EP3743933B1 - Switching element for a stepping switch and corresponding stepping switch - Google Patents

Description

The invention relates to a switching element for a tap changer for switching between different taps of a transformer and a tap changer with such a switching element.

The use of vacuum interrupters in switching elements of tap changers, in particular on-load tap changers (OLTC), for interrupting current-carrying connections is known. Such vacuum interrupters have a fixed and a moving contact. The movable contact is connected to a plunger, which is moved axially relative to the vacuum interrupter when it is actuated. From the DE 38 33 126 A1 such a switching element for a tap changer is known. The switching element comprises a vacuum interrupter, which includes a movable contact, a plunger connected to the movable contact and a housing, inside which the movable contact is arranged, an actuating device for actuating the plunger and thus the movable contact, and a guide device which is outside of the housing and is attached to the plunger, so that the guide device is moved when the movable contact is actuated, the guide device surrounding the housing at least in part. One

Misalignment or misalignment of the moving contact with respect to the fixed contact can reduce the dielectric strength of the vacuum interrupter when open. As a result, the maximum current that can be switched with the vacuum interrupter cannot be fully utilized and the vacuum interrupter may have to be oversized.

It is therefore an object of the present invention to specify an improved concept for a switching element of a tap changer, which enables safe operation of the tap changer at higher currents.

This object is solved by the subject matter of the independent claim. Further embodiments are subject of the dependent claims.

The improved concept is based on the idea of equipping the vacuum interrupter with a guide device which moves when the movable contact is actuated and which can be supported in a partial area on a housing of the vacuum interrupter and which moves away.

As a result, a bearing point is formed on the partial area of the guide device and the housing, which ensures reliable guidance of the movable contact and the movable plunger connected thereto.

According to the improved concept, a switching element for a tap changer is specified, which includes a vacuum interrupter, an actuating device and a guide device. The vacuum interrupter comprises a moving contact, an electrically conductive plunger connected to the moving contact, and a housing. The movable contact is arranged inside the housing. The actuating device is designed to actuate the plunger, in particular to move the plunger axially, and thus to actuate the movable contact.

The guide device is arranged outside, in particular completely outside, the housing and is attached to the actuating device. Therefore, when the movable contact is actuated by the actuating device, the guide device is also moved, in particular axially. The guide device at least partially surrounds the housing. At least a portion of the guide device is in contact with the housing, in particular the outside of the housing.

Due to the fact that the partial area rests against the housing, the guide device can be supported with the partial area on the housing in order to counteract tilting of the actuating device or the plunger and the movable contact. When the movable contact is actuated by the actuating device, the partial area is moved along the housing or slides along the housing. The guide device therefore serves to guide the plunger and the movable contact when they are actuated.

The wording "rests on the housing" also includes a technically conditioned play between the partial area of the guide device and the housing, as is readily apparent to the person skilled in the art. The maximum permissible play is defined by the maximum permissible tilting according to the specific requirements in each individual case. For example, the maximum allowable play can be less than or equal to 1 mm.

"Axial" refers here to the axial direction of the vacuum interrupter or of the housing, which is, for example, at least partially cylindrical or essentially cylindrical.

By guiding the plunger and thus the movable contact, a skewed position and an offset of the movable contact with respect to a fixed contact of the vacuum interrupter are prevented. Therefore, the switching capacity of the tap changer is not reduced by the switching element.

According to at least one embodiment, the partial area has a plurality of sections, in particular arranged concentrically.

According to at least one embodiment, the guide device has several, in particular axially running, struts on. End areas of the struts form the sections of the partial area.

According to at least one embodiment, the vacuum interrupter has an external bellows, in particular a spring bellows, which seals the interior of the housing. The bellows can be designed, for example, as metal bellows or steel bellows.

In this context, external means that no housing part of the vacuum interrupter is arranged around the bellows. Vacuum interrupters with external bellows usually do not have an integrated guide for the plunger, for example inside the bellows. For this reason, the improved concept has a particularly advantageous effect when using vacuum interrupters with external bellows, in that the guidance is improved.

According to at least one embodiment, the bellows is connected to the tappet and the housing in an airtight manner for sealing purposes, for example soldered.

According to at least one embodiment, the guide device surrounds the bellows, in particular a further partial area of the guide device surrounds the bellows. This protects the bellows from external mechanical influences. The guiding device is therefore advantageously used for guiding and protecting the bellows at the same time.

