Device for protecting overhead electroconducting lines against lightning

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.

The present invention relates to the field of the transmission of 
electrical energy by overhead lines and more particularly improved means 
to protect such lines and installations which are electrically connected 
to them against lightning. 
It is known that lightning may take place in the form of an electric 
discharge under very high voltage between the ground and, for instance, 
cloud masses, using preferably the electroconductive path offered by 
objects which are elevated above the ground such as trees, buildings and, 
of course, overhead electrical systems. It is known how to protect 
overhead electrical energy transmission systems by devices known as 
arresters, formed by a pair of electrodes each consisting of a galvanized 
steel rod bent to about 45.degree.; the electrodes are arranged in the 
vicinity and generally directly above a group of insulators, a tower or a 
pole in the same plane, the bends thereof facing each other and being 
separated by a certain distance, one of the electrodes being connected to 
the electric line and the other being connected to the ground; one of the 
electrodes is supported via a crossbar directly by the line cable; the 
other electrode is also supported by a crossbar integral with a cable or 
rod for fastening the insulators to the poles; this fastening cable may 
also serve, since it is connected to the ground, as ground conductor for 
the second electrode; generally, the electrodes, their support crossbar 
and the fastening cable are of steel. The use of such a manner of 
protection in actual practice has shown that systems under voltage such as 
transformers, for instance, were protected in the case of discharges not 
exceeding 15 kilo-amperes; in the case of discharges of higher intensity, 
the grounding of the line by arresters of the present design is 
inadequate; a number of transformers and other apparatus forming part of 
the systems are thus damaged by lightning each year. 
Furthermore, for a very long time devices have been known for the grounding 
of lightning protection means, these devices generally consisting of an 
electric conductor buried in the earth or, even better, extending into a 
shaft so as, by means of the underground water, to find in the earth an 
electroconductive mass having the lowest resistance possible. Now the 
ground connections proposed up to the present time, while they are 
entirely suitable for dissipating a continuous electric voltage, seem 
poorly suited to dissipating energy of an electric wave of very great 
amplitude and short period such as that with which the phenomenon of 
lightning generally takes place. 
The basic idea of the present invention rests, on the one hand, on recent 
knowledge as to the nature and behavior of the current forming the 
discharge of the lightning in conductors and, on the other hand, on 
consideration of the fact, which has been known for a longer time, that 
electric charges distribute themselves on the surface of conductors. 
Studies carried out during the last decades have shown that an atmospheric 
discharge entailed a phase of increasing intensity (the discharge front) 
of about 8 microseconds and a phase of decreasing intensity (the discharge 
tail) of about 20 microseconds; it is this intensity wave which is 
propagated along the "discharge channel" and into the conductors 
encountered; thus, while the techniques of the prior art did not take this 
oscillatory, dynamic aspect of the discharge into account, the present 
invention is directed precisely at placing greater store in it, trying to 
reduce to a maximum the impedance of the ground evacuation circuits, in 
particular, by striving to preserve the surface or film conduction effect 
of these circuits. 
Thus the improvements proposed by the invention relate to three kinds of 
means: First of all, the arresters and their manner of connection, 
secondly, the ground connections and their connection; and thirdly, 
connecting or junction means. 
First of all, in accordance with the present invention, an arrester of the 
type comprising a pair of electrodes which are supported by a support 
which is rigidly connected with an insulator and are separted from each 
other, the said pair of electrodes being referred to as an arrester, one 
of the electrodes being connected to said line and the other electrode 
being connected to the ground, is primarily characterized by the fact that 
the said electrode support has the general shape of a T formed of a 
transverse portion and a stem, by the fact that at least the said 
transverse portion has substantially circular symmetry around a 
longitudinal axis, and by the fact that it is provided at each of its ends 
with an axial clamping means intended to make it fast, on the one hand, to 
the said electrode and, on the other hand, to a cable or electro 
conductive rod, and by the fact that at least the said transverse portion 
and its clamping means are made of a non-magnetic electroconductive metal. 
