EP4651166A1

EP4651166A1 - A switching pole for electrical applications

Info

Publication number: EP4651166A1
Application number: EP24176612.0A
Authority: EP
Inventors: Carlo Boffelli; Fabio Giacalone
Original assignee: ABB Schweiz AG
Current assignee: ABB Schweiz AG
Priority date: 2024-05-17
Filing date: 2024-05-17
Publication date: 2025-11-19

Abstract

A switching pole (1) comprises a vacuum interruption chamber (10) housing a fixed contact (2) and a movable contact (3) moving between an open position in which it is separated from the fixed contact (2) and a closed position in which it is electrically coupled to the fixed contact (2). In closed position said movable contact (3) has a closed condition in which it is electrically coupled to the fixed contact (2) and a closed and pressed condition in which it is electrically coupled to the fixed contact (2) under a mechanical load forcing it against said fixed contact (2). The switching pole (1) comprises an improved motion transmission assembly (4) which is operatively coupled to the movable contact (3) and is placed outside said vacuum interruption chamber (10).

Description

The present invention relates to a switching pole for electrical applications. More particularly, the present invention relates to a switching pole having a vacuum interruption chamber and provided with an improved motion transmission assembly for operating a movable contact of said switching pole.
The switching pole, according to the invention, is particularly adapted for being employed in switching units and switching apparatuses installed in medium voltage electrical systems, for example in medium voltage switchgears, switchboards, or electric grids.
Switching apparatuses including switching poles based on vacuum interruption switching technology are well known in the field of electrical systems, particularly in those operating at medium voltage levels.
Even if they can generally provide rather satisfactory performances, most recent switching apparatuses of this type still have some aspects to improve.
The switching poles of these switching apparatuses are relatively bulky, particularly along their main longitudinal axis, which can sometimes make rather problematic their installation in modern electrical systems where installation spaces are often narrow.
These limitations result particularly critical in electrical systems operating at relatively high voltages (e.g., 72 kV), where switching apparatuses including multiple switching poles electrically connected in series, for each electric phase, are typically installed.
The main aim of the present invention is to provide a switching pole for electrical applications, which allows overcoming or mitigating the above-mentioned drawbacks of the known art. Within this aim, a purpose of the present invention is to provide a switching pole having a simple and compact structure with a relatively small size, particularly along its main longitudinal dimension.
A further purpose of the present invention is to provide a switching pole relatively simple and cheap to manufacture at industrial levels.
The above aim and purposes, as well as other purposes that will emerge clearly from the following description and attached drawings, are provided, according to the invention, by a switching pole, according to the following claim 1 and the related dependent claims.
In a general definition, the switching pole, according to the invention, comprises first and second pole terminals and a vacuum interruption chamber housing a fixed contact electrically connected to the first pole terminal and a movable contact electrically connected to the second pole terminal.
In the switching pole, according to the invention, the movable contact can move along a translation axis between an open position, in which it is separated from the fixed contact, and a closed position, in which it is electrically coupled to the fixed contact.
In closed position, the movable contact can take a closed condition, in which it is simply electrically coupled to the fixed contact, and a closed and pressed condition, in which it is electrically coupled to the fixed contact under a mechanical load forcing it against the fixed contact.
The switching pole, according to the invention, comprises a motion transmission assembly placed outside the vacuum interruption chamber and operatively coupled to the movable contact.
The motion transmission assembly comprises:

a bushing element coupled to the movable contact so as to be electrically connected to the movable contact and move together with this latter. The bushing element is in sliding contact with the second pole terminal so as to be electrically connected to this latter;
a pushrod operatively connected to an actuating drive mechanism and partially accommodated in a coupling cavity of the bushing element;
an elastic element accommodated in the coupling cavity of the bushing element and interposed between the bushing element and the pushrod.

