CN102725810A - High-voltage circuit breaker with a removable screen for improving the field gradient - Google Patents

Abstract

The high-voltage circuit breaker makes it possible to reduce the electric field on the arc contacts during cut-offs and consequently the rate of triggering the apparatus. The two contacts (2) and (6) are able to move relative to each other in opposite directions during cut-offs. Their respective supporting members (8) and (16) are also able to move and slide one in relation to the other with respect to a fixed frame. A screen (1) is placed inside the support housing for the first contact (6), by virtue of springs (17), and is moved during an opening operation by means of rods (31). The stops (30) define the instant when the screen starts to move. During its movement, the screen compresses the springs (17) and it keeps this position relative to the arc contact (2) and to the permanent contact (20) until the end of travel. It is applicable to high-voltage circuit breakers.

Description

High voltage circuit breaker with removable shield for improved electric field gradient

technical field

The present invention relates to electrical switching devices where there is a need for improved performance in relation to the electric fields present during switching. In particular, the invention relates to circuit breakers in which it is desirable to improve the coordination of its different components with respect to the electric field during the opening operation of the circuit breaker.

Background technique

High voltage circuit breakers for interrupting high short circuit currents require relatively large pistons to generate the high air pressures needed to blow out the arc when opening the circuit breaker. This requires an extremely wide radial space between the center contact, the stem, and the corresponding permanent contact. Therefore, the value of the electric field becomes extremely high at the end of the rod. Consequently, the performance of high voltage circuit breakers is degraded, especially the ability to withstand the instantaneous recovery voltage inherent in breaking currents in wires, cables, or capacitor batteries.

In order to overcome these disadvantages, it is necessary to have another shape to improve the electric field value at the end of the rod. This includes using a metal shield, or using a shield made of a material with a high dielectric constant and a suitable shape. The shield can slide between the rod and the permanent contact. In this way, the shape of the equipotential lines is changed, therefore, the electric field can be significantly reduced, in other words, to an acceptable value.

To fulfill its purpose, the shield should remain stationary at least until the contacts have separated or until the circuit breaker contacts have traveled a sufficient, defined distance. At the end of the stroke, the position reached by the contact is considered to be the starting point at which the electric field value at the end of the contact starts to be a critical value. At this determined moment, the shield will start moving together with one of the contacts until the end of the stroke of said one contact. A pre-compressed spring defines the initial position of the shield.

Furthermore, US Patent Nos. 5 478 980, 5 585 610, and 6 462 295 describe these circuits using simple movements. A removable shield is attached to the end of the nozzle. When opening the circuit breaker, the shield is covered by permanent contacts during nearly all of its movement. Thus, it is evident that the shield affects the distribution of the electric field only when the circuit breaker is in the off position and only improves the dielectric properties of the circuit breaker.

The devices described in documents US 6 410 873 and US 4 378 477 use a double contact movement. In both documents, the shield is moved by means of nozzles, but said nozzles are not directly connected to the ends of the shield. Since the insulating nozzle continues to surround the contact, which is directly connected to the control mechanism (contact in the form of a clip), the shield moves in the same direction, opposite to that of the rod that is supposed to be protected. Thus, the efficiency of the shield is reduced during opening and closing operations.

US Patent No. 6 410 873 uses a very complex mechanism consisting of a system of levers. US Patent No. 4 132 876 (Fig. 1) utilizes a shield driven by an insulating rod to implement a single contact movement. These very complex mechanisms are unreliable for metal-enclosed circuit breakers, which typically use outer shields. Furthermore, in this arrangement the shield does not need to follow the stationary rod due to the simple contact movement. Thus, the shield stops when it reaches the desired position.

In U.S. Patent No. 4 378 477, the shield is ideally driven by means of the nozzle by using a mechanism that also serves as a transmission system performing the reverse movement. Thus, as in the aforementioned document, the shield moves in the opposite direction to the rod that is the contact desired to be protected. Thus, such devices are not very efficient. When the shield is caused to move in the opposite direction, the position of the shield at the end of the stroke is much ahead of the position of the rod. As a result, it is more difficult to ensure that the ratio of the electric field on the arcing contacts to the electric field on the permanent contacts is sufficient to ensure that when breakdown occurs it always occurs between the arcing contacts. Finally, the disadvantage of this mechanism is that, although the insulating nozzle is a very sensitive part, mechanical shocks are absorbed by the insulating nozzle during the closing operation.

The above mentioned patent documents refer to fixed shields, or shields driven by nozzles or lever systems or rods.

Thus, only the dielectric properties of the circuit breaker in the open position are improved.

The object of the present invention is to overcome the above-mentioned drawbacks associated with the above-mentioned documents.