It results from such an overall design of the arrester, on the one hand, 
that the film circulation of the electric charges is favored to the utmost 
and that the impedance, and therefore the induction phenomena which are 
specific to the wave current of the lightning, are reduced to a minimum. 
For reasons of convenience in mounting and adjustment, it is recommended 
that the electrode supports be themselves formed of several parts; it will 
be noted, still in view of the undulatory short wavelength aspect of the 
discharge, that the surface/surface contacts are not to be feared; the 
composite nature of the electrode supports has advantages in the 
operations of setting up and adjustment. 
In accordance with a first embodiment, the transverse portion of the 
electrode holder is a cylindrical part having at one of its ends a chuck 
of the push-out collet type intended to surround the end of the electrode 
while its other end has a multi-strand cable connecting member with inner 
conical surface and axially bored conical core intended to surround the 
end of a multi-strand conductor of the discharge evacuation circuit. 
In accordance with a second embodiment, the transverse part of the 
electrode support is a cylindrical part provided at each of its ends with 
two push-out collet chucks, one of the chucks surrounding the said 
electrode and the other chuck surrounding a straight conductive rod of the 
same diameter as the electrode, the end of said rod being itself clamped 
in a push-out collet chuck of a connector the other end of which has a 
multi-strand cable connection clamping member with inner conical surface 
and conical core bored axially to surround the end of a multi-strand 
conductor of the discharge evacuation circuit. 
In accordance with a preferred embodiment of the electrode-holder stem, it 
consists of an upper portion comprising an axially bored ring to surround 
the said transverse portion, said ring being connected to a rod, a 
connecting part forming a double push-out collet mandrel and a lower rod 
rigidly connected with an insulator; one end of the upper rod is clamped 
in a collet of the chuck of the connecting part, while one end of the 
lower rod is clamped in the collet of the other chuck of this same part. 
In accordance with another secondary feature of the invention, and, noting 
that it will serve no purpose to lower the impedance of the electrode 
supports if the other portions of the evacuation circuit are of high 
impedance, the present invention proposes arranging the other elements of 
this circuit in such a manner that they are as linear as possible, or that 
at most their curvature is of large radius and at least no element of this 
circuit has a retrogression point, but rather connect wtih each other 
tangentially. 
Thus, the cable connecting the first electrode to the electroconductive 
line is connected tangentially, at a point of connection, while the cable 
which connects the second electrode to the ground has in the vicinity of 
the pole a radius of about 50 cm. 
Secondly, still in accordance with the present invention, a ground 
connector intended for the grounding of heavy overloads, such as caused by 
lightning, of overhead electric lines, the said ground connection being of 
the type consisting of an electric conductor buried in the earth, is 
characterized, in general, by the fact that the said conductor which is 
buried in the earth is a single conductor closed on itself at a looping 
point so as to form a loop and by the fact that the grounding conductor 
coming from the overhead system is connected tangentially to said loop at 
at least one point of connection. 
The looping on itself of the buried conductor is preferably effected by 
means of a device consisting of a double chuck with coaxial collets and 
conical surfaces, while the tangential connection to the loop of the 
grounding conductor is effected by means of a rider. 
The connection of the grounding conductor preferably comprises, 
furthermore, a third conductor element connected tangentially at each of 
its ends, on the one hand, to the said grounding conductor and, on the 
other hand, to the looped conductor, the connection of the latter to the 
loop being effected in a tangential direction opposite that of the said 
connection, the grounding conductor, the conductor of the loop of the 
third connecting conductor forming a sort of triangle, known as a 
connection "equipotential triangle," the sides of this triangle being, in 
fact, substantially circular arcs. 
Said loop preferably has the general shape of a rectangle with corners 
rounded along substantially circular arcs. 
Finally, one of the sides of the "equipotential triangle" is preferably one 
of the rounded corners of said loop. 
