Low and medium voltage electrical enclosures

Abstract

To provide a low and medium voltage electrical enclosure, in which a pressure generated during an internal arc fault can be discharged and an air tight condition as a closed switch board can be maintained even after pressure discharge.SOLUTION: A low and medium voltage electrical enclosure 1 includes a supporting structure which defines an internal space delimited by walls forming one or more compartments housing one or more electrical apparatuses. At least one of the walls is provided with venting openings 20, and the venting openings are provided with a cover 21 closing a corresponding venting opening in a first-closed-operating condition. The enclosure is provided with an actuating device adapted to open the cover in a second-open-operating condition in the case of occurrence of an arc fault inside the internal space. The actuating device includes an actuating mechanism having a Shape Memory Alloy-based (SMA-based) actuating element that has a first dimension at first predetermined temperatures and is reversibly changeable into a second dimension at second predetermined temperatures.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to low and medium voltage electrical enclosures, and more particularly to low and medium voltage electrical enclosures having improved cooling capabilities and characteristics. [Background technology]

[0002] In general, an enclosure for low and medium voltage electrical distribution is a known device formed by a supporting structure bounded by side, rear, top and bottom walls and closed by a door, which houses in one or more internal compartments electrical appliances and devices, e.g. circuit breakers and / or similar devices, busbar systems, electrical equipment and similar devices. Summary of the Invention [Problem to be solved by the invention]

[0003] During operation, internal electrical arcs may be released within the enclosure for a number of reasons. One result of internal arcing is an increase in pressure within one or more compartments of the enclosure. A typical existing solution would be to provide one or more vents (openings), usually protected by a flap that can be opened to allow the escape of gas under the pressure created by the occurrence of an electric arc and restore the normal pressure condition.

[0004] However, the flap vents result in a degradation of the original IP rating and rating relative to a similar enclosure without the flap. In other words, in the current state of the art, existing low and medium voltage electrical enclosures have difficulty in achieving a satisfactory balance between the desired high IP rating and good performance and resistance in the event of an internal arc fault. [Means for solving the problem]

[0005] The present disclosure therefore aims to provide a low- and medium-voltage electrical enclosure making it possible to overcome at least some of the above-mentioned drawbacks. In particular, the present invention aims to provide low and medium voltage electrical enclosures that are able to release the increased pressure generated during an internal arc fault without irretrievably losing their original IP rating.

[0006] More specifically, the present invention aims to provide a low and medium voltage electrical enclosure which maintains a high IP value during normal operation under normal conditions and during an arc flash event, only experiences a temporary reduction in IP value for a limited time. Furthermore, the present invention aims to provide a low- and medium-voltage electrical enclosure which is provided with a device for controlling the pressure increase inside it in the event of an internal arc and which does not require costly maintenance interventions.

[0007] The present invention also aims to provide a low and medium voltage electrical enclosure that is provided with a device for controlling the pressure increase therein in the event of an internal arc and that does not require additional dedicated testing or certification. It is a further object of the present invention to provide a low to medium voltage electrical enclosure that includes a device for controlling the pressure increase therein in the event of an internal arc, that is reliable, and that can be relatively easily manufactured at a competitive cost.

[0008] Thus, the present invention relates to a low- and medium-voltage electrical enclosure comprising a support structure defining an interior space bounded by walls forming one or more compartments for housing one or more electrical devices, characterized in that at least one of said walls comprises one or more vents connecting an exterior of said low- and medium-voltage electrical enclosure to said interior space, said one or more vents comprising covers for closing corresponding vents in a first, closed operational state, said low- and medium-voltage electrical enclosure comprising an actuator adapted to open said covers in a second, open operational state in the event of an arc fault in said interior space. The low to medium voltage electrical enclosure of the present invention is further characterized in that the actuator comprises an actuation mechanism having a shape memory alloy based (SMA based) actuation element having a first dimension at a first predetermined temperature and reversibly changeable to a second dimension at a second predetermined temperature, wherein the reversible change of the SMA based actuation element from the first dimension to the second dimension determines reversible movement of the cover from the first closed operating state to the second open operating state, and vice versa.

