Holding device in the form of an outrigger for a high-voltage electrical cable

Description

[0001] The invention relates to a support device for high voltage electrical cables, greater than 10,000 V, and more particularly a support device in the form of a gantry.

[0002] The present invention relates to the field of high-voltage electrical energy transport and more particularly to a support device for high-voltage electrical cables, notably implemented in underground installations.

[0003] In this regard, it is becoming increasingly common to bury high-voltage power lines, avoiding overhead infrastructure.

[0004] Therefore, these high-voltage power lines are required to run along underground galleries or in suitable technical trenches.

[0005] Specifically, in such technical channels or galleries, large cross-section electrical cables rest on suitable support devices.

[0006] Just as with overhead infrastructure, in the event of damage to such a high-voltage power cable, and therefore a short circuit, it is essential to prevent the formation of electrical arcs. Indeed, due to the available electrical power, such arcs create significant damage that can quickly spread and cause fires, the consequences of which are exacerbated in the confined space of an underground tunnel.

[0007] In a simplified form, such support devices resemble a bracket comprising a support arm on which one or more high-voltage electrical cables can rest. This support arm is attached to a mounting plate suitable for fixing to a wall using appropriate anchoring methods.

[0008] Very frequently, such gantries are designed in steel, taking into account the weight of these high-voltage power line cables and the stresses that the latter are likely to apply to these gantries under the effect of electrical shocks, expansion or other.

[0009] To avoid the aforementioned problems, these steel poles are connected to earth via a copper braid of appropriate cross-section. This allows the energy supplied to flow freely into the ground in the event of a short circuit.

[0010] The main problems observed with this grounding of the gantries are that a faulty connection, due for example to oxidation, can prevent the normal flow of energy to the ground in the event of a short circuit. The formation of destructive electrical arcs is then inevitable.

[0011] We have also observed that these grounding braids for the gallows are simply missing, for example as a result of theft, tearing or other.

[0012] Obviously, in the event of a short circuit, the intensity of the electric arc produced leads to the melting of the metal of the gantry, which can flow onto the installations below, for example onto other high voltage electrical cables, degrading their insulation sheath to cause a chain reaction and the start of a fire in these technical channels or underground galleries.

[0013] It is already known to design high-voltage electrical cable supports from synthetic material, more particularly from dielectric composite material.

[0014] Due to the particularly significant mechanical stresses mentioned above that such gantries can undergo, designing them in composite material makes them particularly expensive.

[0015] Indeed, their design in composite material proves complex when one considers that such gantries can be subjected to bending, torsion and other stresses.

[0016] It was as part of an initial inventive approach that we imagined designing high-voltage electrical cable support devices in the form of steel poles while avoiding their grounding.

[0017] We know of a gantry for high voltage electrical cables, comprising a steel support arm attached by welding to a steel fixing plate.

[0018] Furthermore, along the support arm, openings are provided for the passage of fastening devices, such as straps, clamps, flanges or similar, to secure one or more high-voltage electrical cables to this support arm.

[0019] These openings extend longitudinally along this support arm and are essentially intended for the passage of screws by means of which a flange is capable of securely fixing high-voltage electrical cables to such a gantry.

[0020] However, these fixing screws, often pre-mounted on the stem forming a cradle to retain the cables, can damage them when they are put on these stems, taking into account in particular the weight of these cables.

[0021] Furthermore, these fixing screws, and even the brackets, are made at least partially of metal to resist fire. However, they are conductive elements that can propagate an electric arc in the immediate vicinity of the cable(s).

[0022] Also known from US patent 4,032,096 is a support device in the form of a bracket for electrical cables, consisting of a U-shaped metal profile bent at a right angle. It has a horizontal flange defining a cable support arm and a vertical flange for mounting on a post. The support arm has two parallel vertical flanges extending along the longitudinal edge of a horizontal wall equipped with a series of oblong openings extending transversely. Mounted on this horizontal wall is an adapter piece made of bent sheet metal and shaped like a cradle, on which a high-voltage electrical cable is designed to rest. The cable can be secured to this adapter piece by means of a strap.

[0023] A support device in the form of a gantry for electrical cables is also known from document JP 2006-166541. This device comprises a support arm defined by a vertical plate welded to a mounting plate configured to be fixed to a pole in the form of a circular profile. A porcelain bracket, forming a cradle for receiving a cable, is engaged on the upper edge of the plate forming the support arm.

[0024] Document JP 58-51716 describes a cable support device in the form of a bracket for electrical cables, made of fiberglass-reinforced resin, comprising a cable support arm attached to a mounting plate. This bracket is overmolded onto a T-shaped metal reinforcement insert located at the junction of the support arm and the mounting plate.

[0025] Thus, the invention relates to a support device in the form of a gantry for high voltage electrical cables, greater than 10,000V, according to claim 1.

[0026] Other objects and advantages of the present invention will become apparent during the following description relating to embodiments given by way of example.