Contents of the invention

The idea of the present invention consists in changing and/or reducing the difference between the stationary contact (arc electrode 4 in document US 4 132 876) and the permanent stationary contact (permanent contact in document US 4 132 876) shown in Figure 1 13) Radial space between. This is to flatten the potential lines. After this, the variation of the electric field gradient is substantially reduced and thus the electric field at the tip of the contact is greatly reduced. This reduces the ratio E/N of the electric field divided by the gas density, and reduces the risk of reignition, ie, improves the ability to withstand the transient recovery voltage inherent to breaking current in a wire, cable, or capacitor cell.

To this end, the present invention basically provides a high voltage circuit breaker comprising two contacts movable relative to each other so as to separate from each other to interrupt current flow, the circuit breaker comprising: a shield enclosing the two A first contact of the two contacts having a supporting shell, the shield is defined to follow during the second part of the stroke of the first of the two contacts, the final of the shield The position is defined by the compression of a compression spring, the second of the two contacts also having a housing.

According to the invention, the shielding case is mounted so as to be fixed to the shielding case at the first of the two ends during the relative separation of the two contacts from the start of stroke of the second contact support part and A spring, fixed at the other of these two ends to the right end of the central body, slides in the support housing of the first of the two contacts (which is fixed to the yoke plate) and is driven by fixed to the central body of the second contact of the two contacts, the shield has a joint that is fixed and positioned so that: The housings of the contacts contact the yoke plate as they slide apart, the engagement portion contacts the yoke plate and drives the shield during a second portion of the relative stroke of the first movable contact, wherein the two contacts are in opposite directions to each other Exercise separately.

In the main embodiment of the invention, the relative movement of these elements is controlled by:

a control lever mounted pivotally at its center about an axis which is stationary relative to the housing and driven in rotation by the motor means;

A first operating lever pivotally mounted at a first end to a first end of a control lever and at a second end to a first movable contact support housing by means of a yoke plate the second end of ; and

• Two second operating levers pivotally mounted at a first end to a second end of the control lever and pivotally mounted at a second end thereof to the second movable contact support.

The first contact supporting housing and the second contact supporting part are preferably mounted slidably relative to a stationary housing of the circuit breaker.

Preferably, the joint is mounted on a rod which is screwed to the shield.

The circuit breaker may also have a rod screwed to the shield to pre-compress the spring.

Description of drawings

The present invention and its various technical features can be better understood by reading the following description, provided respectively with reference to several accompanying drawings, in which:

- Figure 1 is a cross-section showing a prior art high voltage circuit breaker with a detachable shield;

· Figure 2 is a cross section showing the high voltage circuit breaker of the present invention;

• The cross-sections in Figures 3A, 3B and 3C show the high voltage circuit breaker of the present invention in three of its operating positions during its opening; and

• Figures 4A, 4B, 5A, 5B, 6A and 6B are graphs showing the results of calculations for the electric fields on the arcing contacts and on the permanent contacts.

Parts Catalog

Shield: 1;

First movable contact: 2;

rods: 3;

arc electrodes: 4;

air nozzles: 5;

Conical part: 5A;

open part 5B;

Body: 5C;

Second movable contact: 6;

caps: 7;

The second contact support part: 8;

stationary subject: 9;

Second contact housing: 10

permanent contacts: 13;

Central insulating tube: 14;

Yoke Plates: 15;

First contact supporting shell: 16;

First contact supporting shell: 16;

spring: 17;

flange: 18;

inner surface: 19;

Left end: 20 (the left end of the first contact supporting shell 16);

Right end: 21 (the right end of the second contact housing 10);

Control lever: 22;

First end: 22A (first end of control lever 22);

Second end: 22B (second end of control lever);

axis: 23;

First operating lever: 24;

First end: 24A (the first end of the first operating lever 24);

Second end: 24B (second end of first operating lever 24);

Second operating lever: 25;

First end: 25A;

End ring: 26 (the end ring of the flared part of the nozzle 5);

Joining portion 28 (joint portion of flange 18 )

rod 29;

joint 30;

rod 31;

Detailed ways

Figure 2 is a cross-section showing the central part of the circuit breaker of the present invention for identifying the position of the shield 1 which is movable and designed to be positioned around the first movable contact 2 in a defined manner , the first movable contact 2 is constituted by the end of a rod 3 located in the center of the circuit breaker and moving in the circuit breaker in longitudinal translation. The other contact 6 is formed by a hollow end piece forming a rotating body placed inside a cap 7 which is located in the second contact support 8 .

The above assembly moves inside an air nozzle 5 comprising: a first conical portion 5A, on the right side in the illustration, next to the first contact 2, a central cylindrical body 5C, and The enlarged portion 5B next to the second contact 6 . This gas nozzle 5 makes it possible to concentrate the gas jet at a defined moment in order to blow out the arc when the two contacts 2 and 6 are moving away from each other.

