Switching apparatus for electric systems

A switching apparatus includes one or more electric pole units, each electric pole unit comprising a fixed contact, a movable contact, a first pole terminal, a second pole terminal, and a motion transmission arrangement to reversibly move the movable contact. The motion transmission arrangement includes a conductive motion transmission member coupled to the movable contact. The first pole terminal is in electrical connection to the fixed contact while the second pole terminal includes a first coupling region in electrical connection with a second coupling region of the conductive motion transmission member. Each electric pole unit further includes a shielding element formed by a conductive hollow body and arranged in a relative fixed position with respect to the second pole terminal and the motion transmission member. The shielding element is arranged to at least partially surround the first coupling and the second coupling region.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to European Patent Application No. EP21150488.1, filed Jan. 7, 2021 and titled “A SWITCHING APPARATUS FOR ELECTRIC SYSTEMS”, which is hereby incorporated by reference in its entirety.

BACKGROUND

The present disclosure relates to a switching apparatus for electric systems, which is capable of providing improved performances in terms of dielectric isolation, reliability in operation and life endurance.

Traditionally, a switching apparatus for electric systems includes a plurality of electric pole units, each including a fixed contact and a movable contact to be mutually coupled or decoupled in order to allow or block a current flowing through the electric pole unit.

The fixed contact and the movable contact of each electric pole unit are electrically connected to corresponding pole terminals couplable with the conductors of an electric line.

Each electric pole unit includes a motion transmission arrangement operatively coupled to suitable actuating means (e.g. an electric or electromagnetic actuator) to move reversibly the movable contact during the manoeuvres of the switching apparatus.

In many switching apparatuses of the state of the art, such a motion transmission arrangement includes a conductive motion transmission member, which is coupled with the movable contact and which is in electrical connection with a corresponding pole terminal in such a way to ensure a conductive path between the movable contact and such a pole terminal.

The above-mentioned motion transmission member may be in sliding contact with the corresponding pole terminal or be electrically connected to said pole terminal through suitable flexible conductors (e.g. multiple conductive braids or conductive laminas).

As is known, during operation of the switching apparatus, wear phenomena normally arise in the electric pole units at the conductive parts in relative movement, namely at the coupling regions of the above-mentioned motion transmission member and pole terminal and, possibly, at the above-mentioned flexible conductors electrically connecting said motion transmission member and pole terminal.

Normally, these wear phenomena are particularly relevant in switching apparatuses, for example contactors, which are required to carry out a large number of manoeuvres (e.g. up to a million) in their operating life.

In general, such wear phenomena may cause, for example:variations of the relative dielectric distances between the conductive parts;variations of the profile of the conductive parts (e.g. the formation of sharpened edges);deposition of metallic dust on internal surfaces of the electric pole unit;reduction of the cross-section of conductive parts.

Therefore, they may have a relevant impact on the overall dielectric isolation performances of the electric pole units. Additionally, they may be also at the origin of overheating phenomena at the conductive parts.

As a consequence of the above, time-consuming and expensive maintenance interventions on the pole units of the switching apparatus are normally required to prevent the occurrence of partial discharges or other destructive events in the electric pole units.

Additionally, a particular care is required while manufacturing and installing the switching apparatus in order not to favor, somehow, the onset of the above-mentioned wear processes at the above-mentioned conductive parts of the electric pole units.

BRIEF DESCRIPTION

The main aim of the present disclosure is to provide a switching apparatus for low-voltage or medium voltage electric systems that allows solving or mitigating the above-mentioned problems.

More in particular, it is an object of the present disclosure to provide a switching apparatus having pole units showing high performances in terms of dielectric isolation.

A further object of the present disclosure is to provide a switching apparatus showing improved performances in terms of reliability and life endurance with respect to the currently available solutions of the state of the art.

As a further object, the present disclosure is aimed at providing a switching apparatus of relatively easy transportation and installation on the field.

Still another object of the present disclosure is to provide a switching apparatus that is relatively easy and cheap to manufacture at industrial level.

In order to fulfill these aim and objects, the present disclosure provides a switching apparatus, according to the following claim1and the related dependent claims.

In a general definition, the switching apparatus, according to the disclosure, includes one or more electric pole units.