[0027] Understanding this description will be facilitated by referring to the attached drawings, in which: [ Fig.1 ] is a schematic and perspective representation of a support device in the form of a gallows according to the invention. Fig.2 ] is a schematic representation of a longitudinal median section of such a gallows illustrated in the figure 1 . [ Fig.3 ] is a schematic and perspective representation of a gantry with a cradle at the support arm, defined by bosses corresponding to the means of fixing high-voltage electrical cables; Fig.4 ] is a schematic, cross-sectional representation of fastening means comprising a cradle in the form of a bracket; [ Fig.5 ] is a schematic representation of a gantry with means for fixing high-voltage electrical cables including a gutter-shaped cradle.

[0028] With reference to these drawings, the invention relates to support devices 1 for high voltage electrical cables exceeding 10,000 V.

[0029] Such a support device 1 is in the form of a gantry 2 comprising, essentially, a steel support arm 3 extending from a steel fixing plate 4 onto which it is attached by welding.

[0030] The support arm 3 is in the form of a profile, here with an inverted U-shaped cross-section, having the particularity of a certain inertia to support, without deformation, high-voltage electrical cables of large cross-section and therefore of significant weight.

[0031] Thus, this support arm 3 essentially comprises two parallel vertical wings 3B extending along the longitudinal edge of a horizontal wall 3A on which the high-voltage electrical cables are intended to rest. Advantageously, this support arm 3 is designed by bending a metal plate so as to define junction edges with a radius of curvature between the two wings 3B and the horizontal wall, thereby preventing any risk of damage to a high-voltage electrical cable.

[0032] To improve the inertia of this support arm 3, the said vertical wings 3B are preferably of increasing width from the free end of this support arm 3 towards the fixing plate 4.

[0033] Note that at this free end of the support arm 3, a spacer wall 3C can be attached to the vertical wings 3B and to the horizontal wall 3A by extending substantially parallel to the fixing plate 4.

[0034] This support device 1 is coated on its entire perimeter by immersion overmolding of a layer of a synthetic dielectric material 6. In short, both the support plate 4 and the support arm 3 are entirely covered, on all their faces, with such a layer of synthetic dielectric material 6.

[0035] According to an advantageous embodiment of the invention, the synthetic dielectric material defining this layer 6 is plasticized polyvinyl chloride which, apart from the good dielectric insulation it provides, has good resistance to acids and bases, but also to solvents and hydrocarbons or to UV.

[0036] In its liquid state, this material also exhibits Newtonian behavior which contributes to perfect control of the coating thickness by immersion molding of the gantry 2.

[0037] According to the invention, this coating layer of a synthetic dielectric material 6 has a thickness 7 defined to withstand a breakdown voltage of at least 10,000 V.

[0038] More specifically, this thickness 7 of layer 6 is preferably greater than 3 mm.

[0039] The fixing plate 4 has at least one, preferably several openings 8 for the passage of a fixing element such as a screw or similar.

[0040] At least one of these openings 8 can be provided an insert 9, again made of synthetic dielectric material whose thickness and / or mechanical resistance can be chosen more particularly according to the constraints imposed by a fixing element on the support 2 at the level of this opening of 8.

[0041] Thus, this or these inserts 9, for example in the form of sockets, can have a defined axial compression resistance so as not to damage the layer 6 of synthetic dielectric material under the action of tightening these fixing elements which are required to pass through the openings 8.

[0042] Similarly, the thickness of the peripheral wall of such socket-shaped inserts 9 can also be chosen according to these constraints, independently of the thickness 7 of layer 6.

[0043] The support arm 3 is equipped with means for fixing at least one high-voltage electrical cable 11.

[0044] In particular, along the support arm 3, especially at the level of its horizontal wall 3A, one or more other openings 10 may be provided for receiving these fixing means 11.

[0045] Such openings 10 can take different forms of realization. Thus they can be in the form of a round or oblong hole and, in this case, extend longitudinally or transversely along this horizontal wall 3A of the support arm 3.

[0046] The fastening means 11 may take the form of straps, collars, brackets or similar devices, to secure one or more high-voltage electrical cables to this support arm 3.

[0047] It should be noted that such means of fixing which contribute to holding high voltage electrical cables on the support arm 3 are less stressed compared to those which contribute to the installation and holding of a gantry 2 against a wall for example.

[0048] However, just as in the openings 8, in at least one of these openings 10, an insert can be provided that is capable of preventing the alteration of the coating layer 6 of synthetic dielectric material.

[0049] Returning to the fastening means 11, they advantageously include a cradle 12 for receiving the high-voltage electrical cable(s) on the support arm 3.

[0050] This cradle 12 can take on different forms. In particular, and as can be seen in the figure 3 , it can be defined by 2 bosses 12A or by a concave shape at the level of the horizontal wall 3A of the support arm 3.

[0051] As seen in the figure 4 , this cradle 12 can be designed by a rider 12B whose retention on the support arm 3 is ensured by means of a strap corresponding to said fastening means 11.

