Retractable hybrid switching device

Abstract

To provide a switching device capable of ensuring the safety of high level even when operation is required under an emergency state.SOLUTION: A switching device 100 for power distribution grid includes a drawable first switching unit capable of having one or more first electric poles and a drawable second switching unit having one or more second electric poles. The second switching unit includes an emergency controller which is electrically connected in series to the first switching unit and permits a user to start making the second switching unit to execute an opening operation.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to switching devices for power distribution grids, such as circuit breakers or similar type devices. [Background technology]

[0002] As is known, low voltage switching devices are used in electrical circuits or power distribution grids to enable the correct operation of specific sections of the electrical circuit or specific sections of the power distribution grid. For example, these devices are used to ensure the availability of nominal current required for some equipment, enable the proper insertion and removal of electrical loads, and protect the power distribution grid and associated electrical loads against fault events, such as overloads, short circuits, etc. (particularly circuit breakers).

[0003] Most conventional switching devices include an electromechanical switching unit having one or more electrical poles, each of which has a pair of electrical contacts that are adapted to connect or disconnect to allow or interrupt the flow of line current along the pole.

[0004] Although they have proven to be very robust and reliable, electromechanical switching devices exhibit relatively long interruption times in DC applications, mainly at relatively high voltages (between 1 kV and 1.5 kV DC). As a result, electric arcs, which usually occur between the separated electrical contacts, can last for a relatively long time. This often leads to severe wear phenomena of the electrical contacts, resulting in a significant decrease in operational reliability and electrical durability.

[0005] To overcome these technical problems, they have designed switching devices (also called solid-state circuit breakers "SSCB") that include, for each electrical pole, one or more solid-state switches, i.e., switching units having semiconductor-based transistors or thyristors adapted to operate in a conducting state that allows current flow or in a blocking state that interrupts current flow.

[0006] The main advantage of SSCBs is that they have potentially unlimited electrical endurance, depending on the circumstances under which the interruption occurs without the formation of an electric arc. Furthermore, their interruption time is very short compared to that of electromechanical switching devices.

[0007] An important drawback of SSCBs is that they generally cannot provide electrical isolation between line conductors connected to each other. Indeed, when a voltage is applied to the power terminals of a solid-state switch (e.g., the collector and emitter terminals of an IGBT), a leakage current usually flows, even if the switch is in the blocking state.

[0008] Recently, they have evolved into switching devices that include an SSCB switching unit and an electromechanical switching unit, electrically connected in series. These switching devices (commonly called "hybrid switching devices") make it possible to fully exploit all the advantages offered by SSCBs in terms of reliability and reduced interruption times, and in addition, they also make it possible to provide electrical isolation between the line conductors connected to each other.

[0009] As is known, many hybrid switching devices are of the "extractable" type, in which both the SSCB switching unit and the electromechanical switching unit are movable relative to a fixed portion of the switching device. Specifically, each switching unit is mounted on a carriage so that it can be reversibly moved between an inserted position and an extracted position relative to the fixed portion of the switching device.

[0010] The extractable type of hybrid switching device has further advantages in terms of efficiency and safety of use: in fact, both the SSCB switching unit and the electromechanical switching unit can be brought into an extracted position in order to easily carry out testing or maintenance in the field with the switching units completely disconnected from the line conductors. Summary of the Invention [Problem to be solved by the invention]

[0011] However, these switching devices also have several aspects which improve them, especially with regard to their operation in emergency situations, and more particularly with regard to their operation when, for some reason, they fail to perform the operation of opening the electromechanical switching unit, for example due to the fact that the switching device cannot receive an external auxiliary power supply.

[0012] As can be easily understood, such an event results in the loss of electrical isolation between the two line conductors electrically connected to the switching device, even if the SSCB switching unit is in the open state. Since leakage currents still flow along the electrical poles of the switching device, this situation is quite dangerous for personnel operating in the field, especially when attempting to pull out the switching unit (e.g., SSCB switching unit).

[0013] The main goal of the present invention is to provide a hybrid switching device of extractable type that makes it possible to overcome or alleviate the above-mentioned technical problems of the state of the art. [Means for solving the problem]

[0014] Within this goal, the object of the present invention is to provide a switching device which ensures a high level of safety even when it has to be operated in emergency situations. Another object of the present invention is to provide a switching device whose operation can be easily controlled without providing complex and expensive control resources. Another object of the present invention is to provide a switching device that is relatively easy and inexpensive to manufacture on an industrial scale. [Effects of the Invention]

[0015] This aim and these objects, together with other objects which will become apparent from the following description and the accompanying drawings, are achieved by the switching device of the invention according to claim 1 and its dependent claims set out below. [Brief explanation of the drawings]

[0016] [Figure 1] 1 shows diagrammatically a switching device according to the invention; [Figure 2] 1 shows diagrammatically an electromechanical switching unit of a switching device according to the invention; [Figure 3] 2 illustrates diagrammatically the operation of a switching device according to the invention; [Figure 4] 2 illustrates diagrammatically the operation of a switching device according to the invention; [Figure 5A] 2 illustrates diagrammatically the operation of a switching device according to the invention; [Figure 5B] 2 illustrates diagrammatically the operation of a switching device according to the invention; [Figure 5C] 2 illustrates diagrammatically the operation of a switching device according to the invention; DETAILED DESCRIPTION OF THE INVENTION

[0017] The switching device of the present invention comprises one or more first line terminals electrically connectable to corresponding first line conductors of the electric wires, one or more second line terminals electrically connectable to corresponding second line conductors of the electric wires, a first switching unit 1 having one or more first electrical poles, a second switching unit having one or more second electrical poles, and a control device arranged to control the operation of the switching device.

[0018] The first electrical pole comprises a first pole contact electrically connectable to a corresponding first line terminal, a second pole contact, and one or more solid-state switches electrically connected to the first and second pole contacts, the solid-state switches operable to pass current in a conducting state or block current in a blocking state. The first switching unit is reversibly switchable between a closed state in which the solid-state switch is conducting and an open state in which the solid-state switch is blocking. The first switching unit is reversibly movable between an inserted state in which the first pole contact is coupled to the first line terminal and a withdrawn state in which the first pole contact is separated from the first line terminal.