[0009] As a result of the particular construction of the low and medium voltage electrical enclosure of the present invention, as will be better explained in the following description, the above mentioned problems can be avoided or at least significantly reduced. In fact, under the pressure and temperature conditions that arise in case of an internal arc flash, a cover closing one or more vents (openings) in the outer wall of the enclosure can be opened, thereby allowing the gases generated during the arc to escape and the overpressure created to escape. At the same time, the vents make it possible to create a convection air circulation inside the enclosure in order to keep the temperature at the desired value.

[0010] In other words, during an arc flash condition, the cover and the corresponding vents are forced into an open position, which may temporarily change the IP rating of the enclosure. As soon as the temperature returns to below a certain predetermined value, the cover is returned to the closed position, thereby restoring the original IP rating. As will be better explained in the following description, the movement of the cover from a closed state to an open state, and more particularly, from an open state to a closed state, is determined and controlled by a temperature sensitive actuator, i.e., an actuator that operates in response to temperature changes without requiring an additional power supply or a dedicated control system.

[0011] In this regard, the actuators used in the housings of the present disclosure are formed by shape memory alloy-based (SMA-based) actuation elements. Shape memory alloys are well-known materials that have the ability to reversibly change their dimensions depending on temperature conditions, which will not be described in further detail. The response speed of shape memory alloys to temperature changes is very fast, and during the dimensional change they can exert enough force to actuate relatively simple mechanisms. Moreover, the temperature coefficient of shape memory alloys (i.e., the temperature value or range at which they undergo a certain dimensional change) can be adjusted and fine-tuned according to needs by selecting the appropriate material based on known criteria.

[0012] In other words, the SMA-based actuating element used in the housing of the present invention changes its dimension depending on the temperature conditions in the housing. In particular, at a first predetermined temperature condition, the SMA-based actuating element has a first dimension, and at a second predetermined temperature condition, the SMA-based actuating element has a second dimension. The SMA-based actuating element can be operatively connected to the cover to move the cover from a closed position to an open position, or vice versa, depending on the temperature conditions in the housing.

[0013] In this manner, for example, if an internal arc flash causes the temperature inside the enclosure to rapidly rise above a predetermined level, the cover can be rapidly moved from a closed position to an open position, thereby releasing the overpressure generated by the arc flash. In this state, a temporary controlled convection air circulation occurs within the enclosure, allowing it to cool, and at the same time, the enclosure's IP rating is temporarily changed. Then, when the temperature falls back below a predetermined level, the cover is moved from the open position back to the closed position, restoring the original IP rating.

[0014] The SMA-based actuating element may be based on a shape memory alloy having a negative temperature coefficient, i.e., a shape memory alloy that contracts when the temperature exceeds the predetermined value or range, in which case the SMA-based actuating element reduces its actuating dimension (i.e., shrinks) when the temperature exceeds the predetermined value or range. Alternatively, the SMA-based actuating element may be based on a shape memory alloy with a positive temperature coefficient, i.e., a shape memory alloy that expands when the temperature exceeds the predetermined value or range, in which case the SMA-based actuating element increases its actuating dimension (i.e., lengthens) when the temperature exceeds the predetermined value or range.

[0015] Furthermore, it is noteworthy that since the operating principle of the SMA-based operating element (e.g., linear movement in response to temperature) is extremely simple, the operating mechanism connecting the SMA-based operating element and the cover is extremely simple and therefore extremely easy to manufacture and maintain. In a preferred embodiment of the low to medium voltage electrical enclosure according to the present invention, one or more covers are hinged to a rim portion of a corresponding vent, the covers being pivotally movable from said first closed operational state to said second open operational state and vice versa under the action of an SMA based actuation element.