According to an aspect of the invention, the bushing element includes a main body at least partially made of a same conductive material.
According to another aspect of the invention, the bushing element includes a main body at least partially made of a first conductive material and it includes one or more internal walls defining the coupling cavity and at least partially covered by a layer of a second conductive material having a higher mechanical resistance compared to the first conductive material.
According to an aspect of the invention, the elastic element of the switching pole is in a discharged or preloaded condition, when the movable contact is in open position and in closed position and in a closed condition, and it is in a loaded condition, when the movable contact is in closed position and in a closed and pressed condition.
The elastic element is compressed during a phase of a closing manoeuvre of the switching pole, in which the movable contact is in closed position and passes from a closed condition to a closed and pressed condition, and it is released during a phase of an opening manoeuvre of the switching pole, in which the movable contact is in closed position and passes from a closed and pressed condition to a closed condition.
According to an aspect of the invention, the pushrod of the switching pole moves together with the movable contact and the bushing element during a first phase of a closing manoeuvre of the switching pole, in which the movable contact moves from the open position to the closed position. The pushrod moves relative to the movable contact and the busing element by sliding along the coupling cavity of the bushing element during a second phase of a closing manoeuvre of the switching pole, in which the elastic element is compressed and the movable contact is in closed position and passes from a closed condition to a closed and pressed condition.
The pushrod of the switching pole moves relative to the movable contact and the bushing element by sliding along the coupling cavity of the bushing element during a first phase of an opening manoeuvre of the switching pole, in which the elastic element is released and the movable contact is in closed position and passes from a closed and pressed condition to a closed condition. The pushrod moves together with the movable contact and the bushing element during a second phase of an opening manoeuvre of the switching pole, in which the movable contact moves from the closed position to the open position.
In a further aspect, the present invention also relates to a switching unit and a switching apparatus including one or more switch poles, according to the invention.
Further features and advantages of the present invention will be more apparent from the description of preferred but not exclusive embodiments of the present invention, shown by way of examples in the accompanying drawings, wherein:

Figure 1 is section view a switching pole, according to the present invention, with its movable contact in an open position;
Figure 2 is section view a switching pole, according to the present invention, with its movable contact in a closed position and in a closed condition;
Figure 3 is section view a switching pole, according to the present invention, with its movable contact in a closed position and in a closed and pressed condition;
Figures 4-5 are partial views of a motion transmission assembly of the switching pole, according to the present invention in different operating conditions;
Figure 5A is a view of the motion transmission assembly of the switching pole, according to another embodiment of the present invention;
Figures 6-6A are partial exploded views of a motion transmission assembly of the switching pole, according to the present invention;
Figure 7 is a schematic view of a switching unit including a pair of switching poles, according to the invention, electrically connected in series;
Figure 8 is a schematic view of a switching apparatus including a switching pole, according to the invention, for each electric phase;
Figure 9 is a schematic view of a switching apparatus including a pair of switching poles, according to the invention, electrically connected in series for each electric phase.

