WO2006040418A1

WO2006040418A1 - Overvoltage protection device provided with arc cutting means and corresponding method

Info

Publication number: WO2006040418A1
Application number: PCT/FR2004/002548
Authority: WO
Inventors: Stéphane BRESCON; Michel Georges Jean Donati; Alain René Robert LAGNOUX
Original assignee: Abb France
Priority date: 2004-10-08
Filing date: 2004-10-08
Publication date: 2006-04-20
Also published as: EP1803137A1; CN1879182B; EP1803137B1; ES2399966T3; CN1879182A

Abstract

The invention relates to a device (1) for protecting an electric installation against overvoltage comprising at least one protection component (10) provided with means for connecting to said electric installation, means for disconnecting the protection component (10) therefrom which are movable from a closed position to an open position, thereby forming an interstitial space (11) between the disconnecting and connecting means in such a way that an electric arc is formed therein. The inventive device is characterised in that it is provided with means (50) which approaches said electric arc from at least two different directions in order to reduce the cross-section thereof. Said invention is used for protecting against overvoltage.

Description

OVERVOLTAGE PROTECTION DEVICE

PROVIDED WITH ARC SHEAR MEANS

AND CORRESPONDING METHOD

TECHNICAL AREA

The present invention relates to the general technical field of protective devices for installations and electrical equipment against transient electrical surges, especially due to lightning.

The present invention relates more particularly to a protection device of an electrical installation against surges comprising: - at least one protection component, provided with connection means to the electrical installation,

a means for disconnecting the protection component with respect to the electrical installation, adapted to ensure the disconnection of the latter at the connection means, and capable of moving from a closed position to a position of opening thus creating an interstitial space between the disconnection means and the connection means, an electric arc then being capable of being formed in the interstitial space between the disconnection means and the connection means.

The present invention also relates to a method for improving the breaking capacity of a protection device of an electrical installation against overvoltages. PRIOR ART

It is now conventional to use protective devices to protect electrical or electronic devices against overvoltages that can be generated for example by discharges due to a lightning strike.

These protection devices generally comprise one or more overvoltage protection components, such as, for example, a varistor and / or a spark gap. When the component or components are exposed to voltages above a predetermined threshold value, they are likely to discharge the fault current to earth while limiting the overvoltage to a value compatible with the strength of the installation and equipment that are connected to it.

At the end of their life, the protection components are likely to present significant heating (usually greater than 150 ⁰ C) that can lead to serious damage to the installation, or even risks for the user (fire for example). This is why overvoltage protection devices are generally provided with thermal disconnection means. These thermal disconnection means are intended to isolate the protection component (s) of the electrical installation to be protected in the event of overheating of the latter exceeding a predetermined value in order to limit the risk of fire.

The thermal disconnection means can thus be formed by a disconnection blade, welded to one of the electrodes of the protection component using for example a thermal weld. The disconnection blade is generally subjected to a mechanical stress tending to move it away from the corresponding electrode so that when excessive overvoltage or prolonged use causes breakage or fusion of the solder, the disconnection blade deviates from the electrode, thus isolating the protective component of the installation to be protected.

Although they are commonly used, such devices nevertheless suffer from significant disadvantages.

Thus, after melting or breaking of the weld, the isolation distance created between the disconnection blade and the electrode of the protection component is generally quite small. Therefore, if the disconnection occurs under unfavorable voltage and current conditions, it may happen that the mechanical opening of the disconnection means is not sufficient to completely isolate the protective component of the electrical installation, the electric arc created during the opening of the disconnection blade being then likely to be maintained between the disconnect blade and the corresponding electrode. It may also happen, in some cases, that an electric arc is reformed between the electrode of the protection component and the disconnection blade a few moments after opening of the latter. This phenomenon has the effect of significantly limiting the breaking capacity of the protective device.

To overcome this drawback, it is known to use an additional breaking device, circuit breaker type or fuse, which ensures the permanent interruption of the current flowing in the protective device. However, the size of the additional cut-off device must in principle be adapted to the capacity of the protection component, which generates technical constraints and increases the costs of implementing the overall protection equipment. Moreover, the additional cut-off device generally ensures the simultaneous and indiscriminate isolation of all the protection components of the device, whereas it is desirable instead to isolate only the component or components of the device. protection which overheats and keeps the other protection components in service.

