CONTACT SYSTEM FOR A LOAD STEP SWITCH

Description

[0001] The invention relates to an on-load tap-changer with a selector device and a contact system.

[0002] On-load tap-changers are used for uninterrupted switching between different winding taps of an inductive device, such as a transformer or a reactor. A fundamental problem is the occurrence of arcing between the current-carrying contacts of the on-load tap-changer. Such arcing occurs when a closed contact pair opens while a current is flowing through the contact pair. This can be an intentional opening, namely when the current is to be switched off. On the other hand, the opening can also be unintentional, for example, when external oscillations, vibrations, or force impulses act on the on-load tap-changer, or when internal movements in the on-load tap-changer transmit force impulses to the contacts.

[0003] The contacts can be surrounded by an insulating fluid, for example, the insulating fluid of the on-load tap-changer. However, the contacts can also be directly surrounded by the insulating fluid of the equipment. In both cases, arcing caused by combustion products leads to a deterioration in the quality of the insulating fluid, particularly increased electrical conductivity, and thus shortens the maintenance intervals or the service life of the on-load tap-changer or the equipment.

[0004] In addition, the arcs also lead to increased wear, particularly burn-off, of the contacts. This also shortens the maintenance intervals and the service life of the on-load tap-changer.

[0005] DE 34 03 478 A1 discloses a tap changeover switch for a transformer. Both the fixed main contacts and the movable contacts are each equipped with auxiliary contacts, which, as cylindrical rollers, can be inserted over the pins of the main or auxiliary contacts. This protects the contacts from erosion caused by arcing during switching.

[0006] DE 17 65 467 B1 discloses a high-voltage switching device. The device has fixed contacts and a movable contact bridge. The fixed contacts comprise a contact rod and a shielding element with a cup, which partially encloses the contact rod. The shielding element has a circular opening through which the contact rod protrudes from the inside of the shielding element to the outside. In a resting state, the contact rod is completely shielded by the shielding element and the cup. During a switching operation, the contact bridge performs a circular movement and presses the cup, counter to the action of a spring, into the cup-shaped shielding element and engages around the contact rod to establish contact.

[0007] DE 10 2014 107 273 A1 discloses a diverter switch for an on-load tap-changer of a variable transformer, as well as a permanent main switch for a diverter switch of an on-load tap-changer. The on-load tap-changer has a primary fixed contact, a primary moving contact, and a primary arc-discharge contact. The primary arc-discharge contact is particularly arc- and arc-resistant and assumes its final position before the associated moving contact during a switchover in order to intercept the arc.

[0008] DE 10 2016 104 499 B3 discloses a selector for an on-load tap-changer with a diverter switch. This selector, with its fixed contacts extending from the first side to the second side, allows two moving contacts to contact a fixed contact simultaneously in a stationary state. This ensures that the entire on-load tap-changer is at a defined potential and thus exhibits high surge voltage resistance.

[0009] EP 0 324 262 A1 discloses an electromagnetic actuator for use with an internal combustion engine starter. The actuator consists of an electromagnetic coil, an armature connected to a pinion assembly of the starter motor, and two fixed electrical contacts. A bridging contact can be moved by the movement of the armature against the action of a return spring to bridge the fixed contacts. An electrically conductive, flexible bridging element moves together with the bridging contact, allowing it to bridge the fixed contacts.

[0010] It is therefore an object of the present invention to provide an improved concept for an on-load tap-changer with a selector device and a contact system by which arcing in a stationary state is reduced.

[0011] This object is achieved by the subject matter of the independent claim. Further embodiments are the subject matter of the dependent claims.

[0012] The improved concept is based on the idea of ​​providing an auxiliary contact in a contact system for an on-load tap-changer with a moving contact and a fixed contact. The auxiliary contact serves to temporarily bridge the moving contact and the fixed contact in the event of an interruption in direct contact between the moving contact and the fixed contact, particularly an unintentional interruption, i.e., an interruption caused by external or internal disturbances or movement. By diverting the current via the path of least resistance, i.e., the auxiliary contact, the formation of an arc between the moving contact and the fixed contact is prevented.

