FR2894383A1 - IMPROVED SAFETY OVERVOLTAGE PROTECTION DEVICE AND METHOD FOR MANUFACTURING THE SAME - Google Patents

Abstract

- The invention relates to a protection device (1) of an electrical installation against surges comprising a housing (2) in which are disposed two electrodes (3, 4) between which an electric arc is likely to form in case overvoltage circuit, and two connection terminals (6, 7) for connecting the electrodes (3, 4) to said installation, said device (1) being characterized in that it comprises, disposed within the housing (2), a circuit breaker (10) capable of passing from a conductive configuration in which it is capable of conducting the current likely to flow between the terminals (6, 7), to an insulating configuration in which it breaks the passage of the current .- Protection devices against overvoltages, in particular transients.

Description

DEVICE FOR PROTECTING AGAINST OVERVOLTAGES WITH IMPROVED SAFETY AND

  CORRESPONDING MANUFACTURING PROCESS

  The present invention relates to the general technical field of protection devices for equipment or electrical installations against overvoltages, and especially against transient overvoltages such as those due to lightning. The present invention relates in particular to the field of surge arresters. , and in particular low voltage surge arresters.

  The present invention relates more particularly to a device for protecting an electrical installation against overvoltages, in particular transients, comprising on the one hand a housing in which at least two electrodes are disposed between which an electric arc is likely to form. case of overvoltage, and secondly two connection terminals for electrically connecting the electrodes to said installation.

  The invention also relates to a method of manufacturing a device for protecting an electrical installation against overvoltages, in particular transients, in which, on the one hand, at least two electrodes are provided within a housing. an electric arc is likely to form in case of overvoltage, and in which on the other hand is provided the housing of two connection terminals for electrically connecting the electrodes to said installation.

  It is known to use, to protect an electrical installation against overvoltages, a low-voltage protection device, such as a spark gap arrester, using the formation of an electric arc between two electrodes for discharging the surge current.

  Such a device is generally in the form of a housing containing the spark gap electrodes, said housing being intended to be connected to the installation to be protected by means of connection terminals.

  This housing is generally associated in series with a complementary disconnection device, adapted to isolate the surge protection device of the electrical installation when said device is traversed by a current of too high intensity. Among the known disconnecting devices, over-current protection devices, such as commercially available fuses or breakers, which are mounted in series with the surge arrester, are most often used.

  Such assemblies, while they generally make it possible to improve operational safety, nevertheless suffer from considerable drawbacks, related first of all to the complexity of the choice of the additional disconnection device. Indeed, the conventional disconnectors of the fuse type or circuit breakers are not designed to discharge lightning currents. This may result in an inadvertent tripping of the disconnector for current amplitudes that are actually not dangerous for the surge arrester. This leads to undesirably reduce the operating range of the surge arrester, correspondingly decreasing the level of protection of the installation.

  In addition, special rules, generally poorly or little known to generalist electricians installers, must be followed for the installation of a disconnector to protect a surge arrester. In particular, in the 25 cases, which are not uncommon, where the surge arrester and the circuit breaker are located at a distance from each other, the impedance of the conductors must be taken into account for the choice of the disconnector, whereas this impedance is often difficult or impossible to calculate precisely. This lack of impedance consideration can lead to errors and an underestimation of the actual protection level of the electrical installation. The distance of the disconnector and the surge arrester does not allow, moreover, to ensure a fine monitoring of operating conditions within the surge arrester.

  Another disadvantage of known assemblies comes from the resettable nature of the circuit breakers conventionally used, which can induce confusion in the mind of the user. Thus, when, following an overcurrent, the circuit breaker trips, the user retains the possibility of rearming, for example manually, the circuit breaker, without taking into consideration the possibility that the surge protection device is faulty, because of the value of the overcurrent. The installation then appears protected in the eyes of the user, while the surge protection device is actually severely degraded, and is no longer able to assume its protection function. Thus, the user runs the risk that a new surge deteriorates the electrical equipment now unprotected.

  The technical complexity, the cost, the size and the risks associated with mounting a circuit breaker (or fuses) to protect a spark gap arrester thus very often constitute a strong incentive not to install lightning arresters, leaving the electrical installation with no protection against overvoltages, in particular transients.

  The objects assigned to the invention therefore aim to propose a new device for protecting an electrical installation against overvoltages that do not have the drawbacks enumerated above and that provide an excellent level of protection against overvoltages while being capable, in the event of failure, to be disconnected from the electrical installation.

