers in which external screens are generally used. In addition, in this device, because of the simple movement of the contacts, the screen does not need to follow the rod which is fixed. Thus, it stops when it reaches the desired position.

In the document US Patent 4,378,477 , the screen is actuated ideally via the nozzle, by means of a mechanism that also plays the role of a double-motion transmission system. So the screen, as for the documents presented previously, moves in a direction opposite to that of the stem, which is the contact that one wishes to protect. Thus, the effectiveness of such a device is low. When the screen is controlled in the opposite direction, the end position is much more advanced than that of the rod. Therefore, it is much more difficult to ensure a sufficient ratio between the electric field on the arcing contacts and that on the permanent contacts such that when a breakdown occurs, it always occurs between the arcing contacts. Finally, one of the disadvantages of this mechanism is that the mechanical shocks are cashed by the insulating nozzle during closing maneuver, while it is an extremely sensitive part.

The aforementioned patent documents refer to a screen attached or actuated by the nozzle or lever or rod systems. Thus, only the dielectric properties of the circuit breaker in the open position are improved.

The object of the invention is to overcome the aforementioned drawbacks relating to the documents mentioned above.

SUMMARY OF THE INVENTION

The concept according to the invention consists in modifying and / or reducing the radial space between the fixed contact (the arc electrode 4 in the document US 4,132,876 ) and the fixed permanent contact (the permanent contact 13 in the document US 4,132,876 ) presented in figure 1 . This is intended to smooth the equipotential lines. Then, the gradient variation of voltage decreases substantially and thus the electric field at the contact ends is greatly diminished. This lowers the ratio E / N electric field / gas density and reduces the risks of re-ignition, that is to say increases the resistance to the transient recovery voltage inherent due to the power cut lines, cables or batteries of capacitors.

For this purpose, the main object of the invention is a high-voltage circuit breaker comprising two movable contacts relative to each other, so as to deviate to effect a power failure, the circuit breaker comprising, among others, a screen which surrounds a first of the two contacts and which has a support housing and must follow during a second part of the stroke of this first of the two contacts, the final position of the screen being defined by compressed springs, the second of the two contacts also having a crankcase.

According to the invention, the screen is slidably mounted in the support housing of the first of the two contacts, is fixed to a rudder and is driven by a central body secured to the support of the second of the two contacts, during the separation of the two contacts as soon as possible. the beginning of the race of this support of the second contact by means of springs which are fixed by a first of its two ends to the screen and by a second of these two ends to the right end of a central body, the screen having a stop that is integral with it and positioned to come into contact with the rudder and to drive the screen in the second part of the relative stroke of the first movable contact by coming into contact with the latter, when sliding apart, the housing of the first movable contact with the housing of the second movable contact , the two contacts moving in opposite directions with respect to each other.

• un levier de commande monté pivotant vers son milieu autour d'un axe fixe par rapport à un bâti fixe et étant actionné en rotation par des moyens moteur ;
• un premier levier de manoeuvre monté pivotant par une première extrémité à une première extrémité du levier de commande et monté pivotant à une deuxième extrémité au carter support du premier contact mobile par l'intermédiaire du palonnier ; et
• deux deuxièmes leviers de manoeuvre montés pivotant par une première extrémité à une deuxième extrémité du levier de commande et montés pivotant à sa deuxième extrémité au carter support du deuxième contact mobile.

In the main embodiment of the invention, the relative movements of these elements are controlled by:

• a control lever pivotally mounted towards its middle about a fixed axis relative to a fixed frame and being actuated in rotation by motor means;
• a first operating lever pivotally mounted at a first end to a first end of the control lever and pivotally mounted at a second end to the support housing of the first movable contact through the lifter; and
• two second operating levers pivotally mounted at a first end to a second end of the control lever and pivotally mounted at its second end to the support housing of the second movable contact.

The first contact support casing and the second contact support are preferably slidably mounted relative to the fixed frame of the circuit breaker.

Preferably, the stop is mounted on a rod screwed into the screen.

It is also possible that the circuit breaker has rods screwed into the screen to pre-compress the springs.

