(19)
(11)EP 3 255 274 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
04.11.2020 Bulletin 2020/45

(21)Application number: 17000950.0

(22)Date of filing:  06.06.2017
(51)International Patent Classification (IPC): 
F03D 1/06(2006.01)
H02G 13/00(2006.01)
F03D 80/30(2016.01)

(54)

LIGHTNING SYSTEM FOR WIND TURBINE BLADES WITH OPTIMIZED MEANS FOR INJECTING LIGHTNING CURRENTS IN CONDUCTIVE COMPONENTS OF THEIR SHELLS

BLITZSCHUTZSYSTEM FÜR WINDTURBINENSCHAUFELN MIT OPTIMIERTEN MITTELN ZUR INJEKTION VON BLITZSTRÖMEN IN LEITENDE KOMPONENTEN IHRER SCHALEN

SYSTÈME DE PROTECTION DE FOUDRE POUR PALES D'ÉOLIENNE DOTÉ DE MOYENS OPTIMISÉS POUR INJECTER DES COURANTS DE FOUDRE DANS LES COMPOSANTS CONDUCTEURS DE LEURS COQUES


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 07.06.2016 ES 201600471

(43)Date of publication of application:
13.12.2017 Bulletin 2017/50

(73)Proprietor: SIEMENS GAMESA RENEWABLE ENERGY INNOVATION & TECHNOLOGY, S.L.
31621 Sarriguren (Navarra) (ES)

(72)Inventors:
  • March Nomen, Victor
    31621 Sarriguren (Navarra) (ES)
  • Madoz Zabalegui, Juan
    31621 Sarriguren (Navarra) (ES)

(74)Representative: Aspacher, Karl-Georg 
Siemens Gamesa Renewable Energy GmbH & Co. KG Otto-Hahn-Ring 6
81739 München
81739 München (DE)


(56)References cited: : 
EP-A1- 2 930 355
DE-A1- 4 445 899
US-A1- 2013 149 153
EP-A2- 2 458 207
JP-A- 2010 059 813
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    FIELD OF THE INVENTION



    [0001] The invention relates to a lightning protection system for wind turbine blades with electrically conductive components in their shells and in particular to the injection of lightning currents in said electrically conductive components.

    BACKGROUND



    [0002] Because of the height reached by wind turbines and their location on elevated areas, they have a high risk of receiving lightning strikes particularly at its blades. Therefore the blades must have a lightning protection system and any additional system installed in them containing conductive elements (metal parts, sensors, beacon systems, etc.) must be protected against direct lightning strikes and indirect effects due to the electromagnetic field induced by them.

    [0003] The primary components of lightning protection system for wind turbine blades are a series of metal receptors mounted on the surface of the blade and a down conductor to drive the lightning from the receptors to the blade root. The evolution in wind turbines development together with the growth of the power provided by them has led to new generations of wind turbines having increasing dimensions both in tower height and rotor diameter. Blade lengthening involves an increase in rigidity. The use of more carbon fiber laminates in the manufacturing of blades is a conventional way to achieve this rigidity whether as "caps" joined to the shells or forming part of the shell structure. However, carbon fiber laminates are conductors and must therefore be connected in parallel with the down conductor of the lightning protection system to prevent internal arcing between the down conductor and the laminates as well as direct lightning strikes on the carbon laminates.

    [0004] WO 2006/051147 A1 describes a lightning protection system comprising means for equipotentializing the carbon fiber laminates with the lightning protection system including derivations from the down conductor to connect it directly to the carbon fiber laminates arranged in the upper and lower parts of the beam of the blade (see Figure 1a). An auxiliary cable 5 derived from down-conductor 6 is connected by a bolted joint to a metal plate 3 in direct contact with the carbon fiber layers of the beam flanges 4 that serves as a means for injecting current into them. The electrical connection can be improved by using conductive resins shaped as carbon nanofibers or nanotubes 11 added both between the metal plate 3 and the carbon fiber layers as in the vicinity of the metal plate 3. Because the high frequency of the lightning current, the local current distribution in the connection, causes that the effective connection area is less than the physical, being the current density much greater in area A near the auxiliary cable 5 that in area B far away from it. The present invention is directed to solving that problem.

    [0005] EP2930355 also discloses a lightning protection system with a potential compensation element and US2013/149153 discloses a wind turbine blade for a wind turbine having a lightning protection system comprising a metal foil.