  Another object of the invention is to propose a new device for protecting an electrical installation against overvoltages that can be disconnected from the electrical installation only when the end-of-life conditions of the device are effectively met.

  Another object of the invention is to propose a new device for protecting an electrical installation against overvoltages of particularly simple and inexpensive design. Another object of the invention is to provide a new device for protecting an electrical installation against construction surges 10 compact and inexpensive.

  Another object of the invention is to propose a new device for protecting an electrical installation against overvoltages having a good reliability of disconnection.

  Another object of the invention is to provide a new device for protecting an electrical installation against overvoltages having an excellent level of security while being of very simple structure. Another object of the invention is to propose a new method of manufacturing a device for protecting an electrical installation against surges particularly easy, fast and inexpensive to implement.

  The objects assigned to the invention are achieved by means of a protection device of an electrical installation against overvoltages, in particular transients, comprising on the one hand a housing in which at least two electrodes are arranged between which an electric arc is likely to form in case of overvoltage, and secondly two connection terminals for electrically connecting the electrodes to said installation, said device being characterized in that it comprises, arranged within the housing and electrically connected in series between the terminals, a circuit breaker capable of passing from a conductive configuration in which it is capable of conducting the electric current likely to flow between the terminals, to an insulating configuration in which it breaks the passage current that may flow between the terminals. The objects assigned to the invention are also achieved by means of a method of manufacturing a device for protecting an electrical installation against overvoltages, in particular transients, in which, on the one hand, there is a housing, at least two electrodes between which an electric arc is likely to form in case of overvoltage, and in which on the other hand is provided the housing of two connection terminals for electrically connecting the electrodes to said installation, said method being characterized in that it comprises a step of mounting a circuit breaker, in which is mounted electrically in series between the terminals, within the housing, a circuit breaker adapted to move from a conductive configuration in which it is capable of conducting the electric current likely to flow between the terminals, to an insulating configuration in which it breaks the passage of the current likely to flow between the terminals. 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 non-limiting illustration, among which

  - Figure 1 illustrates, in a front view, the inside of the housing of a protection device according to the invention. - Figure 2 illustrates, in a perspective view, the components installed in a housing of a protection device according to the invention. - Figure 3 illustrates, in a schematic front view, the protective device of Figures 1 and 2 in its operating position. - Figure 4 illustrates, in a schematic view, the protective device of Figure 3 in its disconnected position.

  The invention relates to a protection device 1 of an electrical installation (not shown) against overvoltages, and in particular against transient overvoltages, such as overvoltages generated by a thunderbolt. The protection device 1 according to the invention is therefore advantageously a surge arrester, and for example a low voltage arrester. By electrical installation, reference is made here to any type of apparatus or electrical network likely to suffer voltage disturbances and possible related damage. The protection device 1 against overvoltages according to the invention is advantageously intended to be mounted between a phase of the installation to be protected and the earth. However, it is conceivable, without departing from the scope of the invention, that the protective device 1, instead of being connected bypass between a phase and the earth, is connected between the neutral and the earth, between the phase and the neutral, or between two phases (case of differential protection). An exemplary embodiment of a protection device 1 according to the invention is illustrated in FIG. 1. As illustrated in FIG. 1, the protection device 1 comprises a housing 2 in which at least two electrodes are arranged. , for example a first electrode 3 and a second electrode 4, between which an electric arc is likely to form in case of overvoltage.

  In other words, the first and second electrodes 3, 4 delimit an inter-electrode gap 5 forming a spark gap. The first and second electrodes 3, 4 thus advantageously form the main electrodes of the spark gap. Within the meaning of the invention, said electrodes 3, 4 between which an electric arc is likely to form are therefore part of the main overvoltage protection component of the device 1, and preferably form the main component for protection against overvoltages of the device. device 1. The device 1 in the sense of the invention is a device whose operating principle is based on the generation of an electric arc in case of overvoltage. The device 1 is therefore in particular not a varistor protection device as the main protection component.

  The housing 2 is for example made of a rigid plastic material, and is preferably formed of two half-shells (one of which is shown in Figure 1) reported against each other to delimit a closed internal volume intended to accommodate the functional part of the device 1.

  The protection device 1 according to the invention also comprises two connection terminals 6, 7 for electrically connecting the electrodes 3, 4 to the electrical installation to be protected. More specifically, the device 1 comprises a first terminal 6 electrically connected to the first electrode 3, and a second terminal 7 electrically connected to the second electrode 4. The terminals 6, 7 can be in any form known to man of career. For example, in a first embodiment (not shown), the terminals 6, 7 may be in the form of tabs projecting towards and outside the housing 2, said tabs being intended to be plugged into an electrically connected base to the installation to be protected.