It is also known to use isolating members, which can be integrated in the protective device, and intended to prevent the formation, maintenance or reformation of the electric arc between the disconnection blade and the electrode. of the protection component. The effectiveness of this kind of device is nevertheless limited and is generally not sufficient to ensure effective disconnection of the protective device when the conditions of voltage, current and temperature are unfavorable.

In particular, in case of high amplitude overvoltage, the electric arc can bypass the isolation device and continue to discharge the current until the voltage across the protective device is canceled. In addition, the electric arc also has the effect of generating a conductive pollution during the opening of the contacts, thus creating a preferential conductive path for the electric arc along the isolation member, between the disconnection blade and the electrode of the protection component. This phenomenon can therefore have the effect of significantly lowering the level of cutoff provided by the isolation member, electric arcs are likely to form and continue despite the presence of the latter.

SUMMARY OF THE INVENTION

The objects assigned to the invention therefore aim to remedy the various disadvantages listed above and to propose a new device for protecting electrical installations against overvoltages which, while being of simple design, has an improved disconnection capacity compared to known devices. Another object of the invention is to propose a new device for protecting electrical installations against overvoltages which makes it possible to guarantee the individual disconnection of each of the protection components of the device.

Another object of the invention is to provide a new device for protecting electrical installations against overvoltages having, with respect to known devices, a better capacity of extinguishing the electric arcs possibly formed during the disconnection.

Another object of the invention is to propose a new device for protecting electrical installations against overvoltages which is of simple and reliable design.

Another object of the invention is to provide a new device for protecting electrical installations against overvoltages which is particularly robust and resistant vis-à-vis the electric arcs likely to form within it.

Another object of the invention is to provide a new device for protecting electrical installations against overvoltages requiring only a limited number of moving mechanical parts to obtain the connection and disconnection functions.

Another object of the invention is to provide a new surge protection device for accelerating the extinction of the electric arc when disconnecting the device.

The objects assigned to the invention also aim to propose a new method for improving the breaking capacity of a protection of an electrical installation against overvoltages to effectively accelerate the final disconnection of the device.

The objects assigned to the invention are achieved by means of a device for protecting an electrical installation against surges comprising: at least one protection component, provided with means of connection to the electrical installation,

a means for disconnecting the protection component with respect to the electrical installation, adapted to ensure the disconnection of the latter at the connection means, and capable of moving from a closed position to a position of opening thereby creating an interstitial space between the disconnection means and the connection means, an electric arc then being capable of being formed in the interstitial space between the disconnection means and the connection means, characterized in that it comprises means for shearing the electric arc, shaped to attack the electric arc in at least two different directions so as to reduce its section.

The objects assigned to the invention are also achieved by means of a method of improving the breaking capacity of a protection device of an electrical installation against overvoltages in which an electric arc is likely to occur. when the protective device is disconnected from the electrical installation, said method comprising a step of shearing the electric arc in which the electric arc is attacked in at least two different directions in such a way that to reduce his section. SUMMARY DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will appear in more detail on reading the description which follows, and with the aid of the accompanying drawings given purely by way of illustration and not limitation, among which:

- Figure 1 illustrates, in a front view, a first embodiment of the overvoltage protection device according to the invention provided with arc shearing means in its operative position (or service).

- Figure 2 illustrates, in a front view, the protective device shown in Figure 1 in its disconnected position.

- Figure 2 'illustrates, in a sectional view, a detail of the action zone of the shearing means shown in Figure 2.

- Figure 2 "illustrates, in a sectional view, a detail of the action zone of the shearing means in the case of another embodiment of the protection device according to the invention.

- Figure 3 illustrates, in a detailed perspective view, a preferred embodiment of the protection device according to the invention, provided with arc shearing means.

- Figure 4 illustrates, in a front view, the protective device shown in Figure 3, in its operative position (or service).

- Figure 5 illustrates, in a front view, the protection device shown in Figure 3, in its disconnected position. BEST MODE OF REALIZING THE INVENTION

The overvoltage protection device according to the invention is intended to be connected bypass (or parallel) on the equipment or electrical installation to be protected. The term "electrical installation" refers to any type of device or network powered electrically and likely to experience voltage disturbances, including transient overvoltages due to lightning.

The overvoltage protection device according to the invention is advantageously intended to be disposed between a phase of the installation to be protected and the earth. It is also conceivable, without departing from the scope of the invention, that the protection device, instead of being connected in shunt between a phase and the earth, is connected between the neutral and the earth, between the phase and neutral or between two phases (case of differential protection).

