EP1698029B1 - Tightening device for protecting against overloads - Google Patents

Abstract

The invention concerns a device (1) for protecting electrical equipment against overloads comprising: a protective unit (2) having at least one first and one second pole (2A, 2B), these poles (2A, 2B) being electrically connected to the equipment via connecting means (3); a functional coupling means (5) of the protective unit (2) for coupling to the connecting means (3), and; a thermal disconnecting means (4) functionally joined to said protective unit (2) for interrupting the electrical connection between the unit (2) and the equipment when the temperature of the unit reaches a predetermined critical value. The invention is characterized in that the coupling means (5) is designed for exerting a tightening of the protective unit (2) in a manner that ensures the electrical connection of the poles (2A, 2B) to the connecting means (3). The invention also relates to an electrical device for protecting against overloads.

Description

TECHNICAL AREA

The present invention relates to the general technical field of protection devices for equipment or electrical installations, such as electrical appliances, circuits or distribution networks, against disturbances, possibly momentary power supply.

The present invention relates more particularly to a device for protecting electrical equipment against voltage disturbances, such as overvoltages, in particular due to lightning.

• une unité de protection comprenant au moins un premier et un deuxième pôles, lesdits pôles étant connectés électriquement audit équipement par l'intermédiaire de moyens de connexion,
• un moyen d'accouplement fonctionnel de l'unité de protection aux moyens de connexion,
• un moyen de déconnexion thermique, relié fonctionnellement à ladite unité pour interrompre la connexion électrique entre l'unité et l'équipement lorsque la température de l'unité atteint une valeur critique prédéterminée.

The present invention relates to a device for protecting electrical equipment against overvoltages comprising:

• a protection unit comprising at least a first and a second pole, said poles being electrically connected to said equipment via connection means,
• a means of functional coupling of the protection unit to the connection means,
• thermal disconnect means operatively connected to said unit for interrupting the electrical connection between the unit and the equipment when the temperature of the unit reaches a predetermined critical value.

PRIOR ART

Protective devices for electrical equipment against overvoltages are known and commonly used.

Such devices, which are sometimes referred to as " surge arresters " or " surge arresters ", are intended to discharge lightning currents to the earth, and possibly to cleave induced surges at levels compatible with the behavior of lightning strikes. equipment and materials connected downstream of protective devices.

Known surge arresters may be based on different technologies, depending on the nature of the active protection element they implement.

In particular, spark gap arresters are known, that is to say using, as an active protective element, a device comprising two electrodes placed facing each other and between which a priming causing a short circuit occurs. circuit, as soon as an overvoltage reaches a predetermined critical level.

Such spark gap arresters may be subject mainly to two types of end of life.

In the first end-of-life situation, which is generally encountered when the surge arrester is connected between one of the phases to be protected and the earth, the spark gap can be subjected to very high intensity short-circuit currents. (several hundreds or thousands of amperes) that could cause its destruction. In order to prevent such an event, a surge arrester (of the fuse or circuit breaker type) is integrated or associated with the surge arrester which, when it comes into action, interrupts the short-circuit current and thus preserves the integrity of the device.

In the second end-of-life situation, which occurs in particular when the surge arrester is connected between the neutral line and the earth, the surge arrester may be subjected to relatively small short-circuit currents (that is to say of which the intensity is for example between a few amps and 200 amps) that can lead to its destruction. Such a situation can for example be caused by a lightning strike causing the spark gap to be triggered, followed or accompanied by an incident in the power supply network (phase failure, imbalance of the network) leading to the introduction of a weak but destructive short-circuit current, since it eventually causes the spark gap to heat up.

In order to remedy the safety disadvantages relating to this second situation, it is known to provide the spark gap arresters, and more particularly spark gap arresters intended to protect the neutral, with a thermal disconnection system.