  In another preferred embodiment, illustrated in FIGS. 1 and 2, the terminals 6, 7 are disposed laterally on either side of the housing 2, and each comprises a housing for receiving a connection cable, said cable being secured to the corresponding terminal 6, 7 by screwing with corresponding screws 6A, 7A. Such an arrangement is well known to those skilled in the art and will not be described in more detail here.

  Thus, when an overvoltage occurs between the terminals 6, 7, the electric current moves from the first terminal 6 (or the second terminal 7) to the first electrode 3 (respectively the second electrode 4), and joins the second electrode 4 (respectively the first electrode 3) in the form of an electric arc, to then flow to the second terminal 7 (respectively the first terminal 6).

  As is well known to those skilled in the art, the device 1 can also be equipped, as illustrated in FIG. 1, with a triggering electronics 8 connected to a priming electrode 9, in order to optimize the control of formation of the electric arc between the main electrodes 3, 4. Such a technical measure is well known as such to those skilled in the art, and therefore will not be described in more detail in the following. Preferably, the inter-electrode gap 5 is filled, at least partially, with a gas, preferably with air, so as to form a dielectric medium between the electrodes 3, 4, as is well known. of the skilled person. In this case, the inter-electrode gap 5 forms an air gap. However, it is quite possible, without departing from the scope of the invention, for the protection device 1 to implement encapsulated spark gap technology, in which the air is replaced by another gas, for example a gas rare maintained under controlled pressure. According to the invention, the device 1 comprises, disposed within the housing 2 and electrically connected in series between the terminals 6, 7, a circuit breaker 10 able to pass from a conductive configuration (shown in FIGS. 1 to 3). in which it is capable of conducting the electric current likely to flow between the terminals 6, 7, to an insulating configuration (illustrated in FIG. 4) in which it breaks the passage of the current likely to flow between said terminals 6 , 7.

  In other words, the circuit breaker 10 is capable, in its conductive configuration, of ensuring directly by itself the passage of the electric current able to flow between the terminals 6, 7 when an electric arc is formed between the first and second electrodes 3, 4. The circuit breaker 10 thus forms part, when in its conductive configuration, of the flow circuit between the terminals 6, 7.

  In contrast, in its insulating configuration, the circuit breaker 10 is designed to interrupt the flow of current between the terminals 6, 7. Thus, even if the electrodes 3, 4 are short-circuited, as a result of a failure Device 1, the latter will be totally electrically isolated from the installation to be protected, so as to avoid any risk of degradation or fire.

  The circuit breaker 10 is of course preferably capable of detecting by itself a malfunction of the device 1 and to automatically switch to the insulating configuration when such a malfunction is detected.

  The general principle of the invention is therefore essentially based on the integration, directly into the housing 2 of the protection device 1, of a circuit breaker 10 interposed directly in the electrical path extending between the first terminal 6 and the second terminal 7.

  Thanks to this technical measure, the installer of the protection device 1 has no particular approach to implement (other than the connection of the terminals 6, 7 to the installation) to protect the device 1 in the event of a malfunction. Such a malfunction or failure may in particular be characterized by the existence of a level of current and / or temperature within the case 2 abnormally high.

  Preferably, the circuit breaker 10 is thus sensitive to heat, so that when the temperature reaches a predetermined value (reflecting abnormal operation) at the circuit breaker 10, the latter goes into an insulating configuration. Preferably, and preferably complementary, the circuit breaker 10 is sensitive to the intensity of the current flowing through it, so that when said current reaches a predetermined value reflecting an abnormal operation, the circuit breaker 10 goes into configuration. insulating.

  Particularly advantageously, the circuit breaker 10 has a fusible character, that is to say that it comprises fusible means so that when the intensity that passes through these fusible means is greater than a predetermined level, thereby generating a heat input by Joule effect, said fusible means melt, thus creating a definitive electrical break between the first terminal 6 and the second terminal 7. The circuit breaker 10 is thus advantageously designed to form at least one insulating void space 11 in the circuit connecting the first terminal 6 to the second terminal 7. This insulating space 11 has a predetermined dimension preferably designed, with respect to the other characteristics of the device 1, to avoid inadvertent reformation of an electric arc at said empty space 11.