LIST OF FIGURES

• figure 1, en coupe, un disjoncteur haute tension à écran amovible, selon l'art antérieur ;
• figure 2, en coupe, une partie du disjoncteur à haute tension, selon l'invention ;
• figures 3A, 3B et 3C, en coupes, le disjoncteur haute tension, selon l'invention, dans trois positions de son fonctionnement, lors de l'ouverture de celui-ci, et
• figures 4A, 4B, 5A, 5B, 6A et 6B, des courbes illustrant les résultat du calcul du champ électrique sur les contacts d'arc et sur les contacts permanents.

The invention and its various technical features will be better understood on reading the following description which is illustrated by several figures respectively representing:

• figure 1 , in section, a high-voltage circuit breaker with removable screen, according to the prior art;
• figure 2 , in section, a portion of the high-voltage circuit breaker, according to the invention;
• Figures 3A, 3B and 3C in sections, the high-voltage circuit breaker, according to the invention, in three positions of its operation, during the opening thereof, and
• Figures 4A, 4B, 5A , 5B, 6A and 6B , curves illustrating the results of the calculation of the electric field on the arcing contacts and on the permanent contacts.

NOMENCLATURE OF PARTS

• Screen: 1;
• First moving contact: 2;
• Stem: 3;
• Arc electrode: 4;
• Blow nozzle: 5;
• Conical part: 5A;
• Flared part: 5B;
• Body: 5C;
• Second moving contact: 6;
• Hood: 7;
• Second contact support: 8;
• Fixed body: 9;
• Second contact housing: 10;
• Permanent contact: 13;
• Central insulating tube: 14;
• Spreader: 15;
• Housing support first contact: 16;
• Springs: 17;
• Edge: 18;
• Internal side: 19;
• Left end: 20 (of the first contact support casing 16);
• Right end: 21 (of the second contact housing 10);
• Control lever: 22;
• First end: 22A (of the control lever 22);
• Second end: 22B (of the control lever);
• Axis: 23;
• First operating lever: 24;
• First end: 24A (of the first operating lever 24);
• Second end: 24B (of the first operating lever 24);
• Second operating levers: 25;
• First end: 25A;
• End ring: 26 (of the flared part of the nozzle 5);
• Stopper: 28 (from the flange 18);
• Stem: 29;
• Stop 30;
• Stem: 31.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

The figure 2 shows, in section, the central part of the circuit breaker according to the invention, for the purpose of locating the screen 1, which is movable and which is intended to be positioned in a predetermined manner around a first movable contact 2, consisting of the end of a rod 3, translating longitudinally in the circuit breaker, in the center thereof. The other contact 6 consists of a hollow tip, of revolution, placed in a cover 7, itself placed on a second contact support 8.

The assembly evolves inside a blowing nozzle 5 comprising a first conical portion 5A, placed on the right in the figures, on the side of the first contact 2, a central and cylindrical body 5C and a part extended 5B placed on the side of the second contact 6. This blowing nozzle 5 allows to concentrate the jet of gas at the determined moment to blow the arc when the two contacts 2 and 6 move away from each other.

The assembly is structured by a central insulating tube 14 through which the movement of the second contact 6 (motor) is transmitted to the first contact 2, placed around the blowing nozzle 5. A first contact support casing 16 is fixed in a crossbar 15 carrying the rod 3, at the end of which is the first contact 2. Finally, a second contact housing 10 is placed around the second contact support 8 carrying the second contact 6.

One of the main parts of the circuit breaker, according to the invention, is a screen 1 placed inside a fixed body 9, positioned on the inner wall of the first contact support casing 16 attached to a lifter 15. Its shape is therefore of hollow revolution and surrounds globally, at a determined distance, the left part of the rod 3. Its role is to follow the latter, in particular the first contact 2 constituting its end, from a given moment of the respective stroke of the two contacts 2 and 6. The presence of the screen 1 contributes to reducing the variation of voltage gradient and thus significantly reduce the electric field at the end of the first contact 2. Thus, we obtain a reduced ratio of the field electrical / gas density and reduces the risk of reboots.

Springs 17 are supported on a flange 18, at the right end of the central body 14. Its other left end is supported on the inner face 19 of the screen 1. The springs 17 are pre-compressed via the rods 29 screwed into the left end of the screen 1 and attached via a stop 28 of the flange 18 so that they can slide in the flange 18.

