EP0135572B1 - Device for protecting overhead electroconducting lines against lightning - Google Patents

Abstract

A lightning protector for overhead electric lines comprises at least one of the following elements: a spark-arrester (111, 112), a ground lead and a device for the connection of electric cables. Measures for reducing the impedance of the elements forming the circuit for the discharge to the ground of the shock wave due to atmospheric charges are proposed.

Description

The present invention is in the field of the transport of electrical energy by overhead lines and it relates more specifically to improved means of lightning protection of such lines and of the installations which are electrically connected to them.

We know that lightning can be in the form of an electrical discharge under very high voltage between the ground and cloudy masses for example, preferably taking the electrically conductive path offered by objects rising above the ground such as trees, constructions and of course overhead electrical installations. It is known to protect aerial installations for transporting electrical energy by means of devices known as spark gaps and consisting of a pair of electrodes each consisting of a galvanized steel rod bent at about 45 °; the electrodes are arranged in the vicinity, and generally plumb with a group of insulators, a pylon or a pole, in a coplanar fashion and their bend facing each other separated by a certain distance, one of the electrodes being connected to the power line, the other being connected to earth; one of the electrodes is supported by a bracket directly by the line cable, the other electrode is also supported by a bracket secured to a cable or rod for fixing the insulators to the posts; this fixing cable can also serve, being connected to earth, as a grounding conductor for the second electrode generally, the electrodes, their support bracket and the fixing cable are made of steel. The practice of such a protection mode has shown that live installations, such as transformers for example, are protected for discharges not exceeding 15 kilo-amperes; for discharges of higher intensity, the earthing of the line by spark gaps of current design is insufficient; a certain number of transformers and other devices belonging to the installations are thus damaged by lightning each year.

Overhead lightning protection means, forming the closest prior art known to the Applicant, are described in publication FR-A-2 094 512 which discloses a device for hanging electrical lines combining a spark gap constituted by a pair of electrodes supported by supports having a general T-shape, the electrodes being connected one to the line, the other to an earth connection by tangential junction means; sometimes, the aim of this invention not being that of the optimal flow of the electric wave that constitutes lightning, its connection means are not described in detail, any more than the nature of the metal constituting them does is specified.

On the other hand, devices for earthing surge protective devices have been known for a very long time, these devices generally being constituted by an electrical conductor buried in the ground, or better still, plunging into a well so as to through the water table, find an electroconductive volume in the soil with the lowest possible resistance. However, the earth connections proposed to date, if they are perfectly capable of dissipating a permanent electric voltage, seem ill-suited to dissipating the energy of an electric wave of very high amplitude and very short period such as that under which the phenomenon of lightning generally occurs.

The main idea of the present invention is based on the one hand on recent knowledge of the nature and behavior of the current composing the discharge of lightning in conductors and on the other hand on taking into account the fact, more anciently known that the electric charges are distributed on the surface of the conductors. Studies carried out in recent decades have shown that an atmospheric discharge comprises a phase of increasing intensity (front of the discharge) of approximately 8 microseconds, and a phase of decreasing intensity (tail of discharge) of approximately 20 micro-seconds; it is this intensity wave which propagates along the "discharge channel" and in the conductors thus encountered, while the techniques of the prior art did not take into account this oscillatory and dynamic aspect of the discharge, the present invention will precisely hold the greatest case by endeavoring to reduce to the maximum the impedance of the evacuation circuits to the ground, in particular by endeavoring to preserve the surface, or film, conduction effect of these circuits .

This objective is achieved according to the characteristics of the first claim.

Thus, the improvements proposed by the invention will relate to three categories of means: first, the spark gaps and their method of connection, secondly the earth plugs and their connection, thirdly means of connection or junction .