These spark gap arresters equipped with a thermal disconnection system are generally in the form of a housing of dielectric material, wherein a spark gap is welded to a circuit comprising on the one hand the disconnector, and on the other hand means connection to connect the surge arrester to the installation to be protected. The thermal disconnector itself comprises a weld which when a predetermined critical temperature of the spark gap is reached, will melt and open the circuit.

These known devices, if they generally give satisfaction, however, have a number of disadvantages.

The first disadvantage arises from the need to use different welding materials to achieve on the one hand the welding of the thermal disconnection means, and on the other hand the other assembly welds. In fact, when the critical safety temperature is reached, only the The thermal disconnect must be fused, which implies that the melting point of this weld must be lower than that of the other welds used for assembly in the device.

This need to use two different welding materials during the manufacturing steps involves a significant risk of reversal of the welds, which can lead to safety problems of use. In order to avoid such manufacturing problems, the manufacturers of these known protection devices are therefore generally led to implement monitoring and control procedures of the manufacturing process which lead to an increase in the price of the surge arresters, without however completely eliminate the risk that the thermal disconnector is manufactured with a simple assembly weld and not with the specific weld that is intended for it.

It is, however, known to US-B-6,614,640 a surge arrester having a housing in which a disk-shaped varistor is tightly mounted between two contact disks provided with an elastic contact element. One of the contact discs is biased against the varistor by a helical spring which is supported on an electrical connection element of the surge arrester which is clipped into the casing, the spring ensuring the electrical conduction between the contact disc and the element of connection. The other contact disk bears against a shoulder of the housing and is connected by a threaded rod to a second electrical connection element of the surge arrester. A fuse link is provided between the disk and the threaded rod and a spring urges the second connecting member through an insulating piece serving as a failure indicator and which is slidably mounted in the housing. When the fuse link melts due to the heating of the varistor, the spring pushes the insulating piece serving as a failure indicator and the second connection element to the outside of the housing, the electrical connection between the varistor and the second element connection is then interrupted.

Furthermore, the design and manufacture of these known surge arresters makes it very difficult, if not impossible, to repair said surge arrester in the case where the spark gap is at the end of its life.

This can lead to the scrapping of devices of which only the active component is degraded.

SUMMARY OF THE INVENTION

The object assigned to the invention therefore aims to remedy the various disadvantages of the prior art mentioned above, and to propose a new device for protecting electrical equipment against overvoltages which is of a design and a particularly simple and inexpensive realization.

Another object of the invention is to propose a new device for protecting electrical equipment against overvoltages that is very easily and quickly repairable.

Another object of the invention is to provide a new device for protecting electrical equipment against overvoltages whose assembly is particularly simple and fast.

A complementary object of the invention is to propose a new device for protecting electrical equipment against overvoltages of particularly compact design.

Another object of the invention is to propose a new device for protecting electrical equipment against overvoltages having an improved level of security of use.

Thus, the invention provides an electrical surge protection device as defined in claim 1. The dependent claims define preferred embodiments.

SUMMARY DESCRIPTION OF THE DRAWINGS

• La figure 1 illustre, selon une vue schématique en coupe longitudinale, un dispositif de protection conforme à l'invention.
• La figure 2 illustre, selon une vue schématique en coupe transversale, une opération d'assemblage du dispositif représenté à la figure 1.
• La figure 3 illustre, selon une vue schématique en coupe longitudinale partielle, le principe de réalisation du déconnecteur thermique équipant le dispositif représenté aux figures 1 et 2.

Other objects and advantages of the invention will appear in more detail on reading the description which follows, with reference to the accompanying drawings given by way of illustrative and non-limiting examples in which:

• The figure 1 illustrates, in a schematic longitudinal sectional view, a protection device according to the invention.
• The figure 2 illustrates, in a schematic cross-sectional view, an assembly operation of the device shown in FIG. figure 1 .
• The figure 3 illustrates, in a schematic view in partial longitudinal section, the embodiment of the thermal disconnect equipping the device shown in FIGS. Figures 1 and 2 .

BEST MODE OF REALIZING THE INVENTION

The figure 1 represents a device 1 for protecting electrical equipment against surges, including temporary.