[0019] The second electric pole comprises a third pole contact that can be electrically connected to the corresponding second pole contact of the first switching unit, a fourth pole contact that can be electrically connected to the corresponding second line terminal, and electrical contacts electrically connected to the third and fourth pole contacts, the electrical contacts being configured to operate in a connected state to pass current or a disconnected state to interrupt current. The second switching unit is reversibly switchable between a closed state in which the electrical contacts are connected and an open state in which the electrical contacts are separated. The second switching unit is reversibly movable between an inserted state in which the fourth pole contact is coupled to the second line terminal and a withdrawn state in which the fourth pole contact is separated from the second line terminal.

[0020] In the switching device of the present invention, the second switching unit includes an emergency control device that can be activated by a user to switch the second switching unit from the closed state to the open state, the emergency control device including an emergency command button that is provided for user operation, and the emergency command button is provided for user access upon removal of one or more structural components of the second switching unit.

[0021] Preferably, the second switching unit includes a first protective panel that covers the emergency command button, the emergency command button being accessible to a user when the first protective panel is removed from the second switching unit. Preferably, the second switching unit comprises a second protective panel covering the first protective panel, and the emergency command button is provided such that a user can access the emergency command button when the first and second protective panels are removed from the second switching unit.

[0022] Preferably, the second electrical pole of the second switching unit includes at least a fixed electrical contact and a movable electrical contact, and the second switching unit includes an actuating mechanism configured to relatively move one or more of the movable electrical contacts of the second switching unit between a position where the movable electrical contact is coupled to a corresponding fixed electrical contact of the second switching unit and a position where the movable electrical contact is separated from the fixed electrical contact.

[0023] The emergency control device is configured to actuate the actuating mechanism to move the movable electrical contact upon activation by a user when the second switching unit is in a closed state, and the actuating mechanism is configured to, in response to actuation by the emergency control device, move the movable electrical contact from a position in which the movable electrical contact is coupled to the fixed electrical contact to a position in which the movable electrical contact is decoupled from the fixed electrical contact, switching the second switching unit from a closed state to an open state.

[0024] Preferably, the emergency control device comprises a trip element operatively connected to the emergency command button, the trip element being arranged to actuate the actuation mechanism when a user operates the emergency command button to an activated position. Preferably, said emergency control device comprises signalling means arranged to provide a user with an optical signal indicative of the operational state of the second switching unit.

[0025] Preferably, the emergency control device comprises detection means arranged to provide a warning signal to the control device indicative of a condition in which the first protective panel has been removed. Preferably, the controller is configured to command the first switching unit to switch from a closed state to an open state in response to receiving the warning signal when the first switching unit is in a closed state. Preferably, the controller is configured to prevent the first switching unit from switching to a closed state in response to receiving the warning signal when the first switching unit is in an open state.

[0026] According to one aspect of the present invention, the control device is configured to control the first switching unit and the second switching unit so that the first switching unit and the second switching unit operate in a combination according to a first operating mode, a second operating mode, or a third operating mode, the first operating mode corresponding to a closed state of the switching device in which both the first switching unit and the second switching unit are in a closed state, the second operating mode corresponding to a standby state of the switching device in which the first switching unit is in an open state and the second switching unit is in a closed state, and the third operating mode corresponding to an open state of the switching device in which both the first switching unit and the second switching unit are in an open state.

[0027] According to one aspect of the invention, the control device comprises an interface section including one or more input ports arranged to receive input commands indicative of a desired mode of operation for the switching device. Preferably, the switching device of the present invention includes a human-machine interface that is communicable with the interface unit. The human machine interface is configured to provide the input commands based on interaction with a user. Preferably, the interface unit is capable of receiving the input commands from a remote computer device. According to one aspect of the invention, the control device is included in a first switching unit.

[0028] Further features and advantages of the present invention will become more clearly apparent from the description of preferred but non-exclusive embodiments thereof, which are described purely by way of example and not of limitation in the accompanying drawings, in which: FIG.

[0029] Referring to the aforementioned drawings, the present invention relates to a switching device 100 for an electrical power distribution grid, such as a circuit breaker, disconnector, contactor, or the like. The switching device 100 is particularly suitable for incorporation into low voltage electrical power distribution grids or systems. However, it may also be successfully employed in medium voltage electrical power distribution grids or systems. For the purposes of the present invention, the term "low voltage" (LV) relates to operating voltages below 1 kV AC and 1.5 kV DC, while the term "medium voltage" (MV) relates to higher operating voltages up to several tens of kV, for example up to 72 kV AC and 100 kV DC.

[0030] In general, the switching device 100 is provided to be electrically connected to an electrical line 50. The electrical line 50 typically comprises one or more first line conductors 51 and one or more second line conductors 52, where the first line conductors 51 may be electrically connected to an equivalent power source (e.g., a power supply system or a power generation system or a portion of an electrical distribution grid) and the second line conductors 52 may be connected to an equivalent electrical load (e.g., an electrical system or an electrical device or a portion of an electrical distribution grid).

[0031] In the embodiment shown in the cited drawings, the electrical line 50 is of the three-phase type, but in principle it can contain a different number of phases. The switching device 100 comprises one or more first line terminals 91 arranged to be electrically connected to corresponding first line conductors 51 of the electric wires 50, and one or more second line terminals 92 arranged to be electrically connected to corresponding second line conductors 52 of the electric wires 50. Conveniently, the first line terminal 91 and the second line terminal 92 are housed in a fixed section of the switching device (not shown), which section is conveniently delimited by a support frame (not shown) of the switching device.

[0032] The switching device 100 comprises a first switching unit 1 of the SSCB type and a switching unit 2 of the electromechanical type, which in operation are electrically connected in series between the above-mentioned line terminals 91, 92. The first switching unit 1 comprises one or more first electric poles 1A. The number of electric poles of the first switching unit can vary as required. In the embodiment shown in the cited drawings, the first switching unit is of a three-phase type and comprises three electric poles. However, according to other embodiments of the invention (not shown), the first switching unit can comprise a different number of electric poles.