Said assembly is constructed by a central insulating tube 14 placed around the air nozzle 5 , through which the movement of the (active) second contact 6 is transmitted to the first contact 2 . The first contact support housing 16 is fastened to the yoke plate 15 carrying the rod 3 at the end of which the first contact 2 is located. Finally, the second contact housing 10 is placed around the second contact support 8 carrying the second contacts 6 .

One of the main components of the circuit breaker of the invention is the shield 1 inside the stationary body 9 , which is positioned on the inner wall of the first contact supporting housing 16 attached to the yoke plate 15 . The shield thus has the shape of a hollow body of revolution and it substantially surrounds the left part of the rod 3 at a certain distance. The role of the shield is to start following the rod at predetermined moments of the respective strokes of the two contacts 2 and 6 , in particular the first contact 2 constituting the end of the rod. The presence of the shield 1 helps to reduce the variation of the electric field gradient and thus significantly reduces the electric field at the tip of the first contact 2 . Thus, a smaller ratio of electric field divided by gas density is obtained and the risk of re-ignition is reduced.

A spring 17 presses against a flange 18 at the right end of the central body 14 . The left end of this central body presses against the inner surface 19 of the shield 1 . The spring 17 is pre-compressed by means of a rod 29 which is screwed at the left end of the shield 1 and is attached by the joint 28 of the flange 18 so that the rod can slide in the flange 18 .

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

In FIG. 3A , the second contact support assembly 8 is located 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 contact housing 10 . Thus, since the central body 14 is fixed to the second contact housing 10 , the components located inside the central body 14 are completely surrounded by the first contact support housing 16 . Thus, the first contact support housing 16 slides around the assembly comprising the second contact housing 10 and the central body 14 .

The three figures 3A, 3B, 3C show in particular the actuation of each part of the circuit breaker, in particular by means of three levers comprising a control lever 22 mounted so as to pivot about a horizontal axis 23 Rotating, the shaft is not stationary relative to the assembly, ie relative to the housing to which the circuit breaker is fixed.

In the closed position of the circuit breaker shown in FIG. 3A , the control lever 22 has a first end 22A hinged to a first end 24A of a first operating lever 24 whose other end 24B is hinged onto the central portion of the yoke plate 15.

Correspondingly, the second end 22B of the control lever 22 is hinged to the first ends 25A of the two second operating levers 25 which are hinged to the opening part 5A of the air nozzle 5 The end ring 26 of the nozzle is also fixed to the assembly comprising the central body 14 and the second contact housing 10 .

In FIG. 3A , the control lever 22 is tilted in such a manner that the first operating lever 24 is pushed leftward. In this way, the yoke plate 15 itself is pushed into its leftmost position. Correspondingly, the two operating levers 25 are pulled to the right, while holding the assembly of the second contact housing 10 and the central insulating tube 14 inside to the right.

In conjunction with FIG. 3B , which shows that in the intermediate open position between the two contacts 2 and 6 , the control lever 22 has been turned so that the first operating lever 24 is pulled to the right and the second operating lever is pushed to the left. 25. In this way, the yoke plate 15 carrying the rod 3 and the first contact 2 moves to the right. As a result, the first contact 2 is removed from the second contact 6 . At the same time, the second operating lever 25 is pushed to the left, thereby pushing the assembly including the central isolation tube 14 carrying the air nozzle 5 and fixed to the second contact housing 10 . As a result, the assembly consisting of the cap 7 of the second contact 6 and the second contact support 8 slides in the second contact housing 10 .

During this intermediate stage shown in FIG. 3B , the left end 20 of the first contact support housing 16 has separated from the right end of the second contact housing 10 . Simultaneously, the rod 3 and the first contact 2 slide inside the air nozzle 5 . This is the moment when the joint 30 on the rod 31 is in contact with the yoke plate 15 , this rod 31 is fixed to the left side part of the shield 1 and slides in the flange 18 and the yoke plate 15 . This is also the moment when the shield 1 starts to move simultaneously with the first contact support shell 16 and the rod 3 .

Referring to FIG. 3C , the control lever 22 has been turned continuously and the first operating lever 24 has been pulled to the right to pull the lever 3 and the contact 2 as far as possible to the right.

However, after the intermediate stage shown in FIG. 3B , the spring 17 has been compressed by the yoke plate 15 becoming abutting the joint 30 fastened on the rod 31 screwed to the left side of the shield 1 . side part, and can slide in the yoke plate 15 and the flange 18.

Fig. 3C shows that the compression of the spring 17 ends, and the first contact 2 and the second contact 6, as well as the components fixed thereto, are separated to the greatest extent. Thus, during compression of the spring 17 , the shield 1 is driven to the right while the spring 17 is compressed by the engagement portion 30 on the right side of the lever 31 .