By electrical equipment is meant here all types of devices, instruments, installations, networks, electrical circuits or telecommunications likely to be subject to random power supply from the point of view of voltage, including overvoltages due to to lightning.

The device 1 for protection against overvoltages according to the invention thus advantageously constitutes a surge arrester.

According to the invention, the device 1 comprises a protection unit or lightning arrestor 2.

The protection unit 2 comprises at least, in a conventional manner, a first pole 2A and a second pole 2B, said poles being electrically connected to the equipment to be protected (not shown) via connection means 3.

Said protection unit 2 comprises at least one non-linear electrical component, such as for example a varistor, a Zener diode, or a spark gap (air or gas for example). The invention is not limited to a particular type of component.

In what follows, reference will be made more particularly to a protection unit 2 comprising a spark gap 2C, and more specifically a spark gap 2C specially designed to protect a neutral line, that is to say be connected between the neutral and the Earth.

Such a spark gap 2C is advantageously in the form of a cylindrical unitary housing comprising two parallel plane faces 20A, 20B respectively supporting the first and second poles 2A, 2B, and a lateral envelope extending between said planar faces.

The connection means 3 consist of connection elements for electrically connecting the surge arrester 2 constituted by the spark gap 2C, the installation to protect.

According to the invention, the protection device 1 also comprises a thermal disconnection means 4, functionally connected to the unit 2 to interrupt the electrical connection between the unit 2 and the equipment to be protected when the temperature of the unit 2 reaches a predetermined critical value, beyond which the heat generated by the protection unit 2 may damage or ignite the surrounding elements. The thermal disconnection means 4 is thus arranged relative to the protection unit 2 to be sensitive to the heat generated by the latter, so as to be triggered in case of overheating to interrupt the flow of current.

The device 1 also comprises a functional coupling means 5 of the protection unit 2 to the connection means 3. This functional coupling means 5 makes it possible to ensure the electrical connection of each of the poles 2A, 2B to the connection means. 3, the latter being intended to be connected to the electrical installation, for example between the neutral and the earth.

All of the aforementioned elements, namely the protection unit 2, the connection means 3, the thermal disconnection means 4 and the functional coupling means 5 are preferably mounted in a housing 1A (shown in FIG. figure 1 ), made of insulating material, to form a unitary monoblock subset.

Preferably, the functional coupling means 5 ensures, in addition to its thermal connection function of the unit 2 to the connection means 3, a function for holding said unit 2 in position in the case 1 A.

According to an important characteristic of the invention, the coupling means 5 is designed to exert a clamping of the protection unit 2, so as to ensure the electrical connection of said poles 2A, 2B to the connection means 3.

Thus, unlike the devices of the prior art which used, as coupling means of the protection unit 2 to the connection means 3, welds, the device 1 according to the invention achieves this. coupling only by the exercise of a suitable clamping force of the protection unit 2, without the use of welding.

In this way, the only solder present in the device 1 will be that possibly corresponding to thermal disconnection means. The presence of a single nature of welding thus makes it possible to limit any risk of confusion during the manufacturing process, and thus promotes a good level of quality of the device according to the invention, at a lower cost.

The general principle of the invention is therefore based on the replacement of a connection by welding by a "cold" assembly , obtained by the implementation of a clamping force preferably applied directly to the unit 2.

The coupling means 5 is thus designed to apply a pinch or clipping mechanical stress on the protection unit 2 itself, this clamping making it possible to bring the protection unit 2 into electrical contact with the connection means. 3. This clamping advantageously also ensures a holding in position of the protection unit 2 relative to the connection means 3 and the housing 1 A.

Therefore, advantageously, the coupling means 5 exerts, by virtue of its clamping action, both a function of electrical connection of the poles 2A, 2B to the connection means 3, and a function of holding in position (immobilization ) of the protection unit 2 in the housing 1A.