Damage to the bellows can reduce the service life of the vacuum interrupter or, in the event of a leak, destroy it. The additional protection of the bellows is particularly advantageous in the case of vacuum tubes with external bellows, since the bellows would otherwise be freely accessible.

According to at least one embodiment, the further partial area completely or substantially completely surrounds the bellows. In this context, essentially completely means that the partial area can have openings, for example, but these are small enough to ensure reliable protection of the bellows. The size of acceptable openings depends on the specific application and can be, for example, in the range of 3 to 5 mm for vacuum interrupter sizes that are usual for use in tap changers.

According to at least one embodiment, the actuating device comprises a bolt which is connected to the tappet and is arranged coaxially with it. Bolt and ram therefore move together in the axial direction.

According to at least one embodiment, the actuating device comprises a bearing block which forms a bearing point for the bolt and guides the bolt during actuation. In particular, the bolt is passed through a tubular part of the bearing block.

As a result, two bearing points are formed, the bearing point mentioned in the bearing block and the bearing point mentioned further above in the contact area of the guide device and the housing of the vacuum interrupter. The two bearing points ensure that the bolt, the plunger and the moving contact are guided in a particularly reliable manner. Configurations in which the support spacing, ie the spacing between the two bearing points, is as large as possible are particularly advantageous.

According to at least one embodiment, the vacuum interrupter, in particular the housing, comprises an interrupter chamber, within which the movable contact is arranged, and an insulating body, which is arranged between the interrupter chamber and the bellows. The contact area between the guide device and the housing and thus the second bearing point is then, for example, at the level of the switching chamber. This achieves a high support distance.

According to at least one embodiment, the actuating device comprises an actuating lever which is connected to the bolt for actuating the bolt and the plunger.

According to at least one embodiment, the guide device has a first opening for receiving the actuating device, in particular the bolt or the plunger, and a second opening for receiving the housing. As a result, the guide device can be plugged onto the vacuum interrupter to a certain extent. The openings are, for example, circular or substantially circular and are located at opposite axial ends of the guiding device.

The bellows is arranged, for example, on the side of the housing facing the bolt and is therefore located completely within the guide device.

According to at least one embodiment, the guide device has an electrically conductive insert or an electrically conductive sleeve, which is electrically connected to the plunger and is arranged, for example, in the first opening. In particular, the insert and the plunger are each in contact at the front and are thus electrically connected.

According to at least one embodiment, the insert includes brass, a brass alloy, copper, or a copper alloy.

According to at least one embodiment, the guide device is attached to the plunger and/or the bolt. Alternatively or additionally, the guiding device can be connected to the actuating device in that the guiding device, in particular the insert, is clamped between the bolt and the plunger.

According to at least one embodiment, the switching element has a connection contact, for example a connection plate, a connection wire or a connecting strand, which is electrically connected to the insert.

The connection contact is used to electrically connect the movable contact to another component of the tap changer. The movable contact can be, for example, a main switching contact or a resistance contact (transition contact). In this regard, reference is made to the customary nomenclature in accordance with IEC 60214-1:2014 or DIN EN 60214-1:2014.

According to at least one embodiment, the guide device and/or the partial area which is in contact with the housing of the vacuum interrupter is rotationally symmetrical or essentially rotationally symmetrical. This avoids a resultant net force being exerted on the vacuum interrupter by the guide device.

The term "rotationally symmetrical" is to be understood in such a way that it includes both discrete rotational symmetries and continuous rotational symmetry, ie rotational symmetry.

According to the improved concept, a tap changer, in particular an on-load tap changer, is also specified, which comprises at least one switching element according to the improved concept.

In accordance with at least one embodiment, the tap changer is designed as a high-speed resistor switch (OLTC type resistor) or as a reactor type OLTC switch.

According to at least one embodiment of the tap changer, the tap changer includes a diverter switch, which includes the switching element or a load selector (English: selector switch), which includes the switching element.

According to at least one embodiment of the tap changer, the movable contact serves as a switching contact or as a resistance contact of the tap changer.

According to at least one embodiment of the tap changer, several, preferably all, switching contacts and/or several, preferably all, resistance contacts are designed, each with a switching element according to the improved concept.

The invention is explained in detail below using exemplary embodiments with reference to the drawings. Components that are functionally identical or have an identical effect may be given identical reference numbers. Identical components or components having an identical function may only be explained with respect to the figure in which they first appear. The explanation is not necessarily repeated in subsequent figures.