Each electric pole unit of the switching apparatus includes a fixed contact and a movable contact. The movable contact is reversibly movable between a first operating position, at which it is separated from the fixed contact, and a second operating position, at which it is coupled with the fixed contact.

In some embodiments, each electric pole unit of the switching apparatus includes a vacuum chamber, in which the fixed contact and the movable contact are accommodated.

Each electric pole unit of the switching apparatus includes a motion transmission arrangement adapted to transmit mechanical forces to move reversibly the movable contact between said first and second operating positions. Said motion transmission arrangement includes a conductive motion transmission member coupled to the movable contact.

Each electric pole unit of the switching apparatus includes a first pole terminal and a second pole terminal for coupling with a corresponding first line conductor and second line conductor, respectively.

The first pole terminal is in electrical connection to the fixed contact.

The second pole terminal includes a first coupling region in electrical connection with a second coupling region of the conductive motion transmission member.

According to some embodiments of the disclosure, the first coupling region of the second pole terminal and the second coupling region of the conductive motion transmission member are electrically connected one over the other by one or more flexible conductors.

Said one or more flexible conductors may include at least a flexible conductive lamina having opposite ends fixed to the first coupling region of the second pole terminal and the second coupling region of the conductive motion transmission member.

As an alternative, said one or more flexible conductors may include one or more flexible conductive braids having opposite ends fixed to the first coupling region of the second pole terminal and the second coupling region of the conductive motion transmission member.

According to some embodiments of the disclosure, the first coupling region of the second pole terminal and the second coupling region of the conductive motion transmission member have coupling surfaces in sliding contact.

In some embodiments, the switching apparatus of the disclosure includes actuating means operatively coupled to the conductive motion transmission arrangement of each electric pole unit.

According to the disclosure, each electric pole unit of the switching apparatus includes a shielding element formed by a conductive hollow body and arranged in a fixed position with respect to the second pole terminal and the motion transmission member.

The shielding element is arranged in such a way to surround, at least partially, the first coupling region of the second pole terminal and the second coupling region of the conductive motion transmission member. In this way, the first coupling region of the second pole terminal and the second coupling region of the conductive motion transmission member are positioned in an internal volume of the shielding element.

In some embodiments, the aforesaid shielding element is fixed to the second pole terminal of the electric pole unit.

According to some embodiments of the disclosure, said shielding element surrounds, at least partially, the flexible conductors electrically connecting the first coupling region of the second pole terminal and the second coupling region of the conductive motion transmission member.

In this way, said flexible conductors are located in the internal volume of said shielding element.

According to some embodiments of the disclosure, said shielding element surrounds, at least partially, the coupling surfaces of the first coupling region of the second pole terminal and of the second coupling region of the conductive motion transmission member, which are in sliding contact one over the other. In this way, said coupling surfaces are located in the internal volume of said shielding element.

In some embodiments, said shielding element has first and second holes respectively at first and second opposite sides. Said motion transmission member passes through said first and second holes and the internal volume of said electrical shield element.

In some embodiments, said shielding element has an external rounded shape.

In some embodiments, said shielding element is formed by a contoured metallic bushing.

Further characteristics and advantages of the disclosure will emerge from the description of preferred, but not exclusive embodiments of the switching apparatus, according to the disclosure, non-limiting examples of which are provided in the attached drawings.

DETAILED DESCRIPTION

With reference to the cited figures, the present disclosure relates to a switching apparatus1for low-voltage (LV) or medium voltage (MV) electric systems, e.g. electric grids, electrical switchboards, electrical switchgears, and the like.

For the purposes of the present application, the term “low-voltage” relates to operating voltages up to 1 kV AC and 1.5 kV DC whereas the term “medium voltage” relates to higher operating voltages, up to some tens of kV, e.g. up to 72 kV AC and 100 kV DC.

The switching apparatus of the disclosure may be a contactor, i.e. an apparatus designed for manoeuvring purposes, namely for breaking currents under normal circuit conditions (including overload conditions).

As an alternative, the switching apparatus of the disclosure may be a circuit breaker, i.e. an apparatus designed for protection purposes, namely for breaking currents under abnormal circuit conditions, e.g. under short-circuit conditions.