Firstly and according to the present invention, a spark gap of the kind comprising a pair of electrodes supported by a support integral with an insulator and separated from each other, said pair of electrodes being said spark gap, one electrodes being connected to said line, the other electrode being connected to earth, is mainly characterized in that said electrode support has the general shape of a T composed of a transverse part and a foot, in that at least said transverse part has substantially circular symmetry about a longitudinal axis, and in that it is provided at each of its ends with an axial clamping means intended to make it integral on the one hand said electrode, on the other hand of a cable, or electroconductive rod, and in that said transverse part at least, and its clamping means are made of a non-magnetic electroconductive metal.

It follows from such a general design of the spark gap, on the one hand that the film circulation of the electrical charges is favored to the maximum and that the impedance, and therefore the induction phenomena, very particular to the current d Lightning waves are minimized.

For reasons of mounting and adjustment convenience, it is recommended that the electrode supports themselves consist of several parts; it will be noted, still in consideration of the short wave wavelength aspect of the discharge, that surface / surface contacts are not to be feared; the composite nature of the electrode supports has advantages in the positioning and adjustment operations.

According to a first embodiment, the transverse part of the electrode holder is a cylindrical part comprising at one of its ends a mandrel of the type with pushed clamp intended to grip the end of the electrode, while its other end comprises a member for multi-strand cable connection with conical internal reach and axially bored conical core intended to clamp the end of a multi-strand conductor of the discharge discharge circuit.

According to a second embodiment, the transverse part of the electrode support is a cylindrical part provided at each of its ends with two mandrels with pushed pliers, one of the mandrels enclosing said electrode, the other mandrel enclosing a straight conductive rod of the same diameter as the electrode, the end of said rod is itself enclosed in a mandrel with pushed pliers of a connector, the other end of which has a clamping member for multi-strand cable connection with conical internal reach and core taper axially bored to enclose the end of a stranded conductor of the discharge discharge circuit.

According to a preferred embodiment of the electrode holder foot, this consists of an upper part comprising a ring axially bored to grip said transverse part, said ring being connected to a rod, of a connecting piece forming double mandrels with clamps pushed, and a lower rod secured to an insulator, one end of the upper rod is clamped in a clamp of the mandrel of the connecting piece, while one end of the lower rod is clamped in the clamp of the another mandrel from this same part.

According to another secondary characteristic of the invention and, noting that it would be useless to lower the impedance of the electrode supports, if the other parts of the evacuation circuit were to have a high impedance, the present invention proposes to arrange the other elements of this circuit in such a way that they are as straight as possible, at most that their curvature is of large radius and at least that no element of this circuit has a cusp, but rather, they connect tangentially.

Thus the cable for connecting the first electrode to the electrically conductive line is made tangentially, at a connection point, while the cable for connecting the second electrode to earth has a vicinity of the pole a radius of about 50 centimeters. .

Secondly and still according to the present invention, an earth connection intended for the earthing of heavy overloads, such as caused by lightning, of overhead electric lines, said earth connection being of the type constituted by a buried electrical conductor in the ground, is generally characterized in that said conductor buried in the ground is a single conductor closed on itself at a loop point to form a loop and in that the ground conductor in coming from the aerial installation is tangentially connected to said loop at at least one connection point.

Preferably, the buried conductor is looped back on itself by means of a device constituted by a double mandrel with pliers and with coaxial conical surfaces.

More preferably, the connection of the earthing conductor further comprises a third conductive element tangentially connected to each of its extremities on the one hand to said earthing conductor and on the other hand, to the loop conductor, the connection of the latter to the loop being carried out in a tangential direction opposite to that of the aforementioned connection, the earthing conductor, the loop conductor and the third connection conductor forming a kind of triangle, called "equipotential triangle" of connection, the sides of this triangle being in fact substantially arcs of a circle.

Preferably, said loop has the general shape of a rectangle with rounded angles along sensitively arcs of a circle.

Preferably finally, one of the sides of the "equipotential triangle" is one of the rounded angles of said loop.