With reference to the above-mentioned figures, the present invention relates to a switching pole 1 for electrical applications.
The switching pole 1 is particularly adapted for being employed in switching units and switching apparatuses (particularly in circuit breakers) to be installed in medium voltage electrical systems, for example in medium voltage switchgears, switchboards, or electric grids. In principle, however, the switching pole 1 can be employed in switching units and switching apparatuses to be installed in low voltage electrical systems.
For the purposes of the present invention, the term "medium voltage" is intended to designate electrical systems operating at voltage levels higher than 1 kV AC and 1.5 kV DC up to some tens of kV, e.g., up to 72 kV AC and 100 kV DC, while the term "low voltage" is intended to designate electrical systems operating at voltage levels lower than 1 kV AC and 1.5 kV DC.
The switching pole 1 comprises first and second pole terminals 11, 12.
When the switching pole is installed, the first pole terminal 11 can be electrically connected to a conductor of an electric line while the second pole terminal 12 can be electrically connected to a conductor of an electric line or to a conductive component of a switching unit or switching apparatus, in which the switching pole is arranged.
The pole terminals 11, 12 are preferably made by shaped pieces of conductive material suitably fixed to other support components of the switching pole.
The switching pole 1 comprises a vacuum interruption chamber 10 housing a fixed contact 2 and a movable contact 3.
The vacuum interruption chamber 10 has an outer enclosure defining an internal volume, in which a vacuum atmosphere is obtained. Such an outer enclosure includes first and second airtight apertures 10B, 10C through which the above-mentioned fixed contact 2 and the movable contact 3 are inserted.
The fixed contact 2 is preferably formed by a shaped piece of conductive material fixed to the outer enclosure of the vacuum interruption chamber and passing through the first airtight aperture 10B of the latter. The fixed contact 2 is coupled to or forms one piece with the first pole terminal 11.
The movable contact 3 can move relative to the vacuum interruption chamber 10 along a translation axis A between an open position (figure 1), in which it is separated from the fixed contact 2, and a closed position (figures 2-3), in which it is electrically coupled to the fixed contact 2.
In closed position, the movable contact 3 can take a closed condition (figure 2), in which it is electrically coupled to the fixed contact 2, and a closed and pressed condition, in which it is electrically coupled to the fixed contact 2 under a mechanical load, which forces it against the fixed contact 2 (figure 3).
A transition of the movable contact 3 from an open position to a closed position and a closed and pressed condition forms a closing manoeuvre of the switching pole while a transition of the movable contact 3 from a closed position and a closed and pressed condition to an open position forms an opening manoeuvre of the switching pole.
The movable contact 3 is preferably formed by a solid elongated conductive body extending along the translation axis A. For instance, with reference to the above-mentioned figures, the movable contact 3 may have a substantially cylindrical body having the translation axis A as a main longitudinal axis.
The movable contact 3 passes through the second airtight aperture 10B of the vacuum interruption chamber and it has a first end 36, which is placed inside the vacuum interruption chamber 10 and has a contact surface 360 that can be coupled to a corresponding contact surface 20 of the fixed contact 2, when the movable contact reaches the closed position, and a second end 37, which is opposite to the first end 36 and is placed outside the vacuum interruption chamber 10.
Advantageously, the second end 37 of the movable contact 3 includes a first coupling surface 370 for coupling to a motion transmission assembly of the switching pole.
In general, the vacuum interruption chamber 10 and the related contact system 2, 3 can be realized in practice according to solutions of know type. In the following, these components will be described only in relation to the aspects of interest of the invention, for the sake of brevity.
The switching pole 1 comprises a motion transmission assembly 4 placed outside the vacuum interruption chamber 10 and operatively coupled to the movable contact 3.
The motion transmission assembly 4 comprises a conductive bushing element 8 coupled to the movable contact 3 in such a way to be electrically connected to the movable contact 3 and move together with this latter.
