FR2877155A1 - IMPROVED DISCONNECTION OVERVOLTAGE PROTECTION DEVICE AND CORRESPONDING METHOD - Google Patents

Abstract

The invention relates to a device for protection against overvoltages due to the impact of thunder, said device being connected to an electrical installation, comprising at least two electrodes (2,3) defining a space between the electrodes (4) forming a gap protector, in addition to detection means (8) which are sensitive to the state of the gap protector, enabling detection of the malfunctioning of said gap protector, and disconnection means (8) which can ensure, dependent upon the detection means, the insulation of the protection device (1) in relation to the electrical installation if an error is detected in the gap protector by said detection means. The invention is characterized in that the disconnection means (9) are formed by insulating means (10) which can be positioned between the electrodes (2,3) in order to increase the insulation therebetween dependent upon the detection means (8).

Description

OVERVOLTAGE PROTECTION DEVICE WITH IMPROVED DISCONNECTION AND

CORRESPONDING METHOD

  The present invention relates to the general technical field of equipment protection devices or electrical installations against overvoltages, and in particular transient overvoltages due to lightning.

  The present invention relates more particularly to a protection device against overvoltages due in particular to a lightning strike intended to be connected to an electrical installation and comprising at least two electrodes defining an inter-electrode space forming a spark gap.

  The invention also relates to a method for electrically isolating a surge protection device intended to be connected to an electrical installation and comprising at least two electrodes delimiting an inter-electrode space forming a spark gap.

  It is known to use, to protect an electrical installation against overvoltages, a low-voltage protection device using the technology of spark gaps, such as spark gap arrester. This device is generally associated in series with a complementary external cut-off device, able to isolate the protection device against overvoltages of the electrical installation when a current of excessively high current passes through it.

  Among the known cutting members, it is most often used overcurrent protection devices, such as circuit breakers. These devices thus make it possible to isolate the overvoltage protection device, while avoiding the opening of the other general breaking devices of the electrical installation, in order to ensure continuity of service of the power supply.

  Such assemblies, while they make it possible to optimize the operation of the electrical installation while guaranteeing the resistance to overvoltages, nevertheless suffer from considerable disadvantages related first of all to the complexity of the choice of the various components.

  It is indeed difficult, with the known assemblies, to control and optimize the level of protection of the electrical installation. In particular, such assemblies generally involve taking into account, in order to achieve the level of protection of the desired installation, not only the protection level of the arrester but also the own impedance of the circuit breaker.

  In addition, the surge arrester and the circuit breaker are sometimes located at a distance from each other and the impedance of the connecting conductors is often difficult, if not impossible to calculate precisely, which can lead to errors and an underestimation of the actual level of protection of the electrical installation.

  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, due in particular to the intensity of the overvoltage. The installation then appears protected in the eyes of the user, while the surge protection device is highly degraded, and is no longer able to assume its protection function. Thus, the user runs the risk that a new overvoltage deteriorates unprotected electrical equipment.

  Yet another disadvantage of the known assemblies comes from the technical complexity, the size and significant manufacturing costs generated by the combination of a surge arrester and a circuit breaker.

  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 listed above and that, in case of failure, to be disconnected permanently from the installation. electric.

  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 propose a new device for protecting an electrical installation against overvoltages which is particularly easy to use, thus limiting the risk of error for the operator.

  Another object of the invention is to propose a new device for protecting an electrical installation against overvoltages having a compact, robust and inexpensive construction structure.

  Another object of the invention is to provide a new device for protecting an electrical installation against overvoltages whose manufacture requires only standard components, and which can be obtained easily without fundamentally modifying the overall structure of the protective devices. spark gap known.

  Another object of the invention is to propose a new device for protecting an electrical installation against overvoltages whose operating state can be easily monitored.

  The objects assigned to the invention are also intended to propose a new method of electrical insulation of a protection device of an electrical installation against overvoltages allowing, in a simple way and using standard components, to effectively isolate the device in case of failure of the latter.

  Another object of the invention is to propose a new method of electrical insulation of a protection device of an electrical installation against overvoltages allowing a close monitoring of the operating state of the device.