For the sake of simplicity only, the cited figures refer to embodiments of the disclosure, in which the switching apparatus1is a contactor designed to operate at MV levels. This choice is not intended to limit in any way the scope and purposes of the present disclosure. As a matter of fact, the switching apparatus of the disclosure may be of different type, for example a LV or MV circuit breaker, or a LV contactor, or a switching apparatus of yet a different type (e.g. a circuit breaker-disconnector) that can be used in LV or MV electric grids.

According to the disclosure, the switching apparatus1includes one or more electric pole units3, namely an electric pole unit for each electric phase.

In some embodiments, the switching apparatus1is of the multi-phase type, more particularly of the three-phase type, as shown in the cited figures.

As shown in the cited figures, the electric pole units3of the switching apparatus, in some embodiments, are overlapped to a lower actuation section16of the switching apparatus (reference is made to a normal installation position of the switching apparatus).

In some embodiments, each electric pole unit3includes a housing2made of electrically insulating material (which may be of known type).

In some embodiments, the insulating housing2of each electric pole unit defines an internal volume, in which the components of the corresponding electric pole unit are accommodated.

In some embodiments, the electric pole units3have their insulating housing2formed by an elongated body of electrically insulating material, which extends along a main longitudinal axis and has a lower end, which is fixed to the actuation section of the switching apparatus, and an opposite free upper end.

According to the disclosure, each electric pole unit3includes a fixed contact4and a movable contact5, which is reversibly movable between a first operating position A (opening position—FIG.2), at which it is separated from the corresponding fixed contact5, and a second operating position B (closing position—FIG.3), at which it is mechanically and electrically coupled with the corresponding fixed contact5(FIGS.5-6).

The passage of the movable contacts5of the switching apparatus from the first operating position A to the second operating position B is a closing manoeuvre of the switching apparatus whereas the passage of the movable contacts5from the second operating position B to the first operating position A is an opening manoeuvre of the switching apparatus.

In some embodiments, during a manoeuvre of the switching apparatus, each movable contact5moves linearly (towards or away from the corresponding fixed contacts4) along a displacement axis along the main longitudinal axis of the corresponding electric pole unit3.

According to some embodiments of the disclosure (shown in the cited figures), each electric pole unit3includes a vacuum chamber15accommodating the fixed contact4and the movable contact5of said electric pole unit.

According to other solutions of known type, however, each electric pole unit3may include a breaking section, which is not segregated from the remaining internal volume of the electric pole unit. In this case, the internal volume of each electric pole unit3may be filled with a suitable insulating gas (e.g. SF6) or air.

According to the disclosure, each electric pole unit3includes a motion transmission arrangement adapted to transmit mechanical forces to move reversibly the corresponding movable contact5between the above-mentioned first and second operating positions A, B. Such a motion transmission arrangement conveniently includes a conductive motion transmission member6operatively coupled to the corresponding movable contact5in such a way to be electrically and mechanically connected with this latter.

In some embodiments, the motion transmission member6is formed by a plunger of electrically conductive material, which has an end solidly coupled (e.g. screwed) with the corresponding movable contact5and an opposite end solidly coupled with a further plunger made of electrically insulating material.

In some embodiments, during a manoeuvre of the switching apparatus, the motion transmission member6moves linearly (towards or away from the fixed contact4) along the displacement axis of the corresponding movable contact5.

In some embodiments (FIG.1A), the above-mentioned motion transmission arrangement includes a further motion transmission element7made of electrically insulating material (e.g. a thermoplastic material or a thermosetting material, and the like).

In some embodiments, the motion transmission member7is made of electrically insulating material solidly coupled with an end of the conductive plunger forming the motion transmission member6.

In some embodiments, during a manoeuvre of the switching apparatus, the motion transmission member7moves linearly (towards or away from the fixed contact4) along the displacement axis of the corresponding movable contact5.

In some embodiments, the motion transmission member7is arranged coaxially with a bushing insulator70of known type (FIGS.2-3).

Conveniently, the motion transmission member7of each electric pole unit is operatively coupled with actuating means14of the movable contacts5through a suitable kinematic chain (not shown).