Thirdly, still in accordance with the present invention, an electric 
junction device for electroconductive cables is characterized, in general, 
by the fact that it incorporates at least one part of elongated shape 
curved on itself in the direction of its width so as to form, by itself 
alone or in combination with another similar part, a sleeve intended to 
completely surround two electric cables which are parallel to each other 
in said sleeve, the said part being formed of a non-magnetic 
electroconductive metal; the two adjacent shell edges are advantageously 
pressed against each other in close electrical contact. 
It results from these arrangements that the junction thus formed is of very 
low impedance with respect to electric discharges of the type of those of 
lightning or induced by it. 
Preferably, the aforementioned shell or shells are stopped by suitable 
means around conductors, these means being arranged in the vicinity at 
least of each of the ends of the shell. 
A junction device according to the invention preferably furthermore 
incorporates a part, known as the contact part, which has 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 in accordance with the present invention will find use in 
the side-by-side junction of electric conductors as such junctions appear 
in the aforementioned patent applications, particularly when there is 
concerned the "grounding" of an anti-lightning installation and in 
particular when the ground connection of such installations is formed of 
several electric conductors buried in the earth; in this case, the 
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 said device. 
Applied to the case in which two grounding conductors penetrate into the 
earth in the vicinity of each other, these two conductors are connected, 
on the one hand, by at least one device such as described above and, on 
the other hand, by an electroconductive segment, the electroconductive 
segment and the said conductors forming underground a connection triangle 
known as an equipotential triangle.

Referring to FIG. 1, by way of illustration of the prior art in this field 
a medium-voltage electroconductive line stop 101, for instance, comprises 
a mast 102, a connection 103 to the subsequent installations, an insulator 
assembly 104 and an anti-lightning protective device, itself comprising a 
pair of electrodes 105 and 106 and an evacuation conduit 107 towards a 
ground connection 108; subsidiarily, an "anti-bird" rod is arranged 
between the electrodes in order to avoid the electrocution of those 
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 stem of 
the electrode serves as conductor and that, in general, the electrode is 
connected to its stem by means of an eyehole and a bolting through the 
eyehole; in general, furthermore, both the electrode and its support stem 
are made of galvanized iron. This device for the protection of the 
subsequent installation from the effects of lightning, known as an 
arrester, is, in general, as has been stated above, ineffective for 
discharges in excess of 15 kA and it is fully representative of the known 
prior art. 
In FIG. 2, which shows an improved arrester in accordance with the 
invention, electrodes 111 and 112 for instance of copper, are supported by 
supports 113 and 114 respectively, having in general a T shape; each 
support such as the support 114 is formed of a transverse portion 115 and 
a stem 116. The particular structure of these supports will be described 
further below, but it should be noted here that the transverse portion has 
a generally cylindrical shape, along the axis of which there are connectd 
the electrode 112, on the one hand, and the cable 117 connecting this 
first electrode to the electroconductive or discharge shunting line; it 
will be noted that the same is true with regard to the other electrode 
with the cable 118 connecting the second electrode to the ground. 
It will also be evident from the figures that, in accordance with what is 
recommended by the present invention, the cable 117 is connected 
tangentially to the line 101' at a point 119 which is at least 1.50 meters 
from the arrester and that the cable, which is insulated for a minimum of 
1000 volts, which connects the second electrode to the ground, has, in the 
vicinity of the mast 102', a curvature 120 of rather large radius (on the 
order of 50 cm for example). 
FIG. 3 shows in cross section, on a larger scale and in greater detail, an 
electrode holder such as the electrode holder 114 of the preceding figure; 
this electrode holder is essentially formed of a transverse portion 115 
and a stem 116; the transverse portion 115 is a substantially cylindrical 
part or else a part symmetrical with respect to the axis 121; at one of 
its ends 122 it has a chuck 123 of the push-out collet type surrounding 
the end of the electrode 112; and its other end 127 it has a connecting 
member for the multi-strand cable 117 comprising a nut 124 with conical 
inner surface and conical core 125 which is bored axially; this type of 
connection of the multi-strand cables is known per se and it will be 
recalled that the tightening of the nut 124 brings the inner end of the 
core and the clamped strands in contact with the end stop 126. The 
push-out collet chuck of the end 122 is also known per se; it will be 
noted, however, that the cylindrical part or transverse portion 115 is 
provided with an inner bore 128 which is sufficiently deep to permit the 
electrode to engage to a greater or lesser extent therein. 