Thirdly and still according to the present invention, an electrical junction device for electrically conductive cables is generally characterized in that it incorporates at least one piece of elongated shape and bent over itself in the direction of its width to form on its own; or in association with another similar part, a sleeve intended to completely surround two electric cables parallel to each other in said sleeve, said part being made of a non-magnetic electroconductive metal; advantageously, the two adjacent shell edges are pressed against each other in close electrical contact.

It follows from these provisions that the junction thus formed has a very low impedance with respect to electric discharges, of the kind of lightning strikes or induced by it.

Preferably the above-mentioned shell or shells are clamped by suitable means around the conductors, these means being arranged in the vicinity of each of the ends of the shell at least.

More preferably, a joining device according to the invention also incorporates a so-called contact part having a double cradle profile and a length substantially equal to that of a shell, the radius of curvature of a cradle being substantially equal. to the radius of a conductor.

A junction device according to the present invention will find its application in the junction side by side of electrical conductors, as such junctions appear in the aforementioned patent applications, mainly when it is a question of "earthing" of a lightning arrester installation and in particular when the earth connection of such installations will consist of several electrical conductors buried in the ground; in this case the conductors buried in the ground are connected to each other by electrically conductive segments themselves buried, the junction of a segment with a conductor being carried out by means of said device.

Applied in the case where two earthing conductors penetrate the ground in the vicinity of one another, these two conductors are connected on the one hand by at least one device as described above and on the other hand by an electrically conductive segment, the electrically conductive segment and said conductors forming underground a connecting triangle called an equipotential triangle.

• - la fig. 1 est une illustration schématique d'un montage typique de l'art antérieur,
• - la fig. 2 est une illustration d'un dispositif de protection antifoudre conforme à l'invention,
• - la fig. 3 est un détail en coupe et à plus grande échelle d'un organe de la figure précédente,
• - les fig. 4 sont des illustrations d'autres formes de réalisation,
• - la fig. 5 est une illustration analogue d'une autre variante et la fig. 5a en est un détail en coupe,
• - la fig. 6 illustre diverses applications pour lignes MT, HT et THT,
• - les fig. 7, 7a, 7b illustrent un éclateur pour la basse tension (BT),
• - la fig. 8 illustre une réalisation des pieds de support,
• - la fig. 9 est une illustration schématique simplifiée d'une prise de terre conforme à l'invention,
• - la fig. 10 est un détail en coupe de la figure précédente,
• - la fig. 11 est un détail en coupe de la fig. 9,
• - la fig. 12 est une illustration en perspective d'une application à un terminal de ligne, d'une prise de terre telle que celle de la fig. 9,
• - les fig. 13 à 16 illustrent de façon analogue à la fig. 9 des cas particuliers plus complexes de réalisation d'une prise de terre conforme à l'invention,
• - la fig. 17 illustre un poste de transformation comportant une prise de terre conforme à l'invention,
• - la fig. 17a est un détail à plus grande échelle de la figure précédente,
• - la fig. 18 illustre la mise à la terre d'un pylône conformément à l'invention et faisant application des dispositifs en relevant,
• - la fig. 19 est une illustration de face et de côté d'un dispositif de jonction à pièce unique de l'invention,
• - la fig. 20 est une illustration analogue d'un dispositif de jonction à deux coquilles,
• - la fig. 21 est une illustration en bout d'une jonction de conducteurs de grosseur différente, et
• - les fig. 22 et 22a illustrent des dispositifs de jonction incorporant une pièce de contact intermédiaire.