The bushing element 8 preferably includes a main conductive body, which is partially hollow, and it has an elongated shape extending along an axis parallel to or coinciding with the translation axis A of the movable contact 3.
Preferably, the bushing element 8 is aligned with the movable contact 3 along the translation axis A of this latter.
The bushing element 8 includes a second coupling surface 83 for coupling to a corresponding first coupling surface 370 of the movable contact 3.
Preferably, the bushing element 8 includes a first portion 81 defining a first coupling cavity 87. Advantageously, the first coupling cavity 87 extends along the translation axis A and it is open outwards in such a way that the second end 37 of the movable contact 3 is inserted therein.
Preferably, at the first coupling cavity 87, the first portion 81 includes the above-mentioned second coupling surface 83 of the bushing element. Conveniently, the first portion 81 includes an internal wall 870 defining laterally the first coupling cavity 87 and including the second coupling surface 83, which extends along the translation axis A.
According to preferred embodiments of the invention, the above-mentioned first and second coupling surfaces 370, 83 are threaded surfaces so that the movable contact 3 and the bushing element 3 can be screwed one to another.
According to other embodiments of the invention, however, the movable contact 3 and the bushing element 8 can be made in one piece. In this case, first and second coupling surfaces 370, 83 are structurally integrated.
Preferably, the bushing element 8 includes a second portion 82 opposite to the first portion 81 and defining a second coupling cavity 80 for accommodating further components of the motion transmission assembly 4.
Advantageously, the second coupling cavity 80 extends along the main longitudinal axis of the bushing element (e.g., the translation axis A) and it is open outwards in such a way that further components of the motion transmission assembly 4 can be inserted therein.
At the second coupling cavity 80, the bushing element 8 includes a third coupling surface 86 for coupling with a further component of the motion transmission assembly 4.
Preferably, the second portion 82 includes an internal wall 802 defining the bottom of the first coupling cavity 80 and comprising the third coupling surface 86, which extends transversally relative to the translation axis A.
According to preferred embodiments of the invention, the second coupling cavity 80 is in communication with the first coupling cavity 87 through a hole 88 coaxially aligned with the above-mentioned coupling cavities. This solution is quite advantageous for securing the bushing element 8 to the movable contact 3. A securing screw can in fact be inserted through the hole 88 and through a threaded hole of the second end 37 of the movable contact 3, when this latter is inserted into the first coupling cavity 87.
Preferably, the bushing element 8 includes a ring cover 85 removably coupled (e.g., screwed) to the second portion 82 of the bushing element. When it is coupled to the second portion 82 of the bushing element, the ring cover 85 forms a stop element for the components of the motion transmission assembly that are accommodated in the second coupling cavity 80.
Preferably, when the cover ring 85 is mounted, an elastic blocking ring 851 is positioned in a dedicated groove 852 of the ring cover 85 and a corresponding groove 801A of the internal wall 801 laterally defining the coupling cavity 80 in such a way to prevent the accidental disengage of the ring cover 85 in operation.
The bushing element 8 is in sliding contact with the second pole terminal 12 in such a way to be electrically connected to this latter. In this way, a conductive path can be formed along the movable contact 3, the bushing element 8 and the second terminal 12.
Preferably, the second pole terminal 12 includes a contact ring 120 having a contact surface in sliding contact with an outer surface of the second portion 82 of the bushing element.
According to some embodiments of the invention, the main body of the bushing element 8 is at least partially made of a same conductive material, for example aluminium, brass, or copper.
According to other embodiments of the invention, when the main body of the bushing element is made of relatively "soft" conductive material (e.g., copper or aluminium), the internal wall 801 has an internal surface 84, which laterally defines the coupling cavity 80, at least partially covered by a layer 801B of a second material (e.g. steel), which has a higher mechanical resistance (figure 5A).