Simultaneously, the backward movement of the two subassemblies associated with the first contact 2 and the second contact 6 causes the second contact housing 10 of the second contact support 8 to move away from the stationary piston (not shown). Between FIGS. 3A and 3B , this translational movement is beneficial to reduce the inner volume of the second contact housing 10 and is necessary to blow out the arc.

The main advantage of the present circuit breaker is the improved ability to withstand the transient recovery voltage, especially for very high voltages, which is inherent in breaking currents in wires, cables or capacitor batteries.

变化，其中w是源频率，t是时间，且U是可适用的均方根电压，因此，

的最大值将会在明确定义的时间长度(约为可适用的电网频率的周期的一半)之后施加。因此，触头在这一时刻分开越远，在触头的末端的电场则越弱。因此，通过利用屏蔽罩1来减小触头末端处的场的值，在触头之间的距离能够减小，从而使得可以减小触头的速度，导致机械应力减小。这个效果在图4A、4B和4C中示出。Almost simultaneously with the separation of the arcing contacts 2 and 6, the low capacitive current is interrupted. Since the recovery voltage depends on the relationship

Variation, where w is the source frequency, t is time, and U is the applicable rms voltage, therefore,

The maximum value of will be applied after a well-defined length of time (approximately half the period of the applicable grid frequency). Thus, the further apart the contacts are at this moment, the weaker the electric field at the ends of the contacts. Thus, by using the shield 1 to reduce the value of the field at the tip of the contacts, the distance between the contacts can be reduced, making it possible to reduce the speed of the contacts, resulting in reduced mechanical stress. This effect is illustrated in Figures 4A, 4B and 4C.

Figures 4A and 4B show the values of the electric field gradient calculated for a velocity of 13 meters per second (m/s) without the movable shield, and Figures 5A and 5B show the values without the movable shield The values of the electric field gradient were calculated for a velocity of 19 m/s, while Figures 6A and 6B show the values of the electric field gradient calculated for a velocity of 13 m/s with a movable shield. In Figures 4A, 5A and 6A the results are shown in relation to the voltage applied next to the rod (first movable contact 2), while in Figures 4B, 5B and 6B the calculated values are shown in relation to the It is related to the voltage applied next to the head (second movable contact 6).

Claims (5)

CLAIMS 1. A high voltage circuit breaker comprising: two contacts (2, 6) movable relative to each other in such a way that they can be separated from each other to interrupt current flow, said circuit breaker comprising: A shield (1) surrounding a first contact (2) of the two contacts having a first contact support housing (16), the shield (1) being defined as: including the During the second part of the stroke of the assembly of the first contact (2) and its first contact support housing (16), following said first contact support housing (16) and said first contact (2) , the final position of the shield (1) is defined by the compression of a compression spring (17), the second contact (6) has a second contact support (8), and the high voltage circuit breaker characterized in that, Said shield (1) is mounted so as to be fixed on said two movable contacts (2, 6) during separation from each other from the start of stroke of said second contact support (8) The spring at the first end on the left side of the shield (1) and the second end on the right side of the central body (14) fixed to the second contact support housing (8) is fixed to the yoke plate ( 15) slides in the first contact support housing (16) and is driven by the central body (14), the shield (1) has an engagement portion (30) which is fixed and positioned so that when said shield (1) slides apart from each other due to the two movable contacts (2, 6) in opposite directions together with their respective housings and supports, the first contact supports the housing During the second part of the stroke of (16), the engagement portion (30) contacts the yoke plate (15) and drives the shield (1). 2. The 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), a first operating lever (24) and a second operating lever (25), wherein, · The control lever (22) is mounted at its center to pivot about an axis (23) stationary relative to the housing and driven in rotation by the motor means; The first operating lever (24) is pivotally mounted at its first end (24A) to the first end (22A) of said control lever (22) and at its second end by means of the yoke plate (15) pivotally mounted to said first contact support housing (16) at (24B); and · The second operating lever (25) is pivotally mounted at its first end (25A) to the second end (22B) of said control lever (22) and is pivotable at the second end (25B) ground mounted to the second contact support (8). 3. The high voltage circuit breaker according to claim 1 or 2, characterized in that the first contact supporting shell (16) and the second contact supporting part (8) are installed relative to the stationary body ( 9) Slide so as to separate from each other in opposite directions. 4. The high voltage circuit breaker according to claim 1, characterized in that the engaging part (30) is mounted on a rod (31) fixed on the shielding case (1) by screws. 5. The high voltage circuit breaker according to claim 1, characterized in that it has a rod (29) screwed on the shield (1) to pre-compress the spring (17).

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