The present invention will be better understood and details will be apparent from the description which will be given on the one hand and briefly of the technique of the prior art and on the other hand of preferred embodiments according to the technique of the invention in relation to the figures of the attached plates in which:

• - fig. 1 is a schematic illustration of a typical assembly of the prior art,
• - fig. 2 is an illustration of a lightning protection device according to the invention,
• - fig. 3 is a detail in section and on a larger scale of a member of the previous figure,
• - figs. 4 are illustrations of other embodiments,
• - fig. 5 is a similar illustration of another variant and FIG. 5a is a detail in section,
• - fig. 6 illustrates various applications for MV, HV and THT lines,
• - figs. 7, 7a, 7b illustrate a spark gap for low voltage (LV),
• - fig. 8 illustrates an embodiment of the support legs,
• - fig. 9 is a simplified schematic illustration of an earth connection according to the invention,
• - fig. 10 is a detail in section of the previous figure,
• - fig. 11 is a detail in section of FIG. 9,
• - fig. 12 is a perspective illustration of an application to a line terminal, of an earth connection such as that of FIG. 9,
• - figs. 13 to 16 illustrate in a similar manner to FIG. 9 more complex particular cases of making an earth connection in accordance with the invention,
• - fig. 17 illustrates a transformer station comprising an earth connection in accordance with the invention,
• - fig. 17a is a detail on a larger scale of the previous figure,
• - fig. 18 illustrates the grounding of a pylon in accordance with the invention and making use of the devices for raising it,
• - fig. 19 is a front and side illustration of a single-piece joining device of the invention,
• - fig. 20 is a similar illustration of a junction device with two shells,
• - fig. 21 is an illustration at the end of a junction of conductors of different size, and
• - figs. 22 and 22a illustrate joining devices incorporating an intermediate contact piece.

In fig. 1, by way of illustration of the prior art in this area, a medium-voltage electroconductive line stop 101 for example, comprises a pole 102, a connection 103 to subsequent installations, an insulator assembly 104 and a lightning protection device comprising itself even a pair of electrodes 105 and 106 and a discharge conduit 107 to an earth connection 108; incidentally, an "anti-bird" rod is placed between the electrodes to avoid electrocution of these animals. It will be noted that the connection of each electrode via its support comprises at least two right angles; it is noted that the base of the electrode serves as a conductor and that, in general, the electrode is connected to its base by means of an eyelet and of bolting through the eyelet in general still, both the electrode and its support leg are made of galvanized iron. This device for protecting the subsequent installation against the effects of lightning known as a spark gap is generally, as said above, ineffective for discharges exceeding 15 kA and it is entirely representative of the known prior art.

In fig. 2 illustrating an improved or improved spark gap according to the invention, electrodes 111 and 112 of copper for example are each supported by a support, 113 and 114 respectively, having a general T shape; each support such as the support 114 consists of a transverse part 115 and a base 116. The particular structure of these supports will be described below, but it should already be noted that the transverse part has a rough shape cylindrical along the axis of which are connected the electrode 112 on the one hand and the cable 117 for connection of this first electrode to the electroconductive line or bypass of the discharge; it will be noted that it is the same for the other electrode with the connection cable 118 of the second electrode to earth.

It also appears in the figures that, in accordance with what is recommended by the present invention, the cable 117 is tangentially connected to the line 101 'at a point 119 at least 1.50 meters from the spark gap and that the connection cable insulated at 1,000 volts minimum, from the second electrode to earth present in the vicinity of the pole 102 'a curvature 120 of fairly large radius (of the order of 50 centimeters for example).

In fig. 3 is shown in section on a larger scale and in more detail an electrode holder such as the electrode holder 114 of the previous figure; this electrode holder essentially consists of a transverse part 115 and a foot 116; the transverse part 115 is a substantially cylindrical part or else with an axis symmetry 121; it comprises at one of its ends 122 a mandrel of the pliers type push 123 enclosing the end of the electrode 112; it comprises at its other end 127 a member for connecting the multi-strand cable 117 comprising a nut 124 with conical internal bearing and conical core 125 axially bored; this type of connection of multi-strand cables is known in itself and it is recalled that the tightening of the nut 124 brings the internal end of the core and of the strands enclosed in contact with the bottom stop 126. The collet chuck end thrust 122 is also known in itself; it will however be noted that the cylindrical part, or transverse part 115, is provided with an inner bore 128 deep enough to allow more or less to engage the electrode.