In accordance with the invention, the component parts of the transverse 
portion are formed of one or more non-magnetic metals, or else 
non-ferromagnetic metals such as copper, brass, bronze, aluminum or the 
like, to the exclusion of metals having ferromagnetic properties. 
The stem 116 is connected to the transverse portion 115 by an axially bored 
ring 129. 
In FIG. 4, an electrode support 130 is formed of a transverse part 131 
provided at each of its ends with two push-out collet chucks similar to 
the push-out collet chucks 123 of the preceding figure; one of the chucks 
serves to clamp the electrode 112 while the other chuck clamps a rod 132 
which, in its turn, is connected to the multi-strand conductor 117 via a 
connector 133 having substantially the same functional structure as the 
transverse part of the preceding figure; this connector is illustrated in 
greater detail in FIGS. 5 and 5a. The stem of the electrode support 130 is 
formed of an upper portion formed by a rod 116 and by a ring 129 which is 
bored axially in order to surround the transverse portion 131 of a 
connecting part 134 forming two push-out collet chucks and of a rod 136 
which is rigidly connected with an insulator portion 137 at one of its 
ends, its other end being engaged in one of the chucks of the part 134. 
The advantage of this assembly with intermediate part 134 is that it 
permits easy adjustment in height and orientation of the electrode 112. 
In FIG. 4a, a variant mounting of the arrester differs from the preceding 
one in that the transverse part 131' comprises at one of its ends a 
necked-down portion 132' similar to the part 132 and at its other end an 
axial clamping chuck formed by a nut 160 with conical inner tapping and by 
an outer thread 161, itself conical, of the end of the transverse part 
131; said threaded end has several longitudinal slits which, upon the 
tightening of the nut, permit the clamping of the electrode 112'. The 
other portions of this electrode mounting are similar to those of the 
preceding figure. 
In FIGS. 5 and 5a the connecting part 133 of the preceding figure is 
formed, with respect to a first portion 140, by a push-out collet chuck 
and, with respect to a second portion 141, by a multi-strand cable 
connection member comprising a nut 142 with conical inner surface and 
axially bored conical core 143; this connecting member is entirely similar 
in itself to that formed by the part 127 of the transverse part of FIG. 3. 
It will be noted that the connecting part 134 of FIG. 4 is formed of two 
portions 140 of the part of FIG. 3. 
It will be noted that the connecting part 134 of FIG. 4 is formed of two 
portions 140 of the part shown in FIG. 3. 
FIG. 5a recalls that a push-out collet such as the collet 145 of FIG. 5 is 
an axially bored conical part split along a generatrix. 
In FIG. 6 various examples of the use of the device of the invention are 
illustrated as applied to different lines. It will be noted that the 
electrode support stem can be doubled, as is true in the case of a stem 
150, for instance, which is applied for the anti-lightning protection of a 
very high voltage line, in view of the great length of the insulator line. 
In FIGS. 7 and 7a an arrester also applies the principles of the invention 
in that the electrode support is formed of a transverse part such as 152 
axially clamping an electrode 153 and connected, still axially, to the 
conductor 117'. Stems such as 154 are made of an insulating material such 
as porcelain and are fastened on a support plate 155 which may be of 
aluminum. The connection of the electrodes to the multi-strand cable 117' 
is effected, for instance, via a part 133 similar to that of FIG. 4 and by 
an end chuck 158 of the transverse part 152. In FIG. 7a, the chuck 154 of 
the preceding figure is replaced by a transverse screw clamping 156. 