    SUMMARY OF THE INVENTION



    [0006] The invention provides a lightning protection system of a wind turbine blade whose shells include an electrically conductive component embedded into them having injection means of lightning currents in said conductive component that achieve a balanced distribution of the current in the injection zone.

    [0007] Such injection means comprise a current receptor element of lightning currents arranged over an area of the shells close to the electrically conductive component and a current injection element arranged over the electrically conductive component that are connected between them by at least two distribution cables.

    [0008] Such lightning currents may come from a ground down conductor that runs through the inside of the blade or from cables connected directly to blade lightning receptors.

    [0009] In one embodiment, the conductive component is a "cap" embedded in a shell and the injection means comprise a current receptor element and a current injection element that are connected by two distribution cables and configured to prevent areas with high current density in the current injection element.

    [0010] In one embodiment, the conductive component is a carbon fiber laminate embedded in a shell and the injection means comprise a current receptor element and a current injection element which are connected by three distribution cables and configured to prevent areas with high current density in the current injection element.

    [0011] In one embodiment, the conductive component in a metal mesh embedded in a shell and the injection means comprise a current receptor element and a current injection element which are connected by four distribution cables and configured to prevent areas with high current density in the current injection element.

    [0012] Other features and advantages of the present invention will be understood from the following detailed description in relation with the enclosed figures.

    BRIEF DESCRIPTION OF FIGURES



    [0013] 

    Figures 1a and 1b are, respectively, a perspective view and a schematic plan view of a known lightning protection system of a wind turbine blade showing how a lightning current is injected into a "cap" of the beam of the wind turbine blade.

    Figure 2a is a schematic plan view of a lightning protection system of a wind turbine blade according to the invention showing how a lightning current is injected into a "cap" attached to a shell of a wind turbine blade. Figure 2b is an electrical sketch of said current injection and Figure 2c shows graphically the distribution of currents at characteristic frequencies of lightning (kHz).

    Figure 3a is a schematic plan view of a lightning conductor system a wind turbine blade according to the invention showing how a lightning current is injected into carbon fiber a laminate of embedded in a shell of a wind turbine blade. Figure 3b is an electrical sketch of said current injection and Figure 3c shows graphically the distribution of currents at characteristic frequencies of lightning (kHz).

    Figures 4a and 4b are schematic plan views of a lightning protection system of a wind turbine blade according to the invention showing how a lightning current is injected into a metal mesh integrated in a shell of the wind turbine blade.


    DETAILED DESCRIPTION OF THE INVENTION



    [0014] The present invention relates to lightning protection systems of wind turbine blades whose shells include electrically conductive components and, in particular, shells of the following types:
    • shells incorporating "caps" made of carbon fiber laminates;
    • shells whose structure includes carbon fiber laminates (often called structural shells);
    • shells whose structure includes metal meshes, as in the case of shells with radar absorbing material.


    [0015] In the first of the mentioned types, the typical lightning protection system comprises (see Figure 1b) a down conductor cable 21 of lightning currents received by one or more lightning receptors typically located at the tip of the blade which runs through the inside of the blade 20, nearest, normally, to its trailing edge 23 than to its leading edge 25, connected to a metal plate 24 arranged over the "cap" 22 attached to the shell. The black square indicates the connection of the cable derived from the down conductor 21 with the metal plate 24 and the grey circumference of thick line the area of high current density.

    [0016] In the embodiment of the invention illustrated in Figures 2a, 2b and 2c, the injection means of lightning currents derived from down conductor cable 21 via an auxiliary cable (hereinafter called input cable) in the "cap" 22 comprise a current receptor element 27 and a current injection element 28 (made for example of metal plates) connected by two distribution cables 31, 32 of greater inductance than the current receptor element. The current injection element 28 is arranged over the "cap" 22 and the current receptor element 27, connected to the input cable, is located in a close area to it, located preferably at a distance lesser than 5m.

    [0017] The configuration described allows improving the current distribution in the injection zone as indicated by the thickness of the grey circumferences compared with that of the circumference of Figure 1b. The peak current can be reduced to half and, thus, the value of the electric field is reduced in the local injection area with the consequent reduction of the temperature increase.