According to the invention, the constituent parts of the transverse part consist of one or more non-magnetic metals, or even non-ferromagnetic metals such as copper, brass, bronze, aluminum or other excluding metals having ferro- magnetic.

The foot 116 is connected to the transverse part 115 by a ring 129 axially bored.

In fig. 4 an electrode holder 130 consists of a transverse piece 131 provided at each of its ends with two collet chucks similar to the collet chucks 123 of the previous figure; one of the mandrels is used to enclose the electrode 112, the other mandrel encloses a rod 32 itself connected to the multi-stranded conductor 117 via a connector 133 having substantially the same functional structure as the transverse part of the previous figure; this connection is illustrated in more detail in figs. 5 and 5a. The base of the electrode support 130 consists of an upper part formed by a rod 116 and by a ring 129 axially bored to enclose the transverse part 131 of a connection piece 134 forming double mandrels with pushed pliers and a rod 136 secured to an insulator part 137 at one of its ends, its other end being engaged in one of the mandrels of the part 134. The advantage of this assembly with intermediate part 134 is to allow easy adjustment in height and orientation of the electrode 112.

In fig. 4a, a spark gap mounting variant differs from the previous one in that the transverse part 131 'has at one of its ends a low-cut part 132' similar to the part 132 and at its other end an axial clamping mandrel constituted by a nut 160 with internal conical thread and by an external thread 161, itself conical, from the end of the transverse piece 131, this threaded end has several longitudinal slots allowing, during the screwing of the nut, the tightening of the electrode 112 '. The other parts of this electrode assembly are similar to those of the previous figure.

In fig. 5 and 5a, the connecting piece 133 of the previous figure is constituted for a first part 140, by a chuck with pushed clamp and for a second part 141 by a multi-strand cable connection member comprising a nut 142 with internal reach taper and tapered core 143 axially bored; this connecting member is completely similar in its own to that comprised by the part 127 of the transverse part of FIG. 3.

It will be noted that the connecting piece 134 of FIG. 4 consists of two parts 140 of the part of FIG. 3.

It will be noted that the connecting piece 134 of FIG. 4 consists of two parts 140 of the part of FIG. 3.

Fig. 5a recalls that a pushed clamp such as the clamp 145 of FIG. 5 is a conical piece axially bored and split along a generator.

In fig. 6 various examples of use of the device of the invention are illustrated applied to different lines. It will be noted that the electrode support foot can be doubled, as is the case for a 150 foot for example, applied to the lightning protection of a very high voltage line, and this because of the long length of the insulator line.

In fig. 7 and 7a a spark gap also applies the principles of the invention in that the electrode support consists of a transverse piece such as 152 enclosing an electrode 153 axially and always connected axially to the conductor 117 '. Legs such as 54 are made of an insulating material such as porcelain and are fixed to a support plate 155 which may be made of aluminum. The connection of the electrodes to the multi-strand cable 117 ′ is carried out for example by means of a part 133 similar to that of FIG. 4 and by a mandrel 158 at the end of the transverse part 152. In FIG. 7a, the mandrel 154 of the previous figure is replaced by a screw tightening transverse 156.

There is shown in FIG. 7b an alternative embodiment of FIG. 7 in which the electrodes 153 of the previous figure are replaced by spherical electrodes 157. Such spherical electrodes which are slightly more expensive than the horn electrodes hitherto described, can just as well be fitted to all the spark gaps previously described and be substituted for horn electrodes; the electrodes with spheres are in principle slightly more effective than the electrodes with horns but it will be noted that this increase in efficiency is quite minimal compared to that supported by the mounting of the electrodes whatever they are, recommended by the invention.

