Abstract:
A device for protecting an electrical system against surge voltages, comprising one or more protection components ( 10 ), means ( 20 ) for disconnecting the protection component ( 10 ) and means ( 30 ) for visually indicating the state of the component ( 10 ), operationally connected to the disconnection means ( 20 ) and comprising at least one control part ( 40 ) and at least one means ( 50 ) for indicating the state of the protection component ( 10 ), combined with the control part ( 40 ), whereby the relative arrangement of the control part ( 40 ) and the disconnection means ( 20 ) is such that, when the disconnection means are opened ( 20 ), the disconnection means release the control part ( 40 ), thereby allowing the control part to move.

Description:
PRIORITY CLAIM 
   This patent application is the U.S. National Phase of International Application No. PCT/FR2004/000960, filed Apr. 19, 2004, the disclosure of which is incorporated herein by reference in its entirety. 
   FIELD OF THE INVENTION 
   The present invention relates to devices for protecting electrical installations and equipment against transient electrical voltage surges. 
   More particularly, the present invention relates to a device for protecting an electrical installation against voltage surges, the device comprising:
         at least one protection component;   disconnector means for disconnecting the protection component, adapted to disconnect it from the electrical installation and suitable for moving between a closed position in which the protection component is connected, and an open position in which the protection component is disconnected; and   indicator means for indicating the state of the protection component, functionally connected to the disconnector means, and comprising:
           at least one control part distinct from the disconnector means and suitable for moving under the dependency thereof; and   at least one indicator for indicating the state of the protection component and associated with the control part in such a manner that the indicator indicates whether the protection component is in operation or disconnected, as a function of the position of the control part.   
               

   BACKGROUND OF THE INVENTION 
   Devices for protecting electrical installations are commonly used in particular for protecting electrical or electronic apparatus against surges that can be generated by lightning discharges, for example. 
   In general, such devices comprise an active portion formed by one or more protection components, such as a varistor or a spark gap. 
   Varistors are components commonly used for protecting electrical installations or equipment against transient voltage surges. 
   When a surge occurs within the installation, the varistor is subjected to a current shock that has the effect of degrading it and causing it to heat up, making thermal disconnection thereof necessary. 
   The degradation of a varistor is difficult or impossible to predict, insofar as it depends not only on the number of current shocks the varistor has suffered over its lifetime, but also on their amplitude. 
   Consequently, it is difficult to predict, a priori, the lifetime and the degree of aging of a varistor, and users often discover a posteriori that the varistor has been destroyed, such that the installation runs the risk of operating without any protection during some length of latency time. 
   In order to enable a defective varistor to be identified quickly and thus reduce the above-mentioned latency time, it is known to fit each varistor with indicator means suitable for informing a third party that the varistor is out of operation. 
   The varistors that are generally encountered are thus associated with disconnector means adapted to disconnect a varistor once it is in a degraded state and before it heats up excessively, which disconnector means are functionally connected to means for indicating the state of the varistor, that are generally actuated themselves by the disconnector means, and that serve to inform a third party whether the varistor is in operation or is disconnected. 
   The indicator means can thus be in the form of a slider associated with an indicator and suitable for moving in translation under drive from the disconnector means so that its position indicates the state of the varistor, with this being done by putting the indicator, e.g., a colored screen, in register with a viewing window formed in the housing of the protection device. 
   In known protection devices, the slider and the indicator are either secured to the disconnector means, in particular a disconnector blade, or else they are independent therefrom, while being controlled and actuated thereby. 
   In any event, moving the disconnector means towards their open position causes the slider to move in a manner that is controlled or guided by the disconnector means or by independent guide means. 
   Unfortunately, it can happen that the slider or the indicator is impeded in its movement, in particular when the slider and/or the indicator are poorly dimensioned or if the guide means are defective, thus leading to the slider being poorly guided. 
   In this situation, the slider and/or the indicator can impede or even prevent disconnection of the varistor. The varistor then remains connected and the indicator means do not indicate any abnormality in spite of the varistor being badly degraded, and in danger of causing a fire on being overheated. 
   In addition, configurations in which the slider and/or the indicator are actuated and moved under control by the disconnector means generally require the component parts to be accurately dimensioned, firstly so as to avoid slack arising between the parts, and secondly to avoid any risk of the disconnector and/or indicator system jamming. 
   In addition, in order to avoid the slider and/or the indicator slowing down disconnection, disconnector blades are generally designed in such a manner as to present a strong spring effect suitable for overcoming any braking effect exerted by the slider and/or the indicator. 