    [0018] By performing a simulation of the electric sketch of Figure 2b for a current receptor element 27 of an inductance L=0.1µH (and resistance R) and two distribution cables 31, 32 of inductances L1=1µH and L2=1µH has being found that an almost equal distribution of the intensity of the lightning current It received by the current receptor element 27 between the currents 11 and 12 transmitted by distribution cables 31, 32 can be achieved as it is also shown in Figure 2c: It curve 35, 11 and 12 curves 36, 37.

    [0019] In the embodiment of the invention illustrated in Figures 3a, 3b and 3c, applicable to a wind turbine blade 20 with structural shells and beams 15, 17, the injection means of lightning currents transmitted by the input cable on the carbon fiber laminate 42 of a shell comprise a current receptor element 47 and a current injection element 48 (made for example of metal plates) connected by three distribution cables 51, 52, 53 (because the carbon fiber laminate 42 normally has a greater width than the "cap" 22 of Figure 2a) of greater inductance than current receptor element 47. The current injection element 48 is arranged over the carbon fiber laminate 42 and the current receptor element 27, connected to the cable input, is located in a close area to it.

    [0020] This configuration improves the current distribution in the injection area analogously to the above embodiment.

    [0021] Performing a simulation of the electrical sketch of Figure 3b for a current receptor element 47 of inductance L = 0.1µH (and resistance R) and distribution cables 51, 52, 53 of inductances L1=1µH, L2=1µH y L3=1µH has been found that an almost equal distribution of the intensity of the lightning current It received by the current receptor element 27 between the currents 11, 12 and 13 transmitted by distribution cables 51, 52, 53 can be achieved as it is also shown in Figure 3c: It curve 55, 11, 12 and 13 curves 56, 57, 58.

    [0022] In the embodiment of the invention illustrated in Figure 4a, applicable to a wind turbine blade 20 with shells including a metal mesh 62 (which is part of a radar absorbing structure) and beams 15, 17, the injection means of lightning currents transmitted by the input cable in the metal mesh 62 comprise a current receptor element 67 and a current injection element 68 (made for example of metal plates) connected by four distribution cables 71, 72, 73, 74 (because the metal mesh 62 normally have a greater width than the "cap" 22 of Figure 2a and the carbon fiber laminate of Figure 3a) of greater inductance than the current receptor element 67.

    [0023] The current injection element 68 is arranged over the metal mesh 62 and the current receptor element 67, connected to the cable input, is located in a close area to it.

    [0024] This configuration improves the current distribution in the injection area analogously to the above embodiment as illustrated by the grey circumferences of Figure 4a indicating the area of maximum density or "influence" of the injection element.

    [0025] The embodiment illustrated in Figure 4b it is similar to that of Figure 4a. The only difference is that instead of a current injection element 68 two current injection elements 69, 69' are used.

    [0026] All the above is also applicable when the input cable is a cable connected directly to a lightning receptor as can happen in the case of lightning protection systems that, in addition to typical lightning receptors located on the tip of the blade connected to a down conductor such as the represented in the Figures with number 21, also include lateral lightning receptors in certain transverse sections of the blade.

    [0027] Among the advantages of the invention it can be highlighted that:
    • The effective area of current transmission is increased.
    • The local voltage is reduced at the injection areas.
    • The temperature increase in the material is reduced (ensuring structural integrity).


    [0028] Another significant advantage is that the lightning protection system of the invention can be installed in shells manufactured by infusion procedures as the system injection means can be arranged in corresponding locations during the manufacture of each of the shells of the blade and make the proper connections during assembly of the blade. Since, in particular, in that process the beams 15, 17 must be "joined" to the shells is particularly advantageous to use injection means such as metal plates, which can be "pressed" by the flanks of the beams 15, 17. That would not be possible with cables (they would be broken).

    [0029] The invention is especially applicable to offshore carbon blades since the amount of current is much higher and therefore need improvements of systems currently used for injecting current into "caps" and also to "stealth" blades requiring improvements in their current injection systems.