In fig. 8 shows an assembly of lightning protection spark gaps according to the invention quite similar to that shown in FIG. 2 to 4 (the equivalent bodies are assigned the same references); we note however that in this figure, the spark gap support legs such as 161 and 162 are bars, or flats, of rectangular section, visible respectively in the inserts 163 and 164; the lower part of the stand 161 is connected by means of a bolt 169 to a connecting member 165 of the line 101 to a first insulator 166 while the lower part of the stand 162 is fixed to a second insulator 167 by a bolt 168 .

We also note in this figure that an anti-bird device 170 is also constituted by a flat whose rectangular section is visible in the insert 171; this flat part is twisted by a quarter turn near its lower part to be fixed by means of a bolt 172 on the connection part of two neighboring insulators 166 and 167.

Note also in this figure the insulation sheath 175 of the cable 120 which is an insulation sheath at 1,000 volts minimum.

In fig. 9, a single electrical conductor is closed on itself in a loop 202 by a looping device 201; the loop has a substantially rectangular shape whose straight parts have lengths greater than 1 meter and preferably at least 5 meters; the conductor is a bare copper cable with a cross section of 25 to 150 mm ² ; the sides of the loop are connected to each other in curved parts with a radius of about 0.5 meters.

A grounding conductor 203, for example of spark gaps or variable resistance lightning arresters of the aerial installation, is an electrical conductor with the same characteristics as that of the loop 202 but it is preferably isolated at least on its aerial part; this earthing conductor is tangentially connected a first time to the loop 202 at a first connection point 204 by means of a connection device; it is still tangentially connected a second time to the loop at a second connection point 204 by means of a third conductor 208 which is itself connected tangentially, at each of its ends to the conductor 203 and to the loop 202 in a third connection point 204; the first and second connection points 204 on the loop have opposite tangential directions; the conductors 202, 203 and 208 are bent in the vicinity of their connection point and they form a sort of triangle 210, called the equipotential triangle; the curved sides of this triangle are substantially arcs of a circle having a radius of approximately 0.5 meters; the third conductor 208 is of course similar to the other conductors of the earth connection.

In fig. 10, the looping device 201 is constituted by a double mandrel with pliers and coaxial conical surfaces, known in itself in the connections of electrical conductors; in the application which is made of it in the invention, the constituent elements, ie body 211, clamp 212 and nuts 213 are made of non-magnetic metal and preferably of bronze.

In fig. 11, a connection device 204 consists of a jumper 215 with two nuts 216 and clamping plate 217, also of known type, the constituent elements of which, in accordance with the invention, are made of non-magnetic metal.

In fig. 12, there is shown schematically a pole 220 at the end of the line comprising a transformer station 221 and surge arrester means constituted by a spark gap 222 grounded by an insulated conductor 203; the loop 202 located at a distance of about 1 meter or 2 below the ground surface and around the base of the post, is for example similar to that shown in FIG. 16; there is in particular a conductor 223 for earthing the ground of the aerial installation and / or the network neutral; this conductor 223 is itself tangentially connected to the loop 202.

In fig. 13, 14, 15 and 16 of the earth connections have a structure and / or a geometry substantially different from the earth connection of FIG. 9; these earth connections are intended for air installations larger than a simple pole; for example the earth connections of fig. 13, 14 and 15 may be intended for the earthing of processing installations while the earth connection of FIG. 16 will be suitable for example for a high voltage line pylon. It will be noted that the higher the aerial installation, the more the loop 202 must be extended; for optimal protection, the dimensions of the loop will preferably be greater than the largest dimension of the protected installation, and the loop should preferably surround the track on the ground of the installation. Note however that these earth connections are generally suitable for all high, medium and low voltage installations. One recognizes in their structure of the elements stated in the description of the earthing in fig. 9: a looping member 201, one or more single-conductor loops 202, equipotential connection triangles 210, connecting members such as 204 and various grounding conductors such as 203 and 223.

Finally, it will be noted in all of FIGS. 9 to 16, the tangential and / or coaxial connection of the conductors; by coaxial connection of the conductor means the connection of the conductor in the extension of itself, this essential characteristic of the invention having the effect of reducing the impedance of the conductors vis-à-vis the electric wave of lightning .