[0033] Each electrical pole 1A is arranged to electrically connect to a corresponding first line conductor 51 of the electrical wire 50 and to an electrical pole of the second switching unit 2. Each electrical pole 1A comprises a first pole contact 11 and a second pole contact 12, the first pole contact being arranged to electrically connect to a corresponding first line terminal 91 of the switching device and the second pole contact being arranged to electrically connect to a corresponding pole contact 23 of the second switching unit 2. Each electrical pole 1A comprises one or more solid state switches 10 arranged to operate in a conducting state to pass current and in a blocking state to interrupt current.

[0034] The solid state switch 10 (“SSCB”) may include, for example, a MOSFET, an insulated gate bipolar transistor (“IGBT”), a gate turn-off thyristor (“GTO”), an integrated gate commutated thyristor (“IGCT”), or the like. The solid state switch 10 of each electrical pole 1A is electrically connected between pole contact 11 and pole contact 12, for example, in a series configuration or other more complex well known types of circuit configuration.

[0035] In operation, the first switching unit 1 can be reversibly switched between a closed state (ON) and an open state (OFF), where in the closed state the solid-state switch 10 of the electrical pole 1A is conducting, and in the open state the solid-state switch 10 of the electrical pole 1A is blocking. When the first switching unit 1 is in the closed state (ON), line current can flow along the electrical pole 1A. On the other hand, when the switching unit 1 is in the open state (OFF), line current cannot flow along the electrical pole 1A. However, the expected leakage current that normally affects a solid-state switch in the blocking state will still flow.

[0036] A transition from the closed state ON to the open state OFF forms an opening operation of the first switching unit 1, while a transition from the open state OFF to the closed state ON forms a closing operation of the first switching unit 1. The first switching unit 1 may perform the opening or closing operation upon receiving a first trip signal T1 from the control device 3. Preferably, the first switching unit 1 includes one or more first drive circuits (not shown) configured to receive a first trip signal T1 and drive a control terminal (e.g., a gate terminal or a base terminal) of the solid-state switch 10 in response to the first trip signal T1.

[0037] The second switching unit 2 comprises one or more second electric poles 2A. Also, in this case, the number of electric poles 2A of the switching unit 2 may vary as required. In general, the number of electric poles 2A corresponds to the number of electric poles 1A of the first switching unit 1.

[0038] Each electric pole 2A is arranged to be electrically connected in series with a corresponding electric pole 1A of the first switching unit 1 and to be electrically connected to a corresponding second line conductor 52 of the electric wire 50. Accordingly, each electric pole 2A comprises a third pole contact 23 and a fourth pole contact 24, the third pole contact 23 being arranged to be electrically connected to a corresponding second pole contact 12 of the first switching unit 1, and the fourth pole contact 24 being arranged to be electrically connected to a second line terminal 92 of the switching device. Each second electric pole 2A comprises an electric contact 20 which can function to pass current in a connected state or to interrupt current in a disconnected state. Advantageously, the electrical contacts 20 of each electrical pole 2A comprise a fixed electrical contact and a movable electrical contact (not shown), each movable contact being movable into or away from the fixed contact.

[0039] In operation, the second switching unit 2 can be reversibly switched between a closed state (ON) and an open state (OFF), in which the electrical contacts 20 of the electrical pole 2A are connected in the closed state (ON) and are separated in the open state (OFF). When the second switching unit 2 is in the closed state (ON), the line current can flow along the electrical pole 2A. On the other hand, when the second switching unit 2 is in the open state (OFF), the line current cannot flow along the electrical pole 2A.

[0040] A transition from the closed state ON to the open state OFF constitutes an operation to open the second switching unit 2 , whereas a transition from the open state OFF to the closed state ON constitutes an operation to close the second switching unit 2 . Preferably, the second switching unit 2 comprises one or more trip actuators 25 (which may be of a known type) arranged to cause actuation of the movable contacts of said switching units to perform the above-mentioned opening and closing operations (FIGS. 1 and 2). By way of example, the trip actuators 25 may comprise an open coil actuator 25A and a close coil actuator 25B, the open coil actuator 25A being arranged to cause actuation of the movable contact of the electrical pole 2A to perform the opening operation, and the close coil actuator 25B being arranged to cause actuation of the movable contact of the electrical pole 2A to perform the closing operation.

[0041] The trip actuator 25 may be operatively linked to an actuating mechanism 29 (FIG. 2) arranged to move the movable contact of the second switching unit 2. Such an actuating mechanism (which may be of a known type) is conveniently arranged to move the movable contact of the second switching unit 2 upon actuation by the trip actuator described above. The second switching unit 2 may perform an opening or closing operation upon receipt of a trip signal T2 from the controller.

[0042] Preferably, the second switching unit 2 may include one or more second drive circuits (not shown) arranged to receive the above-mentioned trip signal T2 and drive the trip actuator 25 based on said trip signal. When driven in accordance with the trip signal T2, the trip actuator 25 activates the above-mentioned actuating mechanism which moves the movable contact of the second switching unit to perform a closing or opening operation of the second switching unit.

[0043] Preferably, the second switching unit 2 comprises one or more contact detection means 26 arranged to provide the control device with a detection signal S1 indicative of the operating state of the second switching unit 2. By way of example, the detection means 26 may comprise a close microswitch (which may be of a known type) arranged to signal a closed state ON of the switching unit 2, and an open microswitch (which may be of a known type) arranged to signal an open state OFF of the switching unit 2.

[0044] According to the invention, the switching device 100 is of the extractable type, so that both the first switching unit 1 and the second switching unit 2 can be extracted from their normal operating position in order to disconnect the electric wire 50. The first switching unit 1 can be reversibly moved between an inserted state A and a pulled-out state B, and in the inserted state A the first pole contact 11 is connected to the first line terminal 91, and in the pulled-out state B the first pole contact 11 is separated from the first line terminal 91.

[0045] Preferably, when in the inserted state A, the first switching unit 1 has the second pole contact 12 connected to the third pole contact 23 of the second switching unit 2. Preferably, when in the extracted state B, the first switching unit 1 has the second pole contact 12 separated from the third pole contact 23 of the second switching unit 2.