    Claims

    1. Lightning protection system of a wind turbine blade (20), whose shells include at least one electrically conductive component (22; 42; 62) embedded into them, comprising injection means of lightning currents in said electrically conductive component (22; 42; 62) upon receipt through an input cable connected directly or indirectly with one or more lightning receptors of the blade, wherein said injection means of lightning currents comprise:

    - a current receptor element (27; 47; 67) connected to said input cable and arranged over an area of the shells close to the electrically conductive component (22; 42; 62); and characterized in that said injection means of lightning currents further comprise

    - a current injection element (28; 48; 68; 69, 69') arranged over the electrically conductive component (22; 42; 62) and connected to the current receptor element (27, 47, 67) by at least two distribution cables (31, 32; 51, 52, 53; 71, 72, 73, 74); and in that

    the electrically conductive component is a "cap" (22) and the injection means comprise a current receptor element (27) and a current injection element (28) that are connected by the at least two distribution cables (31, 32) and configured to achieve a distribution of currents in said distribution cables (31, 32) that prevents areas with high current density in the current injection element (28); and the value of the electric field is reduced in the local injection area with the consequent reduction of the temperature increase.
     
    2. Lightning protection system according to claim 1, characterized in that said input cable is a cable derived from a down conductor (21) disposed within the wind turbine blade (20) for carrying lightning currents to ground.
     
    3. Lightning protection system according to claim 1, characterized in that said input cable is connected directly to a blade lightning receptor.
     
    4. Lightning protection system according to claims 1-3, characterized in that the distance between the current receptor element (27; 47; 67) and the current injection element (28; 48; 68; 69, 69') is lesser than 5m.
     
    5. Lightning protection system according to claim 1, characterized in that the current receptor element (27) and the current injection element (28) are metal plates.
     
    6. Lightning protection system according to any of claims 1-4, characterized in that the electrically conductive component is a carbon fiber laminate (42) and the injection means comprise a current receptor element (47) and a current injection element (48) that are connected by three distribution cables (51, 52, 53) and configured to achieve a distribution of currents in said distribution cables (51, 52, 53) that prevents areas with high current density in the current injection element (48).
     
    7. Lightning protection system according to claim 6, characterized in that the current receptor element (47) and the current injection element (48) are metal plates.
     
    8. Lightning protection system according to any of claims 1-4, characterized in that the electrically conductive component is a metal mesh (62) and the injection means comprise a current receptor element (67) and a current injection element (68) that are connected by four distribution cables (71, 72, 73, 74) and configured to achieve a distribution of currents in said distribution cables (71, 72, 73, 74) that prevents areas with high current density in the current injection element (68).
     
    9. Lightning protection system according to claim 8, characterized in that the current receptor element (67) and current injection element (68) are metal plates.
     
    10. Lightning protection system according to any of claims 1-4, characterized in that the electrically conductive component is a metal mesh (62) and the injection means comprise a current receptor element (67) and two current injection elements (69, 69') that are connected by four distribution cables (71, 72, 73, 74) and are configured to achieve a distribution of currents in said distribution cables (71, 72, 73, 74) that prevents areas with a high current density in the current injection elements (69, 69').
     
    11. Lightning protection system according to claim 10, characterized in that the current receptor element (67) and the current injection elements (69, 69') are metal plates.
     


    Ansprüche

    1. Blitzschutzsystem für ein Windturbinenblatt (20), dessen Mäntel mindestens eine in sie eingebettete elektrisch leitende Komponente (22; 42; 62) aufweisen, mit Einspeisemitteln für Blitzströme in der elektrisch leitenden Komponente (22; 42; 62) nach Aufnahme über ein Eingangskabel, das direkt oder indirekt mit einem oder mehreren Blitzrezeptoren des Blatts verbunden ist,
    wobei die Einspeisemittel für Blitzströme Folgendes umfassen:

    - ein Stromrezeptorelement (27; 47; 67), das mit dem Eingangskabel verbunden und in einem Bereich der Mäntel in der Nähe der elektrisch leitenden Komponente (22; 42; 62) angeordnet ist, und dadurch gekennzeichnet, dass die Einspeisemittel für Blitzströme ferner Folgendes umfassen:

    - ein Stromeinspeiselement (28; 48; 68; 69, 69'), das an der elektrisch leitenden Komponente (22; 42; 62) angeordnet und über mindestens zwei Verteilungskabel (31, 32; 51, 52, 53; 71, 72, 73, 74) mit dem Stromrezeptorelement (27, 47, 67) verbunden ist, und dass

    es sich bei der elektrisch leitenden Komponente um eine "Kappe" (22) handelt und die Einspeisemittel ein Stromrezeptorelement (27) und ein Stromeinspeiselement (28) umfassen, die über die mindestens zwei Verteilungskabel (31, 32) verbunden und so konfiguriert sind, dass eine Verteilung von Strömen in den Verteilungskabeln (31, 32) erzielt wird, durch die Bereiche mit hoher Stromdichte in dem Stromeinspeiselement (28) vermieden werden, und sich der Wert für das elektrische Feld im lokalen Einspeisebereich bei entsprechender Reduzierung der Temperaturerhöhung reduziert.
     