The protection device 1 according to the invention comprises at least one protection component 10 intended to protect the electrical installation against overvoltages. In the remainder of the description, it is considered that each overvoltage protection component is formed by a varistor, it being understood that the use of a varistor is only indicated by way of example and does not constitute any a limitation of the invention.

The protection device 1 according to the invention comprises at least one varistor 10, in particular one or more varistors 10, each varistor 10 being provided with connection means 20 to the electrical installation. The varistor 10 is preferably disposed within an electrically insulating housing 60 which may be in the form of a cartridge adapted to be electrically connected to a base fixed (not shown) using at least a first and a second connection pads 22, 23. One of the poles of the varistor 10 is thus connected directly to the first connection pad 22, the other pole of the varistor 10 being connected to the connection means 20. The latter are preferably formed by an electrode 21, for example in the form of a metal blade. The electrode 21 preferably protrudes, for example at 90 °, from one of the faces 10A of the varistor 10.

According to the invention, the protection device 1 also comprises a disconnection means 30 capable of disconnecting the varistor 10 from the electrical installation. The disconnecting means 30 is specifically shaped and adapted to ensure the disconnection of the varistor 10 at the connection means 20 and is for this purpose capable of moving from a closed position, illustrated for example in Figure 1 towards an open position illustrated in FIG. 2, thus creating an interstitial space 11 between the disconnection means 30 and the connection means 20.

Preferably, the disconnection means 30 is formed by an electrically conductive and advantageously metallic disconnection plate 31 which, in the closed position, is stress-welded to the connection means 20, specifically to the electrode 21, for example to using a heat-fusible weld (not shown). The disconnection blade 31 advantageously extends between a free end 31 A and a fixed end 31 B. The free end 31 A then comes into electrical contact with the electrode 21 via the weld, the fixed end 31 B being in permanent electrical contact with the second connection pad 23.

The disconnection blade 31 is then elastically constrained between its closed position, in which it comes into contact with the electrode 21 by means of the thermal welding and its open position, in which the disconnection blade 31 is no longer in contact with the corresponding electrode 21. Thus, during the transition from its closed position to its open position, the disconnection blade 31, in particular the free end 31A of the latter, moves away, by spring effect, from the electrode 21. disconnection 31 can thus have an intrinsic elasticity or be mounted elastically movable via an independent spring (not shown).

When opening the disconnection means 30, an electric arc 40 (shown in dashed lines in FIG. 2) is capable of being formed in the interstitial space 11 between the disconnection means 30 and the connection means 20. Thus, after the opening of the disconnection means 30, the spacing distance between the latter and the connection means 20 may not be sufficient to prevent the initiation, maintenance or rebooting of an electric arc 40, especially in case overvoltages of strong energies. This electric arc 40 then continues to discharge a current, thus preventing effective disconnection of the protection component 10.

To overcome this drawback, and according to an essential characteristic of the invention, the protection device 1 according to the invention is provided with shearing means 50 of the electric arc 40.

The term "shear" here refers to the stresses exerted on the electric arc, along at least two directions (or directions) distinct from the space, so as to reduce its section, without necessarily cutting it. The shearing means 50 are therefore different, in the sense of the invention, from a simple isolating member adapted to come between the electrode 21 and the disconnection blade 31 in order to prevent formation or maintenance. electric arcs between these conductive parts. Experience shows that it is in practice difficult or impossible to "cut" an electric arc, and thus to interrupt the passage of the current before the cancellation of the voltage, with the aid of a simple isolation organ. Indeed, it is observed that the electric arc systematically manages to bypass the isolation member, thus continuing to flow the current along the surface of the latter until the cancellation of the voltage across the device of the device. protection.

For important values of the intensity of the current, the formation of a conductive deposit on the surface of the isolating member is then observed, thus creating a preferential path for the electric arc between the disconnection blade 31 and the In this case, the electrical insulation provided by the isolation device is greatly reduced.

According to an essential characteristic of the protection device 1 according to the invention, the shearing means 50 are shaped so as to increase the impedance of the electric arc 40 by decreasing its section, in order to reduce the intensity of the current that can to be passed by this bow. This thus makes it possible to limit the formation of the conductive deposit on the isolation member, and to increase the efficiency of the latter.

The term "section" here refers to the cross section of the electric arc 40, determined in consideration of a dummy sectional plane substantially perpendicular to the longitudinal direction of extension of the electric arc 40 between the connecting means 20 and the disconnecting means 30.