FIG. 7b shows a variant embodiment of FIG. 7 in which the electrodes 153 of 
the preceding figure are replaced by electrodes with spheres 157. Such 
sphere electrodes, which are slightly more expensive than the horn 
electrodes described up to now, may also be provided on all of the 
arresters previously described and be substituted for the horn electrodes; 
sphere electrodes are, in principle, slightly more effective than horn 
electrodes, but it will be noted that this increase in effectiveness is 
entirely minimal as compared with that provided by the mounting of the 
electrodes, whatever they are, which are recommended by the invention. 
In FIG. 8, there is shown a mounting of anti-lightning arresters in 
accordance with the invention which is rather similar to that shown in 
FIGS. 2 to 4 (equivalent parts are provided with the same reference 
numbers); it will be noted, however, that in this figure the arrester 
support stems such as 161 and 162 are bars or flats of rectangular cross 
section, which are also respectively shown in FIG. 8c (Section taken along 
8c--8c of 161) and FIG. 8a (Section taken along 8a--8a of 162); the lower 
portion of the stem 161 is connected by means of a bolt 164 to member 165 
connecting the line 101 to a first insulator 166 while the lower portion 
of the stem 162 is fastened to a second insulator 167 by a bolt 168. 
It will also be noted from this figure that an anti-bird device 170 is also 
formed by a flat the rectangular section of which is shown in FIG. 8b 
(Section taken along 8b--8b of 170) which flat is twisted a quarter of a 
turn in the vicinity of its lower portion in order to be fastened via a 
bolt 172 on the connecting portion of two adjacent insulators 166 and 167. 
There will also be noted in this figure the insulating sheath 175 of the 
cable 120, which is an insulation sheath of at least 1000 volts. 
In FIG. 9 a single electric conductor is closed on itself to form a loop 
202 by a looping device 201; the loop has a substantially rectangular 
shape the straight portions of which have lengths greater than one meter 
and preferably of at least 5 meters; the conductor is a bare copper cable 
of a cross section of 25 to 150 mm.sup.2 ; the sides of the loop are 
connected to each other along curved portions of a radius of about 0.5 
meter. 
A grounding conductor 203 of, for instance, arresters or anti-lightning 
devices of variable resistance of the overhead system is an electric 
conductor having the same characteristics as the conductor of the loop 202 
but it is preferably insulated at least on its overhead portion; this 
grounding conductor is connected tangentially once to the loop 202 at a 
first point of connection 204 by means of a connecting device; it is again 
connected a second time tangentially to the loop at a second point of 
connection 204 by means of a third conductor 208, which, in its turn, is 
connected tangentially at each of its ends to the conductor 203 and to the 
loop 202 at a third point of connection 204; the first and second points 
of connection 204 on the loop have opposite tangential directions; the 
conductors 202, 203 and 208 are curved in the vicinity of their point of 
connection and they form a sort of triangle 210, called an equipotential 
triangle; the curved sides of this triangle are substantially circular 
arcs having a radius of about 0.5 meter; the third conductor 208 is, of 
course, similar to the other conductors of the ground. 
In FIG. 10, the looping device 201 is formed of a double chuck with coaxial 
conical surfaces and collets, known per se in connectors for electrical 
conductors; in the application made of it in the present invention, the 
component elements, namely body 211, collet 212 and nuts 213 are of 
non-magnetic metal, preferably of bronze. 
In FIG. 11, a connecting device 204 is formed by a rider 215 with two nuts 
216 and safety washer 217, which is also of known type, the component 
elements of which are developed, in accordance with the invention, of 
non-magnetic metal. 
FIG. 12 shows diagrammatically a line-end mast 220 comprising a transformer 
station 221 and lightning protection means consisting of an arrester 222 
grounded by an insulated conductor 203; the loop 202, which is located at 
a distance of about 1 or 2 meters below the surface of the earth and 
around the base of the mast, is, for instance, similar to the one shown in 
FIG. 16; there will also be noted a conductor 223 for grounding the mass 
of the overhead system and/or the neutral of the network; this conductor 
223 is in its turn connected tangentially to the loop 202. 
In FIGS. 13, 14, 15, and 16, ground connections have a structure and/or 
geometry which is substantially different from the ground connection of 
FIG. 9; these ground connections are intended for overhead installations 
larger than a single mast; for instance, the ground connections of FIGS. 