In some embodiments, the switching apparatus1has the actuating means14operatively coupled to the motion transmission arrangement6,7of each electric pole unit3in order to move the movable contacts5during the manoeuvres of the switching apparatus.

Conveniently, the actuating means14are accommodated in the actuation section16of the switching apparatus.

The actuating means14may include one or more actuators, for example a single actuator for the whole switching apparatus or an actuator for each electric pole unit. Such actuators may include, for example, by electric motors or electromagnetic actuators.

According to the disclosure, each electric pole unit3includes a first pole terminal9for coupling with a corresponding first line conductor and a second pole terminal8for coupling with a second line conductor.

In some embodiments, each pole terminal9,8is formed by an electrically conductive body shaped as an elongated plate having rounded edges.

In some embodiments, each pole terminal9,8is arranged at a corresponding port of the insulating housing2of the electric pole unit in such a way to protrude externally from this latter.

The pole terminals9,8may be co-molded with the insulating housing2or mechanically connected (e.g. screwed) to the insulating housing2.

The first and second pole terminals9,8of each electric pole unit are electrically connected with the corresponding fixed contact4and movable contact5of the electric pole unit, respectively.

In some embodiments, the first pole terminal9is in electrical connection with a conductive assembly90, which is in turn coupled to the fixed contact4to support this latter. In this way, a conductive path is ensured between the pole terminal9and the fixed contact4.

Conveniently, the first pole terminal9includes a suitable coupling region, at which it is fixed (e.g. screwed) to the conductive assembly90, which is in turn fixed (e.g. screwed) to the fixed contact4.

The second pole terminal8is in electrical connection with the conductive motion transmission member6, which is in turn coupled to the movable contact5. In this way, a conductive path is ensured between the second pole terminal8and the movable contact5.

In particular, the second pole terminal8includes a first coupling region81electrically connected to a second coupling region61of the conductive motion transmission member6.

In some embodiments, at the first coupling region81, the second pole terminal8includes a through hole82for the passage of the conductive motion transmission member6.

According to some embodiments of the disclosure (FIGS.4-6), the first coupling region81of the second pole terminal8and the second coupling region61of the conductive motion transmission member6are electrically connected by one or more flexible conductors12,13.

In the embodiment ofFIGS.4-5, the first coupling region81of the second pole terminal8and the second coupling region61of the conductive motion transmission member6are electrically connected by means of a flexible conductive lamina12(e.g. made of copper).

The conductive lamina12includes a holed central portion120fixed in known manner to the motion transmission member6, at the second coupling region61of this latter. Conveniently, the motion transmission member6passes through the holed central portion120.

The flexible lamina12has opposite ends121that are bent with respect to the central holed portion120and fixed in known manner to the first coupling region81of the second pole terminal8.

Since it is fixed to the motion transmission member6, which is movable, and to the second pole terminal8, which is instead in a fixed position, the flexible lamina12is subject to deformations when the movable contact5moves during a manoeuvre of the switching apparatus.

In particular, as it is evident fromFIGS.4-5, the flexible lamina12is compressed when the movable contact5moves from the first operating position A to the second operating position B (opening manoeuvre) and it is subject to a relaxation when the movable contact5carries out an opposite movement (closing manoeuvre).

In some embodiments, as shown in the cited figures, the flexible lamina12is arranged in a distal position from the movable contact5with respect to the second pole terminal8. In this case, it has its opposite ends121bent upwards (i.e. in direction of the movable contact5) with respect to the holed central portion120. This solution is quite convenient as it allows reducing the overall vertical size of the corresponding electric pole unit.

In principle, however, the flexible lamina12might be arranged at the opposite side of the second pole terminal8, along the main longitudinal axis of the corresponding electric pole unit. In this case, the conductive lamina12would be bent in an opposite direction.

In the embodiment ofFIG.6, the first coupling region81of the second pole terminal8and the second coupling region61of the conductive motion transmission member6are electrically connected by means of conductive braids13(e.g. made of copper).

Each conductive braid13has an end fixed (e.g. riveted) to a conductive support element30, which is in turn fixed to the motion transmission member6, at the second coupling region61of this latter, and an opposite end fixed (e.g. riveted) to the first coupling region81of the second pole terminal8.