The shearing means 50 of the electric arc 40 are thus preferably shaped to simultaneously attack the electric arc 40 in at least two distinct directions. According to a particularly advantageous characteristic of the invention, the shearing means 50 are shaped to attack the electric arc 40 by a lateral edge, that is to say along a plane intersecting or perpendicular to the longitudinal direction of extension of the electric arc 40, and following at least two directions F1, F2 substantially opposite and centripetal, that is to say oriented towards the center of the section of the electric arc 40 (Figures 2 ', 2 ").

The shearing means 50 are further preferably arranged and arranged within the housing 60 so as to be controllable, and in particular released by the movement of the disconnecting means 30.

Several embodiments of the invention will now be described with reference to Figures 1 to 5.

According to a first embodiment of the invention, illustrated in particular in Figures 1 and 2, the shearing means 50 comprise at least two active parts 51, 52 electrically insulating, able to approach one another when the opening of the disconnection means 30 so as to ensure, by mutual cooperation, the shearing of the electric arc 40.

For the purposes of the invention, the expression "active parts" refers to the parts of the shearing means 50 directly involved in the shearing action of the electric arc 40. In particular, these are parts of the shearing means 50 able to come directly in physical contact with the electric arc 40.

Within the meaning of the invention, the shearing means 50 may comprise a single movable active part 51 able to move in the interstitial space 11 during the opening of the disconnection means 30 or two mobile active parts (variant not shown ), fit to move closer to one another when opening said disconnection means 30. In the case where the shearing means 50 comprise a single movable active part 51, they also comprise at least one fixed active part 52 preferably forming a stop against the moving active part 51.

Advantageously, the mobile active part 51 and the disconnection means 30 are relatively mounted such that when opening the disconnection means 30, the latter releases the mobile active part 51, thus allowing the displacement of the latter. When the disconnecting means 30 is in the closed position, the mobile active part 51 advantageously abuts against the disconnection means 30. The disconnection disc 31 is then preferably mounted in such a way that, when it is opened, it deviates sufficiently from the electrode 21 to no longer constitute an obstacle against the displacement of the movable active part 51.

The force responsible for moving the movable active part 51 may be of any kind, but will preferably be an elastic restoring force. For this purpose, the shearing means 50 advantageously comprise a resilient biasing means 70, of the spring type, mounted so as to exert an elastic restoring force on the movable active part 51, said elastic restoring force acting in one direction. substantially parallel to the axis of compression of the elastic return means 70. This elastic restoring force thus tends to push the active mobile part 51 towards the other active part, and in particular towards the fixed active part 52.

According to a first variant embodiment illustrated in FIGS. 1 and 2, the mobile active part 51 is mounted so as to be able to move in translation along the direction F during the opening of the disconnection means 30. According to another variant illustrated in FIGS. 3 to 5, the movable active part 51 is mounted so as to be able to move in rotation about an axis of rotation 100 and in the direction S when the disconnecting means 30 is opened. .

Preferably, the mobile active part 51 comprises an insulating flap 53 (or isolation member) intended to be interposed between the disconnection means 30 and the connection means 20 when the disconnection means 30 is in the open position.

According to a preferred embodiment illustrated in FIGS. 3 to 5, the insulating flap 53 is preferably formed by an envelope, shaped so as to at least partially surround the disconnection means 30 and / or the connection means 20 when the means disconnection 30 is in the open position.

According to a first variant not shown, the envelope may comprise a central portion, for example flat, intended to be interposed between the disconnection blade 31 and the electrode 21, and preferentially curved side portions so as to come to coat, at least partially, the electrode 21 or the disconnection blade 31, thus increasing the isolation distance between these two parts.

According to another variant embodiment illustrated in FIGS. 3 to 5, the envelope is formed by a sleeve 44 intended to surround, at least partially, the disconnection blade 31 or the electrode 21.

Preferably, the sleeve 44 has a U-shaped cross section and is delimited laterally by three walls 44A, 44C, 44D and longitudinally by a bottom 44B. All of these walls thus delimit an inner housing 45 opening at an opening 46. allowing the sleeve 44 to come around on the electrode 21, thus coating the latter (Figure 5).