   Nevertheless, such a measure presents the drawback of weakening the soldered connection between the disconnector blade and the corresponding electrode of the varistor. 
   In general, the mechanical complexity of known devices requires the operations of manufacturing the parts to be very well controlled, thereby significantly increasing the cost of manufacturing such devices. 
   The above remarks naturally apply to devices that use other protection components, in particular spark gaps, in which it can be necessary in certain applications to make use of thermal disconnections. 
   It can thus be seen that there is a need to make a voltage surge protection device that, while being simple and inexpensive in design, is nevertheless capable, in the most reliable and effective manner possible, of disconnecting the protection component in the installation to be protected, and of simultaneously indicating to a third party that the protection component in question is out of operation. 
   SUMMARY OF THE INVENTION 
   Consequently, the features provided by the invention seek to provide a remedy to the various drawbacks listed above and to propose a novel device for protecting electrical installations against voltage surges, which device guarantees disconnection of the protection component in a manner that is particularly reliable and fast. 
   One feature of the invention seeks to provide a novel device for protecting electrical installations against voltage surges, which device is capable of indicating the state of the protection component in a manner that is simple, reliable, and immediate. 
   Another feature of the invention seeks to provide a novel device for protecting electrical installations against voltage surges, which device is of a design that is particularly simple and inexpensive. 
   Another feature of the invention seeks to provide a novel device for protecting electrical installations against voltage surges, which device requires only a limited number of parts both to obtain the connection and disconnection function, and to obtain the indication function. 
   Another feature of the invention seeks to provide a novel device for protecting electrical installations against voltage surges, which device enables the states of a plurality of protection components connected in parallel to be indicated simultaneously and distinguishably. 
   Another feature of the invention seeks to provide a novel device for protecting electrical installations against voltage surges, which device enables an indication about the state of the protection component to be delivered remotely. 
   The features provided by the invention are achieved with the help of a device for protecting an electrical installation against voltage surges, the device comprising:
         at least one protection component;   disconnector means for disconnecting the protection component, adapted to disconnect it from the electrical installation and suitable for moving between a closed position in which the protection component is connected, and an open position in which the protection component is disconnected; and   indicator means for indicating the state of the protection component, functionally connected to the disconnector means, and comprising:
           at least one control part distinct from the disconnector means and suitable for moving under the dependency thereof; and   at least one indicator for indicating the state of the protection component and associated with the control part in such a manner that the indicator indicates whether the protection component is in operation or disconnected, as a function of the position of the control part;
 
the protection device being characterized in that the control part and the disconnector means are relatively disposed in such a manner that during opening of the disconnector means the disconnector means release the control part thus allowing it to move.
   
               

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of the invention appear more clearly and can be seen in greater detail on reading the following description made with reference to the accompanying drawings, given purely by way of non-limiting illustration, and in which: 
       FIG. 1  is a section view of a device in accordance with the invention for providing protection against voltage surges, the device being shown with its protection component in service; 
       FIG. 2  is a section view of the protection device shown in  FIG. 1  when the connection component is disconnected; 
       FIG. 3  is a perspective view of an exemplary protection device in accordance with the invention provided with two varistors connected in parallel; 
       FIG. 4   a  is a diagrammatic view showing a system for indicating the state of two varistors connected in parallel respectively when both varistors are in service; 
       FIG. 4   b  is a diagrammatic view showing a system for indicating the state of two varistors connected in parallel respectively when only one of the varistors is in service; 
       FIG. 4   c  is a diagrammatic view showing a system for indicating the state of two varistors connected in parallel respectively when both varistors are disconnected; 
       FIG. 5   a  is a diagram showing an improved variant of the system for indicating the states of two varistors connected in parallel respectively when both varistors are in service; 
       FIG. 5   b  is a diagram showing an improved variant of the system for indicating the states of two varistors connected in parallel respectively when only one of the varistors is in service; 
       FIG. 5   c  is a diagram showing an improved variant of the system for indicating the states of two varistors connected in parallel respectively when both varistors are disconnected; 
       FIG. 6   a  is a diagram showing a variant of the protection device in accordance with the invention in which the device is adapted to be connected to a remote signaling system, the figure showing a first state in which both varistors are in service; 
       FIG. 6   b  is a diagram showing a variant of the protection device in accordance with the invention in which the device is adapted to be connected to a remote signaling system, the figure showing a second state in which one of the varistors is in service; 
       FIG. 6   c  is a diagram showing a variant of the protection device in accordance with the invention in which the device is adapted to be connected to a remote signaling system, the figure showing a second state in which the second of the varistors is in service; 
       FIG. 7  is a perspective view of a socket suitable for having a protection cell in accordance with the invention plugged thereto; and 
       FIG. 8  is a perspective view showing a preferred embodiment of the protection device in accordance with the invention combining a direct indicator member and an indicator for signaling remotely. 