Preferably, the coupling means 5 is also designed to allow a removable coupling of the protection unit 2 to the connection means 3. In other words, the coupling means 5 allows the user to connect and disconnect at will, simply and quickly, the protection unit 2 to the connection means 3.

Such a technical arrangement allows an easy repair of the device 1 in case of failure of the protection unit 2 itself, since the invention allows the replacement substantially immediately and without the need for special tools (such as soldering iron and braid desoldering) of the protection unit 2.

Preferably, the coupling means 5 comprises a first holding member 5A, arranged to bear against the first pole 2A, and a second holding member 5B, arranged to bear against the second pole 2B, the first and second holding members 5A, 5B cooperating to exert a compression of the protection unit 2, preferably along the axis XX 'passing through its poles 2A, 2B.

In the embodiment illustrated in the figures, the first and second holding members 5A, 5B cooperate to apply on each face 20A, 20B carrying the poles 2A, 2B of the spark gap 2C forces of identical intensities but in opposite directions, such that the spark gap is held in position and in electrical contact with the connection means 3.

The holding members 5A, 5B and pinch the unit 2 along the axis X-X ', said pinching to ensure both an electrical connection and a mechanical hold.

Advantageously, the connection means 3 comprise on the one hand a first connector 3A, electrically connected to the first holding member 5A, which is made, at least partially, of a first electrically conductive material, and on the other hand a second 3B connector, electrically connected to the second holding member 5B, which is formed, at least partially, a second electrically conductive material. Preferably, the second holding member 5B and the second connector 3B are formed by a single piece 50B, as shown in FIGS. Figures 1 to 3 .

It is also conceivable that the first holding member 5A and the first connector 3A are formed by a single piece.

Advantageously, the thermal disconnection means 4 is thermally connected, in particular by conduction, to the second connector 3B and / or to the second holding member 5B. In other words, the second connector 3B and / or the second holding member 5B acts as the conductor (s) of the thermal information from the unit 2 to the thermal disconnection means 4.

Advantageously, the first holding member 5A is functionally and structurally different from the second holding member 5B.

In particular, the first holding member 5A is more specifically dedicated to the generation of a positive clamping action of the unit 2, whereas the second holding member 5B is more specifically dedicated to the optimal transmission to the thermal disconnector 4 of FIG. the heat possibly produced by unit 2.

Preferably, the first holding member 5A thus comprises a pressure piece 50A of the clip type, which is in the form of an elastic member whose deformation capacity produces, when it is stressed, a reactive setting force. in pressure.

Preferably, the pressure piece 50A is in the form of a U-shaped cross-section leaf spring, one of the arms 6 of the U bearing on the first connector 3A, while the other arm 7 bears against and on the first pole 2A, the arms 6, 7 being connected by a core 51.

The first material from which the pressure piece 50A is made will advantageously be selected to have good elasticity characteristics. For example, this first material may be based on a copper alloy.

As for the second holding member 5B, it preferably comprises a heat transfer part 50B, intended to communicate by conduction the heat emitted by the protection unit 2 by means of thermal disconnection 4.

Advantageously, the heat transfer part 50B also forms a stop piece for the unit 2, that is to say that the latter is pressed longitudinally along the axis XX 'by the pressing piece 50A against the workpiece 50B abutment, the latter preferably having a rigid character.

Advantageously, the abutment piece 50B is shaped so that the contact interface between the protection unit 2 and said abutment piece 50B has a maximum area, depending on the space constraints inherent in the design of the device 1, in order to optimize the heat transfer by conduction between the unit 2 and the abutment piece 50B.

To this end, the abutment piece 50B may advantageously have a flat bearing surface 8 of sufficient size to completely cover, in plane support, the face 20B of the unit 2 carrying the second pole 2B, as shown. to the Figures 1 and 2 .

In order to optimize the heat transfer mentioned above, the second material from which the abutment piece 50B is made will be selected to have excellent thermal conductivity. By way of example, this second material may be substantially pure copper.