[0046] A transition from the inserted state A to the extracted state B constitutes an operation of extracting the first switching unit, while a transition from the extracted state B to the inserted state A constitutes an operation of inserting the first switching unit. When in the extracted state B, the first switching unit 1 may be in a test position, in which the first switching unit 1 is electrically connected to the power supply stage of the switching device and has its low voltage components supplied by the power supply stage, and in the fully extracted position the first switching unit 1 is electrically disconnected from all electrical circuits.

[0047] Preferably, the switching apparatus 100 comprises a first carriage (not shown) on which the first switching unit 1 is mounted. Conveniently, such first carriage is slidably connected to a support frame of the switching apparatus 100. In this way, both the first switching unit 1 and the first carriage can move relative to a fixed part of the switching apparatus.

[0048] The switching device 100 comprises a first actuation device 7 (which may be of a known type) arranged to move the first switching unit 1 upon activation by a user (e.g., activation via a suitable command button) to perform at least the operation of withdrawing the first switching unit. According to a preferred embodiment of the present invention, the first actuation device 7 is arranged to move the first switching unit 1 upon activation by the user (e.g., activation via an appropriate command button) even during the operation of inserting the first switching unit 1.

[0049] According to another embodiment of the present invention, the operation of inserting the switching unit 1 may be performed directly by a user, for example by using a mechanical tool that may be operatively coupled to a suitable kinematic chain operatively coupled to the switching unit 1 and the support frame of the switching device. Relative to the first switching unit 1, the second switching unit 2 is reversibly movable between an inserted state A and an extracted state B, in which the fourth pole contact 24 is coupled to the second line terminal 92 and in which the fourth pole contact 24 is not coupled to the second line terminal 92.

[0050] Preferably, when in the inserted state A, the second switching unit 2 has a third pole contact 23 that is connected to the second pole contact 12 of the first switching unit 1. Preferably, when in the extracted state B, the second switching unit 2 has a third pole contact 23 that is separated from the second pole contact 12 of the first switching unit 1.

[0051] A transition from the inserted state A to the extracted state B constitutes an operation of extracting the switching unit 2, while a transition from the extracted state B to the inserted state A constitutes an operation of inserting the switching unit 2. When in the extracted state B, the switching unit 2 may be in a test position in which the switching unit 2 is electrically connected to the power supply stage of the switching device and has its low voltage components supplied by the power supply stage, and in the fully extracted position the switching unit 2 is electrically disconnected from all electrical circuits.

[0052] Preferably, the switching apparatus 100 comprises a second carriage (not shown) on which the switching unit 2 is mounted. Conveniently, such second carriage is slidably connected to the support frame of the switching apparatus 100, so that the second carriage (together with the second switching unit 2) can move relative to the fixed part of the switching apparatus.

[0053] The switching device 100 comprises a second actuation device 8 (which may be of a known type) arranged to move the second switching unit 2 upon activation by the user (e.g., activation via an appropriate command button) at least in the operation of pulling out the second switching unit 2.

[0054] According to some embodiments of the present invention, the second actuation device 8 is arranged to move the second switching unit 2 upon activation by the user (e.g., activation via an appropriate command button) even during the operation of inserting the second switching unit 2. According to some embodiments of the present invention, the act of inserting the switching unit 2 may be performed directly by a user, for example using a mechanical tool that can be operably coupled to a suitable kinematic chain that is operably connected to the switching unit 2 and the support frame of the switching apparatus.

[0055] FIG. 3 shows diagrammatically the operating configurations that the switching unit 100 can assume when an operation to withdraw or insert the switching unit 1, 2 is performed. According to Configuration #1, both switching units 1 and 2 are in the inserted state. According to Configuration #2, switching unit 1 is in the pulled-out state B and switching unit 2 is in the inserted state A. In this case, switching unit 1 may be in the test position or in the fully pulled-out position as needed.

[0056] In order for the switching device to transition from mode #1 to mode #2, it is necessary to perform an operation to withdraw only the first switching unit 1. In order for the switching device to transition from mode #2 to mode #1, it is necessary to perform an operation to insert only the first switching unit 1. According to configuration #3, the first switching unit 1 is in the inserted state A and the second switching unit 2 is in the extracted state B. In this case, the second switching unit 2 may be in the test position or in the fully extracted position depending on the need.

[0057] In order for the switching device to transition from mode #1 to mode #3, it is necessary to perform an operation to withdraw only the second switching unit 2. In order for the switching device to transition from mode #3 to mode #1, it is necessary to perform an operation to insert only the second switching unit 2. According to configuration #4, both switching units 1 and 2 are in the extended state. In this case, each of switching units 1 and 2 may be in the test position or in the fully extended position depending on the need.

[0058] In order for the switching device to transition from mode #2 to mode #4, it is necessary to perform an operation to withdraw only the second switching unit 2. In order for the switching device to transition from mode #4 to mode #2, it is necessary to perform an operation to insert only the second switching unit 2.

[0059] In order for the switching device to transition from mode #3 to mode #4, it is necessary to perform an operation to extract only the first switching unit 1. In order for the switching device to transition from mode #4 to mode #3, it is necessary to perform an operation to insert only the first switching unit 1.

[0060] In principle, the switching device 100 may take any of the above-mentioned forms depending on the need. However, the operation of pulling out the switching units 1 and 2 can be performed only when the switching units 1 and 2 are in a certain operating state. Specifically, the operation of pulling out each of the switching units 1 and 2 can be performed only when the switching unit is in the open state OFF.

[0061] In general, the switching units 1, 2 may include several additional elements arranged at industrial level according to solutions of known type, which in the following, for the sake of brevity, will not be described in further structural detail.

[0062] According to the invention, the switching device 100 comprises a control device 3 arranged to control the operation of the switching device 100, in particular the operation of the switching units 1,2. According to some embodiments of the invention (FIG. 1), the control device 3 is an autonomous device that is not included in either of the switching units 1, 2. According to another embodiment of the invention (not shown), the control device 3 is included in one of the switching units 1, 2, preferably in the first switching unit 1.