   

   DESCRIPTION OF THE INVENTION 
   The device of the invention for providing protection against voltage surges is designed to be connected in parallel with the electrical equipment or the installation to be protected. The term “electrical installation” refers to any type of apparatus or network that might be subjected to voltage disturbances, in particular to transient voltage surges due to lightning. Under such circumstances, the device is thus formed by a lightning arrestor. 
   The device of the invention for providing protection against voltage surges is advantageously designed to be placed between one of the phases of the installation that is to be protected and ground. 
   Without going beyond the ambit of the invention, it is also possible to envisage that instead of being connected in parallel between one of the phases and ground, the device is connected between neutral and ground, between a phase and neutral, or between two phases (for differential protection). 
   The protection device comprises at least one protection component  10  forming the active portion of a lightning arrestor, for example, that is to protect the electrical installation. 
   In the description below, it is considered that each protection component  10  present in the device is formed by a varistor, it being understood that the use of a varistor is mentioned purely by way of example and does not constitute any kind of limitation on the invention. 
   The protection device provided by the invention comprises at least one varistor  10 , e.g., one or two varistors  10 , disconnector means  20  for each varistor, which disconnector means are sensitive to the degree of varistor aging and are adapted to disconnect each varistor individually from the electrical installation when the varistor is found to be in a degraded state. 
   The protection device provided by the invention also comprises indicator means  30  for indicating the state of each varistor  10  and functionally connected to the disconnector means  20 . 
   Advantageously, the protection device is formed by a protection cell  1  capable of having one or more modules  2 , each containing a varistor  10  ( FIGS. 1 ,  2 , and  3 ). Each module  2  advantageously comprises a base  3  of an electrically insulating material, a varistor  10 , two electrically conductive electrodes  4  constituting the poles of the varistor  10 , and disconnector means  20 . 
   In unpluggable versions of the device shown in  FIGS. 1 and 2 , each module  2  is adapted to be electrically connected to a socket  400  ( FIG. 7 ) via connection pins  8 ,  9  for inserting in orifices  405 ,  406  provided in the socket  400 . 
   Thus, one of the poles of the varistor  10  is directly connected to a connection pin  8 , the other pole of the varistor being connected to an electrode  4  which is soldered to the disconnector means  20  that are in permanent electrical contact with the other connection pin  9 . 
   The disconnector means  20  are preferably formed by a thermal disconnector, such as, for example, a disconnector blade  21  in thermal and electrical contact with the associated varistor  10 , so that any heating of the varistor associated with the varistor reaching the end of its lifetime leads to the disconnector blade  21  opening, thereby isolating the varistor from the lines to be protected. 
   The disconnector means  20  are thus suitable for moving between a “closed” position in which the varistor  10  is connected to the electrical installation or the network, and an open position in which the varistor  10  is disconnected from the electrical installation. These two positions are shown in  FIGS. 1 and 2 . 
   Advantageously, the disconnector blade  21  extends between two ends  21 A,  21 B, one of the ends  21 A preferably being held to one of the electrodes  4  by solder that melts on being heated. The end  21 A of the disconnector blade  21  is thus preferably soldered while under stress so that when the varistor  10  reaches the end of its lifetime, it heats up and causes the solder to melt and break, so that once broken it releases the disconnector blade  21 . 
   Because of its intrinsic elasticity, the disconnector blade  21 , and specifically the end  21 A of the disconnector blade  21 , then moves away from the electrode  4 , while the other end  21 B remains stationary, as shown in  FIG. 2 . 
   There follows a detailed description of the structure of the indicator means  30 . 
   The indicator means  30  are adapted to inform a third party about the state of the varistor(s) contained in the protection cell  1 . These indicator means  30  are functionally connected to the disconnector means  20 , i.e., there are intermediate means enabling the position of the disconnector means  20  to be associated with the indication provided by the indicator means  30 . 
   According to the invention, the indicator means  30  comprise, for each protection cell  1 , a control part  40  that is distinct from the disconnector means  20  and that is suitable for moving under the dependency thereof. This control part  40  advantageously provides the functional connection between the disconnector means  20  and the indicator means  30 . 
   The indicator means  30  also comprise an indicator  50  for indicating the state of the varistor  10  associated with the control part  40 , such that, as a function of the position of the control part  40 , the indicator  50  indicates whether the varistor  10  is in service or is disconnected. 
