RU2247439C1 - High-voltage vacuum load switch - Google Patents

Abstract

FIELD: building high-voltage switching devices.

SUBSTANCE: proposed vacuum switch has support insulators in each phase, vacuum arc-control chamber and its contacts disconnecting gear, as well as main movable and fixed contacts, and movable breaking contact. Movable contacts are intercoupled. In addition switch is provided with shaft incorporating leverage for transferring rotary motion from operating mechanism. Vacuum arc-control chamber is installed on main fixed contact. Disconnecting gear has contact roller engageable with shaped pushrod secured on movable breaking contact. Profile of pushrod surface is formed by two circle arcs with center disposed on axis of revolution of breaking contact.

EFFECT: enhanced reliability, simplified design, and reduced size of switch.

1 cl, 5 dwg

Description

The invention relates to electrical engineering, namely to high-voltage switching apparatus engineering, more specifically to load switches.

The main requirements for load breakers are the ability to switch rated currents and be resistant to through short-circuit currents. Since load breakers are the most common among various types of switching devices, they are also subject to the requirements of simplicity and low cost of construction. A large number of types and designs of load switches (autogas, SF6, vacuum) are known. The most common among them is an autogas load switch [1], in which a chamber made of gas-generating material (for example, plexiglass) is used for extinguishing. Under the influence of an electric arc, a large gas flow forms in the chamber, which extinguishes it.

An autogas load switch contains a metal frame on which three pairs of insulators are fixed, two for each phase, one of them has a fixed main contact and an arcing chamber, and the other has a main and arcing moving contacts that rotate around a common axis, transmitting motion from the drive to the moving contacts is carried out from a common shaft through levers and insulating rods.

The advantage of an autogas switch lies in the simplicity and cheapness of the design, as well as in the presence of a visible gap between the contacts in the off position, i.e. an autogas switch simultaneously acts as a disconnector. Another advantage of it is that the separation of the contacts into the main current-carrying and arcing ones is performed. This allows you to make the drive easier, since there is no need to create the force of additional contact compression during the passage of through currents of short circuit. In an autogas circuit breaker, this problem is solved by the design of the main current-carrying contacts, in which additional preload forces are created by electrodynamic forces arising from the passage of through currents.

At the same time, autogas circuit breakers have significant drawbacks that are well known, such as low breaking capacity, low switching resource, low reliability, open arc discharge.

Known solutions [2, 3], which offer devices combining the functions of a vacuum circuit breaker and a disconnector, their disadvantage is that through short-circuit currents pass through the contacts of the vacuum chamber, which requires providing the necessary additional efforts pressed contacts and their thermal and electrodynamic persistence. Closest to the proposed solution is the design of the vacuum circuit breaker, proposed in [4]. It uses the main current-carrying contacts and disconnecting contacts. They are mounted on supporting insulators, mounted on a common frame, and rotate, which is transmitted from the drive through a system of levers and insulator rods. Moreover, the vacuum interrupter chamber is mounted on a movable disconnecting contact. In this case, the main movable contacts are connected through the disconnection mechanism with the movable contact of the vacuum chamber and the disconnecting contact in such a way that the following sequence of operations when disconnecting is realized:

- opening of the main contacts;

- opening the contacts of the vacuum chamber;

- opening the disconnecting contacts.

The disadvantages of this design are as follows:

- the vacuum chamber is mounted on a movable disconnecting contact, moving to create a visible gap, and is subjected to shock loads when performing operations on and off;

- the duration of the time interval necessary for the extinction of the arc in all phases and determined from the moment the contact opening of the chamber starts to the moment the disconnecting contact begins to form a visible gap depends on the ratio of the power characteristics of the elastic elements of the circuit breaker, which makes it difficult to obtain the necessary accuracy and reliability of the circuit breaker;

- the design is complex and bulky.

The aim of the invention is to increase reliability, simplify the design and reduce the size.

This goal is achieved by the fact that in the known high-voltage vacuum circuit-breaker the load contains in each phase support insulators, a vacuum arcing chamber, a mechanism for opening its contacts, the main movable and fixed contacts, disconnecting the movable contact, and the movable contacts are interconnected, as well as the shaft with the system levers transmitting rotational movement from the drive. What is new is that the vacuum arrester is mounted on the main fixed contact, and the disconnecting mechanism contains a contact roller interacting with a profiled pusher mounted on a movable disconnecting contact, while the surface profile of the pusher is formed by two circular arcs centered on the axis of rotation of the opening contact, the difference between the values of the radii of which is equal to the sum of the values of the stroke of the movable contact of the vacuum interrupter chamber and the course of the additional preload, Jicin smaller radius is determined by the condition of contact of the contact roller and the cam surface of the pusher and the length S of the circular arc of smaller radius determined by the condition:

S≥ 3/2 V / ν,

where V is the speed of the pusher;

ν is the frequency of the alternating current.

In more detail, the design of the device is illustrated using the drawings presented in figures 1, 2, 3, 4, 5.