  In a preferred embodiment illustrated in the figures, the device 1 comprises two conductive pads 12, 13 for electrically connecting respectively each terminal 6, 7 to the corresponding electrode 3, 4. At least one (and preferably each) of said lands 12, 13 comprises a fuse zone 12A, 13A forming a circuit breaker 10. In the variant illustrated in the figures, the circuit breaker 10 is thus formed of two fuse elements respectively interposed in the electrical connection connecting the first terminal 6 to the first electrode 3 and in the electrical connection connecting the second terminal 7 to the second electrode 4. It is of course conceivable that the circuit breaker 10 is formed of a single fuse element, for example, connected in series only between the first terminal 6 and the first electrode 3 (or between the second terminal 7 and the second electrode 4). The symmetrical configuration illustrated in the figures is, however, preferred. Advantageously, said range 12, 13 is formed of a one-piece integral piece having at least one section of reduced section forming said fuse zone 12A, 13A.

  According to this particularly simple, efficient and economical variant, the connection between each terminal 6, 7 and the corresponding electrode 3, 4 is ensured by a unitary metal strip, for example made of stainless steel, a portion of which between the terminal 6, 7 and the corresponding electrode 3, 4 has a cross section smaller than the cross section of the rest of the strip. When the temperature at the metal strip increases sharply to a predetermined level, for example in response to a large number of lightning strikes to which the arrester would be subjected, the section of reduced section yields, thus providing an insulating gap 11 interrupting the passage of the current and thus the process of destruction of the device 1.

  Advantageously, as is well known per se, the device 1 also comprises a breaking chamber 14 of the electric arc that may be formed between the electrodes 3, 4. The operation of such a breaking chamber 14 is based on the fractionation of the electric arc produced between the electrodes 3, 4. The operation of such a chamber 14 is well known as such, and will not be described further here. The electrodes 3, 4 are advantageously arranged so that the electric arc is transferred to and in the breaking chamber 14 under the effect of its own electric field.

  Preferably, the device 1 according to the invention also comprises at least one isolation spark gap 15, 16 electrically connected in series between at least one of the electrodes 3, 4 and the breaking chamber 14.

  Advantageously, the interrupting chamber (which may also be called arc extinguishing chamber) 14 is delimited by two end plates 17, 18 between which are interposed a series of elementary splitting plates 19 spaced apart from each other. other so as to decompose the electric arc formed between the electrodes 3, 4 into a plurality of elementary arcs.

  Preferably, the device 1 comprises two isolation gaps 15, 16 interposed respectively between the first end plate 17 and the first electrode 3 and the second end plate 18 and the second electrode 4. Each isolation gap 15, 16 is preferably formed by a void space (filled with air, or another gas, or a dielectric) separating the end of each electrode 3, 4 from the corresponding outer plate 17, 18. Said insulation gaps 15, 16 preferably have a sufficient breaking power to ensure, in case of failure of the arc extinguishing chamber 14, the definitive extinction of the electric arc during the zero crossing. current in the device 1 by preventing the rebooting of the electric arc.

  The combination of an isolation spark gap 15, 16 with a circuit breaker 10 proves particularly advantageous, since it allows, in a particularly simple way and without harming the protection properties of the device 1 against overvoltages, to obtain a insulating vacuum space of predetermined size particularly important when the circuit breaker 10 is passed in its insulating configuration, without implying a circuit breaker of large size, which could adversely affect the reliability of the device 1.

  For example, in the embodiment illustrated in FIG. 4, the overall isolation distance of the surge arrester 1 after operation of the circuit breaker 10 corresponds to the sum e + c + d + f, the dimensions e and f respectively corresponding to the dimensions of the free spaces obtained by fusing the fusible zones 12A, 13A forming a circuit breaker 10, while the dimensions c and d respectively correspond to the free space dimensions of the isolation gaps 15, 16.

  For example, the distances e and f may be between 0.5 and 3 mm, and preferably between 1 and 2 mm, while c and d may be between 0.5 and 2 mm, and preferably equal to 1 mm.

  The presence of the isolation gaps 15, 16 thus makes it possible, in order to obtain a given isolation distance, to reduce the size of the fusible zones 12A, 13A (which contributes to making the device 1 more reliable), with respect to a device 1 which do not include an isolation spark gap 15, 16.