   According to the invention, the control part  40  and the disconnector means  20  are disposed relative to one another in such a manner that, when the disconnector means  20  open, they release the control part  40 , thus allowing it to move freely, i.e., in a manner that is not controlled by the disconnector means  20 . 
   Once released, the control part  40  is thus free to move, i.e., it is neither actuated nor guided in its movement by the disconnector means  20 . 
   In particularly advantageous manner, while the disconnector means  20  are in the closed position, they are mounted in such a manner as to form an abutment against the control part  40 . Thus, the control part  40  advantageously includes a bearing zone  40 A which, while the disconnector means  20  are in the closed position, comes to bear thereagainst ( FIG. 1 ). 
   The disconnector blade  21  thus performs three functions:
         in normal operation, it provides an electrical connection to the varistor  10 ;   at the end of the lifetime of the varistor  10 , it serves to disconnect the varistor; and   finally, it also serves to release the indicator means  30 , thus leading to a change in the indication concerning the state of the varistor  10 .       

   Advantageously, the control part  40  and the disconnector means  20  are disposed in such a manner that while the disconnector means  20  are in the closed position ( FIG. 1 ), the control part  40  is under resilient stress and comes to bear against the disconnector means  20 , in particular via its bearing zone  40 A, thereby exerting drive stress on the disconnector means  20 , urging them towards the open position. 
   The indicator means  30  thus perform two functions:
         firstly, via the indicator  50 , they serve to provide an indication concerning the state of the varistor  10 ; and   secondly, via the control part  40 , they contribute to disconnecting the varistor  10  by urging the disconnector means  20 , and in particular the disconnector blade  21 , towards the open position.       

   Such a configuration thus serves to bring forward and make secure the disconnection of the protection component. It also makes it possible to use a disconnector blade  21  that presents only a moderate spring effect, and thus to reduce the risk of the thermal release solder being weakened mechanically. 
   The design of the protection device of the invention, and in particular the way the indicator means  30  for indicating the state of the varistor are configured, thus makes it possible to ensure that the protection component is disconnected quickly and reliably, by virtue of the small number of parts that co-operate with one another and the limited number of points of contact between these parts. This reliability is further increased by the fact that the indicator means  30  are separate from the disconnector means s 20 . 
   In addition, because of the simultaneous or almost simultaneous movement of the indicator means  30  and of the disconnector means  20 , a third party can see very quickly that a varistor has been disconnected. 
   In particularly advantageous manner, and as shown in  FIGS. 1 and 2 , the control part  40  is formed by a slider  41  of electrically insulating material that is suitable for moving in a substantially rectilinear direction F. 
   Advantageously, the front portion  41 A of the slider  41  is specially designed to bear against the disconnector means  20 , firstly when they are in the closed position, and secondly while they are opening, so that the slider  41  is continuously in contact with the disconnector means  20 . 
   In the exemplary embodiment of the invention shown in  FIGS. 1 and 2 , the indicator means  30  are advantageously formed by mechanical means mounted in a housing  60 , which housing also contains the varistor  10 . 
   In particularly advantageous manner, the indicator means  30  also comprise resilient means  70  such as a spring adapted to exert a return force on the control part  40  and responsible for moving it. 
   As shown in  FIGS. 1 and 2 , the resilient means  70  is preferably interposed between the control part  40  against which it bears resiliently, and a stationary abutment, e.g., formed by one of the inside walls of the housing  60 . 
   The resilient means  70  is thus advantageously adapted to occupy a compressed position when the control part  40  is stressed longitudinally, i.e., in a direction that is substantially parallel to the travel direction F and a rest position, on the control part  40  being released from the disconnector means  20  ( FIG. 2 ). The resilient means  70  thus constitutes prestress means acting on the control part  40 . 
   In the exemplary embodiment shown in  FIGS. 1 and 2 , the slider  41  extends longitudinally in the direction F, and is preferably sufficiently rigid for its front portion  41 A to be capable of bearing firmly against the disconnector means  20 , and more particularly against the end  21 A of the disconnector blade  21 . 
   When the solder breaks, under the effect of the varistor  10  heating, the end  21 A of the disconnector blade  21  moves in the direction F and thus ceases to constitute an obstacle or an abutment against the control part  40 . The initially compressed resilient means  70  then tends to relax ( FIG. 2 ), thereby driving the slider  41  to move in the direction F. As it moves, the slider  41 , still bearing against the end  21 A of the disconnector blade  21 , tends to force the blade towards its open position, thereby actively contributing to disconnecting the protection component. In particularly advantageous manner, the return force exerted by the resilient means  70  on the end  21 A of the disconnector blade  21  is preferably greater than the opposing resistance of the disconnector blade  21  so as to constrain the blade to move further away from the electrode  4 . 