[0013] According to the improved concept, an on-load tap-changer with a selector device having a contact system is specified. The contact system comprises a movable contact, occasionally also called a moving contact, and a fixed contact, as well as an additional contact. The movable contact is arranged and configured such that, in a stationary state, it makes direct contact with the fixed contact, i.e., is mechanically and electrically connected to it. In addition to this direct contact, in the stationary state, there is indirect contact between the movable contact and the fixed contact via the additional contact. During the stationary state, the additional contact thus electrically connects the movable contact to the fixed contact, in particular, this creates a parallel current path.In addition, the additional contact is designed and arranged in such a way that, in the event of an interruption of the direct contact, it can conduct a current between the fixed contact and the movable contact, in particular a current that had flowed essentially via the direct contact before the interruption.

[0014] In this context, an interruption means that the mechanical connection between the moving contact and the fixed contact is temporarily interrupted and immediately restored after the interruption. In particular, this is an unintentional interruption and not, for example, an intentional opening, which is required, for example, to perform a tap-change operation.

[0015] If an on-load tap-changer with the contact system is installed in an inductive operating device, in particular a transformer or a choke, according to at least one embodiment the movable contact and the fixed contact are in direct contact with an insulating liquid of the on-load tap-changer or the operating device.

[0016] According to at least one embodiment, during the stationary state, a contact force is exerted by the movable contact on the fixed contact, or, due to Newton's third law, a corresponding counterforce is also exerted. The contact force can be generated, for example, by a spring, in particular a preloaded compression spring, which presses the movable contact toward the fixed contact.

[0017] According to at least one embodiment, the direction of the contact force is not collinear, in particular, the contact force is perpendicular, to a direction of movement of the movable contact relative to the fixed contact during a switching of the on-load tap-changer. This applies in particular in the stationary state.

[0018] According to at least one embodiment, the interruption corresponds to the creation of a distance, in particular a contact distance, in the direction opposite to the contact force between the movable contact and the fixed contact.

[0019] According to at least one embodiment, the additional contact is designed and arranged to conduct the current between the fixed contact and the movable contact when the direct contact is interrupted, provided that the distance is not greater than a maximum contact distance.

[0020] The maximum contact distance corresponds to the maximum distance, particularly parallel to the contact force, between the moving contact and the fixed contact that can be expected during the interruption, for example, including a tolerance or safety margin and / or a surcharge to account for geometric conditions. The geometric conditions can, for example, be the shape of the moving contact and / or the shape of the fixed contact.

[0021] The maximum contact distance can therefore also depend on the contact force and the circumstances that lead to the interruption. These circumstances can include, for example, the mechanical collision of other components of the on-load tap-changer. In this case, these are internal movements in the on-load tap-changer which, on their own or in combination, can cause a direct or indirect impulse transmission to the moving contact and thus the interruption, also known as bouncing or lifting. However, the circumstances can also include external vibrations or oscillations, for example of the equipment, or impulse transmissions from outside the on-load tap-changer to the on-load tap-changer and the moving contact, which, on their own or in combination with other internal or external circumstances, cause the interruption.

[0022] Taking momentum conservation into account in closed systems, estimates can be calculated for each individual case. For typical on-load tap-changer dimensions, these values ​​for the maximum contact spacing can be in the order of 10 µm or a few 10 µm to a few 100 µm.

[0023] As described, the auxiliary contact bridges the gap between the moving contact and the fixed contact during the break. This allows a current that flows directly between the moving contact and the fixed contact before the break to flow through the auxiliary contact during the break. Since the electrical resistance of the gap, which is filled with insulating fluid, for example, is much greater than that of the auxiliary contact, no arc is formed, thus solving the problems mentioned above.

[0024] It should be noted that the duration of the interruption is typically very short, on the order of several hundred µs, for example, approximately 500 µs. This ensures that the thermal load on the auxiliary contact is very low, so that even at the high currents typically encountered in an on-load tap-changer, ranging from several hundred A to several thousand A, very small cable cross-sections and thus masses are sufficient for the auxiliary contact. The mass of the auxiliary contact can therefore be one or several orders of magnitude lower than that of the moving contact.

[0025] According to at least one embodiment, the additional contact is mechanically coupled to the fixed contact.

[0026] According to at least one embodiment, the additional contact is mechanically coupled to the movable contact in such a way that it moves with the movable contact.

[0027] The term "co-movement" here means that the additional contact moves with the movable contact when the additional contact is moved from the fixed contact to another fixed contact or vice versa, i.e., in particular, during a switching operation of the on-load tap-changer. In particular, the term "co-movement" here does not mean that the additional contact moves with the movable contact during the interruption, in particular parallel to the contact force. While the latter is possible in various embodiments, it is not the case in others.