As for the above-illustrated embodiment of the disclosure, the flexible braids13are subject to deformations when the movable contact5moves during a manoeuvre of the switching apparatus.

Also, similarly to the above, the conductive braids13are arranged in a distal position from the movable contact5with respect to the second pole terminal8.

In principle, however, they might be arranged at the opposite side of the second pole terminal8, along the main longitudinal axis of the corresponding electric pole unit.

In the embodiment ofFIG.7, the first coupling region81of the second pole terminal8and the second coupling region61of the conductive motion transmission member6are electrically connected by means of a sliding contact arrangement.

In particular, the first coupling region81of the second pole terminal8and the second coupling region61of the conductive motion transmission member6have coupling surfaces (not shown) in sliding contact one over the other. In this way, no additional conductors have to be used to connect electrically the motion transmission element6and the second pole terminal8.

In general, most of the components of the pole units3, such as the insulating housing2, the electric contacts4-5, the pole terminals8-9, the motion transmission arrangement6,7and the above-mentioned coupling arrangements between the mobile contact5and the second pole terminal8, may be realized at industrial level according to solutions of known type. Therefore, in the following, they will be described in relation to the aspects of interest of the disclosure only, for the sake of brevity.

According to the disclosure, electric pole unit3includes a shielding element10, which is arranged in a fixed position with respect to the second pole terminal8and the motion transmission member.

The shielding element10is formed by a conductive hollow body (e.g. made of steel).

In some embodiments, as shown in the cited figures, such a conductive hollow body have a solid structure.

According to alternative embodiments of the disclosure, however, such a conductive hollow body may have a meshed structure.

The shielding element10is arranged in a fixed position with respect to the motion transmission member6and the second pole terminal8in such a way that it surrounds at least partially, the first coupling region81of the second pole terminal8and the second coupling region61of the conductive motion transmission member6.

In this way, the first coupling region81of the second pole terminal8and the second coupling region61of the conductive motion transmission member6are located in an internal volume11of the shielding element, which is defined by its hollow conductive body.

In the embodiments of the disclosure shown inFIGS.4-6, the shielding element10is designed in such a way to surround, at least partially, the flexible conductors12,13electrically connecting the first coupling region81of the second pole terminal8and the second coupling region61of the conductive motion transmission member6. Conveniently, said flexible conductors are accommodated in the internal volume11of the shielding element10.

In the embodiment of the disclosure shown inFIG.7, the shielding element10is designed in such a way to surround, at least partially, the coupling surfaces of the first coupling region81of the second pole terminal8and the second coupling region61of the conductive motion transmission member6, which are in sliding contact one over the other. Conveniently, said coupling surfaces are accommodated in the internal volume11of the shielding element10.

In some embodiments, as shown in the cited figures, the shielding element is fixed (e.g. riveted) to the second pole terminal8, conveniently at the first coupling portion81of this latter.

In some embodiments, the shielding element10includes opposite first and second sides10C,10D respectively positioned in proximal position and in distal position with respect to the fixed contact4of the corresponding electric pole unit.

In some embodiments, the shielding element10is fixed to the to the second pole terminal8at its first side10C in such a way that the first coupling region81of the second pole terminal is enclosed in the internal volume11of the shielding element.

In some embodiments, at the above-mentioned first and second sides10C-10D, the shielding element10includes first and second holes10A,10B that are coaxial with the displacement axis of motion transmission member6and with the hole82of the second pole terminal8. In this way, the motion transmission member6can pass through said first and second holes10A,10B and the internal volume11of the electrical shield element.

The above-illustrated arrangement remarkably simplifies the structural integration of the shielding element10with the motion transmission member6and second pole terminal8, thereby reducing the overall size.

In some embodiments, the shielding element10has an external rounded shape. This solution allows equalising the electric fields external to the shielding element itself (which arise during operation of the switching apparatus) and it favours a suitable design of the dielectric distances between the conductive parts of the electric pole unit in proximity of the shielding element10.

In some embodiments, the hollow body of the shielding element10has a tubular shape with an elliptical cross-section and it is positioned in such a way to have its main longitudinal axis perpendicular to the main longitudinal axis of the electric pole unit3and lying on a plane parallel to the lying planes of the pole terminals8,9.