   In this exemplary embodiment of the invention, the indicator  50  is advantageously formed by an indicator member, preferably by a panel  51 , e.g., a rectangular panel that is preferably disposed on the slider  41 . The panel  51  may be constituted by a piece of insulating plastics material, e.g., stuck to the slider  41 , however it could equally well be formed merely by a colored strip painted on the slider  41 . The panel  51  is more advantageously disposed in such a manner as to move simultaneously with the control part  40  so as to be in register with a window  61  formed through one of the faces  60 B of the housing  60  situated remote from the base  3  so as to obtain a different visual appearance through the window  61  depending on the position of the control part  40 . 
   Thus, when the disconnector means  20  are in the closed position ( FIG. 1 ), the resilient means  70  is compressed and the panel  51  is in a position where it is offset away from the window  61 , such that in this configuration it cannot be seen from the outside. Thus, when looking through the window  61 , it is the slider  41  that is seen and, by way of example, it may present a green color to inform third parties that the varistor is in operation. 
   In contrast, when the disconnector means  20  are in the open position, as shown in  FIG. 2 , the panel  51  lies in the field of the window  61 . It can then be seen from the outside, and preferably presents a colored appearance, e.g., red, informing third parties that the varistor is disconnected. 
   In a second exemplary embodiment of the invention, shown in  FIG. 3 , the device comprises a protection cell  1  having first and second varistors  10  connected in parallel and respectively associated with first and second disconnector means  20 A and  20 B. 
   In this exemplary embodiment, the indicator means  30  are preferably functionally connected to the first and second disconnector means  20 A,  20 B so as to provide differing indications about the states of each of the varistors  10  taken individually ( FIGS. 4   a ,  4   b ,  4   c ). 
   In this exemplary embodiment, the control part  40  is preferably formed by a slider  41  provided with a front portion  41 A mounted to move resiliently between:
         an initial position ( FIG. 4   a ) corresponding to a state in which both protection components are connected, in which the slider  41  is held in position simultaneously by both of the disconnector means  20 A,  20 B, its front portion  41 A bearing against both of them;   an intermediate position ( FIG. 4   b ) offset from the initial position, corresponding to a state in which only one of the disconnector means  20 A,  20 B has disconnected, in which the slider  41  is held in position by the closed disconnector means  20 A; and   a final position ( FIG. 4   c ) offset relative to the intermediate position, corresponding to both disconnector means  20 A,  20 B being in the disconnected state. In this final position the slider  41  is not necessarily held in place by the disconnector means  20 A,  20 B but may come into abutment against them, as shown in  FIG. 4   c.          

   In this exemplary embodiment of the invention, the indicator  50  is preferably formed by an indicator member, preferably being a panel  51  mounted on or made integrally with the slider  41  and preferably located at its end remote from the front portion  41 A so as to move in register with the viewing window  61 . 
   The panel  51  is preferably divided into two zones  51 A and  51 B that are disposed in such a manner that when the disconnector means  20 A,  20 B are in the closed position ( FIG. 4   a ), the zone  51 A that is preferably colored green lies substantially in register with the viewing window  61 . In this way, the window appears green, thus indicating that the protection components are in operation. In contrast, when both disconnector means  20 A,  20 B are in the open position ( FIG. 4   c ), it is the other zone  51 B, preferably colored red, that is in register with the window  61 . In this configuration, the window  61  appears red, thus indicating that both varistors are disconnected. In the intermediate position shown in  FIG. 4   b , the window  61  is occupied simultaneously by at least a portion of each of the two zones  51 A and  51 B such that a portion thereof, e.g., half of its area, appears to be red while another portion or half appears to be green. The visual appearance of the window  61  thus informs third parties that only one of the varistors is disconnected. 
   The amplitude of the movement of the slider  41  is thus adjusted in such a manner as to generate a different visual appearance through the window  61  as a function of the configuration of the disconnector means  20 A,  20 B. 
   In the exemplary embodiment shown in  FIGS. 4   a ,  4   b , and  4   c , the slider  41  is resiliently stressed by resilient means  70  urging it to bear via its front portion  41 A against the disconnector means  20 A,  20 B ( FIG. 4   a ). 