This last solution is quite advantageous as it allows limiting possible wear phenomena at the internal wall 801 in sliding contact with the components of the motion transmission assembly accommodated in the second coupling cavity 80.
The motion transmission assembly 4 comprises a pushrod 5 operatively connected to an actuating drive mechanism 100 of the switching pole and partially accommodated in the second coupling cavity 80 of the bushing element 8.
Preferably, the pushrod 5 includes a first end 51, which is operatively connected to the actuating drive mechanism 100, and a second end 52, which is opposite to the first end 51 and is accommodated in the second coupling cavity 80 of the bushing element.
Preferably, the pushrod 5 includes a solid elongated body of steel or another material with high mechanical resistance, which is aligned with the second coupling cavity 80 of the bushing element.
The pushrod 5 includes a fifth coupling surface 55 for coupling to a further component of the motion transmission assembly.
Preferably, the pushrod 8 has a collar 50 including the above-mentioned fifth coupling surface 55 that extends transversally relative to the translation axis A.
Conveniently, the second end 52 of the pushrod 5 passes through the ring cover 85 of the bushing element, which can thus provide guide and support to the pushrod. In operation the ring cover 85 forms a stop for the collar 50 of the pushrod, thereby preventing the second end 52 of the pushrod to get out of the second coupling cavity 80 of the bushing element.
The motion transmission assembly 4 comprises an elastic element 7 arranged coaxially to the bushing element 8.
The elastic element 7 is accommodated in the second coupling cavity 80 of the bushing element and it is interposed between the bushing element 8 and the pushrod 5.
Advantageously, the elastic element 7 is interposed between the third coupling surface 86 of the bushing element 8 and the fifth coupling surface 55 of the pushrod 5.
Preferably, the elastic element 7 is a spring, e.g., a coil spring or a cup spring.
The elastic element 7 provides the necessary pressing force on the contacts 2, 3 when the contacts 2, 3 are closed during a closing manoeuvre of the switching pole. Namely, the elastic element 7 determines the passage from a closed condition to a closed and pressed condition of the movable contact 3, when this latter has reached the closed position.
From an operational standpoint, the elastic element 7 is in a discharged or preloaded condition, when the movable contact 3 is in open position and in closed position and in a closed condition, and it is in a loaded condition, preferably a fully loaded condition, when the movable contact 3 is in closed position and in a closed and pressed condition.
In practice, with reference to the attached figures, in the position of figures 1 and 2 the elastic element 7 is in a discharged or preloaded condition, while in the position of figure 3 it is in a loaded condition, preferably a fully loaded condition, thereby providing the required necessary pressing force on the coupled electric contacts 2, 3.
Thus, in general, the elastic element 7 acts only during the pressing stroke of the pushrod 5 (i.e., when the movable contact 3 is in closed position and passes from a closed condition to a closed pressed condition) and provides the required contact pressure on the contact system in the vacuum interruption chamber 10.
Preferably, the elastic element 7 is inserted into the second coupling cavity 80 in a preloaded condition. When it is not compressed, the elastic element 7 pushes the pushrod 5 against the ring cover 85 of the bushing element (figures 1-2).
The motion transmission assembly 4 comprises a support element 6 positioned fixed with respect to the vacuum interruption chamber 10.
The support element 6 surrounds at least partially the bushing element 8 and the remaining components of the motion transmission assembly 4 and it provides guide and support to these latter. Preferably, the second pole electrode 12 is fixed to the support element 6.
According to some embodiments of the invention (not shown or described in further details for the sake of brevity), the motion transmission assembly 4 comprises a further elastic element mounted on the bushing element 8 and interposed between the bushing element and the support element 6. Advantageously, such a further elastic element, which may be a spring realized according to solutions of known type, can be coaxially mounted on the bushing element 8. The operation of the switching pole, according to the invention, is now described in the following.