With reference to the figure 3A , which shows the circuit breaker, according to the invention, in the closed position, the two contacts 2 and 6 are in contact with each other. More precisely, the first contact 2 is located inside the second contact 6 of hollow form of revolution.

On this figure 3A , the second contact support assembly 8 is placed a little to the left, inside the second contact housing 10. The left end 20 of the first contact support housing 16 surrounds the right end 21 of the second housing contact 10. Thus, the assembly located inside the central body 14 is completely surrounded by the first contact support casing 16, since the central body 14 is integral with the second contact casing 10. There is therefore a sliding of the first contact support casing 16 around the whole of the second contact housing 10 and the central body 14.

The three Figures 3A, 3B and 3C show, among others, the actuation of all its parts of the circuit breaker, thanks, in particular, to three levers, which are a control lever 22, pivotally mounted about a horizontal axis 23, which is fixed relative to the together, that is to say fixed relative to a frame on which is fixed the circuit breaker.

In the closed position of the circuit breaker, illustrated by this figure 3A , the control lever 22 has a first end 22A, to which is mounted, in an articulated manner, a first end 24A of a first operating lever 24 whose other end 24B is hingedly mounted on the central portion of the rudder 15.

Correspondingly, a second end 22B of the control lever 22 is hingedly connected to a first end 25A of two second operating levers 25, whose second end is hingedly mounted on an end ring 26 of the part flared 5A of the blast nozzle 5, also integral with the assembly of the central body 14 and the second contact casing 10.

It states that on this figure 3A the control lever 22 is inclined, so that the first operating lever 24 is pushed to the left. In this way, the rudder 15 is itself pushed to its extreme position to the left. In correspondence, the two operating levers 25 are pulled to the right, keeping the entire second contact housing 10 of the central insulating tube 14, inside, to the right.

With reference to the figure 3B , representing an intermediate position of the opening between the two contacts 2 and 6, the control lever 22 has been rotated so as to pull to the right the first operating lever 24 and to push to the left the second operating levers 25. In this way, the lifter 15 carrying the rod 3 and the first contact 2 begins a shift to the right. As a result, the first contact 2 leaves the second contact 6. At the same time, the second operating levers 25 are pushed to the left and itself pushes the assembly consisting of the central insulating tube 14, carrier of the blast nozzle 5 and integral with the second contact housing 10. As a result, the assembly consisting of the cover 7 of the second contact 6, of the second contact support 8, slides in the first contact housing 10.

In this intermediate phase, represented by the figure 3B , the left end 20 of the first contact support casing 16 is already separated from the right end of the second contact casing 10. Together, the rod 3 and the first contact 2 slide inside the blast nozzle 5 This is the moment when a stop 30 placed on a rod 31 which is fixed on the left part of the screen 1 and which slides in the rim 18 and in the rudder 15 comes into contact with the rudder 15. also the moment when the screen 1 begins to move together with the support casing of the first contact 16 and the rod 3.

With reference to the figure 3C , the control lever 22 continued its rotation and pulled the first operating lever 24 to the right, pulling at its maximum the rod 3 and the contact 2 to the right.

However, after the intermediate phase, schematized by the figure 3B , the springs 17 have been compressed by means of the spreader 15 which abuts on the stop 30 fixed on the rod 31 and which is screwed into the left part of the screen 1, which can slide in the rudder 15 and in the ledge 18.

The figure 3C shows the end of this compression of springs 17. The maximum separation of first contact 2 and second contact 6 and elements that are integral with them. During this compression of the springs 17, the screen 1 was thus driven, together with the compression of the springs 17 to the right, by means of the stop 30, placed to the right of the rod 31.

Together, the spacing of the two subassemblies relative to the first contact 2 and the second contact 6 has caused the spacing to the left of the second contact housing 10 of the second contact support 8 relative to the fixed piston, not shown. This translation contributes, between Figures 3A and 3B , at the decrease of the volume inside the second contact housing 10 and is necessary to create the blowing of the arc.

The main advantage of this circuit breaker is an improved resistance to the transient recovery voltage inherent due to the power cut of the lines, cables or capacitor banks, especially for very high voltages.