Figur 1

eine perspektivische Darstellung einer beispielhaften Ausführungsform eines Schaltelements gemäß dem verbesserten Konzept;

Figur 2

eine weitere perspektivische Ansicht des Schaltelements aus Figur 1;

Figur 3

eine Längsschnittdarstellung des Schaltelements aus Figur 1;

Figur 4

eine perspektivische Ansicht einer beispielhaften Ausführungsform einer Führungsvorrichtung für ein Schaltelement gemäß dem verbesserten Konzept; und

Figur 5

eine Längsschnittdarstellung der Führungsvorrichtung aus Figur 4.

Show it

figure 1

a perspective view of an exemplary embodiment of a switching element according to the improved concept;

figure 2

Another perspective view of the switching element figure 1 ;

figure 3

a longitudinal sectional view of the switching element figure 1 ;

figure 4

a perspective view of an exemplary embodiment of a guide device for a switching element according to the improved concept; and

figure 5

a longitudinal sectional view of the guide device figure 4 .

Figures 1, 2 and 3 12 show perspective illustrations and a longitudinal section illustration of an exemplary embodiment of a switching element according to the improved concept. With the exception that the guiding device F in figure 2 not shown are Figures 1 and 2 identical.

The switching element includes a vacuum interrupter V with a housing. The case has a switching chamber S, which has, for example, a partially circular-cylindrical outer wall and can consist at least partially of metal. The housing also has an insulating body IK, which is essentially designed as a tubular section with an annular cross section and consists at least partially of an electrically insulating material, for example a ceramic material. The insulator IK is placed on the switching chamber S and connected to it.

The vacuum interrupter V has a contact K1 that is movable axially with respect to the vacuum interrupter V, a stationary contact K2, and a movable plunger ST, which is connected to the movable contact K1. The contacts K1, K2 are arranged in the switching chamber S.

Furthermore, the vacuum interrupter V has an external bellows B, for example a steel bellows, which is placed on the insulating body IK and connected to the insulating body IK, in particular airtight. The ram ST runs from outside the housing through the bellows B into the switching chamber S. The bellows B is also connected to the ram ST in an airtight manner.

The vacuum interrupter can be opened and closed by actuating the plunger ST and thus the movable contact K1. The bellows B is stretched or compressed in the process.

The exemplary switching element has a bolt BZ, which is connected to the tappet ST and is oriented coaxially with it. The bolt BZ can be actuated using an operating lever H (in figure 3 not shown), which is designed here by way of example as an angle lever, are actuated.

The switching element shown has, for example, a bearing block L (in figure 3 not shown) with a tubular guide bearing FL, through which the bolt BZ is guided from the vacuum interrupter V to the actuating lever H. The bearing block L can be attached to another component of the tap changer, for example a frame or rack.

The exact configuration of the actuating device, in particular the bolt BZ, the actuating lever H and the bearing block L, depends on the particular configuration of the tap changer in which the switching element is to be used.

The switching element also has a guide device F, which is designed for example as a cage and partially encloses the vacuum interrupter V, in particular completely surrounds the bellows B. The guide device F is plugged onto the vacuum tube V, for example. The guiding device F is in Figures 4 and 5 shown separately.

The guide device F has a first opening O1 in which, for example, an electrically conductive insert E is arranged. The insert E is essentially tubular or designed as a sleeve. The opening O1 accommodates the bolt BZ, in particular the bolt BZ is guided through the insert E. The bolt BZ is attached to the guide device F, so that the guide device F is moved back and forth when the bolt is actuated. For this purpose, the insert E, and thus the guide device F, can be clamped between the bolts BZ and the ram ST. Alternatively or additionally, the bolt BZ can be connected to the insert E.

With the exception of the insert E and optionally components for fastening the insert E in the opening O1, the guide device F consists of electrically insulating material, for example a plastic, and can be designed in one piece.

The insert E is electrically connected to a connection contact AK of the switching element and to the plunger ST.

To accommodate the housing, in particular the switching chamber S, the guide device F has a second opening O2 opposite the first opening O1. In the exemplary embodiment shown, the guide device F has a plurality of concentrically arranged fingers or struts FI, which are connected to one another by means of an annular component R, for example near the second opening O2. The ring-shaped component R and/or end regions of the fingers or struts FI, in particular end regions arranged around the second opening O2, form a partial region of the guide device F which bears against the switching chamber S.