The sleeve 44 is advantageously secured to an articulated arm 49, preferably formed by a plate. Preferably, the sleeve 44 is integral with the arm 49, forming with the latter one and the same functional part. The sleeve 44 advantageously projects from the plate formed by the arm 49. Thus, the walls 44A and 44C of the sleeve 44 extend substantially perpendicularly with respect to the arm 49, thus forming the inner housing 45 which opens on the side of the face 10A of the varistor 10. The arm 49 is advantageously rotatably mounted around the axis of rotation 100, so as to be pivotable about this axis under the action of the restoring force exerted by the means of / elastic call 70. The arm 49 then simultaneously drives the insulating shutter 53 in the same rotational movement.

Advantageously, the elastic return means 70 preferably extends between a first fixed end 71, for example secured to the housing 60, and a second end 72, fixed on or bearing against the arm 49 and capable of moving with the latter in the housing 60. Once the movable active portion 51 released from the disconnection blade 31, the elastic return means 70 exerts on the arm 49 a driving force, driving the latter in a rotational movement around the rotation axis 100.

Particularly advantageously, the sleeve 44 has an extension 47, substantially perpendicular to the face 44C of said sleeve. The extension 47 thus comes, in the open position, between the disconnection blade 31 on the one hand and one of the faces 10A of the varistor 10 on the other hand, so as to prevent the flap bypassing insulation 53 by an electric arc. Preferably, the opposite faces 44A, 44C of the sleeve 44 may advantageously be curved, so as to adapt to the rotational movement of the insulating flap 53. This allows in particular to adjust more precisely the dimensions of the inner housing 45 to dimensions of the electrode 21.

In the case of the variant illustrated in Figures 1 and 2, for which the movable active part 51 moves in translation, the insulating flap 53 may also comprise a sleeve (not shown) capable of moving in a substantially straight vertical and parallel direction to the plane of extension of the face 10A of the varistor 10. The device may then comprise, according to this variant, guide means (not shown) for providing translation guidance of the mobile active part 51.

According to a particularly advantageous characteristic of the invention, the active parts 51, 52 are mounted so as to bear against one another during the opening of the disconnection means 30, thus ensuring the strangulation of the electric arc 40 (Figure 2).

Preferably, the mobile active part 51 thus bears against the fixed active part 52 at a contact interface 54, the electric arc 40 then being sheared between said active parts 51, 52, on the one hand because of the driving force FM exerted by the mobile active part 51 under the action of the elastic return means 70, and secondly because of the reaction force R, substantially opposite to the driving force FM, exerted by the part active fixed 52 (Figures 2, 2 ', 2 ").

The fixed active part 52 may advantageously be formed by a blade of insulating material, for example ceramic, projecting at 90 ° with respect to one of the lateral faces of the housing 60 (FIG. 3). Thus, during the opening of the disconnection means 30, the mobile active part 51 moves in direction of the fixed active part 52 until its front portion 55 bears against said fixed active part 52.

In order to perfect the contact between the fixed and movable active parts 52 and 51 and thus to promote the shearing of the electric arc 40, the shearing means 50 comprise contact means 56, able to ensure a substantially sealed support of the parts. 51, 52 at the contact interface 54. The contact means 56 are thus advantageously arranged and shaped so as to form the contact interface 54 between the active parts 51, 52 when the disconnection means 30 is in position. opening position (Figure 2 ').

The contact means 56 are advantageously formed by a substantially flexible material, such as an elastomeric material, preferably located at the end of one of the active parts 51, 52. Preferably, the material forming the contact means 56 is flexible enough to match the shape of the active portion 51 or 52 located opposite. In particular, in the case of the variant embodiments illustrated in the figures, the contact means 56 are formed by a material that is sufficiently flexible to conform to the shape of the front portion 55 of the mobile active portion 51 with sealing. 56 can thus be integrated structurally with one of the active parts 51, 52, forming for example the end of an active part 51, 52 but can also be formed by a layer of flexible material, disposed on the surface of at least one of the active parts 51, 52, and possibly on the surface of each active part 51, 52.

According to another preferred embodiment, the contact means 56 may be formed by an independent piece attached to one of the active parts 51, 52, for example on the fixed active part 52, as shown in the figures. In order to limit the rebound phenomenon when the active parts 51, 52 are pressed against each other, the shearing means 50 advantageously comprise damping means. The damping means are preferably formed by an elastic and compressible buffer 57 forming the contact interface 54 between the active parts 51, 52, and adapted, by compressing itself, to store the energy corresponding to the momentum of the part active mobile 51, thus preventing the latter from bouncing against the fixed active part 52.