[0016] In most preferred embodiments of the low and medium voltage electrical enclosure of the present invention, the SMA based actuating element advantageously comprises a bar or wire having a first predetermined length at said first predetermined temperature and a second predetermined length at said second predetermined temperature. In fact, according to this embodiment, the SMA based actuating element shortens or lengthens in a linear actuating direction along its longitudinal extension depending on the temperature conditions, thereby making it very easy to couple with the actuating mechanism of the cover. For example, in this case the actuation mechanism may conveniently comprise a lever having a first end operably connected to the cover and a second end operably connected to the first end of the bar or wire, such that linear movement of the SMA based actuation element is immediately transmitted to the cover in a very simple manner. In a particular embodiment of the low to medium voltage electrical enclosure of the present invention, the bar or wire then preferably has a second end fixed to a fixed point on the enclosure. Indeed, according to this embodiment, the movement of the SMA-based actuating element is only in one direction, as will be better explained below.

[0017] Alternatively, in a particular embodiment of the low-medium voltage electrical enclosure of the present invention, the enclosure comprises one or more pairs of first and second vents provided with corresponding first and second covers. In this embodiment, the SMA-based actuation element advantageously comprises a bar or wire having a first predetermined length at said first predetermined temperature and a second predetermined length at said second predetermined temperature. Furthermore, said actuation mechanism comprises first and second levers having first ends connected to said first and second covers, respectively. And, said bar or wire advantageously has a first end operably connected to said first lever and a second end operably connected to said second lever.

[0018] Indeed, according to this embodiment, an SMA-based actuation element is positioned between the two vents and the corresponding covers, the movement of which is performed in two directions acting simultaneously on said first and second levers, as will be better explained below. In a particular embodiment of the low- and medium-voltage electrical enclosure according to the invention, the rim of said vent is raised with respect to the corresponding wall surface in which it is located. In particular, in such a case, the cover may advantageously comprise a first portion extending from a rim portion to which the cover is hinged over the vent, and a second portion extending from the rim portion opposite the vent.

[0019] In fact, according to this embodiment, the weight of the first part of the cover is at least partially counterbalanced by the second part of the cover, which extends in the opposite direction relative to the axis of rotation of said cover, so that the movement of the cover from the closed position to the open position and vice versa requires only minimal actuation energy due to the overall balanced weight relative to the axis of rotation of the cover. In a preferred embodiment of the low to medium voltage electrical enclosure of the present invention, the SMA based actuating element has a negative temperature coefficient, i.e., the first predetermined temperature is lower than the second predetermined temperature and the first dimension of the SMA based actuating element is greater than the second dimension of the SMA based actuating element.

[0020] The number and location of vents on the walls of low and medium voltage electrical enclosures may vary as required. For example, one or more vents may be advantageously located in the top wall of the enclosure, such a location being relatively safe for venting gases that would normally be exhausted in the event of an internal arc. Alternatively, or in combination with the above-described embodiments, one or more vents may be located in a sidewall of the enclosure, depending on safety considerations. Further features and advantages of the present invention will become more apparent from the description of preferred, but not exclusive, embodiments of a low- and medium-voltage electrical enclosure according to the invention, given by way of example in the accompanying drawings. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a perspective view of a first embodiment of a low- to medium-voltage electrical enclosure according to the present invention. [Figure 2a] FIG. 2a is a perspective view of a first embodiment of a cover and corresponding vent for use in an enclosure according to the present invention, showing a second, open operational state. [Figure 2b] FIG. 2b is a front view of a first embodiment of a cover and corresponding vent for use in an enclosure according to the present invention, showing a first closed operational state. [Figure 3a] FIG. 3a is a first side view of a first embodiment of a cover and corresponding actuator used in an enclosure according to the present invention, showing a first closed operational state. [Figure 3b] FIG. 3b is a second side view of the first embodiment illustrating a second opening operational state of the cover and corresponding actuator used in the housing according to the present invention. [Figure 4a] FIG. 4a is a perspective view of a second embodiment of a cover and corresponding vent for use in an enclosure according to the present invention, showing a second, open operational state. [Figure 4b] FIG. 4b is a front view of a second embodiment of a cover and corresponding vent for use in an enclosure according to the present invention, showing a first closed operational state. [Figure 5a] FIG. 5a is a first side view of a second embodiment of a cover and corresponding actuator used in a housing according to the present invention, showing a first closed operational state. [Figure 5b] FIG. 5b is a second side view of the second embodiment showing a second opening operational state of a cover and corresponding actuator for use in an enclosure according to the present invention. [Figure 6a] FIG. 6a is a perspective view of a third embodiment of a cover and corresponding vent for use in an enclosure according to the present invention, showing a second, open operational state. [Figure 6b] FIG. 6b is a front view of a third embodiment of a cover and corresponding vent for use in an enclosure according to the present invention, showing a first closed operational state. [Figure 6c] FIG. 6c is a side view of a third embodiment of a cover and corresponding vent for use in an enclosure according to the present invention, showing a first closed operational state. [Figure 7a]FIG. 7a is a perspective view of a fourth embodiment of a cover and corresponding vent for use in an enclosure according to the present invention, showing a second, open operational state. [Figure 7b] FIG. 7b is a front view of a fourth embodiment of a cover and corresponding vent for use in an enclosure according to the present invention, showing a first closed operational state. [Figure 7c] FIG. 7c is a side view of a fourth embodiment of a cover and corresponding vent for use in an enclosure according to the present invention, showing a first closed operational state.