   In particularly advantageous manner, the control part  40 , and specifically the slider  41 , has two bearing zone stages  42  and  43  placed one behind the other in the travel direction F of the control part  40  so as to hold it successively in the initial position and in the intermediate position. The structure of the control part  40  thus serves to generate stepwise movement thereof between the initial, intermediate, and final positions. 
   In even more preferred manner, the control part  40  has a “downstream” pair of bearing zones  42 A,  42 B designed to come into abutment in the initial position ( FIG. 4   a ) against the two disconnector means  20 A,  20 B. 
   The control part  40  also comprises a pair of “upstream” bearing zones  43 A,  43 B located upstream from the downstream pair of bearing zones  42 A,  42 B relative to the travel direction F of the control part  40 , in such a manner that in the intermediate position ( FIG. 4   b ), one of the upstream bearing zones  43 A comes into abutment against the corresponding disconnector means  20 A that is in the closed position. 
   Naturally, if the other disconnector means  20 B were to be the first to open, then it would be the other upstream bearing zone  43 B that would come into abutment against the corresponding disconnector means  20 B. 
   In this configuration, the indicator means  30  advantageously present symmetry about the plane S defining the separation between the two varistors. 
   In more particularly advantageous manner, the upstream bearing zones  43 A,  43 B are preferably formed by fingers  44  projecting from opposite sides of the control part  40  and extending in a direction that is substantially perpendicular to the main travel direction F of the control part  40 . 
   In preferred manner, the device includes means for guiding the movement of the control part  40  that are adapted to allow said part to move angularly when one of the disconnector means  20 A,  20 B opens, so as to allow the corresponding downstream bearing zone  42 A,  42 B to go past the other disconnector means  20 A,  20 B. The means for guiding movement are advantageously formed by the side walls  60 C,  60 D of the housing  60 . The slider  41  is then advantageously placed inside the housing  60  in such a manner as to maintain sufficient clearance between the outline of the slider  41  and the walls  60 C,  60 D to allow for such angular movement. 
   Thus, in order to go from the initial position shown in  FIG. 4   a  to the intermediate position shown in  FIG. 4   b , the slider  41  needs to go past one of the disconnector means  20 A that has remained in the closed position, and to do this it must turn a little through an angle α that enables it to disengage from the disconnector means  20 A. The slider  41  can then continue its stroke until the upstream bearing zone  43 A comes into abutment against the disconnector means  20 A. 
   In order to make it even easier for the slider  41  to go past the disconnector means  20 A that have remained in the closed position, the slider is provided with disengagement means  45 . The disengagement means  45  are preferably constituted by ramps formed on either side of the slider  41  in the vicinity of its front portion  41 A, these ramps thus forming the downstream bearing zones  42 A,  42 B. 
   In the same manner as in the above-described exemplary embodiment shown in  FIGS. 1 and 2 , the resilient means  70  likewise serve to bring forward and make safe the disconnection of the varistors, ensuring that the front portion  41 A of the slider  41  is caused to bear under stress against the disconnector means  20 A,  20 B. 
   Another exemplary embodiment of the invention is described below with reference to  FIGS. 5   a ,  5   b , and  5   c.    
   In this exemplary embodiment, the indicator means  30  advantageously include guide means  80  adapted to cause the control part  40  to move along a predetermined path formed by combining a movement in rotation with a movement in translation. 
   The control part  40  is subjected to resilient stress by the resilient means  70  interposed between the control part  40  and an abutment  62  mounted in stationary manner within the housing  60 . 
   Under the action of the resilient means  70 , such as a spring, the control part  40  comes to bear against the disconnector means  20 A,  20 B. For this purpose, the control part  40  has two end portions  46 A,  46 B, e.g., in the form of projecting horns, adapted to bear against respective ones of the disconnector means  20 A,  20 B when they are both in the closed position ( FIG. 5   a ). 
   The guide means  80  of the control part  40  are advantageously formed by a stud  81 , preferably placed on the control part  40 , and a corresponding groove  82 , preferably having a V-shape, within which the stud  81  can move when the control part  40  passes successively between its initial, intermediate, and final positions shown in  FIGS. 5   a ,  5   b , and  5   c.    
   This exemplary embodiment operates as follows. 
   In the initial position shown in  FIG. 5   a , the control part  40  is in stable equilibrium and is interposed between the resilient means  70  and the disconnector means  20 A,  20 B. 
   When one of the disconnector means  20 B moves into the open position, it releases the control part  40 , at least in part, so that it then turns through an angle β until it comes into contact with one of the walls  60 D of the housing  60 , as shown in  FIG. 5   b.    