Preferably, and as illustrated in the figures, the contact means 56 and the damping means are formed by the same elastomer pad 57. By preventing the rebound phenomenon, the damping means thus make it possible to improve the efficiency of the shearing of the electric arc 40.

The support of the active parts 51, 52 appears to the applicant as a particularly effective technical solution to ensure the shearing of the electric arc 40. However, it is of course conceivable, without departing from the scope of the invention, that the active parts 51, 52 do not come directly against each other but are mounted so as to cross, preferably with a small clearance, when opening the disconnecting means 30. In this case, the active parts 51, 52 simultaneously exert on the electric arc 40 substantially opposite shear stresses.

According to another embodiment of the invention, the shearing means 50 comprise means for releasing a gas, the latter being designed to generate gaseous flows Φ, Φ 'large enough to ensure the shearing of the electric arc 40 (Figure 2 ', 2 "). The gaseous flows Φ, Φ' thus generated are directed towards the electric arc 40 in different directions, preferably centripetal, and exert pressure sufficient mechanical forces on the electric arc to obtain a reduction of its section.

According to the preferred variant illustrated in FIGS. 2 ', 2 ", the release means are preferably formed by at least one of the active parts 51, 52, which is composed of a material capable of releasing a gas under the effect of the heat generated by the electric arc 40. The combined mechanical action of the active parts 51, 52 on the one hand and gas streams Φ, Φ 'on the other hand thus makes it possible to obtain a particularly effective reduction of the cross-section. of the electric arc.

According to the variant illustrated in FIG. 2 ', only one of the active parts 51, 52, namely the moving active part 51, forms the release means. Thus, during its displacement, the mobile active part 51 comes into contact with the electric arc 40, heats up, at least locally in the region located near the arc. This heating releases gaseous flows Φ, which directly attack the electric arc 40, moreover stuck between the mobile active part 51 and the fixed active part 52.

In an alternative embodiment illustrated in FIG. 2 ", each active part 51, 52 is composed of a material capable of releasing a gas under the effect of heat, the release means then making it possible, in this configuration, to generate substantially opposite gaseous flows permettant, Φ 'allowing a circumferential and centripetal attack of the electric arc 40 even more effective than the configuration illustrated in Figure 2'.

Preferably, the material used to produce the release means will have the ability to release, under the effect of heat, hydrogen, this gas being known for its cooling properties. The released hydrogen can thus act on the electric arc 40 not only by exerting a mechanical pressure on the latter, but also by cooling. By decreasing the temperature and the section of the electric arc 40, the shearing means 50 according to the invention thus make it possible to significantly increase the impedance of the electric arc 40, and thus to reduce the intensity of the electric arc 40. current passed by the latter. As an illustrative and non-limiting example, polyacetal or polyoxymethylene may be used as material capable of releasing a gas.

It is also conceivable, without departing from the scope of the invention, that the contact means 56 or damping are also formed by a material capable of releasing a gas. This material will then, of course, have additional properties of elasticity and flexibility giving the contact means 56 or damping their functional characteristics.

The use of the active parts 51, 52 as release means thus makes it possible, as the latter approach each other and the electric arc 40, to generate gaseous flows Φ, Φ 'converging towards the electric arc in different directions, thus ensuring more efficient shearing of the latter. However, it is obviously possible to use other gas release means, separate from the active parts 51, 52, and without departing from the scope of the invention.

However, this preferred embodiment makes it possible, by means of the same parts, to increase the efficiency of the mechanical shear of the electric arc 40 by means of the mechanical pressure exerted simultaneously on the one hand by the gas flows Une, Φ 'and secondly by the driving forces FM and R reaction. Such an arrangement therefore makes it possible, with a minimum number of parts, to accelerate the effective disconnection of the protection component 10 by ensuring a rapid extinction of the 40 electric arc possibly formed. The present invention also relates to a method of improving the breaking capacity of a protection device 1 of an electrical installation against overvoltages, within which an electric arc 40 is likely to form during the disconnection of the device. protection 1 vis-à-vis the electrical installation.

Within the meaning of the invention, the process advantageously comprises a step (a) of shearing of the electric arc 40, during which the electric arc is attacked, preferably simultaneously, in at least two different, preferably opposite directions, so as to reduce its section.

Advantageously, the shearing step (a) comprises a phase of constriction of the electric arc 40 between at least two active parts 51, 52.