  The objects assigned to the invention are achieved by means of a surge protection device due in particular to a lightning strike intended to be connected to an electrical installation and comprising at least two electrodes delimiting an inter-electrode gap forming spark gap, characterized in that the protection device comprises: detection means, sensitive to the state of the spark gap and able to detect a malfunction of the latter, and - disconnection means, able to provide, dependent detection means, the isolation of the protective device vis-à-vis the electrical installation when a failure of the spark gap is detected by the detection means.

  The objects assigned to the invention are also achieved by means of a method of electrically isolating an overvoltage protection device intended to be connected to an electrical installation and comprising at least two electrodes delimiting an interfering space. -electrode forming spark gap, said method comprising successively: - a step (a) of detecting a malfunction of the spark gap, - a step (b) of disconnection of the spark gap vis-à-vis the electrical installation 5 when a failure is detected during step (a).

  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: FIG. according to a sectional view, an overvoltage protection device 10 according to the invention.

  - Figure 2 illustrates, in a schematic view, a first embodiment of the overvoltage protection device according to the invention in its operating position.

  - Figure 3 illustrates, in a schematic view, the protective device 15 shown in Figure 2 in its disconnected position.

  - Figure 4 illustrates, in a schematic view, a second embodiment of the protection device according to the invention in its service position.

  - Figure 5 illustrates, in a schematic view, the protective device 20 shown in Figure 4 in its disconnected position.

  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 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 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.

  As illustrated in FIG. 1, the protection device 1 is advantageously in the form of a spark gap arrester. The protective device 1 thus comprises at least two electrodes, for example a first electrode 2 and a second electrode 3 delimiting an inter-electrode gap 4 forming a spark gap. The first and second electrodes 2, 3 can thus advantageously form the main electrodes of the spark gap.

  The protection device 1 according to the invention also advantageously comprises connecting branches 5, 6 to the electrical installation or to the power supply network, making it possible to electrically connect the protection device 1 to the electrical installation ( not shown) to protect.

  As illustrated in FIGS. 2 to 5, the electrodes 2, 3 and the connecting branches 5, 6 may advantageously be formed by the same conductive part, for example a metal part. All of these elements is advantageously mounted within an insulating casing 7. According to a variant not shown in the figures, the housing 7 may constitute a plug-in module (or cartridge) on a base, thus facilitating the installation or removal of the protection device 1 by the operator.

  Preferably, the inter-electrode space 4 is filled, at least partially, with a gas, preferably with air so as to form a dielectric medium between the electrodes 2, 3. The interelectrode space 4 forms in this case an air gap. In the remainder of the description, it is considered that the protection device 1 is based on the technology of the air gaps. However, it is of course conceivable, without departing from the scope of the invention, that the protective device 1 according to the invention uses encapsulated spark gap technology, the air then being replaced by a gas, for example a rare gas maintained under controlled pressure.

  Such spark gaps, whether air-type or encapsulated, undergo, during their lifetime, degradation. This degradation can be gradual or abrupt, especially the spark gap is used intensively or repeatedly, with a high frequency. Several phenomena, specific to the gaps, can lead to this degradation of the protective device.

  Thus, when an overvoltage occurs, exceeding a predetermined threshold value corresponding to the trigger threshold voltage of the spark gap, an electric arc 15, corresponding to the ionization of the gas located in the inter-electrode space 4, is formed. between the electrodes 2, 3 and flows, for example to earth, the current corresponding to the overvoltage. The protective device 1 then deflects the current and allows to preserve the electrical installation. However, in case of overvoltage amplitude too large, or repeated or prolonged operation of the protective device 1, the electric arc can cause erosion of the electrodes 2, 3, tearing metal particles on the surface thereof. These metal particles are then likely to be deposited at another place in the inter-electrode space, thus creating a conductive pollution within the spark gap. This pollution can lead, when important, to a failure of the spark gap, several evolutions then being possible until the end of life of the spark gap.