(ou w est la fréquence source, t c' est le temps, et U c'est la tension effective assignée), la valeur maximale, $2.\sqrt{(2.}U)$

sera appliquée après un instant temporel bien défini, d'environ un demi cycle de la fréquence assignée au réseau. Donc plus les contacts sont écartés à cet instant plus la valeur du champ électrique au bout des contacts est faible. En conséquence, en réduisant cette valeur de champ au but des contacts par l'intermédiaire d'un écran 1, la distance entre les contacts peut être réduite, donc il est possible de diminuer la vitesse des contacts entraînant la réduction des contraintes mécaniques. Cet effet est illustré dans les figures 4A, 4B et 4C.The interruptions of the small capacitive currents occur almost simultaneously with the separation of the arcing contacts 2 and 6. As the recovery voltage varies according to the law $\sqrt{\left(2.U\right)}\mathrm{.}\left(1-\cos \left(\mathit{wt}\right)\right)$

(where w is the source frequency, tc 'is the time, and U is the rated effective voltage), the maximum value, $2.\sqrt{(2.}U)$

will be applied after a well defined time of about half a cycle of the frequency assigned to the network. Therefore, the more the contacts are spaced apart at this moment, the lower the value of the electric field at the end of the contacts. In Accordingly, by reducing this field value to the purpose of the contacts via a screen 1, the distance between the contacts can be reduced, so it is possible to reduce the speed of the contacts resulting in the reduction of mechanical stresses. This effect is illustrated in Figures 4A, 4B and 4C .

The Figures 4A and 4B illustrate the values of the gradient of the electric field calculated for a speed of 13 m / s without moving screen. The Figures 5A and 5B illustrate the values of the gradient of the electric field calculated for a speed of 19 m / s without a mobile screen and the Figures 6A and 6B illustrate the values of the gradient of the electric field calculated for a speed of 13 m / s with moving screen. In these Figures 4A, 5A and 6A , the results presented relate to the voltage that has been applied on the side of the rod (first movable contact 2) and on the Figures 4B , 5B, 6B , the calculations presented relate to the voltage that has been applied to the side of the tulip (second movable contact 6).

Claims (5)

1. A high voltage circuit breaker including two contacts (2, 6) that are movable relative to each other, in such a manner as to move apart in order to break an electric current, the circuit breaker including:

   • a shield (1) surrounding a first one of the two contacts (2) possessing a first contact support casing (16), the shield (1) being constrained to follow the first contact support casing (16) and the first contact (2) during a second portion of the stroke of the assembly comprising the first contact (2) and its first contact support casing (16), the final position of the shield (1) being defined by the compression of compressed springs (17), the second contact (6) having a second contact support (8), and the circuit breaker being characterized in that the shield (1) is mounted to slide in the first contact support casing (16) fastened to a yoke plate (15) and is driven by a central body (14) secured to the second contact support casing (8), during relative separation of the two movable contacts (2, 6) from the start of the stroke of the second contact support (8) and by means of the springs (17) that are fastened at a left first end to the shield (1) and at a right second end to the central body (14), the shield (1) possessing an abutment (30) that is secured and positioned so as to make contact with the yoke plate (15) and drive the shield (1), during the second portion of the stroke of the first contact support casing (16) while it is sliding as a result of two movable contacts (2, 6) moving apart in opposite directions together with their respective casings and supports.
2. A high voltage circuit breaker according to claim 1, characterized in that the relative movement of its constituent elements is controlled by:

   • a control lever (22) that is mounted, towards its center, to pivot about an axis (23) that is stationary relative to a housing and that is driven in rotation by motor means;

   • a first operating lever (24) that is pivotally mounted at a first end (24A) to a first end (22A) of the control lever (22), and that is pivotally mounted at a second end (24B) to the first contact support casing (16) by means of the yoke plate (15); and

   • second operating levers (25) that are pivotally mounted at a first end (25A) to a second end (22B) of the control lever (22) and that are pivotally mounted at a second end (25B) to the second contact support (8) ;
3. A high voltage circuit breaker according to claim 1 or claim 2, characterized in that the first contact support casing (16) and the second contact support (8) are mounted to slide relative to a stationary body (9), in such a manner as to move apart in opposite directions.
4. A high voltage circuit breaker according to claim 1, characterized in that the abutment (30) is mounted on a rod (31) that is screw-fastened in the shield (1).
5. A high voltage circuit breaker according to claim 1, characterized in that it possesses bars (29) screw-fastened in the shield (1) in order to pre-compress the springs (17) .

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