The shearing step (a) advantageously also comprises a gas flow generation phase Φ, Φ 'of intensities sufficiently large to ensure the shearing of the electric arc 40.

The process according to the invention finally advantageously comprises a step (b) of cooling the electric arc 40 making it possible, by decreasing the temperature of the arc, to increase the impedance of the latter and thus to reduce the intensity. of the elapsed current.

Preferably, the steps (a) of shearing and (b) cooling are performed simultaneously, with means for releasing a common gas.

The operation of the protection device 1 according to the invention will now be described with reference to the preferred variants shown in FIGS. 1 to 5. When an overvoltage of sufficient amplitude occurs, the protective device 1, shunted in relation to the electrical installation, becomes conductive and flows to the earth surge current, thus preserving the installation. When a current of excessive intensity or prolonged use causes excessive heating of the device, the thermal welding ensuring the contact connection between the disconnection blade 31 (or the disconnection means 30) and the electrode 21 (or the connection means 20) of the protective component 10 melts or breaks. The disconnection blade 31 then moves away, by spring effect, from the electrode 21, thus creating the interstitial space 11, formed by an insulating air space. It can then be formed, simultaneously with the opening, an electric arc 40 in the air located in the interstitial space 11, this electric arc 40 then extending substantially longitudinally between the electrode 21 and the disconnection blade 31. preferably using the shortest path between these two rooms.

By moving aside, the disconnection blade 31 releases the mobile active part 51, initially resting against the blade. Under the action of the restoring force exerted by the elastic return means 70, the movable active part 51 is pushed towards the fixed active part 52 until it comes into abutment against the latter, by means of the contact means 56. In particular, the front portion 55 of the mobile active part 51 collapses against the contact means 56 and / or damping which thus provide a firm, tight and / or without rebound of the active parts 51, 52 l against each other. At the relative approximation of the active parts 51, 52, the space available for the electric arc 40 is reduced, which has the effect of strangling and reducing its section, thus increasing its impedance. When the active parts 51, 52 come into contact, the electric arc 40 is sheared between the latter, which results in an even greater reduction of its section. The front part 55 of the moving active part 51, situated near or in contact with the electric arc 40, sees its temperature increase strongly and then releases gaseous flows Φ of intensities and speeds sufficiently high to ensure the shearing of the In the terminal position illustrated in FIG. 2 ', the electric arc 40 is thus sheared on the one hand between the mobile active part 51 and the fixed active part 52 and on the other hand between the gas flows Φ converging towards the electric arc 40 at the contact interface 54 between the active parts 51, 52.

As illustrated in FIGS. 2 ', 2 ", the electric arc 40 is thus enclosed in a" mini-cavity "58 where it is subjected on the one hand to the driving forces FM and R of the active parts 51 , Shear means 50, and on the other hand convergent gas streams Φ, Φ '.

The liberated gases, preferably hydrogen, also have the effect of lowering the temperature of the electric arc which, in combination with the reduction of its section, contributes to increasing its impedance and decreasing the intensity of the current flowing. , so that the final insulation of the protection component 10 is more rapidly obtained with respect to the electrical installation.

The protection device 1 according to the invention thus makes it possible, thanks to a particularly simple, robust and reliable mounting, to ensure a rapid and systematic disconnection of the protection component 10 in the event of degradation or failure of the latter.

The protection device 1 according to the invention thus has significantly better performance than known devices in terms of isolation and disconnection. The protective device 1 according to the invention also has an improved resistance to degradation and conductive pollution generated by the electric arc 40, thus keeping its isolation capabilities longer.

POSSIBILITY OF INDUSTRIAL APPLICATION

The invention finds its industrial application in the manufacture of devices for protection against overvoltages.

Claims

- Protection device (1) of an electrical installation against overvoltages comprising:

at least one protection component (10) provided with connection means (20) for the electrical installation,

- Disconnection means (30) of the protection component (10) relative to the electrical installation, adapted to disconnect the latter at the connection means (20), and capable of moving from a closing position to an open position thereby creating an interstitial space (11) between the disconnecting means (30) and the connecting means (20), an electric arc (40) then being able to form in the interstitial space (11) between the disconnecting means (30) and the connecting means (20), characterized in that it comprises shearing means (50) of the electric arc (40), shaped to attack the electric arc (40) in at least two different directions so as to reduce its section.

- Device according to claim 1 characterized in that the shearing means (50) are shaped to attack the electric arc (40) by lateral approach along at least two directions (F1, F2) substantially opposite.