  Firstly, if the spark gap is provided with an insulating initiation aid, for example in the form of a dielectric lamella interposed between the electrodes, the metal particles can be deposited on the surface of the dielectric lamella , thus forming a conductive deposit between the electrodes. This conductive deposit gradually forms a metal bridge between the electrodes, short-circuiting the spark gap. A large short-circuit current can then flow, by conduction, to the surface of the dielectric lamella, thus causing significant heating of the spark gap.

  In the absence of an insulating initiation aid, the tearing of the metal particles on the surface of the electrodes can lead to: - either a degradation of the level of protection of the spark gap, because of the uncontrolled increase of the trigger threshold voltage of the spark gap, or the formation of a preferential conductive path between the electrodes, resulting from the formation of a partial or total conductive bridge between the electrodes. In the latter case, we also observe the passage of a large current along this bridge, causing abnormal heating of the spark gap.

  When this phenomenon occurs, the protection device should be disconnected as soon as possible and replaced, since it is no longer able to properly protect the electrical installation.

  However, the end of life of the spark gap is random, so that it is particularly difficult, if not impossible, to predict in advance its replacement.

  This is the reason why, according to an essential characteristic of the invention, the protection device 1 according to the invention comprises detection means 8, sensitive to the state of the spark gap and able to detect a malfunction of this last. In other words, the detection means are designed to detect a possible failure of the behavior of the spark gap, causing, for example, excessive heating of the latter.

  More specifically, the detection means 8 are advantageously sensitive to excessive heating of the spark gap, which may occur when the spark gap is faulty. In other words, the detection means 8 are sensitive to the temperature, and are advantageously located near the spark gap to detect as soon as possible an abnormal heating of the latter, regardless of the heating of a possible circuit associated tripping electronics, or other breaking means, of the circuit breaker type, located near the protection device 1.

  When a failure of the spark gap is detected, the protective device 1 of the electrical installation should be disconnected as soon as possible and then replaced.

  For this purpose, and according to an essential characteristic of the invention, the protection device 1 according to the invention comprises disconnection means 9, able to ensure, under the control of the detection means 8, isolation of the device of the invention. protection 1 vis-à-vis the electrical installation when a failure of the spark gap is detected.

  Thus, the detection means 8 being directly sensitive to the state of heating of the spark gap, they are designed to trigger the disconnection means 9 when the temperature of the spark gap exceeds a predetermined threshold value. The isolation of the spark gap is immediate, which in particular limits the risk of fire.

  Advantageously, the disconnection means 9 are formed by moveable insulating means 10 capable of coming, under the control of the detection means 8, that is to say when a failure of the spark gap is detected by the latter, positioned between the electrodes 2, 3 to increase the isolation between them. In other words, the insulating means 10 are adapted to increase the electrical isolation capacitances of the inter-electrode space 4, and therefore the energy required for an electric arc to be formed between the electrodes 2, 3.

  Thus, by controlling the design of the insulating means 10, and the quality of the insulation created between the electrodes 2, 3, it is possible to guarantee the electrical insulation of the protection device 1 for given conditions of use.

  In addition to its compactness, the protection device 1 according to the invention also makes it possible to avoid using a complex additional cut-off device, such as a circuit breaker. The insulating means 10 according to the invention, associated with the detection means 8, thus make it possible to ensure a quick and reliable disconnection of the protection device 1 in case of failure of the latter.

  Several embodiments of the protection device 1 according to the invention will now be described with reference to FIGS. 2 to 5.

  According to a first embodiment of the invention, illustrated in Figures 2 and 3, the insulating means 10 are formed by an insulating part 11 mounted movably within the housing 7 so as to be able to move between the electrodes 2, 3 in to increase the isolation distance between the latter when a failure, and in particular a heating of the spark gap, is detected by the detection means 8.

  The expression isolation distance here refers to the distance that the electric arc must travel to electrically connect the electrodes 2, 3. When the spark gap is operational, ie, non-degraded, there exists a so-called functional isolation distance, which corresponds substantially to the width of the inter-electrode space 4 necessary for an electric arc to start when an overvoltage reaching or exceeding a predetermined threshold value occurs. The insulating part 11 is therefore advantageously designed to increase the isolation distance between the electrodes 2, 3, so that the latter exceeds the above-mentioned functional isolation distance.