Figure 1 - shows a General view of the switch in the on position;

figure 2 - the main contacts are open, the beginning of the opening of the contacts of the vacuum chamber;

figure 3 - the end of the current shutdown, the beginning of the divergence of the NC contacts;

figure 4 shows the fully disconnected position of the switch;

figure 5 - turning on the switch, the main contacts are closed, and the contacts of the vacuum chamber are open.

The switch contains: a common frame 1; support insulators 2, two for each phase; main fixed contact 3; the main 4 and disconnecting 5 movable contacts making a rotational movement around a common axis 6; a common shaft 7, transmitting movement to each phase from the drive through levers 8 and insulating rods 9. A vacuum arcing chamber 10 is mounted on the main fixed contact 3 using an insulating stand 11 and a current lead 12 and is connected to a disconnect mechanism containing disconnect springs 13 and preloaded 14 ; guide cylinder 15 with sleeve 16; flexible connection 17; contact roller 18; mounting details: axles 19 and 20, pin 21, clip 22. The disconnect spring holds the contacts of the vacuum interrupter chamber in a normally open position with the circuit breaker open. A profiled pusher 23 is installed at the end of the disconnecting contact 5. An earring 24 is installed on the main movable contact 4 with an arcuate groove through which an axis 25 passes, mounted on the movable disconnect contact 5. The fixed contact 26 of the vacuum chamber 10 is connected electrically to the main contact 3. The movable contact 27 of the vacuum chamber mechanically by means of parts (studs 21, guide sleeve 16, clips 22, axles 19, 20) and electrically via flexible coupling 17 is connected to the contact roller 18. In this case, the pusher 23 at the end of the movable disconnecting contact 5 interacts with its profiled surface with a contact roller 18, closing and opening the contacts of the vacuum chamber 10.

The movement to the movable disconnecting contact 5 is transmitted from the main movable contact 4 by means of the earring 24 and the axis 25 passing through its groove. To provide the necessary values for the move of the movable contact of the camera, the course of the additional preload and the interaction time of the roller 18 and the pusher 23, the shaped surface of the pusher has a shape formed two circular arcs of smaller R ₁ and R ₂ larger radii centered on the axis of rotation of the movable contacts 6, wherein the difference between the values of the radii of the circles R ₂ -R ₁ is the sum of the quantities stroke the movable contact of the vacuum chamber and the additional compression of the stroke, and the magnitude of the smaller radius R _1, is determined from the tangency conditions of the contact roller 18 with a profiled surface of the pusher 23. S the arc length of the circle of radius R ₁ (including transition portion with R ₁ R ₂₎ determined by the condition:

where V is the speed of the pusher;

ν is the frequency of the alternating current.

This condition is obtained on the basis of the requirement of an arc-free opening of the contact roller and pusher. The contact time of the roller and the pusher from the moment of opening the contacts of the vacuum chamber to the moment of their discrepancy is equal to:

 Since arc quenching in a vacuum chamber occurs when the current passes through zero, and also taking into account the three-phase switching mode and the possible intermittent opening in phases, it is necessary that the duration of contact of the roller and pusher be more than 3 / 2T, where T = 1 / ν, AC frequency period, i.e.:

whence formula (1) follows. During this time, the current will pass through zero at least twice and will be switched off by vacuum chambers in all phases of the circuit breaker.

An example of calculation according to formula (1), provided that the peripheral speed V = 2 m / s and the frequency of the alternating current is 50 Hz, gives that the arc length S should be:

If the arc length S is less than the calculated value, then when switching the current in three-phase mode, if there is a certain difference in the opening of the contacts of the vacuum chambers (non-synchronous in phase), there is a possibility that the current in the vacuum chamber will not go through zero and the arc will not be extinguished. In this case, an arcing will occur between the contact roller 18 and the profiled pusher 23.

To explain the operation of the switch, figure 1, 2, 3, 4, 5 presents the positions of the elements of the switch at various times when the operations of opening and closing are performed. In the on position (Fig. 1), the main contacts of the circuit breaker are closed, the arcing contact 5 is in the position when the pusher 23, with a section of the profile with a large radius R _2, acts on the contact roller 18, compressing the disconnection and preload springs in the guide assembly and holding the contacts of the vacuum chamber in closed position. The rated current or through short-circuit current passes through the main contacts of the circuit breaker, only a small part of it passes through the contacts of the vacuum chamber, since the electrical resistance of this section of the circuit is much greater.

In the first stage of the shutdown operation (figure 2), the movement from the drive through the common shaft 7 is transmitted by levers 8 and insulating rods 9 to the main movable contacts 4 in each of the phases. They come into motion, they open with fixed contacts 3 and diverge. In this case, the opening contact 5 continues to remain in the same position until the gap in the arcuate groove between the axis 25 and the earring 24 is completely selected.