Closing manoeuvre of the switching pole

During a first phase of the closing manoeuvre of the switching pole, the movable contact 3 moves from the open position (figure 1) to the closed position and in a closed condition (figure 2). At this stage of the closing manoeuvre, the elastic element is not compressed. The pushrod 5 moves together with the bushing element 8 and the movable contact 3 that is brought to the closed position.
During a second phase of the closing manoeuvre of the switching pole, the movable contact 3 is in closed position and passes from a closed condition to a closed and pressed condition (figure 3). At this stage of the closing manoeuvre, the movement of the pushrod 5 is decoupled from the movable contact 3 and the bushing element 8. The pushrod 5 moves relative to these latter by sliding along the coupling cavity 80 and it causes the compression of the elastic element 7, which exerts a pressing force bringing the movable contact 3 in closed and pressed condition.

Opening manoeuvre of the switching pole

During a first phase of an opening manoeuvre of the switching pole, the movable contact 3 is in closed position and passes from a closed and pressed condition (figure 3) to a closed condition (figure 2). At this stage of the closing manoeuvre, the movement of the pushrod 5 is decoupled from the movable contact 3 and the bushing element 8. The pushrod 5 moves relative to these latter and it slides along the coupling cavity 80 (along an opposite direction compared to a closing manoeuvre). The elastic element 7 is released, thereby bringing the movable contact 3 in closed condition.
During a second phase of the opening manoeuvre of the switching pole, the movable contact 3 moves from the closed position and in closed condition (figure 2) to the open position (figure 1). At this stage of the opening manoeuvre, the elastic element is not compressed. The pushrod 5 thus moves together with the bushing element 8 and the movable contact 3 that is brought to the open position.
The operation of the switching pole, according to the invention, is substantially the same if the motion transmission assembly 4 comprises a further elastic element mounted on the bushing element 8. In this case, such a further elastic element contributes to overcome the external atmospheric pressure, which is directed to move the movable contact 3 towards the fixed contact 2, during an opening manoeuvre of the switching apparatus.
In a further aspect the present invention also relates to a switching unit comprising one or more switching poles according to the invention.
Figure 7 shows, as an example, a medium voltage switching unit 200 including a pair of switching poles 1A, 1B electrically connected in series.
Each of the switching poles 1A, 1B is realized according to the invention, as described above. The first pole terminals 11 of the switching poles 1A, 1B can be electrically connected to corresponding conductors of an electric line while the second pole terminals 12 are electrically connected to a conductive enclosure 101 in such a way to be electrically connected in series. The pushrods 5 of the switching poles 1A, 1B are mechanically coupled to a common actuating drive mechanism 100 that is in turn operatively coupled to an actuating drive (not shown). Such an actuating drive can be realized according to solutions of know type. For instance, an actuating drive of the mechanical type can be used, as well as an electro-mechanical actuator, e.g., based on servomotors, or a hydraulic actuator, or any similar actuating device.
Also, the drive mechanism 100 can be realized according to solutions of know type. Preferably, it is arranged (e. g., as a toggle mechanism) in such a way that the switching poles 1A, 1B are operated in a synchronized manner.
Preferably, the drive mechanism 100 is accommodated at least partially in a volume delimited by the conductive enclosure 101.
The switching poles 1A, 1B are aligned along a common translation axis A of the movable components of the switching poles. The movable contacts 3 of the switching poles thus move according to opposite directions during an opening manoeuvre or a closing manoeuvre of the switching poles.
In a further aspect the present invention also relates to a switching apparatus comprising one or more switching poles according to the invention.
Figure 8 shows, as an example, a medium voltage switching apparatus 300 including a switching pole 1, according to the invention, for each electric phase.
In this figure, only the relevant components of the switching poles 1 are represented while the other details are not shown for simplicity purposes.
The switching apparatus 300 comprises a gas tight enclosure 250 which houses the switching poles 1 according to the invention.
The switching apparatus comprises a common drive mechanism 100 operatively connected to the pushrods 5 of the switching poles.
The drive mechanism 100 can be realized according to solutions of know type. Preferably, it is arranged in such a way that the switching poles 1A, 1B are operated in a synchronized manner. Preferably, the drive mechanism 100 is accommodated within the gas tight enclosure 250. The drive mechanism 100 is operatively coupled to an actuating drive 100A.
Also, the actuating drive 100A can be any according to the state of the art.
The actuating drive 100A can be accommodated in the gas tight enclosure 250 or placed externally to this latter.
Figure 9 shows, as a further example, a medium voltage switching apparatus 300 including a pair of switching poles 1A, 1B, according to the invention, electrically connected in series, for each electric phase.
The switching poles 1A, 1B of each electric phase can be electrically connected in series through suitable conductive components electrically connecting the second pole terminals 12 of each pair of switching poles, similarly to the solution shown in figure 7.
The switching apparatus 300 preferably comprises a gas tight enclosure 250 housing the switching poles 1A, 1B and a common drive mechanism 100 operatively connected to the pushrods 5 of the switching poles.
Preferably, the drive mechanism 100 is arranged in such a way that the switching poles 1 of all the switching units 200 are operated in a synchronized manner.
The drive mechanism 100 can be arranged according to solutions of known type (figure 7). The drive mechanism 100 is operatively coupled to an actuating drive 100A, which can be realized according to solutions of known type as well.
The actuating drive 100A can be accommodated in the gas tight enclosure 250 or placed externally to this latter.
The switching pole 1, according to the invention, provides relevant advantages with respect to corresponding known systems of the state of the art.
The switching pole, according to the invention, includes an innovative motion transmission assembly 4 for operating the movable contact 3 during a closing/opening manoeuvre.
The motion transmission assembly 4 includes a bushing element 8 solidly coupled to the movable contact 3 and in sliding contact with the second pole terminal 12.
The bushing element 8 provides a conductive path between the movable contact 3 and the second pole terminal, thereby ensuring a correct electrical operation of the switching pole.
At the same time, the bushing element 8 defines a volume (the coupling cavity 80) accommodating the elastic element 7 and the pushrod 5.
The motion transmission assembly has thus a compact configuration, which allows remarkably reducing the size of the switching pole along its main longitudinal axis (the translation axis A of the movable contact) and, at the same time, confers a relevant structural robustness to the switching pole.
By virtue of such an innovative motion transmission assembly, the switching pole, according to the invention, has a relatively simple structure, which is particularly easy to assembly at industrial level.
The switching pole, according to the invention, can thus be manufactured at competitive industrial costs compared to the available solutions of the state of the art.