  Thus, when the insulating part 11 comes, as is illustrated in FIGS. 1 and 3, to penetrate inside the inter-electrode space 4, it significantly increases the path that the electric arc must travel in order to bypass it, increasing at the same time the energy needed to maintain or reprime the electric arc. The protective device 1 according to the invention is advantageously dimensioned so that this energy is never reached in the usual operating conditions of the spark gap, which ensures the electrical insulation of the latter.

  The width of the inter-electrode space is not necessarily constant and can vary along the electrodes 2, 3. Thus, the electrodes 2, 3 can advantageously have a V shape, the V hollow, which has the distance the weakest isolation, then advantageously forming the ignition zone 40 of the electric arc.

  The insulating part 11 is advantageously mounted movably between a first position (illustrated in FIG. 2) in which it allows the free operation of the protection device 1, and in particular the formation of an electric arc 15 in the inter-electrode space 4 , more precisely in the priming zone 40, and a second position (illustrated in FIG. 3) in which it increases the isolation distance between the electrodes 2, 3, thus preventing the maintenance or rebooting of the electric arc , and simultaneously ensuring the permanent disconnection of the protective device 1 vis-à-vis the electrical installation.

  Advantageously, the insulating part 11 is mounted mobile in translation between its first and second positions, under the constraint of an actuating means, and preferably under the constraint of an elastic return means 12 of the spring type. According to the exemplary embodiment illustrated in FIGS. 2 and 3, the electrodes 2, 3 comprise parallel branches 2A, 3A spaced apart from one another and forming a slideway 13 in which the insulating part 11 is capable of sliding under the stress exerted by the elastic return means 12.

  In its first position illustrated in Figure 2, the insulating part 11 is advantageously maintained by the detection means 8, which are for example formed by a fuse element 14, fixed relative to the housing 7 and for example secured to the latter. The fuse element 14 is preferably located near and preferably in physical contact with the insulating part 11, so as to detect, by conduction, the heating of the latter. Advantageously, the fuse element 14 is preferably formed by a calibrated tin-lead alloy to break or melt beyond the usual operating temperatures of the spark gap. The fuse element 14 is advantageously electrically isolated from the electrodes 2, 3, for example by interposition of a dielectric material.

  Advantageously, the detection means 8 are preferably mounted within the protective device 1 so as to release the disconnection means 9, and in particular the insulating means 10 (for example the insulating part 11) when a malfunction of the spark gap is detected.

  Preferably, the insulating means 10, in particular the insulating part 11, are held directly or indirectly by the fuse element 14, such that the melting or breaking of the latter causes the release of the insulating means 10. The element fuse 14 and the insulating means 10 are thus advantageously mounted relative to each other so that the fuse element 14 forms a stop against the displacement of the insulating means 10 under the action of the restoring force F exerted by the elastic return means 12. According to the variant embodiment illustrated in FIGS. 2 and 3, the restoring force F exerted by the elastic return means 12 is directed towards the inter-electrode space 4, so as to push back the insulating part 11 deeper inside the inter-electrode space 4 when a failure of the spark gap is detected.

  Particularly advantageously, the insulating part 11 can form, in its first position, an insulating initiation aid to control the initiation of the electric arc 15 between the electrodes 2, 3. The insulating part 11 then allows better to control the level of protection of protection device 1 compared to devices without a booster auxiliary. In particular, if an overvoltage greater than the trigger threshold of the spark gap occurs, an electric arc 15 is initiated between the electrodes 2, 3, along the surface S of the insulating piece 11 located at the interface with the gas.

  Nevertheless, it is of course conceivable to provide a protection device 1 provided with an independent priming aid, distinct from the insulating part 11. According to this variant, not shown in the figures, the insulating part 11 and the priming aid can for example be arranged superimposed between the parallel branches 2A, 3A, electrodes 2, 3.

  In this case, the priming aid is preferably fixed and the insulating part 11 movable so as to be able to assume its function of isolating the protection device 1. The insulating part 11 and the priming aid are preferably formed by an insulating material such as ceramic.