13, 14, and 15 can be used for the grounding of transformer installations, 
while the ground connection of FIG. 16 will be suitable, for instance, for 
a high-voltage line mast. It will be noted that the higher the overhead 
installation, the bigger the loop 202 must be; for optimum protection, the 
dimensions of the loop will preferably be greater than the largest 
dimension of the installation protected, and the loop will preferably 
surround the trace of the installation on the ground. It will be noted, 
however, that these ground connections are suitable in general for all 
high, medium and low-voltage installation. There can be noted in their 
structure the elements referred to in the description of the grounding of 
FIG. 9, namely a looping member 201, one or more single-conductor loops 
202, equipotential connection triangles 210, connecting parts such as 204 
and various grounding conductors such as 203 and 223. 
Finally, from all of FIGS. 9 to 16 the tangential and/or coaxial connection 
of the conductors will be noted; by coaxial connection of the conductor 
there is understood the connection of the conductor in the extension of 
itself, this essential characteristic of the invention having the effect 
of decreasing the impedance of the conductors with respect to the electric 
wave of the lightning. 
In FIG. 17, which illustrates diagrammatically a transformer station 326 of 
HV/MV or VHV/HV type, the devices of the preceding figures are indicated 
symbolically by small rectangles 320 bridging two cables side by side. It 
will be noted from this figure that the conductors such as 321 and 322 for 
the grounding of the overhead anti-lightning installation do not have any 
mechanical interruption in the portion thereof which is buried in the 
earth; it will also be noted that in the earth they are connected due to 
junction devices by a segment such as 323 to form connection triangles 
324, so-called equipotential triangles; finally, it will be noted that the 
portion buried in the earth having the general shape of a rectangle, a 
conductor 325, referred to as internal bridge conductor, connects the 
sides of the rectangle in the vicinity of their center. 
In FIG. 18 it is recalled that a ground connection of the type shown in the 
preceding figure may be advantageously combined with arresters such as the 
arrester 330, called a high flow power arrester, as they are defined in 
the first patent application cited above. 
In FIGS. 17 and 18 there will be found the same parts as those mentioned in 
connection with the following figures bearing the same references. It will 
be noted that the radii of curvature r of the conductors, both overhead 
and buried, are at least 0.5 meter. 
In FIG. 19, a device for joining the conductors of the two parallel 
electric cables 301 and 302 is formed essentially of an elongated part 303 
which is curved on itself to form a sleeve surrounding the conductors; it 
is characterized by the fact that the two adjacent edges of the shells are 
pressed against each other along a close electric contact surface 304; 
straps 305 are arranged in the vicinity of the ends of the shell 303 FIG. 
19a is an end view of FIG. 19. 
In FIG. 20, the sleeve surrounding the cables 301 and 302 is formed by a 
pair of identical shells 306 and 307 whose longitudinal edges are 
maintained in close electric contact by means of straps 305 FIG. 20a is an 
end view of FIG. 20. 
In FIG. 21 the electrical junction of conductors 308 and 309 of different 
diameters is assured by shells 310 and 311 which themselves have different 
radii of curvature so as to snugly fit the surface of the conductors. 
FIGS. 22 and 22a show electric junction devices similar to those of the 
preceding figures but differing, however, by the presence between the 
conductors of contact pieces 312 or 313 having a double-cradle profile; 
these contact pieces, as well as the straps, are made of a non-magnetic 
metal or alloy which is a good conductor of electricity. 
Although several elements (arrester, ground connection and connecting 
device) of the present invention have been shown in one or more 
embodiments, it is to be understood that the scope of this invention is 
not limited to these elements by themselves or in combination or the 
embodiment thereof which has been shown or described, but extends to all 
lightning protection devices as well as electrical systems using the 
latter which comprise the general features set forth above in order to 
decrease to the utmost the impedance of the over-voltage evacuation 
circuits, in particular by favoring to the maximum the effect of pedicular 
conduction.