   In this intermediate position, the control part  40  is likewise in a stable position and continues to bear resiliently against the other disconnector means  20 A via its end portion  46 A. The displacement of the control part  40  between the initial position ( FIG. 5   a ) and the intermediate position ( FIG. 5   b ) follows a predetermined path that is directly associated with the path of the stud  81  within the groove  82 . 
   In this exemplary embodiment, the indicator  50  is preferably formed by an indicator member such as a panel  51  that is preferably disposed at one of the ends of the control part  40  so as to move in register with the window  61  formed in the housing  60 . Thus, in the initial position shown in  FIG. 5   a , the indicator panel  51 , preferably green in color, is situated substantially in register with the window  61 , thus indicating that all of the varistors are connected. 
   In the intermediate position shown in  FIG. 5   b , the control part  40  is offset angularly away from its initial position so that the indicator panel  51  is likewise offset away from the window  61 . The window then presents a different visual appearance, indicating that one of the varistors has been disconnected. By way of example, and as shown in  FIG. 4   b , a portion of the viewing window  61  may remain masked by the control part  40 , thus informing third parties that only some of the protection components are disconnected. 
   When the other disconnector means  20 A in turn move to the open position, the control part  40  tends to move in a substantially rectilinear direction F under drive from the resilient means  70 , thereby completely disengaging the viewing window  61  which then takes on a uniform visual appearance, e.g., red in color, indicating that all of the protection components are disconnected and need to be replaced. 
   The movement of the control part  40  between the intermediate and final positions is guided by the stud  81  co-operating with the groove  82 , the stud  81  moving in substantially rectilinear manner in one of the branches of the V-shape formed by the groove  82 . 
   Such a configuration presents the advantage of not interfering with disconnection in the event of the indicator means  30  being jammed. 
   Another advantage of this configuration is that it also makes it possible for the resilient means  70  to participate in disconnection by exerting thrust on the control part  40 , thus encouraging the disconnector means  20 A,  20 B to move when the solder melts. 
   Another advantage of this configuration is that it is relatively insensitive to any vibration or impacts that can occur, for example during transport, since the control part  40  can always return to its initial position under the effect of the return force exerted by the resilient means  70 . 
   In another exemplary embodiment of the invention shown in  FIGS. 6   a ,  6   b  and  6   c , the indicator  50  is formed by a remote indicator (not shown) that is functionally connected to the control part  40  via a remote signaling system. The indicator  50  may thus be formed by a visible indicator, an audible indicator, or by any other type of sensory indicator. 
   In contrast, unlike the various exemplary embodiments described above, the indicator  50  is not mechanically connected to the control part  40  but is remote therefrom, i.e., it is connected thereto by means other than mechanical means, and in particular by remote signaling means. Thus, the indicator is not situated in the direct proximity of the housing  60  but at a non-negligible distance therefrom. 
   This exemplary embodiment of the device is shown for two varistors connected in parallel, but it could naturally also be applied to a device having only one varistor. 
   In this exemplary embodiment, the control part  40  is secured to two pins  52 ,  53  for engaging in corresponding recesses  401 ,  402  formed in a socket  400  ( FIG. 7 ) that is to receive the protection cell  1 . As is well known to the person skilled in the art, the pins  52 ,  53  are for co-operating with a mechanism disposed within the socket  400  and suitable for tripping a microswitch so as to signal changes of state in the device to third parties situated remotely from the housing  60 . Thus, when the two pins  52 ,  53  are in a low position corresponding to a state in which both varistors are connected ( FIG. 6   a ), the mechanism and the associated remote signaling system provide a remote signal that indicates that both of the varistors of the device are connected. 
   In contrast, when one of the varistors is disconnected, as shown in  FIG. 6   c , both pins  52 ,  53  move to a high position, thereby generating electrical signals suitable for indicating remotely that at least one of the varistors of the device is disconnected. 
   According to a particularly advantageous characteristic of the invention, the control part  40  is secured to the pins  52 ,  53  in such a manner that movement thereof leads simultaneously to substantially identical movement of the pins  52 ,  53  within passages  62 ,  63  formed through the bottom wall  60 A of the housing  60 . 
   In particularly advantageous manner, the control part  40  can be formed by a slider, preferably being in the form of an elongate rod provided with a front portion  40 A in the form of a disk or a sphere for bearing against a fold  20 C formed in the disconnector means  20 A,  20 B and designed to constitute an abutment against the control part  40 . 