  According to a second embodiment of the invention, illustrated in FIGS. 4 and 5, the protection device 1 advantageously comprises an isolating insulating auxiliary 16 which, in the operative position, is arranged between the electrodes 2, 3 in a better way control and control the initiation of an electric arc 15 between the electrodes. The electrodes 2, 3, more precisely the parallel branches 2A, 3A of the latter, advantageously bear tightly against the priming aid 16. The electric arc 15 is then formed in the air, along the surface S 'of the priming aid 16.

  The priming aid 16 is advantageously mounted movably between its functional position (illustrated in FIG. 4) and a withdrawal position (illustrated in FIG. 5) in which it is located outside the inter-electrode space 4. In FIG. case of degradation of the spark gap, and formation of a conductive deposit 18 on the surface S 'of the ignition auxiliary 16, a large short-circuit current flows between the electrodes 2, 3, along of the ignition auxiliary 16, which has the effect of significantly increasing the temperature of the spark gap, and therefore, by conduction, that of the ignition auxiliary 16.

  The detection means 8, in particular the fuse element 14, advantageously situated in proximity and preferably in physical contact with the priming aid 16 then detect, by conduction, the heating of the latter and release, by fusion or rupture. , the ignition aid 16. The latter is then brought back, under the action of an elastic return means 12 ', to its retracted position illustrated in Figure 5. In particular, the elastic return means 12 is designed to exert a restoring force F 'directed in the opposite direction to the inter-electrode space 4 so as to ensure the removal of the priming aid 16. The elastic return means 12' is thus designed to pass of an extension configuration, illustrated in FIG. 4, to a rest configuration illustrated in FIG.

  In this embodiment, the insulating means 10 are advantageously formed by a gas, and for example by the air G located inside the housing 7 and able to be substituted, in the inter-electrode space 4, for the ignition aid 16 when the latter comes into its withdrawal position shown in FIG. 5. Thus, the used ignition auxiliary 16 and the conductive deposit 18 are simultaneously removed from the inter-electrode space 4, and replaced by the gas. The gas, whose insulating capacity is greater (lower dielectric constant) than the priming aid 16, thus effectively ensures the isolation of the electrodes 2, 3 relative to each other.

  Whatever the embodiment used, the protective device 1 according to the invention may advantageously comprise indicating means (not shown) of the state of the spark gap. These indication means are advantageously functionally connected to the detection means, and preferably mechanically connected, directly or indirectly, to the insulating piece 11 or to the triggering aid 16. The indication means can be formed by a separate piece dela insulating part 11 or triggering auxiliary 16, capable of moving opposite a window in the housing 7, when a failure of the spark gap is detected. It is also conceivable to provide a protection device 1 in which the indication means and the insulating part 11 (or the priming aid 16) are formed by one and the same piece.

  In a conventional manner and known as such, the protective device 1 according to the invention advantageously comprises a breaking chamber 20, formed by an arrangement of metal splitting plates 21 located at the end of the inter-electrode space. 4 opposite to the priming zone 40. The interrupting chamber 20 thus ensures the cutting of the electric arc into a plurality of elementary arcs, so as to allow its extinction.

  In particular, in the case of the first embodiment of the invention illustrated in FIGS. 2 and 3, the electric arc 15, initially formed in the priming zone 40, propagates, thanks to the V-shape of the electrodes 2, 3, to the breaking chamber 20 where it extinguishes. In case of failure of the spark gap, and in particular in case of pollution of the inter-electrode space 4 or the insulating part 11, the displacement of the latter inside the inter-electrode space 4, in the direction of of the breaking chamber 20, has the effect of causing an elongation of the electric arc 15 and to drive the latter to the breaking chamber 20, thus accelerating its extinction.

  The present invention also relates to a method of electrical insulation of a protection device 1 of an electrical installation against overvoltages comprising at least two electrodes 2, 3 delimiting an inter-electrode gap 4 forming a spark gap. According to the invention, the method comprises a step (a) of detecting a malfunction of the spark gap, followed, if a failure is detected, with a step (b) of disconnection of the spark gap vis-à-vis of the electrical installation.