Advantageously, the connection means 3 also comprise a third connector 3C, said first connector 3A and third connector 3C being intended to be electrically connected to the equipment to be protected.

Advantageously, the thermal disconnection means 4 is designed to be able to pass from a closure configuration (shown in the figures), in which it provides an electrical contact between the second and third connectors 3B, 3C, to an opening configuration. wherein said electrical contact between the second and third connectors 3B, 3C is broken.

Preferably, the thermal disconnection means 4 comprises a slider 4A, preferably having a rigid character, mounted to elastically elastic sliding between a first return position, corresponding to the interruption of the electrical connection between the unit 2 and the equipment to be protected, and a second position in which the slider 4A makes an electrical contact between the second and third connectors 3B, 3C, said slider being held immobilized in second position by a fuse means 4B, welding type.

As schematically represented in the figure 3 , the slider 4A is preferably mounted to elastic axial sliding against a spring 9, for example compression.

Preferably, the slider 4A also has a sweep flange 4C which makes it possible to scrape the weld 4B when the slider 4A moves from its second position to its first return position, so as to eliminate any residue of liquid weld that could establish a inadvertent connection between the second and third connectors 3B, 3C.

Thus, the thermal disconnection means 4 allows the opening of the contact simultaneously at two points, namely at the second connector 3B and at the third connector 3C. The cutoff distance is optimized, since it represents twice the distance traveled by the slider 4A from its second position to its first position. This technical arrangement is particularly advantageous in the case where the intensity of the current to be cut is in a high range (for example between 100 and 200 A in the case of a protector protection of the neutral line).

The invention is however not limited to the specific means of thermal disconnection which has been previously described. As an alternative, the thermal disconnection means can implement, instead of a rigid slider, a flexible conductive braid system, or even only a fuse means. It is also conceivable to use a thermal disconnection means which is exactly in the form of that illustrated in the figures, but which uses instead of a fuse means as a means for holding the slider 4A in the second position, a bimetal arranged to deflect when the temperature reaches the critical predetermined value, this deflection generating the release of the slider 4A.

We will now briefly describe the manufacture and use of the device according to the invention, based on the embodiment corresponding to the Figures 1 to 3 .

During the step of manufacturing the arrester 1, the protection unit 2, which is in this case constituted by a spark gap 2C, is inserted in force between the pressure clip 50A and the abutment piece 50B. During this insertion phase, the first planar face 20A of the spark gap 2C pushes the arm 7 of the pressure piece towards the other arm 6. In response, the arm 7 exerts a force against said face 20A, according to a substantially linear or pseudo-linear support, said support being sufficient to ensure adequate electrical connection of the spark gap 2C with the pressure piece 50A. During the insertion phase, the second planar face 20B bears flat against the bearing surface 8 of the abutment piece 50B. This surface support optimizes the heat transfer between the unit 2 and the abutment piece 50B. At the end of the insertion phase, a clipping of the spark gap 2C is thus obtained. Said clipping simultaneously generates the electrical connection, the locking in position and the thermal connection of the spark gap 2C.

The housing 1A is then closed, so that one has a unitary cartridge provided with two connection pins formed by the first and third connectors 3A, 3C. This cartridge is then connected to the electrical panel of the installation to be protected, for example between neutral and phase.

In the case where an abnormal heating of the spark gap 2C occurs, this heating is communicated by conduction to the weld 4B, via the abutment piece 50B provided especially for this purpose. The weld 4B melts, which releases the slider 4A which returns to the return position under the effect of the action of the spring 9. The electrical contact between the installation and the spark gap 2C is thereby broken, which stops at the same time the heating of the spark gap, thus preventing any risk of fire.

The out of service spark gap 2C can be very easily replaced by a new spark gap, since it suffices to open the case 1A, extirpate manually the used spark gap 2C, and interpose the new spark gap between the pressure piece 50A and the stop piece 50B.

The invention thus makes it possible to benefit from a modular arrester having excellent electrical and thermal connections of its protection unit 2 with the rest of the device 1, without the use of assembly welds.