[0022] With reference to the accompanying drawings, a low to medium voltage electrical enclosure shown in various embodiments having the reference numeral 1, in its more general definition, comprises a support structure 11 defining an interior space bounded by a top wall (external wall, wall) 13, a side wall (external wall, wall) 14 and having one or more compartments for housing one or more electrical devices. One of the features of the low- and medium-voltage electrical enclosure 1 of the present invention is given by the fact that at least one of the outer walls 13, 14 is provided with one or more ventilation openings 20, 30 leading between the exterior of the low- and medium-voltage electrical enclosure 1 and the interior space.

[0023] The vents 20, 30 are conveniently provided with corresponding covers 21, 31 for closing the vents 20, 30 in a first closed operational state at a first predetermined temperature, and the electrical enclosure 1 is conveniently provided with an actuator 40 adapted to move the covers 21, 31 from the first closed operational state to a second open operational state at a second predetermined temperature. A further feature of the low to medium voltage electrical enclosure 1 of the present invention is provided by the fact that said actuation device 40 conveniently comprises an actuation mechanism 41 having a shape memory alloy based (SMA based) actuation element 42, 421 reversibly changeable to a first dimension at a first predetermined temperature and to a second dimension at a second predetermined temperature.

[0024] Thus, when the SMA-based actuation elements 42, 421 reversibly change dimension from a first dimension to a second dimension, the reversible movement of the covers 21, 31 is determined by the movement from a first closed operating state to a second open operating state, and vice versa. Thus, in the open state, controlled convection ventilation of the low to medium voltage electrical enclosure 1 is possible until the temperature is restored to below the first predetermined temperature, at which point the SMA-based actuating element 42, 421 changes its dimension from the second dimension to the first dimension, thereby moving the cover 21, 31 from the second open operational state to the first closed operational state, restoring the original closed state and original IP rating of the enclosure 1.

[0025] As shown in the accompanying figures, in a preferred embodiment of the presently disclosed low and medium voltage electrical enclosure 1, the covers 21, 31 are hingeable to the rim portions 211, 311 of the corresponding vents 20, 30, and the covers 21, 31 are pivotable between a first, closed and second, open operational condition in accordance with the mechanism previously described by rotating about the hinge axis. In most preferred embodiments of the low to medium voltage electrical enclosure 1 of the present invention, the SMA based actuating element 42, 421 preferably comprises a bar or wire having a first predetermined length at a first predetermined temperature and a second predetermined length at a second predetermined temperature.

[0026] As shown in the accompanying figures, when the SMA-based actuation element 42, 421 is formed of a bar or wire, the actuation mechanism can be very simple. With particular reference to Figures 3 and 5, in such a case, the actuation mechanism 41 can advantageously comprise a lever 51 having a first end 511 operably connected to the corresponding cover 21, 31 and a second end 512 operably connected to the first end 43, 431 of the bar or wire 42, 421. In the embodiment of the low-medium voltage electrical enclosure 1 shown in Figures 3a and 3b, the bar or wire 42 has a second end 44 fixed to a fixed point 45 on the enclosure 1. The movement of the SMA-based actuating element 42 is therefore only in one direction, with the first end 43 of the bar or wire 42 acting on the second end 512 of the lever, which determines its displacement and the resulting movement of the cover 21 from the closed position to the open position and vice versa.