[0028] The advantage of the mechanical coupling of the additional contact with the movable contact is that if there are several fixed contacts that can be connected by the movable contact, as is usual for on-load tap-changers, only one additional contact is required.

[0029] The term mechanical coupling includes, for example, detachable connections such as plugging, clamping or similar, as well as fixed connections such as gluing, soldering or similar.

[0030] According to at least one embodiment, in the stationary state, the movable contact contacts the fixed contact at a first region of the fixed contact, and the additional contact contacts the fixed contact at a second region of the fixed contact. The first and second regions are spaced apart by a distance greater than or equal to a predetermined minimum distance.

[0031] The contact in the first area establishes the direct contact between the moving contact and the fixed contact, the contact in the second area establishes the indirect contact between the moving contact and the fixed contact via the additional contact.

[0032] The distance is to be understood here in particular as the distance in the direction parallel to the contact force, i.e. as the magnitude of the projection of the shortest connecting vector between the first and second area onto the direction of the contact force.

[0033] According to at least one embodiment, the distance between the first and second regions is greater than or equal to the maximum contact distance between the movable contact and the fixed contact.

[0034] This is a way to ensure that in the event of an interruption, indirect contact via the additional contact is maintained and no arc is created.

[0035] According to at least one embodiment, the additional contact is designed as a lamella or sheet metal strip, in particular a self-sprung one, which is firmly connected to the movable contact and is pressed against the surface of the fixed contact during the stationary state. During the interruption, the additional contact drags along the fixed contact, maintaining electrical contact.

[0036] According to at least one embodiment, in the stationary state, an additional contact force parallel to the contact force is exerted by the additional contact on the fixed contact. At least a portion of the additional contact and the movable contact are movable relative to each other in the direction of the contact force.

[0037] For example, the auxiliary contact part is in direct contact with the fixed contact during the stationary state. Because the auxiliary contact and the movable contact are movable relative to each other, direct contact between the auxiliary contact and the fixed contact can be maintained even during the interruption, thus preventing arcing. This is especially true if the mass of the auxiliary contact is significantly smaller than that of the movable contact.

[0038] According to at least one embodiment, the part of the auxiliary contact that is movable relative to the movable contact is preloaded against the fixed contact in the stationary state. This is a further way to ensure that indirect contact via the auxiliary contact is maintained during an interruption and that no arc is generated.

[0039] According to at least one embodiment, a mass of the additional contact is at least one order of magnitude, i.e. a factor of 10, smaller than a mass of the movable contact.

[0040] According to at least one embodiment, the movable contact consists at least partially of a solid metal, for example copper, or a solid metal alloy, in particular in order to ensure a low electrical resistance and a high current-carrying capacity.

[0041] According to at least one embodiment, the additional contact consists at least partially of a copper alloy, for example a bronze, in particular a beryllium bronze or beryllium copper, such as CuBe2, or a tin bronze, such as CuSn6.

[0042] This achieves high mechanical strength with sufficiently low electrical resistance. In particular, the electrical resistance requirements of the auxiliary contact are lower than those of the moving contact. This is due to the fact that the auxiliary contact only has to carry a current during the relatively short interruption period, whereas the moving contact must carry the current continuously.

[0043] According to at least one embodiment, the additional contact is designed to be self-sprung, meaning it is at least partially elastically deformable. In particular, the additional contact is designed as a sheet metal strip shaped according to the given spatial conditions.

[0044] According to at least one embodiment, the additional contact is spring-mounted or mounted on the movable contact.

[0045] According to at least one embodiment, the additional contact is spring-mounted or mounted on a component of the contact system or of the on-load tap-changer, which moves with the movable contact.

[0046] The component can be, for example, a shaft, a gear or a Geneva wheel.

[0047] According to at least one embodiment, the selector device comprises an insulating plate having a first side and a second side, the second side being opposite the first side. The movable contact is arranged on the first side. The contact system comprises a further movable contact arranged on the second side. The further movable contact is configured to directly contact the fixed contact. In particular, the movable contact and the further movable contact can both directly contact the same movable contact in the stationary state.