    2. Blitzschutzsystem nach Anspruch 1, dadurch gekennzeichnet, dass es sich bei dem Eingangskabel um ein Kabel handelt, das von einem in dem Windturbinenblatt (20) angeordneten Ableiter (21) zum Abführen von Blitzströmen in die Erde abgezweigt ist.
     
    3. Blitzschutzsystem nach Anspruch 1, dadurch gekennzeichnet, dass das Eingangskabel direkt mit einem Blatt-Blitzrezeptor verbunden ist.
     
    4. Blitzschutzsystem nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass der Abstand zwischen dem Stromrezeptorelement (27; 47; 67) und dem Stromeinspeiselement (28; 48; 68; 69; 69') weniger als 5 m beträgt.
     
    5. Blitzschutzsystem nach Anspruch 1, dadurch gekennzeichnet, dass es sich bei dem Stromrezeptorelement (27) und dem Stromeinspeiselement (28) um Metallplatten handelt.
     
    6. Blitzschutzsystem nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass es sich bei der elektrisch leitenden Komponente um ein Kohlenstofffaserlaminat (42) handelt und die Einspeisemittel ein Stromrezeptorelement (47) und ein Stromeinspeiselement (48) umfassen, die über drei Verteilungskabel (51, 52, 53) verbunden und so konfiguriert sind, dass eine Verteilung von Strömen in den Verteilungskabeln (51, 52, 53) erzielt wird, durch die Bereiche mit hoher Stromdichte in dem Stromeinspeiselement (48) vermieden werden.
     
    7. Blitzschutzsystem nach Anspruch 6, dadurch gekennzeichnet, dass es sich bei dem Stromrezeptorelement (47) und dem Stromeinspeiselement (48) um Metallplatten handelt.
     
    8. Blitzschutzsystem nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass es sich bei der elektrisch leitenden Komponente um ein Metallgitter (62) handelt und die Einspeisemittel ein Stromrezeptorelement (67) und ein Stromeinspeiselement (68) umfassen, die über vier Verteilungskabel (71, 72, 73, 74) verbunden und so konfiguriert sind, dass eine Verteilung von Strömen in den Verteilungskabeln (71, 72, 73, 74) erzielt wird, durch die Bereiche mit hoher Stromdichte in dem Stromeinspeiselement (68) vermieden werden.
     
    9. Blitzschutzsystem nach Anspruch 8, dadurch gekennzeichnet, dass es sich bei dem Stromrezeptorelement (67) und dem Stromeinspeiselement (68) um Metallplatten handelt.
     
    10. Blitzschutzsystem nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass es sich bei der elektrisch leitenden Komponente um ein Metallgitter (62) handelt und die Einspeisemittel ein Stromrezeptorelement (67) und zwei Stromeinspeiselemente (69, 69') umfassen, die über vier Verteilungskabel (71, 72, 73, 74) verbunden und so konfiguriert sind, dass eine Verteilung von Strömen in den Verteilungskabeln (71, 72, 73, 74) erzielt wird, durch die Bereiche mit hoher Stromdichte in den Stromeinspeiselementen (69, 69') vermieden werden.
     
    11. Blitzschutzsystem nach Anspruch 10, dadurch gekennzeichnet, dass es sich bei dem Stromrezeptorelement (67) und den Stromeinspeiselementen (69, 69') um Metallplatten handelt.
     