- Device according to claim 1 or 2 characterized in that the shearing means (50) comprise at least two active parts (51, 52) adapted to approach one another when opening the means of disconnection (30), so as to ensure, by mutual cooperation, the shearing of the electric arc (40).

- Device according to claim 3 characterized in that the active parts (51, 52) are mounted so as to bear against each other during the opening of the disconnection means (30), thus ensuring the throttling of the electric arc (40).

- Device according to claim 3 characterized in that the active parts (51, 52) are mounted to intersect at the opening of the disconnecting means (30), thereby ensuring the shearing of the electric arc (40) .

- Device according to one of claims 3, 4 or 5 characterized in that the shearing means (50) comprise at least one movable active portion (51), adapted to move in the interstitial space (11) during the opening of the disconnecting means (30) and provided with an insulating flap (41) to be interposed between the disconnecting means (30) and the connecting means (20) when the disconnecting means (30) is in position opening.

- Device according to claim 6 characterized in that the shearing means (50) comprise at least one fixed active portion (52) forming a stop against the movable active part (51).

- Device according to claim 6 characterized in that the shearing means (50) comprise at least two moving active parts, adapted to approach one another when opening the disconnecting means (30). 9 - Device according to claim 4 characterized in that the shearing means (50) comprise contact means (56), adapted to ensure a substantially sealed bearing of the active parts (51, 52).

10 - Device according to claim 9 characterized in that the contact means (56) are arranged to form the contact interface (54) between the active parts (51, 52) when the disconnecting means (30) is in the open position.

11 - Device according to claim 9 or 10 characterized in that the contact means (56) are formed by a substantially flexible material, such as an elastomeric material, located at the end of one of the active parts (51, 52).

12 - Device according to claim 4 characterized in that the shearing means (50) comprise damping means, adapted to prevent, when the active parts (51, 52) are in abutment, the rebound of one said active parts (51, 52) relative to each other.

13 - Device according to claim 12 characterized in that the damping means are constituted by a buffer (57) elastic forming the contact interface (54) between the active parts (51, 52).

14 - Device according to claims 9 and 13 characterized in that the contact means (56) and the damping means are formed by the same buffer (57) elastic and flexible.

15 - Device according to one of the preceding claims characterized in that the shearing means (50) comprise means for releasing a gas, designed to generate gas flows (Φ, Φ ') large enough to ensure the shearing of the electric arc (40).

- Device according to claims 3 and 15 characterized in that at least one of the active parts (51, 52) is composed of a material capable of releasing a gas under the effect of the heat generated by the electric arc (40), said active portion then forming the release means.

- Device according to claim 16 characterized in that the gas is hydrogen.

- Device according to claim 16 or 17 characterized in that the material is based on polyacetal or polyoxymethylene.

- Device according to claim 6 characterized in that the movable active part (51) and the disconnection means (30) are relatively mounted such that when opening the disconnecting means (30), it releases the part active mobile (51), thereby allowing the movement of the latter.

- Device according to claim 6 characterized in that the shearing means (50) comprise an elastic return means (70) mounted to exert an elastic return force on the movable active part (51) tending to push it towards the other active part (52).

- Device according to claim 6 characterized in that the movable active part (51) is mounted so as to be able to move in translation.

- Device according to claim 6 characterized in that the movable active part (51) is mounted so as to be able to move in rotation. - Device according to claim 6 characterized in that the insulating shutter is formed by a casing, shaped so as to surround, at least partially, the disconnecting means (30) and / or the connecting means (20) when the means disconnection device (30) is in the open position.

- Device according to claim 23 characterized in that the casing is formed by a sleeve (44) having a U-shaped cross section.

- Method for improving the breaking capacity of a protection device (1) of an electrical installation against overvoltages in which an electric arc (40) is likely to form during the disconnection of the protection device ( 1) with respect to the electrical installation, said method comprising a step (a) of shearing the electric arc (40) during which the electric arc (40) is attacked in at least two different directions so as to reduce its section.

- Method according to claim 25 characterized in that the step (a) shearing comprises a throttling phase of the electric arc (40) between at least two active parts (51, 52).

- Method according to claim 26 characterized in that the step (a) of shearing comprises a gas flow generation phase (Φ, Φ ¹ ) intensities sufficiently large to ensure the shearing of the electric arc (40).

- Method according to one of claims 25 to 27 characterized in that it comprises a step (b) of cooling the electric arc (40).