Claims

A switching pole (1) comprising first and second pole terminals (11, 12) and a vacuum interruption chamber (10) housing a fixed contact (2) electrically connected to said first pole terminal (11) and a movable contact (3) electrically connected to said second pole terminal (12),
wherein said movable contact (2) is movable along a translation axis (A) between an open position, in which it is separated from the fixed contact (2), and a closed position, in which it is electrically coupled to the fixed contact (2),

wherein, in said closed position, said movable contact (3) takes a closed condition, in which it is electrically coupled to the fixed contact (2), and a closed and pressed condition, in which it is electrically coupled to the fixed contact (2) under a mechanical load forcing it against said fixed contact (2),

characterized in that it comprises a motion transmission assembly (4) placed outside said vacuum interruption chamber (10) and operatively coupled to said movable contact (3), wherein said motion transmission assembly comprises:
- a bushing element (8) coupled to said movable contact so as to be electrically connected to said movable contact (3) and move together with said movable contact (3), wherein said bushing element (8) is in sliding contact with said second pole terminal (12);

- a pushrod (5) operatively connected to an actuating drive mechanism (100) and partially accommodated in a coupling cavity (80) of said bushing element;

- an elastic element (7) accommodated in said coupling cavity (80) and interposed between said bushing element and said pushrod;

- a support and guiding element (6) positioned fixed with respect to said vacuum interruption chamber (10).
Switching pole, according to claim 1, characterised in that said bushing element (8) includes a main body at least partially made of a same conductive material.
Switching pole, according to claim 1 or 2, characterised in that said bushing element (8) includes a main body at least partially made of a first conductive material, wherein an internal wall (801) defining said coupling cavity (80) is at least partially covered by a second material (801B) having a higher mechanical resistance compared to said first conductive material.
Switching pole, according to one of the previous claims, characterised in that said elastic element (7) is in a discharged or preloaded condition, when the movable contact (3) is in said open position and in said closed position and in a closed condition, and it is in a loaded condition, when said movable contact (3) is in said closed position and in a closed and pressed condition.
Switching pole, according to one of the previous claims, characterised in that said elastic element (7) is compressed during a phase of a closing manoeuvre of said switching pole, in which said movable contact (3) is in said closed position and passes from a closed condition to a closed and pressed condition, and it is released during a phase of an opening manoeuvre of said switching pole, in which said movable contact (3) is in said closed position and passes from a closed and pressed condition to a closed condition.
Switching pole, according to claim 5, characterised in that said pushrod (5) moves together with said movable contact (3) and said bushing element (8) during a first phase of a closing manoeuvre of said switching pole, in which the movable contact (3) moves from said open position to said closed position, and it moves relative to said movable contact (3) and said busing element (8) by sliding along said coupling cavity (80) during a second phase of a closing manoeuvre of said switching pole, in which said elastic element (7) is compressed and said movable contact (3) is in said closed position and passes from a closed condition to a closed and pressed condition.
Switching pole, according to one of the claims from 5 to 6, characterised in that said pushrod (5) moves relative to said movable contact (3) and said busing element (8) by sliding along said coupling cavity (80) during a first phase of an opening manoeuvre of said switching pole, in which said elastic element (7) is released and said movable contact (3) is in said closed position and passes from a closed and pressed condition to a closed condition, and it moves together with said movable contact (3) and said bushing element (8) during a second phase of an opening manoeuvre of said switching pole, in which said movable contact (3) moves from said closed position to said open position.
A switching unit (200) characterised in that it comprises one or more switching poles (1), according to one the previous claims.
Switching unit, according to claim 8, characterised in that it comprises first and second switching poles (1A, 1B), according to one the claims from 1 to 7, electrically connected in series.
A switching apparatus (300) characterised in that it comprises a switching pole (1), according to one the claims from 1 to 7.
Switching apparatus, according to claim 10, characterised in that it comprises first and second switching poles (1A, 1B), according to one the claims from 1 to 7, electrically connected in series, for each electric phase.