In fig. 17 which schematically illustrates a transformer station 326 of the HT / MT or THT / HT type of the devices of the preceding figures are symbolized by the small rectangles 320 bridging two cables side by side. It can be seen in this figure that the conductors such as 321 and 322 for earthing the aerial lightning protection installation do not undergo any mechanical interruption in their part buried in the ground; it will also be noted that in the ground they are connected by means of junction devices by a segment such as 323 to form connection triangles 324 called equipotential triangles; finally, it will be noted that the part buried in the ground having the general shape of a rectangle, a conductor 325 called an internal bridge connected on the side of the rectangle around their middle.

In fig. 18 it will be recalled that an earth connection of the kind shown in the previous figure is advantageously associated with spark gaps such as spark gap 330 said spark gap with great flow power,

See figs. 17 and 18 the same elements as those cited in relation to the following figures with the same references. It will be noted that the radii of curvature r of the conductors, both aerial and buried, are at least 0.5 m.

In fig. 19 a device for joining the conductors of the two parallel electric cables 301 and 302 essentially consists of an elongated piece 303 bent over itself to form a sleeve surrounding the conductors; it is remarkable that the two adjacent edges of the shells are pressed against one another in a surface 304 of close electrical contact; flanges 305 are arranged in the vicinity of the ends of the shell 303.

In fig. 20, the sleeve enclosing the cables 301 and 302 consists of a pair of identical shells 306 and 307, the longitudinal edges of which are maintained in close electrical contact by means of flanges 305.

In fig. 21, the electrical junction of conductors 308 and 309 of different diameters is provided by shells 310 and 311, themselves of different radii of curvature to match the surface of the conductors.

In fig. 22 and 22a electrical junction devices similar to those of the previous figures, however, differ in the presence between the conductors of contact parts 312 or 313 having a double cradle profile; these contact parts, as well as the flanges, are made of a metal or non-magnetic alloy which is a good conductor of electricity.

Claims (11)

1. A protector device against lightning for overhead electric energy transmission lines and installations connected to such lines, the said device comprising,

- at least one arrester of the type comprising a pair of electrodes which are supported by a support which is firmly connected to an insulator and are spaced from each other, the first of the said electrodes being connected by means of a first connecting cable to the said transmission line, the second electrode being connected to the ground by means of a second connecting cable, and,

- at least a ground connection of the type comprising at least an electroconductive cable buried in the ground, characterized:

- on the one hand,

by the fact that each electrode being supported by a support, the said electrode support has the general shape of a T formed of a transverse portion (115) and a stem (116),

by the fact that at least the said transverse portion has substantially circular symmetry around a longitudinal axis and,

by the fact that the said transverse portion is provided at least at one of its ends with an axial clamping means (123, 124) intended to secure it firmly, on the one hand, to the said electrode (111, 112), on the other hand, to a cable (117) or rod (132) which is electroconductor,

by the fact that said transverse portion at least and its clamping means are made of non-magnetic electroconductive metal,

- on the other hand,

by the fact that said conductor which is buried in the ground is a single conductor closed on itself at a looping point (201) so as to form a loop (202), and,

by the fact that the grounding conductor (203) coming from the overhead installation is connected tangentially to the said loop at at least one point of connection (204), and

by the fact that the cable (119) which connects the first electrode to the electroconductive line (101) is connected tangentially at a connection point (119), and

by the fact that the cable (120) which connects the second electrode to the ground has a radius of about 50 cm in the vicinity of the mast;

2. A device according to claim 1, characterized:

by the fact that said transverse portion is a cylindrical part having at one of its ends (127) a chuck of the push-out collet type (123) intended to clamp the end of the electrode, while its other end (127) has a member for connection of multi-strand cables with conical inner surface and axially bored conical core (124) intended to clamp the end of a multi-strand conductor of the discharge evacuation circuit;