[0063] Preferably, the control device 3 comprises a data processing unit 31 arranged to process and provide data or control signals for implementing the required functions. In general, the data processing unit 31 may include digital or analogue data processing resources such as, for example, one or more microprocessors or DPSs. Preferably, the control device 3 comprises a trip section 32 arranged to communicate with the data processing section 31 to generate trip signals T1, T2 for controlling the operation of the switching units 1, 2. In general, the trip section 32 may include digital or analogue data processing resources, such as, for example, one or more microprocessors or DSPs.

[0064] Preferably, the control device 3 is arranged to receive and process input commands CM1, CM2, CM3 (e.g. generated by appropriate control signals) indicating desired operating states for the switching device 100 in order to control the operation of the switching units 1, 2. Preferably, the control device 3 comprises an interface section 33 including one or more input ports arranged to receive the input commands CM1, CM2, CM3. Preferably, the switching device 100 comprises a human machine interface 5 in communication with the interface unit 33 of the control device 3. The human machine interface 5 is arranged to provide input commands CM1, CM2, CM3 upon interaction with a user.

[0065] According to another embodiment of the invention (not shown), the human machine interface 5 is included in one of the switching units 1, 2, preferably in the first switching unit 1. According to some embodiments of the present invention, the interface unit 33 of the control device 3 is arranged to communicate with a remote computing device 99 (which is generally not part of the switching device 100), for example a digital relay. Advantageously, the interface unit 33 may receive input commands CM1, CM2, CM3 from the computing device 99.

[0066] Generally, the control device 3 and the human-machine interface 5 can be arranged at industrial level according to known types of hardware solutions, and therefore, in the following, for the sake of brevity, they will not be described in further structural or electrical details.

[0067] In the switching apparatus 100, the closing or opening of each switching unit is generally performed depending on the desired operating state of the switching apparatus 100. Accordingly, the control device 3 is advantageously configured to command the performance of the opening or closing of each switching unit 1, 2 by generating the above-mentioned trip signals T1, T2 in response to receiving the above-mentioned input commands CM1, CM2, CM3. In principle, the operations of pulling out and inserting the switching units 1 and 2 may be performed as needed. However, as mentioned above, the operations of pulling out each of the switching units 1 and 2 are performed based on activation by the user only when the switching units are in the open state OFF.

[0068] Preferably, the control device 3 is configured to prevent (via suitable enabling means, not shown) the first actuating device 7 from moving the first switching unit 1 from the inserted state A to the extracted state B when the first switching unit 1 is in the closed state ON. Thus, the control device 3 only allows the first actuating device 7 to move the first switching unit 1 from the inserted state A to the extracted state B when the first switching unit 1 is in the open state OFF.

[0069] Preferably, the control device 3 is configured to prevent the first actuating device 7 from moving the first switching unit 1 from the inserted state A to the extracted state B, even when the second switching unit 2 is in the closed state ON. In this case, the control device 3 allows the first actuating device 7 to move the first switching unit 1 from the inserted state A to the extracted state B only if both switching units 1, 2 are in the open state OFF. This solution makes it possible to prevent the extraction of the first switching unit 1 when leakage currents are flowing along the electrical poles of the switching units due to the second switching unit 2 being in the closed state ON. In this way it is possible to avoid discharge phenomena (due to interruption of leakage currents) at the pole contacts 11, 12 of the first switching unit, which are very dangerous for personnel working at the site.

[0070] Preferably, the second actuation device 8 is arranged to move the second switching unit 2 from the inserted state A to the extracted state B only if the second switching unit 2 is in the open state OFF. Advantageously, the second actuation device 8 incorporates suitable enabling means (not shown) which prevent the execution of an operation to withdraw the second switching unit 2 when the second switching unit 2 is in the closed state ON.

[0071] Preferably, the switching device 100 is connected to an external auxiliary power supply V AUXand a power supply stage 4 adapted to receive and use the received voltage to supply low-voltage components (electrical or electronic) internal to the switching device, such as the control device 3, the trip actuator 25, the operating devices 7, 8, the above-mentioned drive circuits included in the switching units 1, 2, etc. In general, an external auxiliary power supply V AUX is obtained from electrical line 50 via a suitable auxiliary power interface device (not shown). Such auxiliary power interface device (which is not typically included in the switching device) may be of any known type.

[0072] Preferably, the power supply stage 4 is connected to an external power supply voltage V AUX and one or more driver circuits (not shown) arranged to receive the voltage Vs from the power supply stage and to supply a charging current for charging suitable energy storage means (not shown) of said power supply stage. Advantageously, said energy storage means (e.g. a capacitor bank storage device) make it possible to supply a suitable power supply voltage Vs to the low-voltage internal components of the switching device by drawing electrical energy from the energy storage means. Generally, the power supply stages 4 may be arranged at an industrial level according to solutions of known type. Therefore, in the following, for the sake of brevity, they will not be described in further structural or electrical circuit details.

[0073] Preferably, the control device 3 is configured to implement a special control logic for controlling the operation of the switching device 100 by controlling the operation of the switching units 1, 2. According to such control logic, when the switching units 1, 2 are in the inserted state A, the first switching unit 1 and the second switching unit 2 may be combined in only a number of specific operating modes, each of which corresponds to a predetermined one of the operating states of the switching device 100 (FIG. 4).

[0074] Preferably, the control device 3 is arranged to control the switching units 1, 2 so that they can operate in combination only in the following operating modes: - a first operating mode [I] in which both switching units 1 and 2 are in the closed state ON; a second operating mode [X] in which the first switching unit 1 is in the open state OFF and the second switching unit 2 is in the closed state ON; - A third operating mode [O] in which both switching units 1 and 2 are in the open state OFF.

[0075] When the switching units 1 and 2 are operating according to the first operating mode [I], the line Current can flow through the electric poles 1A, 2A of the switching units 1, 2. Thus, there is electrical continuity between the first line conductor 51 and the second line conductor 52 of the electric wire 50. Therefore, the first operating mode [I] of the switching units 1, 2 is This corresponds to a closed state of 100.

[0076] When the switching units 1 and 2 are operating according to the second operating mode [X], the first switching unit 1 is in the open state OFF, so that the line current cannot flow along the electric poles 1A and 2A of the switching units 1 and 2. Therefore, the first line conductor 51 and the second line conductor 52 of the electric wire 50 are not connected. However, the second switching unit 2 is in the closed state ON and leakage currents associated with the solid-state switch 10 can still flow along the electrical poles 1A, 2A, so that there is no electrical isolation between the line conductors 51 and 52. The second operating configuration [X] of the switching units 1, 2 corresponds to a standby state of the switching device 100 which is intermediate between the closed and open states.