[0048] According to at least one embodiment, the selector device is configured to switch the movable contact from a further fixed contact of the contact system to the fixed contact and then switch the further movable contact from the further fixed contact or from a further fixed contact to the fixed contact. In other words, the fixed contact can be considered the first fixed contact, the further fixed contact the second fixed contact, and the additional further fixed contact the third fixed contact.

[0049] According to at least one embodiment, the selector device comprises a Geneva wheel which is rotatably mounted on the insulating plate about an axis, is arranged on the first side and carries the movable contact.

[0050] According to at least one embodiment, the additional contact is attached or mounted to the Geneva wheel in a resilient manner, for example by means of a spring.

[0051] According to at least one embodiment, the selector device comprises a further Geneva wheel which is rotatably mounted on the insulating plate about the axis or a further axis, is arranged on the second side and carries the further movable contact.

[0052] According to at least one embodiment, the on-load tap-changer is designed to switch the movable contact from the fixed contact to the other fixed contact of the contact system and / or vice versa without current. In the stationary state, however, a current can flow between the movable contact and the fixed contact. This applies accordingly to a further stationary state in which the movable contact directly contacts the other fixed contact.

[0053] This means that the moving contact and the fixed contact are designed to carry high currents, but not necessarily to switch high currents. Such contacts are typically optimized for their electrical resistance, not necessarily for their resistance to arcing. Therefore, the improved concept is particularly advantageous here.

[0054] According to the improved concept, an inductive device is also specified, for example, designed as a transformer, in particular a power transformer, or designed as a choke, wherein the device comprises an on-load tap-changer according to the improved concept. The device comprises a tank for filling with an insulating medium, in particular with an insulating liquid, for example, an insulating oil. When the tank is filled with the insulating medium, i.e., in particular during operation of the device, the movable contact and the fixed contact are in direct contact with the insulating medium.

[0055] Alternatively, the on-load tap-changer itself can include an insulating container for filling with an insulating material. When the insulating container is filled with insulating material, the movable contact and the fixed contact are in direct contact with the insulating material of the on-load tap-changer.

[0056] Further designs and implementations of the selector device, the on-load tap-changer and the equipment result directly from the various designs of the contact system and vice versa.

[0057] The invention will now be explained in detail using exemplary embodiments with reference to the drawings. Components that are functionally identical or have an identical effect may be provided with identical reference numerals. Identical components or components with identical functions may only be explained with reference to the figure in which they first appear. The explanation is not necessarily repeated in subsequent figures.

[0058] It shows Figures 1A and 1B are a schematic representation of an exemplary embodiment of a contact system according to the improved concept; Figure 2 is an exemplary embodiment of a selector device according to the improved concept; and Figures 3A and 3B are a side view and a top view of another exemplary embodiment of a contact system according to the improved concept.

[0059] Figures 1A and 1B show a schematic representation of an exemplary embodiment of a contact system for an on-load tap-changer according to the improved system. The contact system comprises a fixed contact FK, which does not move during a switching operation of the on-load tap-changer, and a movable contact BK. Furthermore, the contact system comprises an additional contact ZK, which is formed, for example, as a sheet metal strip, in particular made of a copper alloy.

[0060] In Figure 1AThe contact system is in a stationary state, meaning any switching process has been completely completed, another switching process has not yet begun, and a current flows between the movable contact BK and the fixed contact FK. The movable contact BK is pressed onto the fixed contact FK with a contact force KK, for example, generated by a spring, so that the movable contact BK and the fixed contact FK are in direct contact with each other in a first region B1. In particular, the first region B1 is located on the mutually facing end faces of the movable contact BK and the fixed contact FK.

[0061] The additional contact ZK is, for example, firmly connected to the movable contact BK, in particular on an outer side of the movable contact BK. At a second area B2 of the fixed contact FK, in particular on an outer side of the fixed contact FK, the additional contact ZK contacts the fixed contact FK. However, there is no fixed connection here; the additional contact ZK, which can be designed to be self-resilient, for example, is pressed onto the fixed contact FK.

[0062] In this situation, the movable contact BK contacts the fixed contact FK directly in the first area B1 and indirectly via the additional contact ZK. Since the electrical resistance of the additional contact ZK is significantly greater than that of the direct contact, the current flows almost exclusively via the latter, as schematically indicated by the corresponding lines I.