After the main contacts 3 and 4 are opened, the current passes through the closed contacts 26 and 27 of the vacuum chamber 10, the flexible connection 17, the contact roller 18, the profiled pusher 23 and the movable disconnecting contact 5. The further movement of the main contact 4 leads to the beginning of the movement of the disconnecting contact 5. B As a result, the contact roller 18 hits the transitional surface section of the profiled pusher 23. Under the action of the trip springs 13 and the preload 14, the forward movement of the contact roller begins. And after the preload stroke is selected, the contacts of the vacuum chamber will open. It is very important that by this moment the main contacts 3 and 4 have already dispersed to a distance at which ignition of the arc is impossible between them.

Further (Fig. 3), the main 4 and the movable disconnecting 5 contacts move together. The contact roller 18, having passed the transitional section of the surface of the profiled pusher 23, is rolled over the area with a smaller radius R ₁ , while maintaining electrical contact with it. The contacts 26 and 27 of the vacuum chamber are open by the stroke and a tripping arc is lit between them until the first or second transition of the disconnected current through zero. Since the moment of opening the contacts of the vacuum chamber with respect to the phase of the current is random, the transition of current through zero and its shutdown can occur on any part of the surface with a radius R _{1 of the} profile of the pusher 23. But with a very high degree of reliability it can be argued that the shutdown of current it will happen until the contact with the roller 18 ceases. After the current is switched off between the contacts 26 and 27 of the vacuum chamber, as well as between the main fixed 3 and the moving 4 and 5 contacts, the voltage is restored. In this case, the movable contacts manage to move to such a distance that the solution formed between them provides the necessary electric strength. The opening of the contact roller 18 and the profiled pusher 23 is arcless.

The fully disconnected position of the switch is shown in the figure (figure 4). A visible gap is created between the switch contacts.

The circuit breaker is as follows.

Under the action of the drive, the movement from the common shaft 7 through the levers 8 and insulating rods 9 is transmitted to the main movable contacts 4. The movable disconnecting contacts 5 come into motion after a gap is selected in the arcuate groove of the earring 24. Since the main movable contacts 4 are leading with respect to the movable disconnecting contacts 5, and the size of the arcuate groove in the earring 24 is selected such that first the main contacts 3 and 4 are closed. The contacts of the vacuum arcing chamber begin to close, then when the transition section from the smaller radius R ₁ to the larger R _{2 of the} surface of the profiled pusher 23 begins to interact with the contact roller 18. Then the compression of the breaking spring 13 occurs, the contacts 26 and 27 of the vacuum chamber are closed and they are additionally pressed by the spring 14. The closing operation has ended, the switch has returned in the starting position (figure 1).

When the switching operation is performed, the processes of touching the roller 18 with the pusher 23 and closing the contacts of the vacuum chamber are arcless, since in the first case the circuit does not short circuit (contacts 26 and 27 of the vacuum chamber are still open), and in the second case the electric circuit is already closed by main contacts 3 and 4. When switching on a short circuit current, electrodynamic forces will be perceived by the main contacts 3 and 4.

Thus, the proposed design of the load switch allows you to get the following positive effect:

1. The circuit breaker in the on position passes through short-circuit currents and the rated current through the main contacts with a minimum force to compress the contacts of the vacuum chamber.

2. When disconnecting, arc extinction is carried out by a vacuum chamber, which significantly increases the switching resource of the circuit breaker, increases the reliability of operation, eliminates the discharge of the arc into the surrounding space, improves environmental friendliness.

3. In the disconnected position, a visible gap is formed, which avoids the need to install a disconnector.

4. The vacuum chamber for such a switch can be small-sized and cheap, since it only works in a very short time interval when switching currents close to the nominal.

Sources of information

1. A.A. Chunikhin. High voltage electrical apparatus.

Circuit breakers. Volume 2. Reference. M .: Informelectro, 1996, p. 117.

2. US patent No. 4484044; cl. 200-144, publ. 11/20/1984.

3. British patent No. 2301227; publ. 11/27/1996, class H1N.

4. US patent No. 3824359, CL 200-146; publ. 07/16/1974 (prototype).

Claims (1)

A high-voltage vacuum load switch containing in each phase support insulators, a vacuum arcing chamber, a mechanism for opening its contacts, the main movable and fixed contacts, disconnecting the movable contact, the movable contacts being interconnected, and also a shaft with a system of levers transmitting rotational movement from the drive, characterized in that the vacuum arcing chamber is mounted on the main fixed contact, and the shutdown mechanism contains a contact roller interacting with the profile a pusher mounted on a movable disconnecting contact, while the surface profile of the pusher is formed by two arcs of circles centered on the axis of rotation of the opening contact, the difference between the radii of which is equal to the sum of the values of the stroke of the movable contact of the vacuum interrupter chamber and the course of the additional preload, the smaller radius being determined the condition of contact of the contact roller and the profiled surface of the pusher, and the length of the arc of a circle S of a smaller radius is determined by the condition S≥3 / 2 V / ν, where V is the speed of the pusher; ν is the frequency of the alternating current.

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