[0077] When the switching units 1, 2 operate according to the third operating mode [O], both switching units 1, 2 are in the open state OFF, so that the line current and any possible leakage current cannot flow along the electrical poles 1A, 2A of the switching units 1, 2. The first line conductor 51 and the second line conductor 52 of the electric wire 50 are not connected, and electrical insulation between the first line conductor 51 and the second line conductor 52 is ensured. Thus, the third operating mode [O] of the switching units 1, 2 corresponds to the open state of the switching device 100.

[0078] In general, the control device 3 is configured to instruct the switching units 1, 2 to switch from one operating mode to another in response to receiving the above-mentioned input commands CM1, CM2, CM3 indicating a desired operating state for the switching device 100. However, according to the control logic implemented in the control device 30, a transition between the operating modes of the switching units 1,2 must always involve the second operating mode [X], which corresponds to the standby state of the switching device 100 (Fig. 4). In other words, the control device 3 is configured to control the switching units 1,2 in a way that prevents a direct transition between the first operating mode [I] and the third operating mode [O] of the switching units 1,2 (Fig. 4).

[0079] Preferably, when the switching units 1, 2 are in the first operating mode [I] (corresponding to the closed state of the switching device 100), the control device 3 commands the switching units 1, 2 to switch to the second operating mode [X] (corresponding to the standby state of the switching device 100). In fact, according to the control logic implemented in the control device 3, the switching units 1, 2 can only switch from the first operating mode [I] to the third operating mode via the second operating mode [X]. When the switching device is in a closed state (first operating mode [I] of the switching units 1, 2), the switching device 100 can only be switched to an open state via a standby state (second operating mode [X] of the switching units 1, 2).

[0080] Preferably, when the switching units 1, 2 are in the second operating mode [X] (corresponding to the standby state of the switching device 100), the control device 3 can instruct the switching units 1, 2 to switch to the first operating mode [I] (corresponding to the closed state of the switching device 100) or to switch to the third operating mode [O] (corresponding to the open state of the switching device 100). In practice, the control logic implemented in the control device 3 allows the switching units 1, 2 to switch from the second operating mode [X] to either the first operating mode [I] or the third operating mode [O]. When the switching device is in a standby state (switching units 1 and 2 are in the second operating mode [X]), the switching device 100 can be switched to either a closed state (switching units 1 and 2 are in the first operating mode [I]) or an open state (switching units 1 and 2 are in the third operating mode [O]).

[0081] Preferably, when the switching units 1, 2 are in the third operating mode [O] (corresponding to the open state of the switching device 100), the control device 3 can command the switching units 1, 2 to switch to the second operating mode [X] (corresponding to the standby state of the switching device 100). In fact, according to the control logic implemented in the control device 3, the switching units 1, 2 can only switch from the third operating mode [O] to the first operating mode via the second operating mode [X].

[0082] When the switching device is in the open state (switching units 1, 2 in the third operating configuration [O]), in response to receiving input commands CM1, CM2 indicating a desired different operating state, the switching device 100 can only switch to the closed state via the standby state (switching units 1, 2 in the second operating configuration [X]). The control logic described above is configured to be able to perform the operation of pulling out each switching unit 1, 2 upon activation by the user only if that switching unit is in the open state OFF.

[0083] Preferably, the control device 3 is configured to prevent the operation of withdrawing the first switching unit 1 (by disabling the first actuation device 7 as described above) when the first switching unit 1 and the second switching unit 2 are operating in combination according to the first operating mode [I].

[0084] Preferably, the control device 3 is configured to prevent the operation of pulling out the first switching unit 1 also when the second switching unit 2 is in the closed state ON. In this case, the control device 3 is configured to prevent the operation of pulling out the first switching unit 1 also when the first switching unit 1 and the second switching unit 2 operate in a combination according to the second operating mode [X], and the control device 3 is configured to enable the operation of pulling out the first switching unit 1 only when the first switching unit 1 and the second switching unit 2 operate in a combination according to the third operating mode [O].

[0085] Preferably, the second actuation device 8 is arranged to perform the operation of withdrawing the second switching unit 2 only when the second switching unit 2 is in the open state OFF. In this case, the control device 3 is configured to activate the operation of withdrawing the first switching unit 1 only when the first switching unit 1 and the second switching unit 2 operate in combination according to the third operating mode [O]. Advantageously, the control logic described above is made to take into account possible fault conditions of the power supply stage 4.

[0086] In accordance with the present invention, the switching unit 2 is configured such that when an opening operation commanded by the control device 3 (e.g., in which the control logic described above is implemented) cannot be performed for any reason (e.g., because the switching device is unable to receive or use an external auxiliary power supply to supply its low-voltage internal components, or because a fault has occurred in the drive circuitry operatively associated with the trip actuator or in the trip actuator 25), user intervention can force the switching unit 2 to perform the opening operation in an emergency situation.

[0087] Referring again to FIG. 2, the switching unit 2 comprises an emergency control device 27 that can be activated by a user to cause the second switching unit 2 to perform an opening operation, i.e., to switch from the closed state ON to the open state OFF. Advantageously, when the second switching unit 2 is in the closed state ON and an operation to open the second switching unit 2 is initiated by the user, the emergency control device 27 actuates the actuating mechanism 29 of the second switching unit 2 and moves the movable contact 202 of said switching unit to perform the above-mentioned opening operation.

[0088] In response to activation by the emergency control device 27, the operating mechanism 29 moves the movable contact 202 from a position coupled to the fixed contact 201 to a position separated from the fixed contact, and the second switching unit 2 switches from a closed state ON to an open state OFF. The emergency control device 27 preferably includes an emergency command button 271 that can be operated by the user from a rest position to an activated position.

[0089] Preferably, the emergency control device 27 comprises a trip element 272 operatively connected to a command button 271. When the second switching unit 2 is in the closed state ON, movement of the command button 271 to the activated position (as communicated by the user) initiates the actuation mechanism 29. This actuation mechanism 29 separates the movable contact 202 from the corresponding fixed contact 203, and the second switching unit 2 performs an opening operation.