[0027] In an alternative embodiment of the low to medium voltage electrical enclosure 1 shown in Figures 4 and 7, the electrical enclosure 1 advantageously comprises one or more pairs of first and second ventilation openings 20 (and 30) corresponding to the pairs of first and second covers 21 (and 31). In this case, with reference to Figures 5a and 5b, the SMA-based actuation element 421 advantageously comprises a bar or wire having a first predetermined length at a first predetermined temperature and a second predetermined length at a second predetermined temperature. In response, the actuation mechanism 41 advantageously comprises first and second levers 51, 52 each having a first end 511 connected to the first and second covers 21 (and 31). Furthermore, the bar or wire 421 has a first end 431 operably connected to the first lever 51 and a second end 441 operably connected to the second lever 52.

[0028] Indeed, according to this embodiment, the SMA-based actuating element 421 is arranged between the two vents 20 (and 30) and the corresponding covers 21 (and 31), mirroring each other. The movement of the bar or wire 421 is performed in two opposite directions acting simultaneously on the first and second levers 51, 52, such that a first end 431 of the bar or wire 421 acts on a first lever 51 and a second end 441 of the bar or wire 421 acts on a second lever 52, thereby determining their opposite displacements and the resulting movement of the covers 21 (and 31) from the closed position to the open position and vice versa.

[0029] 6 and 7, in certain embodiments of the low to medium voltage electrical enclosure 1 of the present disclosure, the rim of the vent 30 is raised relative to the surface of the corresponding wall in which it is located. In turn, according to a preferred embodiment, the cover 31 is hinged to the rim portion 311 and advantageously comprises a first portion 312 extending from the rim portion 311 in the direction towards and above the vent 30. The cover 31 further comprises a second portion 313 extending from the rim portion 311 in a direction opposite the vent 30 and the first portion 312.

[0030] As described above, according to this embodiment, the second portion 313 of the cover 31 at least partially offsets the weight of the first portion 312 of the cover 31, thereby facilitating rotation of the cover 31 about the hinge axis. The actuating mechanisms and elements used to move cover 31 in Figures 6 and 7 are not shown, but can essentially be substantially similar to those used in the embodiment of Figures 2 and 4 and represented in Figures 3 and 5. Additionally, the vents, covers and actuators may be formed directly on any of the exterior walls of the housing 1 or on plates 301, 302, 303, 304 that can be attached to any of the exterior walls.

[0031] In the embodiment of the low to medium voltage electrical enclosure 1 shown in the accompanying figures, the first predetermined temperature is lower than the second predetermined temperature and the first dimension of the SMA based actuating element 42, 421 is greater than the second dimension of the SMA based actuating element 42, 421. In other words, in the illustrated embodiment, the SMA-based actuating element 42, 421 is based on a shape memory alloy with a negative temperature coefficient, i.e., a shape memory alloy that contracts when the temperature exceeds a predetermined value or range. Thus, the SMA-based actuating element 42, 412 contracts when the temperature exceeds a predetermined value or range.

[0032] Alternatively, according to an embodiment based on the reverse operating condition, not shown, the SMA-based actuating element 42, 421 can be based on a shape memory alloy with a positive temperature coefficient, i.e., a shape memory alloy that expands when the temperature exceeds a predetermined value or range, in which case the SMA-based actuating element 42, 421 increases its actuating dimension (i.e., lengthens) when the temperature exceeds the predetermined value or range.

[0033] 1, in one embodiment of the low to medium voltage electrical enclosure 1 of the present invention, the vent 20 is located in the top wall 13 of the enclosure 1. This location is highly preferred for safety reasons. However, as previously mentioned, the location of the vent 20 may vary depending on the likelihood of arc flash in various compartments within the enclosure 1. Regarding the number and position of the ventilation openings 20, 30 in the low to medium voltage electrical enclosure 1 of the present invention, it is clear that any combination of the above described embodiments is possible depending on the needs and the layout of the enclosure.