  In a particularly advantageous manner, the step (a) of detection comprises a phase of detection of the heating of the spark gap. Moreover, the step (b) of disconnection advantageously comprises a phase of interposition of insulating means 10 between the electrodes 2, 3 of the protection device 1 so as to increase the isolation between the latter, thus ensuring the electrical isolation the protection device 1 vis-à-vis the electrical installation.

  The interposition phase advantageously comprises a phase of increasing the isolation distance between the electrodes 2, 3 with the aid of an insulating part 11. For this purpose, the interposition phase comprises a phase of displacement of the insulating part 11 in the inter-electrode space 4.

  A variant of this method, which can be implemented when the protection device 1 comprises an insulating initiation aid 16, arranged between the electrodes 2, 3, consists in carrying out, during the interposition phase, a substitution of the ignition auxiliary 16 by a gas, in particular air, the gas then forming the insulating means 10.

  Particularly advantageously, the isolation method according to the invention further comprises a step (c) of indicating to a third party, for example to an operator, that the protective device 1 is faulty and that it is necessary to make his change.

  The operation of the protection device according to the invention will now be described with reference to FIGS. 1 to 5.

  In the functional configuration illustrated in FIGS. 2 and 4, the insulating part 11, or the priming aid 16, are arranged so as to enable the initiation of an electric arc 15 along the surface S, S between the electrodes 2, 3. The electric arc 15 then makes it possible to discharge, for example to earth, the current generated by the overvoltage. This electric arc 15 can lead, gradually or rapidly, depending on the intensity and duration of the voltage disturbances, to an erosion of the surface of the electrodes 2, 3, thus causing the formation of a conductive pollution in the internal space. electrodes 4, and in particular on the surface S of the insulating part 11 or on the surface S 'of the priming aid 16.

  This conductive pollution is reflected in particular by the formation of a conductive deposit 18 on the surface S or S '. In this case, there is conduction of a large current along the conductive deposit 18, resulting in excessive heating of the spark gap and the insulating part 11 (respectively of the priming aid 16).

  This excessive heating is then transmitted, for example by conduction, to the fuse element 14 which, when the temperature exceeds a predetermined critical value, begins to melt (or to break). The fusion (or rupture) of the fuse element 14 then releases the insulating means 10, for example the insulating part 11 or the gas, which then penetrate inside the inter-electrode space 4, interposing between the electrodes 2, 3 so as to increase the isolation; and for example the isolation distance between them.

  If the insulating means 10 are formed by the insulating part 11, the electric arc 15 elongates, then is driven to the interrupting chamber 20 where it extinguishes. The energy required for the formation of a new electric arc being particularly high because of the large isolation distance between the electrodes 2, 3, the protection device 1 is then isolated, effectively and permanently, from the Electrical Installation.

  The invention therefore ensures, in the event of failure of the spark gap, a quick and reliable disconnection of the protection device 1 vis-à-vis the electrical installation, without disturbing the latter.

  Another advantage of the protection device 1 according to the invention is that it can be in the form of an interchangeable cartridge, thus facilitating its handling by a non-expert user.

  Another advantage of the protective device 1 according to the invention is that it is not resettable and consequently constitutes a safer device than the devices of the prior art.

  The protection device 1 according to the invention also makes it possible to immediately report to the user any malfunction, thus enabling its rapid replacement.

Claims (21)