[0090] According to the present invention, the command button 271 is normally not accessible to the user because it is covered by one or more components of the second switching unit 2, preferably by one or more panels that are walls 28 (usually the front wall) of the second switching unit 2. Thus, the command button 271 is only accessible to the user when one or more structural components 28A, 28B of the second switching unit 2 are removed.

[0091] Preferably, on the wall 28 (preferably the front wall), the second switching unit 2 comprises a first protective panel 28A that covers the emergency command button 271. Thus, the command button 271 can be accessed by a user by removing the first protective panel from the second switching unit 2. Preferably, the second switching unit 2 includes a second protective panel 28B that covers the first protective panel 28A on the same wall 28. Therefore, the command button 271 can be accessed by a user by removing the first and second protective panels from the second switching unit 2.

[0092] Preferably, the emergency control device 27 comprises a signalling means 273 arranged to provide a user with an optical signal L indicating the operating state of the second switching unit 2, more preferably the optical signal L indicating that the second switching unit 2 is in the closed state ON.

[0093] Preferably, the signaling means 273 may include a detection device (e.g., a microswitch) configured to detect the position of the movable contact 202 of the second switching unit 2, and an LED device operatively connected to said detection device and configured to emit a light signal L in response to receiving a detection signal indicating that the movable contact 202 is in a position connected to the corresponding fixed contact 201.

[0094] Advantageously, the light signal L emitted by the signaling means 273 can always be seen by the user without removing parts of the switching unit 2. When the signaling means 273 (in particular its LED device) is arranged on the same wall 28 on which the command button 271 is arranged (as shown in FIG. 2), the protective panels 28A, 28B covering the emergency command button 271 are made (for example by providing a suitable window) so as not to hide the light signal L emitted by the signaling means 273. In general, the protective panels 28A, 28B and the signaling means 273 may be made on an industrial level according to solutions of known types. In the following, for the sake of brevity, they will not be described in further structural detail.

[0095] 5A, 5B and 5C show diagrammatically how a user can activate the emergency control device 27 of the second switching unit 2 to force the second switching unit 2 to perform an opening operation. When the operation to open the second switching unit 2 fails, the user can recognize that this switching unit 2 is still in the closed state ON by seeing the light signal L emitted by the signaling means 273 (FIG. 5A).

[0096] The user can then remove the second protective panel 28B from the appropriate wall 28 (usually the front wall) of the second switching unit 2. This allows the user to access the first protective panel 28A (FIG. 5B). The user removes the first protective panel 28A to access the command button 271. At this stage, the user can operate (e.g., press) the command button 271 to cause the second switching unit 2 to perform an opening operation.

[0097] Preferably, the emergency control device 27 comprises detection means 274 arranged to provide the control device 3 with a warning signal SA indicative of the above-mentioned condition of removal of the first protective panel 28A. Preferably, when the first switching unit is in the closed state ON, the control unit 3 commands the first switching unit 1 to switch to the open state OFF in response to receiving the warning signal SA.

[0098] Preferably, when the first switching unit 1 is in the open state OFF, the control unit 3 prevents the first switching unit 1 from switching to the closed state ON in response to receiving the warning signal SA. This solution is very effective for improving the safety of the switching device's operation. That is, the control unit 3 provides for transitioning the first switching unit 1 to a safe state (i.e., being in the open state OFF) or maintaining the safe state of the first switching unit 1 when the user gains access to the emergency control unit 27 for any reason. In this way, the possible danger of pulling out the second switching unit 2 (especially when the first switching unit 1 is in the closed state ON) is automatically prevented when the user gains access to the emergency control unit 27.

[0099] The switching device 100 of the present invention offers important advantages over corresponding solutions available in the state of the art. In the switching device 100, the electromechanical switching unit 2 is equipped with an emergency control device 27 that can force the electromechanical switching unit 2 to perform an opening operation if the normal opening operation fails for some reason (for example, due to a lack of an auxiliary power supply). This solution prevents the execution of an operation to pull out the second switching unit 2 in the presence of leakage currents that may still be flowing when the second switching unit 2 is in the closed state ON (even if the solid-state switch is in the blocking state and the switching unit 1 is in the open state OFF).

[0100] According to one aspect of the present invention, the control device 3 of the switching device is configured to control the switching device 100 to switch between a closed state (the switching units 1 and 2 are in the first configuration [I]) and an open state (the switch The switching device 100 is configured to control the switching units 1,2 such that they can be in a standby state (the switching units 1,2 are in the second configuration [X]) in addition to a standby state (the switching units 1,2 are in the third configuration [O]). Such a solution makes it possible to relax the time synchronization constraints between the switching units 1,2 when the switching device 100 needs to perform an opening operation (i.e., a transition from a closed state to an open state) or a closing operation (i.e., a transition from an open state to a closed state).

[0101] As anticipated by the present invention, it is clear that the introduction of an emergency control device 27 is worthwhile for the safe implementation of such control logic. If the switching operation commanded by the control device 3 fails for some reason, the user can activate the emergency control device 27 to force the switching device to transition from a standby state (switching units 1 and 2 are in the second configuration [X]) to an open state (switching units 1 and 2 are in the third configuration [O]).

[0102] Therefore, the switching device 100 can operate according to a robust control logic that can improve its overall efficiency and safety. Switching device 100 is relatively easy to produce on an industrial scale and can be manufactured at a price competitive with similar state-of-the-art devices.