  In the case where the isolation spark gaps 15, 16 are short-circuited as a result of a malfunction of the device 1, or in the absence of such gaps 15, 16, the overall isolation distance obtained after triggering the circuit breaker 10 would be equal to the sum e + f + a + b to which is added the sum of the interstitial spaces separating each plate from the series of plates 19, the distances a and b respectively corresponding to the distances separating the outer plates 17, 18 of the series 19 of elementary plates. The invention thus makes it possible to provide an electrical isolation function of the particularly reliable device 1, and this in a particularly simple, compact and inexpensive manner. Advantageously, a mechanical or electrical display system can be integrated in the housing 2, said display system (not shown) being functionally connected to the circuit breaker 10 so as to indicate to the user the state of the surge arrester 1, to operate or not the replacement of the latter.

  Finally, the invention also relates to a method of manufacturing a protection device 1 of an electrical installation against surges, particularly transient, such as that just described.

  According to the method of the invention, at least two electrodes 3, 4 are disposed within a housing 2, between which an electric arc is likely to form in case of overvoltage, to discharge the overvoltage current.

  In another step of the method, the housing 2 is provided with two connection terminals 6, 7 for electrically connecting the electrodes 3, 4 to the installation to be protected. The method according to the invention also includes a step of mounting a circuit breaker 10, in which is mounted electrically in series between the terminals 6, 7, within the housing 2, a circuit breaker 10 adapted to pass through a conductive configuration in which it is capable of conducting the electric current capable of flowing between the terminals 6, 7, to an insulating configuration in which it breaks the passage of current flowing between said terminals 6, 7.

Claims (11)

  1 Protection device (1) for an electrical installation against overvoltages, in particular transients, comprising on the one hand a housing (2) in which at least two electrodes (3, 4) are disposed between which an electric arc is capable of being formed in case of overvoltage, and secondly two connection terminals (6, 7) for electrically connecting the electrodes (3, 4) to said installation, said device (1) being characterized in that it comprises, disposed within the housing (2) and electrically connected in series between the terminals (6, 7), a circuit breaker (10) capable of passing from a conductive configuration in which it is capable of conducting the electric current to flow between the terminals (6, 7), to an insulating configuration in which it breaks the passage of current flowing between the terminals (6, 7).   2 - Device (1) according to claim (1) characterized in that the circuit breaker (10) is sensitive to heat, so that when the temperature reaches a predetermined value at the circuit breaker (10), this last pass in insulating configuration.   3 - Device (1) according to one of claims 1 to 2 characterized in that the circuit breaker (10) is responsive to the intensity of the current flowing through it, so that when said intensity reaches a predetermined value the cut -circuit (10) goes into insulating configuration.   4 - Device (1) according to one of claims 1 to 3 characterized in that the circuit breaker (10) has a fusible character.   5 - Device (1) according to one of claims 1 to 4 characterized in thatcomporte two conductive pads (12, 13) for respectively electrically connecting each terminal (6, 7) to the corresponding electrode (3, 4) at least one of said pads having a fusible area (12A, 13A) forming a circuit breaker (10).   6 - Device (1) according to claim 5 characterized in that said one of said pads (12, 13) is formed of a one-piece piece having at least one section of reduced section fusible zone (12A, 13A).   7 - Device (1) according to one of claims 1 to 6 characterized in that the circuit breaker (10) is designed to form at least one insulating void space (11) of predetermined size (e, f).   8 - Device (1) according to one of claims 1 to 7 characterized in that it comprises a breaking chamber (14) of the electric arc may be formed between the electrodes 3, 4.   9 - Device (1) according to claim 8 characterized in that it comprises at least one isolation gap (15, 16) electrically connected in series between at least one of the electrodes (3, 4) and the chamber of cutoff (14).   10 -Dispositif (1) according to one of claims 1 to 9 characterized in that it constitutes a surge arrester. 11 A method for manufacturing a protection device (1) for an electrical installation against overvoltages, in particular transients, in which, on the one hand, at least two electrodes are disposed within a housing (2) ( 3, 4) between which an electric arc is likely to form in case of overvoltage, and in which on the other hand the housing (2) is provided with two connection terminals (6, 7) intended to electrically connect the electrodes ( 3, 4) to said installation, said method being characterized in that it comprises a step of mounting a circuit breaker (10), in which the terminals (6, 7) are electrically connected in series between the terminals (6, 7), housing (2), a circuit breaker (10) adapted to pass from a conductive configuration in which it is capable of conducting the electric current likely to flow between the terminals (6, 7), to an insulating configuration in which it breaks the passage of the current likely to flow between terminals (6, 7).