POSSIBILITY OF INDUSTRIAL APPLICATION

The invention finds its industrial application in the design, manufacture and use of surge protection devices, such as surge arresters.

Claims (14)

1. A device (1) for protecting electrical equipment against voltage surges, comprising:

   - a protection unit (2) having at least a first and a second pole (2A, 2B), said poles (2A, 2B) being electrically connected to said equipment via connection means (3);

   - functional coupling means (5) for coupling the protection unit (2) to the connection means (3);

   - thermal disconnector means (4) functionally connected to said unit (2) to interrupt the electrical connection between the unit (2) and the equipment when the temperature of the unit reaches a predetermined critical value;
   wherein said coupling means (5) is designed to exert a clamping force on the protection unit (2) in such a manner as to ensure electrical connection between said poles (2A, 2B) and the connection means (3), the coupling means (5) comprising a first holder member (5A) arranged to bear against said first pole (2A) and a second holder member (5B) arranged to bear against said second pole (2B), the first and second holder members (5A, 5B) co-operating to exert compression on the protection unit (2),
   characterized in that the device is designed to allow the protection unit (2) to be inserted by force between the first and second holder members (5A, 5B), the first holder member (5A) comprising a clip-type presser part (50A).
2. The device according to claim 1, wherein the presser part (50A) is a spring blade of U-shaped cross-section, one of the limbs (6) of the U-shape bearing against the first connector (3A), while the other limb (7) bears against the first pole (2A).
3. The device according to claim 1 or 2, comprising a package (1A) in which are mounted the protection unit (2), the connection means (3), the thermal disconnector means (4) and the functional coupling means (5) to form a unitary one-piece subassembly, the package (1A) being closed to constitute a unitary cartridge provided with two connection pins and adapted to be connected to the electricity panel of the installation to be protected.
4. The device (1) according to any one of claims 1 to 3, wherein the protection unit (2) comprises a spark gap (2C).
5. The device (1) according to any one of claims 1 to 4, wherein the coupling means (5) is designed to allow releasable coupling between the protection unit (2) and the connection means (3).
6. The device according to any one of claims 1 to 5, wherein the connection means (3) comprise, firstly, a first connector (3A) electrically connected to the first holder member (5A), which member is made of the first electrically conductive material, and, secondly, a second connector (3B) electrically connected to the second holder member (5B), which member is made of a second electrically conductive material.
7. The device according to claim 6, in which the second holder member (5B) and the second connector (3B) are of a unitary one-piece construction (50B).
8. The device according to claim 6 or 7, in which the thermal disconnector means (4) is thermally connected to the second connector (3B) and/or to the second holder member (5B).
9. The device according to claim 8, in which the first holder member (5A) is structurally and functionally different from the second holder member (5B).
10. The device according to claim 9, in which the second holder member (5B) comprises a heat transmission part (50B).
11. The device according to claim 10, in which the heat transmission part (50B) is an abutment part shaped whereby the contact interface between the protector unit (2) and said abutment part (50B) has a maximum surface area.
12. The device according to any one of claims 8 to 11, in which the second material is selected so as to exhibit excellent thermal conductivity.
13. The device according to any one of claims 8 to 12, in which the first connector (3A) is designed to be connected to said equipment, the connection means (3) also comprising a third connector (3C) designed to be connected to the equipment, the thermal disconnector means (4) being designed to be able to change from a closed configurations, in which it ensures electrical contact between the second and third connectors (3B, 3C), to an opened configuration, in which said electrical contact between the second and third connectors (3B, 3C) is interrupted.
14. The device according to claim 13, in which the thermal disconnection means (4) comprises a slider (4A) mounted to slide elastically in an axial direction between a first or return position corresponding to interrupting the electrical connection between the unit (2) and the equipment, and a second position in which the slider (4A) establishes the electrical contact between the second and third connectors (3B, 3C), said slider being held in a second abutment position by fusible means (4B).

Images