Thanks to this arrangement, the first coupling region81of the second pole terminal8and the second coupling region61can be easily enclosed in the internal volume11of the shielding element10. Additionally, such an arrangement simplifies the coupling of the shielding element10to the second pole terminal8.

In some embodiments, the shielding element10is formed by a contoured metallic bushing (e.g. made of steel).

The adoption of the above-mentioned shielding element10provides remarkable advantages.

During the operation of the switching apparatus, the shielding element10conveniently operates as a Faraday cage for the conductive parts enclosed in its internal volume. The electric fields in the internal volume11of the shielding element10are therefore virtually null. In this way, possible defects at the first coupling region81of the second pole terminal8and/or at the second coupling region61of the conductive motion transmission member6, which might be caused by wear phenomena arising during the operating life of the switching apparatus, do not have any substantial influence on the overall dielectric isolation capabilities of the electric pole unit3.

The arising of dielectric hot-spots at the first coupling region81of the second pole terminal8and/or at the second coupling region61of the conductive motion transmission member6, which are mostly subject to the above-mentioned wear phenomena by construction, is in fact prevented as these conductive parts are not subject to dielectric stresses.

Since it is arranged in fixed position with respect to the motion transmission member6and the second pole terminal8, the shielding element10allows designing more accurately the dielectric distances between said conductive parts at the internal volume region of the electric pole unit3.

Additionally, since it encloses the conductive parts in relative movement one over the other, the shielding element10prevents or reduces the deposition of metallic dust on internal insulating parts of the electric pole unit3, for example on the bushing insulator70. This allows further improving the dielectric isolation capabilities of the electric pole unit3.

The above-mentioned advantages allow achieving a remarkable improvement of the internal dielectric isolation performances of the electric pole units with respect to the traditional solutions of the state of the art. Laboratory tests have shown an increase up to 300% of the inception voltage of partial discharges in the internal volume of the electric pole units with respect to electric pole units having a similar operating history.

The shielding element10intrinsically makes more robust the electrical connection between the first coupling region81of the second pole terminal8and the second coupling region61, thereby providing a protection from possible damages that may be caused during the transportation and the installation the switching apparatus.

The shielding element10allows improving thermal dissipation in the internal volume of the electric pole unit3. Being arranged along the conductive path between the movable contact5and the second pole terminal8, it can effectively dissipate heat generated by the current flowing along the electric pole unit, since it may act as a heat dissipating fin.

The switching apparatus1of the disclosure may be subject to modifications and variants falling within the scope of the present disclosure.

In principle, the shielding element10may be differently arranged with respect to the embodiments of the disclosure shown in the cited figures.

According to some embodiments of the disclosure, the shielding element10may be formed by a substantially closed hollow enclosure, e.g. having a cylindrical, spherical or ellipsoidal shape, and possibly provide with shaped windows to allow its structural integration with the motion transmission member6and the second pole terminal8.

According to some embodiments of the disclosure, the hollow conductive body of shielding element10may be formed be formed by a relatively rigid mesh or cage of metallic material, which may be suitably shaped in such a way to define an internal volume in which the first coupling region81of the second pole terminal8and the second coupling region61of the conductive motion transmission member6may be accommodated.

The switching apparatus1, according to the disclosure, provides remarkable advantages with respect to the known apparatuses of the state of the art.

The switching apparatus of the disclosure has electric pole units provided with shielding elements capable of preventing a possible decay of the dielectric isolation capabilities, which may be due to the effects of wear phenomena one conductive parts in relative movement.

In this way, the electric pole units can show high performances in terms of dielectric isolation.

The switching apparatus of the disclosure therefore shows high levels of reliability and an improved life endurance with respect to the currently available solutions of the state of the art.

The switching apparatus of the disclosure has electric pole units with a robust structure, in particular for what concerns their conductive parts in relative movement one over the other.

The switching apparatus of the disclosure is therefore relatively easy to transport and install on the field with respect to the currently available solutions of the state of the art.

The switching apparatus of the disclosure can be easily manufactured at industrial level, at competitive costs with respect to the solutions of the state of the art.