   On opening, the disconnector means  20 A,  20 B release the control part  40 , thus allowing it to move freely. Otherwise, when the disconnector means  20 A,  20 B are in the closed position ( FIG. 6   a ), the control part  40  is under stress between the resilient means  70  urging it in the direction F, and the disconnector means  20 A,  20 B, and more precisely the folds  20 C formed thereon. 
   The folds  20 C preferably extend in a plane that is substantially perpendicular to the plane in which the disconnector blades  21  extend. In even more preferable manner, the folds  20 C may extend obliquely relative to the disconnector blades  21 , such that the front portion  40 A of the control part  40  exerts driving stress thereagainst tending to push the disconnector blades  21  towards their open positions. 
   The control part  40  and the associated resilient means  70  then constitute means for providing assistance in disconnecting the protection components of the device. 
   In particularly advantageous manner, the control part  40  is sufficiently flexible to allow its front portion  40 A to move angularly. As shown in  FIGS. 6   a ,  6   b , and  6   c , the folds  20 C formed on the disconnector means  20 A,  20 B project so as to form abutments against the front portion  40 A of the control part  40 . Thus, when one of the disconnector means  20 A goes to the open position, the control part  40 , and specifically the front portion  40 A thereof, needs to disengage from the projecting portion of the fold  20 C of the disconnector means  20 B that has remained in the closed position so as to be able to go past it. The lateral flexibility of the control part  40  then allows it to move angularly sufficiently to enable its front portion  40 A to go past the abutment formed by the fold  20 C under drive from the resilient means  70 . In particularly advantageous manner, the control part  40  includes a narrowing  48  in its section imparting flexibility thereto. 
   The operation of the device is described below with reference to  FIGS. 6   a ,  6   b , and  6   c.    
   When both disconnector means  20 A,  20 B, and specifically the disconnector blade  21 , are in the closed position, as shown in  FIG. 6   a , the control part  40  is advantageously resiliently stressed between the resilient means  70  and the disconnector means  20 A,  20 B, and more precisely the abutment formed by their folds  20 C. As soon as one of the disconnector means  20 A,  20 B opens, e.g., the disconnector means  20 A, the control part  40  is released and driven to move by the resilient means  70 . The control part  40  then moves in the main direction F together with a small amount of angular offset γ so as to disengage from the disconnector means  20  that has remained in the closed position with its fold  20 C projecting against the front portion  40 A of the control part  40 . Once the control part  40  has gone past this obstacle it is free to move towards its final position shown in  FIG. 6   c.    
   On moving from the initial position towards the final position, the control part  40  simultaneously entrains the pins  52 ,  53  out form their recesses  401 ,  402  within the socket  400 , thus causing a new signal to be triggered remotely indicating that at least one of the varistors of the device is disconnected. 
   In an even more preferred embodiment of the invention, as shown in  FIG. 8 , the device comprises a plurality of indicator means, i.e., both direct indicator means and remote indicator means. 
   For this purpose, the device comprises a first control part  403  associated with a direct indicator member such as an indicator panel  51 , and also a second control part  404  associated with a remote-signaling indicator (not shown), the first and second control parts  403 ,  404  being adapted to co-operate independently from each other with the disconnector means  20 A,  20 B. Thus, the configuration associating the first control part  403  with the direct indicator member could be of the type shown in  FIGS. 1 ,  2 ,  4   a ,  4   b ,  4   b ,  5   a ,  5   b ,  5   c . The configuration associating the second control part  404  with the remote-signaling indicator may be of the type shown in  FIGS. 6   a ,  6   b ,  6   c.    
   In this embodiment of the invention, opening the disconnector means  20 A,  20 B leads almost simultaneously to the release of the first and second control parts  403 ,  404 , thereby indicating that at least one varistor is disconnected, both by means of the indicator panel  51  and by means of the remote-signaling indicator. 
   Such a device thus makes it possible within a single housing  60  to associate two distinct control parts  403 ,  404  suitable for actuating two complementary indicator means concerning the state of the protection components, i.e., proximity indicator means e.g., in the form of an indicator panel  51 , and remote indicator means, advantageously in the form of a remote-signaling indicator, e.g., a visible indicator an audible indicator. 
   The protection device in accordance with the invention thus makes it possible by means of a particularly simple configuration of the indicator means  30  to provide not only reliable and effective disconnection of the varistors when they are in a degraded state, but also makes it possible simultaneously for a third party to see the state of the varistors, while also limiting any risk of the mechanism ceasing or indeed any problems associated with guiding the parts. 
   Because of the small area of contact between the functional parts, any risk of one part becoming jammed by another is significantly reduced. 
   The application of the invention lies in electrical devices for providing protection against transient voltage surges.