[0063] Figure 1Bshows a situation involving the same contact system, where an interruption has occurred between the moving contact BK and the fixed contact FK. The moving contact BK has moved away from the fixed contact FK by a contact distance KA in the opposite direction to the contact force KK, for example, due to impulse transmission caused by internal and / or external mechanical influences. Due to the current flow in the steady state, an arc would therefore form between the moving contact BK and the fixed contact FK if the additional contact ZK were not present.

[0064] The additional contact ZK is dimensioned and arranged such that the distance A between areas B1 and B2 is always large enough to maintain indirect contact even when the contact distance KA reaches a maximum value. In particular, the distance A is at least as large as the maximum contact distance.

[0065] This ensures that during the interruption the current continues to be conducted via the additional contact ZK, which represents the path of least electrical resistance, as indicated by the schematic lines I. Since the duration of the interruption is very short, the thermal load on the additional contact ZK is low despite its relatively high electrical resistance and the sometimes high currents and is therefore unproblematic. Estimates for a mass of the movable contact BK of 40 g, a contact force KK of 25 N, an interruption duration of 500 µs and a current of 200 A have resulted in a temperature increase of the additional contact ZK of less than 1 K. This was based on an additional contact ZK made of CuBe2 with a cross-section of 1 mm2<.

[0066] Figure 2 shows a section of an exemplary voter device, or voter for short, with a contact system according to the improved concept. Figure 3Ashows part of the contact system in side view, while Figure 3B shows a corresponding top view. The selector comprises a first Geneva wheel M1 and a second Geneva wheel M2, which are arranged on opposite sides of an insulating plate (not shown for reasons of better visualization). Furthermore, the selector comprises a fixed contact F1 and further fixed contacts, two of which are shown as examples: F2, F3. The first Geneva wheel M1 carries a first movable contact B1, and the second Geneva wheel M2 carries a second movable contact B2. In the situation shown, both movable contacts B1, B2 make contact with the fixed contact F1. The movable contacts B1, B2 are each spring-mounted on the corresponding Geneva wheel, for example by a compression spring F, in order to exert a contact force KK from the movable contacts B1, B2 onto the fixed contact F1.

[0067] A first additional contact Z1, which is designed, for example, as a shaped sheet metal strip, rests with one edge on the first movable contact B1 and contacts it. The first additional contact Z1 contacts the fixed contact F1 with one end face. This achieves indirect contact between the first movable contact B1 and the fixed contact F1 via the first additional contact Z1.

[0068] The first additional contact Z1 is, for example, self-sprung; in particular, at least a portion of the front side of the first additional contact Z1 is elastically deformable parallel to the contact force KK. As a result, in the stationary state, an additional contact force parallel to the contact force KK is exerted by the first additional contact Z1 on the fixed contact F1. Furthermore, the mass of the first additional contact Z1 is significantly lower, for example, at least by a factor of 10, than the mass of the first movable contact B1.

[0069] This design ensures that in the event of an interruption between the first movable contact B1 and the fixed contact F1, the indirect contact via the first additional contact Z1 is maintained and arcing is prevented.

[0070] Optionally, the contact system comprises a second additional contact Z2, which is arranged with respect to the second movable contact B2 in the same way as the first additional contact Z1 is arranged with respect to the first movable contact B1. The above statements regarding the first movable contact B1 and the first additional contact Z1 then apply accordingly.

[0071] The selector is designed to actuate the Geneva wheels M1, M2 via a drive of the on-load tap-changer, in particular a drive shaft. This actuation occurs, for example, in such a way that during a switchover, the first movable contact B1 is first switched, without current, from one of the other fixed contacts F2, F3 to the fixed contact F1. Then, in the steady state, current can flow between the fixed contact F1 and the first movable contact B1. The second movable contact B2 is then also switched, for example, from one of the other fixed contacts F2, F3 to the fixed contact F1.