    Revendications

    1. Système de protection contre la foudre d'une pale d'éolienne (20), dont les coques incluent au moins un composant électriquement conducteur (22 ; 42 ; 62) incorporé dans celles-ci, comprenant des moyens d'injection de courants de foudre dans ledit composant électriquement conducteur (22 ; 42 ; 62) lorsqu'ils sont reçus par l'intermédiaire d'un câble d'entrée connecté directement ou indirectement avec un ou plusieurs récepteurs de foudre de la pale,
    dans lequel lesdits moyens d'injection de courants de foudre comprennent :

    - un élément récepteur de courant (27 ; 47 ; 67) connecté audit câble d'entrée et agencé sur une aire des coques à proximité du composant électriquement conducteur (22 ; 42 ; 62) ; et
    caractérisé en ce que lesdits moyens d'injection de courants de foudre comprennent en outre

    - un élément d'injection de courant (28 ; 48 ; 68 ; 69, 69') agencé sur le composant électriquement conducteur (22 ; 42 ; 62) et connecté à l'élément récepteur de courant (27, 47, 67) par au moins deux câbles de distribution (31, 32 ; 51, 52, 53 ; 71, 72, 73, 74) ;

    et en ce que
    le composant électriquement conducteur est un « capuchon » (22) et les moyens d'injection comprennent un élément récepteur de courant (27) et un élément d'injection de courant (28) qui sont connectés par lesdits au moins deux câbles de distribution (31, 32) et configurés pour accomplir une distribution de courants dans lesdits câbles de distribution (31, 32) qui empêche la formation d'aires à densité de courant élevée dans l'élément d'injection de courant (28) ;
    et la valeur du champ électrique est réduite dans l'aire d'injection locale avec la réduction de l'augmentation de température qui en résulte.
     
    2. Système de protection contre la foudre selon la revendication 1, caractérisé en ce que ledit câble d'entrée est un câble dérivé d'un conducteur de descente (21) disposé à l'intérieur de la pale d'éolienne (20) pour transporter des courants de foudre jusqu'à la terre.
     
    3. Système de protection contre la foudre selon la revendication 1, caractérisé en ce que ledit câble d'entrée est connecté directement à un récepteur de foudre de pale.
     
    4. Système de protection contre la foudre selon les revendications 1 à 3, caractérisé en ce que la distance entre l'élément récepteur de courant (27 ; 47 ; 67) et l'élément d'injection de courant (28 ; 48 ; 68 ; 69, 69') est inférieure à 5 m.
     
    5. Système de protection contre la foudre selon la revendication 1, caractérisé en ce que l'élément récepteur de courant (27) et l'élément d'injection de courant (28) sont des plaques métalliques.
     
    6. Système de protection contre la foudre selon l'une quelconque des revendications 1 à 4, caractérisé en ce que le composant électriquement conducteur est un stratifié en fibres de carbone (42) et les moyens d'injection comprennent un élément récepteur de courant (47) et un élément d'injection de courant (48) qui sont connectés par trois câbles de distribution (51, 52, 53) et configurés pour accomplir une distribution de courants dans lesdits câbles de distribution (51, 52, 53) qui empêche la formation d'aires à densité de courant élevée dans l'élément d'injection de courant (48).
     
    7. Système de protection contre la foudre selon la revendication 6, caractérisé en ce que l'élément récepteur de courant (47) et l'élément d'injection de courant (48) sont des plaques métalliques.
     
    8. Système de protection contre la foudre selon l'une quelconque des revendications 1 à 4, caractérisé en ce que le composant électriquement conducteur est un treillis métallique (62) et les moyens d'injection comprennent un élément récepteur de courant (67) et un élément d'injection de courant (68) qui sont connectés par quatre câbles de distribution (71, 72, 73, 74) et configurés pour accomplir une distribution de courants dans lesdits câbles de distribution (71, 72, 73, 74) qui empêche la formation d'aires à densité de courant élevée dans l'élément d'injection de courant (68).
     
    9. Système de protection contre la foudre selon la revendication 8, caractérisé en ce que l'élément récepteur de courant (67) et l'élément d'injection de courant (68) sont des plaques métalliques.
     
    10. Système de protection contre la foudre selon l'une quelconque des revendications 1 à 4, caractérisé en ce que le composant électriquement conducteur est un treillis métallique (62) et les moyens d'injection comprennent un élément récepteur de courant (67) et deux éléments d'injection de courant (69, 69') qui sont connectés par quatre câbles de distribution (71, 72, 73, 74) et sont configurés pour accomplir une distribution de courants dans lesdits câbles de distribution (71, 72, 73, 74) qui empêche la formation d'aires ayant une densité de courant élevée dans les éléments d'injection de courant (69, 69').
     
    11. Système de protection contre la foudre selon la revendication 10, caractérisé en ce que l'élément récepteur de courant (67) et les éléments d'injection de courant (69, 69') sont des plaques métalliques.
     




    Drawing

















    Cited references

    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description