[0034] Because the dimensions of the vents 20, 30 are relatively wide and / or if it is preferred to have some protection thereover, a net or mesh 300 may be conveniently placed over said vents. It will be apparent from the above description that the low to medium voltage electrical enclosure of the present invention fully achieves its intended objectives and overcomes the above-mentioned problems of existing enclosures. In particular, in the low and medium voltage electrical enclosures of the present invention, a satisfactory balance can be achieved between a desirable high IP rating and good performance and resistance during internal arcing faults.

[0035] In fact, in the low and medium voltage electrical enclosures of the present invention, the increased pressure generated during an internal arc fault can be discharged without irretrievably losing the original IP rating. Thus, a high IP rating is maintained during normal operation under normal conditions, while a reduction in IP value occurs only temporarily and for a limited time during an arc flash event. Furthermore, it is noteworthy that the device for controlling the increase in temperature and pressure in the event of an internal arc (used in the low- and medium-voltage electrical enclosures of the present invention) does not require burdensome maintenance interventions.

[0036] Moreover, by predetermining the opening and closing temperatures of the vent cover and appropriately selecting the material of the SMA-based actuating element, the internal temperature change can be easily controlled. In this way, the actuation device used in the low and medium voltage electrical enclosure of the invention does not require dedicated cabling or power supplies and can be installed very simply and quickly.

[0037] Furthermore, as a result of the very simple construction of the device for controlling the temperature changes in the enclosure, maintenance interventions are usually not necessary or can be carried out very easily and quickly. The low and medium voltage electrical enclosure thus conceived has several variations, all of which are covered by the appended claims. In practice, the materials used and the incidental dimensions and shapes may be any, depending on the requirements and the state of the art. [Explanation of symbols]

[0038] 1: Low and medium voltage electrical enclosures (enclosures) 11:Support structure 13: Upper wall (outer wall, wall) 14: Side wall (outer wall, wall) 20, 30: Ventilation hole (opening) 21: Cover (first cover) 31: Cover (Second cover) 40: Actuator 41: Operating mechanism 42, 421: Actuating element (bar or wire) 43, 431: first end 44: Second end 45: Fixed point 51: Lever (first lever) 52: Second Lever 211, 311: Rim part 300: Net or mesh 301, 302, 303, 304: Plates 311: Rim 312: First part 313: Second part 441: Second end 511: First end 512: Second end

Claims

1. A low and medium voltage electrical enclosure (1) comprising a support structure (11) defining an interior space bounded by walls (13, 14) forming one or more compartments for housing one or more electrical devices, At least one of the walls (13, 14) has one or more ventilation openings (20, 30) connecting the exterior of the low and medium voltage electrical enclosure (1) to the interior space, the one or more vents (20, 30) having covers (21, 31) for closing the corresponding vents (20, 30) in a first, closed operational state, and an actuator (40) adapted to open the covers (21, 31) in a second, open operational state in the event of an arc fault within the interior space; The actuation device (40) comprises an actuation mechanism (41) having a shape memory alloy-based (SMA-based) actuation element (42, 421) having a first dimension at a first predetermined temperature and reversibly changeable to a second dimension at a second predetermined temperature; a reversible dimensional change of the SMA-based actuation element (42, 421) from the first dimension to the second dimension determines a reversible movement of the cover (21, 31) from the first closed operational state to the second open operational state, and vice versa; the electrical enclosure (1) comprises one or more pairs of first and second vents (20, 30) provided with corresponding first and second covers (21, 31); the SMA-based actuating element (42, 421) comprises a bar or wire (42, 421) having a first predetermined length at the first predetermined temperature and a second predetermined length at the second predetermined temperature; The low-medium voltage electrical enclosure (1), characterized in that the actuating mechanism (41) comprises first and second levers (51, 52) having a first end (511) and a second end (512), respectively, connected to the first and second covers (21, 31), and the bar or wire (42, 421) has a first end (431) operatively connected to the first lever (51) and a second end (441) connected to the second lever (52).