When the vacuum interrupter V is actuated by means of the actuating lever H, bolt BZ, ram ST and contact K1, the guide device F moves with it. Since the partial area is in contact with the switching chamber S, the guide device F can be supported on the outer wall of the switching chamber S and partially moves along it. This counteracts or prevents tilting of bolt BZ, plunger ST or movable contact K1.

As a result, two bearing points are realized. A first bearing point is formed by the guide bearing FL, a second by the adjacent to the switching chamber S portion of the guide device F. This is a significantly improved management of Bolt BZ, ram ST and contact K1 achieved than would be the case without the guide device F, since in the latter case only a single bearing point would be given, namely in the guide bearing FL. Advantageously, the two bearing points (under technically specified boundary conditions) can be as far apart as possible, so that particularly reliable guidance is achieved.

With a switching element or a tap changer according to the improved concept, due to the improved guidance of the actuating device and the moving contact of the vacuum interrupter, tilting and displacement of the moving contact are prevented or minimized. In addition, a misalignment is prevented by installing the vacuum interrupter at an angle when installing the tap changer. A disadvantageous reduction in the dielectric strength is thus prevented. By avoiding the oblique installation of the vacuum interrupter, it is also achieved that stresses in the vacuum interrupter are avoided. In addition, mechanical wear of the vacuum interrupter and the actuating device can be reduced. If vacuum interrupters with external bellows are used, the guide device also protects the bellows from mechanical damage and from overstressing.

REFERENCE MARKS

V

vacuum interrupter

S

switching chamber

IC

insulator

B

bellows

K1

moving contact

K2

solid contact

ST

pestle

f

guiding device

BZ

bolt

AK

connection contact

L

bearing block

FL

guide bearing

FI

finger

R

annular component

H

operating lever

O1, O2

openings

E

mission

Claims (13)

1. Switching element for a tap changer, the switching element comprising

   - a vacuum interrupter (V) comprising a movable contact (K1), a plunger (ST) connected with the movable contact (K1) and a housing, in the interior of which the movable contact (K1) is arranged;

   - an actuating device for actuating the plunger (ST) and thus the movable contact (K1); and

   - a guiding device (F) which is arranged outside the housing and attached to the actuating device, so that when actuation of the movable contact (K1) takes place the guiding device (F) is moved therewith;

   - wherein the guiding device (F) surrounds the housing at least in part and at least a sub-region of the guiding device (F) bears against the housing, so that when the movable contact (K1) is actuated the sub-region is moved along the housing.
2. Switching element according to claim 1, wherein the vacuum interrupter (V) comprises an externally disposed bellows (B) sealing off the interior of the housing.
3. Switching element according to claim 2, wherein the guiding device (F) surrounds the bellows (B) and thereby protects the bellows (B) from external mechanical effects.
4. Switching element according to any one of claims 1 to 3, wherein the actuating device comprises

   - a bolt (BZ) connected with the plunger (ST); and

   - a bearing block (L) which forms a bearing point for the bolt (BZ) and guides the bolt (BZ) when actuated.
5. Switching element according to claim 4, wherein the guiding device (F) is attached to the bolt (BZ) and/or the plunger (ST) or is firmly clamped between the bolt (BZ) and plunger (ST).
6. Switching element according to any one of claims 1 to 5, wherein the guiding device (F) has a first opening (O1) for receiving the actuating device and a second opening (O2) for receiving the housing.
7. Switching element according to claim 6, wherein the guiding device (F) comprises an electrically conductive insert (E) which is arranged in the first opening (O1) and electrically connected with the plunger (ST).
8. Switching element according to claim 7, wherein the switching element has a terminal contact (AK) electrically connected with the insert (E).
9. Switching element according to any one of claims 1 to 8, wherein the vacuum interrupter (V) comprises a switching chamber, within which the movable contact is arranged, and an insulating body and wherein the sub-region of the guiding device (F) bears against the switching chamber.
10. Switching element according to any one of claims 1 to 9, wherein the guiding device (F) and/or the sub-region is or are formed to be rotationally symmetrical.
11. Tap changer comprising a switching element according to any one of claims 1 to 10.
12. Tap changer according to claim 11, wherein the tap changer comprises a diverter switch or a selector switch, which comprises the switching element.
13. Tap changer according to one of claims 11 and 12, wherein the movable contact (K1) serves as a switching contact or as a resistance contact of the tap changer.

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