[0072] The various designs of a contact system, selector device, or on-load tap-changer can reduce arcing in an on-load tap-changer. This can reduce wear on the contact system due to contact erosion. It also reduces contamination of the insulating fluid of the on-load tap-changer and / or equipment. This extends the maintenance intervals of the on-load tap-changer and / or equipment, and their corresponding service lives. The on-load tap-changer can also be used under external shock loads. REFERENCE SYMBOL

[0073] Fixed contacts FK, F1, F2 movable contacts BK, B1, B2 Additional contacts ZK, Z1, Z2 Maltese wheels M1, M2 Contact force KK Lines for electricity I Feather F Distance A Contact distance KA Contact areas B1, B2

Claims

1. On-load tap-changer characterized by a selector device comprising a contact system, wherein the contact - comprises a fixed contact (FK, F1) and a movable contact (BK, B1, B2) which are arranged to contact the fixed contact (FK, F1) directly in a stationary state; and - an additional contact (ZK, Z1, Z2) which, in addition to the direct contacting, electrically connects the moving contact (BK, B1, B2) to the fixed contact (FK, F1) during the stationary state and; - the additional contact (ZK, Z1, Z2) is designed and arranged to briefly conduct a current between the fixed contact (FK, F1) and moving contact (BK, B1, B2) in the event of an interruption in which the direct contacting between the moving contact (BK, B1, B2) and the fixed contact (FK, F1) is temporarily interrupted and is immediately restored after the interruption.

2. On-load tap-changer according to claim 1, wherein the additional contact (ZK, Z1, Z2) - is mechanically coupled to the moving contact (BK, B1, B2) in such a way that it moves with the moving contact (BK, B1, B2); or - is mechanically coupled to the fixed contact (FK, F1).

3. On-load tap-changer according to one of claims 1 or 2, wherein in the stationary state - the moving contact (BK, B1, B2) contacts the fixed contact (FK, F1) at a first area (B1); - the additional contact (ZK, Z1, Z2) contacts the fixed contact (FK, F1) at a second area (B2); and - the first and second regions (B1, B2) have a distance (A) from one another which is greater than or equal to a predetermined minimum distance.

4. On-load tap-changer according to one of claims 1 or 2, wherein in the stationary state - a contact force (KK) is exerted by the moving contact (BK, B1, B2) on the fixed contact (FK, F1); - a further contact force parallel to the contact force (KK) is exerted by the additional contact (ZK, Z1, Z2) on the fixed contact (FK, F1); and - at least one part of the additional contact (ZK, Z1, Z2) and the movable contact (BK, B1, B2) are movable relative to each other in the direction of the contact force (KK).

5. On-load tap-changer according to any one of claims 1 to 4, wherein a mass of the additional contact (ZK, Z1, Z2) is at least one order of magnitude smaller than a mass of the movable contact (BK, B1, B2).

6. On-load tap-changer according to one of claims 1 to 5, wherein - the additional contact (ZK, Z1, Z2) is self-sprung; or - is spring-mounted or mounted on the moving contact (BK, B1, B2); or - is spring-mounted or mounted on a component (M1, M2) of the contact system, which moves with the moving contact (BK, B1, B2).

7. The on-load tap-changer according to any one of claims 1 to 6, wherein the interruption corresponds to the occurrence of a gap between the movable contact (BK, B1, B2) and the fixed contact (FK, F1).

8. The on-load tap-changer according to any one of claims 1 to 7, wherein the additional contact (ZK, Z1, Z2) comprises a beryllium bronze or a tin bronze.

9. The on-load tap-changer according to any one of claims 1 to 8, wherein the selector device comprises an insulating plate having a first side and a second side opposite to the first side; - the movable contact (B1) is arranged on the first side, - the contact system comprises a further movable contact (B2) arranged on the second side; and - the further movable contact (B2) is set up to contact the fixed contact (F1) directly.

10. On-load tap-changer according to any one of claims 1 to 9, wherein the selector device is arranged to switch the movable contact (B1) from a further fixed contact (F2, F3) of the contact system to the fixed contact (F1) and then to switch the further movable contact (B2) from the further fixed contact (F2, F3) or from an additional further fixed contact (F2, F3) to the fixed contact (F1).

11. On-load tap-changer according to one of claims 9 or 10, comprising a Maltese wheel (M1), which is rotatably fixed to the insulating plate about an axis and carries the movable contact (B1).

12. On-load tap-changer according to one of claims 1 to 11, wherein the on-load tap-changer is designed to switch the moving contact (BK, B1, B2) from the fixed contact (FK, F1) to a further fixed contact (F2, F3) of the contact system in a de-energized state.

13. An inductive operating means comprising an on-load tap-changer according to any one of claims 1 to 12 and a tank for filling with an insulating agent, wherein the movable contact (BK, B1, B2) and the fixed contact (FK, F1, F2, F3) are in direct contact with the insulating agent when the tank is filled with the insulating agent.