2. A low- and medium-voltage electrical enclosure (1) having a support structure (11) defining an interior space bounded by walls (13, 14) forming one or more compartments for housing one or more electrical devices, At least one of the walls (13, 14) has one or more ventilation openings (20, 30) connecting the exterior of the low and medium voltage electrical enclosure (1) to the interior space, the one or more vents (20, 30) having covers (21, 31) for closing the corresponding vents (20, 30) in a first, closed operational state, and an actuator (40) adapted to open the covers (21, 31) in a second, open operational state in the event of an arc fault within the interior space; The actuation device (40) comprises an actuation mechanism (41) having a shape memory alloy-based (SMA-based) actuation element (42, 421) having a first dimension at a first predetermined temperature and reversibly changeable to a second dimension at a second predetermined temperature; a reversible dimensional change of the SMA-based actuation element (42, 421) from the first dimension to the second dimension determines a reversible movement of the cover (21, 31) from the first closed operational state to the second open operational state, and vice versa; the cover (21, 31) is hinged to a rim portion (211, 311) of the corresponding vent (20, 30) and is pivotable between the first closed operational state and the second open operational state; The low- and medium-voltage electrical enclosure (1) is characterized in that the cover (21, 31) has a rim portion that overlaps an outer surface of a rim portion (211, 311) of the corresponding vent (20, 30) when the cover (21, 31) is in a closing operating state for the corresponding vent (20, 30).

3. 3. The low-medium voltage electrical enclosure (1) according to claim 2, characterized in that the SMA-based actuating element (42, 421) comprises a bar or wire (42, 421) having a first predetermined length at the first predetermined temperature and a second predetermined length at the second predetermined temperature.

4. 4. The low-medium voltage electrical enclosure (1) according to claim 3, characterized in that the actuating mechanism (41) comprises a lever (51) having a first end (511) operably connected to the cover (21, 31) and a second end (512) operably connected to the first end (43, 431) of the bar or wire (42, 421).

5. 5. The low-medium voltage electrical enclosure (1) according to claim 4, characterized in that the bar or wire (42, 421) has a second end (44) fixed to a fixing point (45) of the electrical enclosure (1).

6. An electrical housing (1) comprising one or more pairs of first and second vents (20, 30) provided with corresponding first and second covers (21, 31); the SMA-based actuating element (42, 421) comprises a bar or wire (42, 421) having a first predetermined length at the first predetermined temperature and a second predetermined length at the second predetermined temperature; the actuation mechanism (41) comprises first and second levers (51, 52) each having a first end (511) connected to the first and second covers (21, 31), respectively; 4. The low and medium voltage electrical enclosure (1) according to claim 2 or 3, characterized in that the bar or wire (42, 421) has a first end (431) operatively connected to the first lever (51) and a second end (441) connected to the second lever (52).

7. The low and medium voltage electrical enclosure (1) according to any one of claims 2 to 6, characterized in that a rim portion (311) of the vent (30) is raised with respect to the surface of the corresponding wall (13, 14) in which the vent (30) is arranged.

8. 8. The low and medium voltage electrical enclosure (1) according to claim 7, characterized in that the cover (31) has a first part (312) extending from the rim portion (211, 311) at the cover (31) hinged to the vent (30) and a second part (313) extending from the rim portion (311) opposite the vent (30).

9. 9. The low-medium voltage electrical enclosure (1) according to claim 8, characterized in that the second part (313) of the cover (31) at least partially offsets the weight of the first part (312) of the cover (31).

10. The low-medium voltage electrical enclosure (1) according to any one of claims 1 to 9, characterized in that the first predetermined temperature is lower than the second predetermined temperature and the first dimension of the SMA based actuating element (42, 421) is greater than the second dimension of the SMA based actuating element (42, 421).

11. The low and medium voltage electrical enclosure (1) according to any one of claims 1 to 10, characterized in that the one or more vents (20, 30) are arranged in a top wall (13) of the electrical enclosure (1).

12. The low- and medium-voltage electrical enclosure (1) according to any one of claims 1 to 11, characterized in that the one or more vents (20, 30) are arranged in a side wall (14) of the electrical enclosure (1).

Images