Claims

1. 1. A switching device for an electrical power distribution grid, comprising: the switching device comprises one or more first line terminals electrically connectable to corresponding first line conductors of the electric wires, one or more second line terminals electrically connectable to corresponding second line conductors of the electric wires, a first switching unit having one or more first electrical poles, a second switching unit having one or more second electrical poles, and a control device arranged to control operation of the switching device; the first electrical pole comprises a first pole contact electrically connectable to a corresponding first line terminal, a second pole contact, and one or more solid state switches electrically connected to the first and second pole contacts; the solid-state switch is configured to operate to pass current in a conducting state or to block current in a blocking state; the first switching unit is reversibly switchable between a closed state in which the solid-state switch is in a conducting state and an open state in which the solid-state switch is in a blocking state; the first switching unit is reversibly movable between an inserted state in which the first pole contact is connected to the first line terminal and a withdrawn state in which the first pole contact is separated from the first line terminal; the second electric pole comprises a third pole contact electrically connectable to a corresponding second pole contact of the first switching unit, a fourth pole contact electrically connectable to a corresponding second line terminal, and an electric contact electrically connected to the third and fourth pole contacts; The electrical contacts are configured to operate in a connected state to pass current or in a disconnected state to interrupt current; the second switching unit is capable of reversibly switching between a closed state in which the electrical contacts are connected and an open state in which the electrical contacts are separated; the second switching unit is reversibly movable between an inserted state in which the fourth pole contact is coupled to the second line terminal and a withdrawn state in which the fourth pole contact is separated from the second line terminal; the second switching unit includes an emergency control device that can be activated by a user to switch the second switching unit from the closed state to the open state; The emergency control device includes an emergency command button that is operable by a user; the emergency command button is provided so as to be accessible to a user upon removal of one or more structural components of the second switching unit; the emergency control device comprises detection means arranged to provide a warning signal to the control device indicative of a condition in which the first protective panel has been removed; The control device is configured to instruct the first switching unit to switch from a closed state to an open state in response to receiving the warning signal when the first switching unit is in a closed state.

2. A switching device for an electric power distribution grid, comprising: the switching device comprises one or more first line terminals electrically connectable to corresponding first line conductors of the electric wires, one or more second line terminals electrically connectable to corresponding second line conductors of the electric wires, a first switching unit having one or more first electrical poles, a second switching unit having one or more second electrical poles, and a control device arranged to control operation of the switching device; the first electrical pole comprises a first pole contact electrically connectable to a corresponding first line terminal, a second pole contact, and one or more solid state switches electrically connected to the first and second pole contacts; the solid-state switch is configured to operate to pass current in a conducting state or to block current in a blocking state; a first switching unit capable of reversibly switching between a closed state in which the solid-state switch is in a conducting state and an open state in which the solid-state switch is in a blocking state; the first switching unit is reversibly movable between an inserted state in which the first pole contact is connected to the first line terminal and a withdrawn state in which the first pole contact is separated from the first line terminal; the second electric pole comprises a third pole contact electrically connectable to a corresponding second pole contact of the first switching unit, a fourth pole contact electrically connectable to a corresponding second line terminal, and an electric contact electrically connected to the third and fourth pole contacts; The electrical contacts are configured to operate in a connected state to pass current or in a disconnected state to interrupt current; the second switching unit is capable of reversibly switching between a closed state in which the electrical contacts are connected and an open state in which the electrical contacts are separated; the second switching unit is reversibly movable between an inserted state in which the fourth pole contact is coupled to the second line terminal and a withdrawn state in which the fourth pole contact is separated from the second line terminal; the second switching unit includes an emergency control device that can be activated by a user to switch the second switching unit from the closed state to the open state; The emergency control device includes an emergency command button that is operable by a user; the emergency command button is provided so as to be accessible to a user upon removal of one or more structural components of the second switching unit; the emergency control device comprises detection means arranged to provide a warning signal to the control device indicative of a condition in which the first protective panel has been removed; The control device is configured to prevent the first switching unit from switching to a closed state in response to receiving the warning signal when the first switching unit is in an open state.

3. the second switching unit includes a first protective panel covering the emergency command button; 3. A switching device according to claim 1 or 2, wherein the emergency command button is accessible to a user when a first protective panel is removed from the second switching unit.

4. the second switching unit includes a second protective panel covering the first protective panel; 4. The switching device of claim 3, wherein the emergency command button is provided so that the user can access the emergency command button by removing first and second protective panels from the second switching unit.

5. the second electrical pole of the second switching unit includes at least a fixed electrical contact and a movable electrical contact; the second switching unit comprises an actuation mechanism; the actuating mechanism is configured to relatively move one or more of the movable electrical contacts of the second switching unit between a position in which the movable electrical contacts are coupled to corresponding fixed electrical contacts of the second switching unit and a position in which the movable electrical contacts are decoupled from the fixed electrical contacts; the emergency control device is configured to initiate the actuation mechanism to move the movable electrical contact upon activation by a user when the second switching unit is in a closed state; 5. The switching device according to claim 1, wherein the actuating mechanism is configured to, in response to activation by the emergency control device, move the movable electrical contact from a position in which the movable electrical contact is connected to the fixed electrical contact to a position in which the movable electrical contact is separated from the fixed electrical contact, thereby switching the second switching unit from a closed state to an open state.

6. the emergency control device includes a trip element operatively connected to the emergency command button; 6. The switching device of claim 5, wherein the trip element is arranged to actuate the operating mechanism when a user operates the emergency command button to an activated position.

7. A switching device according to any one of claims 1 to 6, wherein the emergency control device comprises signalling means arranged to provide a user with an optical signal indicative of the operational status of the second switching unit.

8. the control device is configured to control the first switching unit and the second switching unit such that the first switching unit and the second switching unit operate in a combination according to a first operating configuration, a second operating configuration, or a third operating configuration; a first operating configuration corresponds to a closed state of the switching device in which both the first switching unit and the second switching unit are closed; a second operating configuration corresponds to a standby state of the switching device in which the first switching unit is in an open state and the second switching unit is in a closed state; A switching device according to any one of claims 1 to 7, wherein a third operating configuration corresponds to an open state of the switching device in which both the first switching unit and the second switching unit are in an open state.

9. 9. A switching device according to any one of claims 1 to 8, wherein the control device comprises an interface section including one or more input ports arranged to receive input commands indicative of a desired mode of operation for the switching device.

10. the switching device includes a human-machine interface that is communicable with the interface unit, 10. The switching device of claim 9, wherein the human-machine interface is configured to provide the input command based on interaction with a user.

11. 11. A switching device according to claim 9 or 10, wherein the interface unit is capable of receiving the input command from a remote computer device.

12. A switching device according to any one of claims 1 to 11, wherein the control device is included in a first switching unit.

Images