3. A device according to claim 1, characterized:

by the fact that said transverse portion (131) is provided at each of its ends with two push-out collet chucks, one of the chucks surrounding the said electrode (112), the other chuck surrounding a straight conductive rod (132) of the same diameter as the electrode, and

by the fact that the end of said rod is itself clamped in a push-out collet chuck (140) of a connector (133) the other end of which comprises a clamping (141) or connector member for a multi-strand cable with a conical inner surface and axially bored conical core in order to surround the end of a multi-strand conductor of the discharge evacuation circuit;

4. A device according to claim 1, characterized: by the fact that said stem consists:

- of an upper portion comprising an axially bored ring (129) to surround the said transverse portion, said ring being connected to a rod (116),

- of a connecting part (134) forming a double push-out collet chuck, and

- of a lower rod (136) rigidly connected with an insulator (137), one end of the upper rod being clamped in a collet of one said chuck while one end of the lower rod is clamped in the collet of the other chuck;

5. A device according to claim 1, characterized:

by the fact that said transverse portion is a cylindrical part (131') comprising, at one of its ends, an axial clamping chuck formed of a nut (160) with conical inner tapping and of an outer thread, itself conical, of the end of the transverse part (131'), said end having several longitudinal slits, and comprising at its other end a necked- down portion (132');

6. A device according to claim 1, characterized:

by the fact that the looping on itself of the buried conductor (202) is effected by means of a device (201) formed by a double chuck with coaxial conical collets and surfaces;

7. A device according to any of the claims 1 and 6, characterized;

by the fact that the connection, tangential to the loop, of the grounding conductor (203) furthermore comprises a third conductive element (208) which is connected tangentially at each of its ends, on the one hand, to said grounding conductor and, on the other hand, to the looped conductor, the connection of the third element to the loop being effected in a tangential direction opposite to that of the connection tangential to the loop, the grounding conductor (203), the conductor (202) of the loop and the third connecting conductor forming a sort of triangle (210) called a connection "equipotential triangle", the sides of this triangle being in fact substantially circular arcs;

8. A device according to claim 7, characterized:

by the fact that said loop (202) has the general shape of a rectangle with corners rounded susbstantially along circular arcs,

by the fact that one of the sides of the "equipotential triangle" is one of the rounded corners of the said loop (202),

by the fact that the dimensions of the loop are at least equal to the largest dimension of the overhead installation protected,

by the fact that the loop surrounds the trace of the installation on the ground,

by the fact that the sole conductor constituting the loop is connected co-axially, that is to say in the extension of itself;

9. A device according to any of the previous claims characterized:

by the fact that the junction of a connecting cable (117) to a transmission line (101'), or from a grounding conductor (203) to a conductor (202) buried in the earth is effected by means of a junction device comprising at least a part (303) of elongated shape curved on itself in the direction of its width to form, by itself alone or in combination with another similar part, a sleeve intended to completely surround two electric cables (301, 302) which are parallel to each other in said sleeve, said part being formed of a nonmagnetic electroconductive metal,

from which it results that the junction thus formed is of very low impedance with respect to electric discharges of the type of those of lightning or those induced by lightning;

10. A device according to claim 9, characterized by the fact that the two adjacent shell edges are pressed against each other in close electrical contact,

by means (305) for strapping the shell or shells around the conductors, said means being arranged at least in the vicinity of each of the ends of the shell at least,

by the fact that it incorporates furthermore a part (306 and 306a) called the contact part having a double-cradle profile and a length substantially equal to that of a shell, the radius of curvature of a cradle being substantially equal to the radius of a conductor;

11. A device according to claim 10, the ground connection of which comprises several electroconductive cables buried in the earth, characterized:

by the fact that the said conductors buried in the earth are connected to each other by electroconductive segments which are themselves buried, the junction of a segment with a conductor being effected by means of one said junction device.

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