  1 - Protection device against overvoltages due in particular to a lightning strike intended to be connected to an electrical installation and comprising at least two electrodes (2, 3) delimiting an interelectrode gap (4) forming a spark gap, characterized in that comprises: - detection means (8), sensitive to the state of the spark gap and able to detect a malfunction of the latter, and - disconnection means (9), able to ensure, under the control of the means of detection (8), the isolation of the protection device (1) from the electrical installation when a failure of the spark gap is detected by the detection means (8).   2 - Device according to claim 1 characterized in that the detection means (8) are responsive to the heating of the spark gap.   3 - Device according to claim 1 or 2 characterized in that the disconnecting means (9) are formed by insulating means (10), able to come, under the control of the detection means (8), to be positioned between the electrodes (2, 3) to increase the isolation between them.   4 - Device according to claim 3 characterized in that the insulating means (10) are formed by an insulating piece (11) movable, able to move between the electrodes (2, 3) so as to increase the isolation distance between these last.   - Device according to claim 4 characterized in that the insulating part (11) is movably mounted between a first position, in which it allows the free operation of the protective device (1), and a second position in which it increases the distance d isolation between the electrodes (2, 3), thus ensuring the disconnection of the protective device (1) vis-à-vis the electrical installation.   6 - Device according to claim 5 characterized in that the insulating part (11) is mounted movable in translation between its first and second positions, for example under the constraint of an elastic return means (12).   7 - Device according to one of claims 4 to 6 characterized in that the insulating part (11) is held in its first position by the detection means (8).   8 - Device according to one of the preceding claims characterized in that it comprises an insulating initiator (16) which, in the operative position, is disposed between the electrodes (2, 3) so as to control the priming an electric arc (15) between the electrodes (2, 3).   9 - Device according to claims 4 and 8 characterized in that the insulating part (11) is formed by the priming aid.   - Device according to claim 8 characterized in that the priming aid (16) is movably mounted between its operative position and a retracted position, in which it is located outside the interelectrode space (4).   11 - Device according to claim 10 characterized in that the insulating means (10) are formed by a gas, for example air, able to substitute, in the inter-electrode space (4), the auxiliary priming (16) when the latter comes into its withdrawal position.   12 -Dispositif according to claim 3 characterized in that the detection means (8) are mounted within the protective device (1) so as to release the insulating means (10), when a malfunction of the spark gap is detected .   13 - Device according to one of the preceding claims characterized in that the detection means (8) are formed by a fuse element (14).   14 - Device according to claims 3 and 13 characterized in that the insulating means (10) are held directly or indirectly by the fuse element (14), so that the melting or breaking of the fuse element (14) causes the release of the insulating means (10).   15 -Dispositif according to claim 2 and one of claims 4 or 8 characterized in that the detection means (8) are located near the insulating part (11) and / or the auxiliary priming (16). ), so as to detect a heating of the latter.   16 -Dispositif according to any one of the preceding claims 20 characterized in that it comprises means for indicating the state of the spark gap.   17 - Device according to claim 16 characterized in that the indicating means are operatively connected to the detection means (8).   18 - Device according to claims 4 and 17 characterized in that the indicating means are mechanically connected to the insulating part (11).   19 -A method of electrical insulation of a surge protection device (1) intended to be connected to an electrical installation and comprising at least two electrodes (2, 3) delimiting an inter-electrode space (4) forming a spark gap , said method comprising successively: - a step (a) of detecting a malfunction of the spark gap, - a step (b) of disconnection of the spark gap vis-à-vis the electrical installation when a failure is detected during step (a).   - Method according to claim 19 characterized in that the step (a) of detection comprises a phase of detection of the heating of the spark gap.   21 Method according to claim 19 or 20 characterized in that the step (b) of disconnection comprises a phase of interposition of insulating means (10) between the electrodes of the protection device (1) so as to increase the isolation between the latter, thereby ensuring the electrical isolation of the protective device (1) vis-à-vis the electrical installation.   22 - Process according to claim 21 characterized in that the interposition phase comprises a phase of increasing the isolation distance between the electrodes (2, 3).   23 - Process according to claim 22 characterized in that the interposition phase comprises a phase of displacement of an insulating part (11) in the inter-electrode space (4) in order to increase the isolation distance between the electrodes (2, 3).   24 - Method according to claim 21 characterized in that the protection device (1) comprises an insulating initiator (16) disposed between the electrodes (2, 3), and in that the interposition phase comprises a substitution phase of the ignition auxiliary (16) by a gas, for example air, the gas then forming the insulating means (10).   25 - Method according to one of claims 19 to 24 characterized in that it comprises a step (c) for indicating to third parties that the protective device (1) is faulty.