[0052] In the figure 5 This cradle 12 takes the form of a trough 12C open at the top for receiving high-voltage electrical cables. This trough 12C has, on its lower face 13, means 14 for interlocking with the support arm 3. Thanks to these interlocking means 14, this trough C can be adjusted in position along the latter.

[0053] The particularity of this gutter 12C is that it has extensions 15A, 15B on either side of the support device 1 capable of guiding the high voltage electrical cable(s) on each side of the pole 2. In this way, this or these high voltage electrical cable(s) are locally less stressed through the latter.

[0054] In addition, and as can be seen in the figure 4 , the fastening means 11 may optionally be supplemented by one or more load distribution brackets 16 on the high voltage electrical cable(s) of the clamping action exerted by a strap, a collar or similar.

[0055] In particular and according to the invention, the fastening means 11 comprise at least two oblong openings 10 extending transversely across the horizontal wall 3A of the support arm 3 on either side of the cradle 12, for the passage of a ratchet strap 11A, complementing these fastening means 11.

[0056] Furthermore, if the strap passes through the openings 10 in the horizontal wall 3A of the support arm 3, in order to secure this or these high voltage electrical cables, the ratchet 11B takes an advantageous position under the support arm 3, between the vertical wings 3B.

[0057] This ratchet 11B, often metallic, is thus protected under the horizontal wall 3A, between the vertical wings 3B and the mounting plate 4, or even the spacer wall 3C. All these walls being perfectly insulated by encasing them in an insulating coating, they prevent a short-circuit arc from reaching this ratchet 11B.

[0058] The advantage of such a solution according to the invention is, compared to a retaining collar, that it requires less bulk for the placement of the strap over the cable(s), strap 11A whose tightening ratchet 11B takes position under the boom, without even generating bulk under the latter because it fits between the vertical wings 3B in particular.

[0059] Preferably, the strap is made of aramid for its fire resistance. In particular, this material, in its application according to the invention, has a lower calorific value compared to other materials and does not contribute to the spread of a fire that might break out in a trench or gallery housing these high-voltage electrical cables.

[0060] In the context of the immersion coating process of such a support device 1, in particular in the form of a gantry 2, with a synthetic dielectric material, more particularly with polyvinyl chloride, it is necessary to ensure that all faces of the support arm 3 and the steel fixing plate 4 are perfectly covered with a coating layer 6 of thickness 7 as required.

[0061] Obviously, to ensure this coating by immersion, it is necessary to handle the steel assembly 5 formed by the support arm 3 and the fixing plate 4, in particular by means of suitable gripping means.

[0062] Such gripping means advantageously take the form of a hook at the end of which the steel assembly 5 of the gantry 2 is hung, in particular through one of its openings 8.

[0063] Specifically, at least one insert 9 is inserted into this opening 8, and then the handling hook is inserted into the latter to dip and immerse the steel assembly 5 in the bath of dielectric synthetic coating material. Thus, this coating material covers all faces of the steel assembly 5, simultaneously sealing the insert 9 in the opening 8 and creating a perfect continuity of the dielectric layer 6 through the insert 9 itself, which is made of a dielectric synthetic material.

[0064] The advantages arising from the present invention lie in the fact that the fastening means 11, as defined above, combined with a perfectly insulated bracket, provide very easy and safe installation and fastening of the high-voltage electrical cable(s) on such a bracket. The presence of the cradle ensures that the cable(s) are held in position without risk of injury before the strap is fitted. The strap can be fitted regardless of the available space. The strap is tightened by means of a ratchet designed to retract, in a protected manner, under the bracket. The strap, being made of aramid, withstands the mechanical stresses that high-voltage electrical cables can exert in the event of a short circuit on such brackets, while also being highly fire-resistant.

Claims

1. A support device in the form of a jib for high-voltage power cables, greater than 10,000V, comprising a steel support arm (3) comprising two vertical parallel wings (3B) extending along the longitudinal edge of a horizontal wall (3A) on which the high-voltage power cables are intended to rest, the support arm (3) further comprising means (11) for fastening at least one high-voltage power cable comprising: • a cradle (12) on the horizontal wall (3A) of the support arm (3) for receiving the high-voltage power cable(s), • at least two oblong-shaped openings (10), extending transversely on the horizontal wall (3A), on either side of the cradle (12), the support arm (3) is mounted by welding on a steel fastening plate (4), said fastening means (11) comprising a strap (11A), said strap (11A) passing through said openings (10) to surround the high-voltage power cable(s), characterised in that the device is further covered over its entire periphery by immersion overmoulding with a layer (6) of synthetic dielectric material, said strap is a strap with a ratchet (11B), and the ratchet (11B) taking position under the support arm (3), between the vertical wings (3B).

2. The support device according to claim 1, characterised in that the cradle (12) is defined by at least two bosses (12A) or a concave shape at the horizontal wall 3A of the support arm 3.

3. The support device according to claim 1, characterised in that the cradle (12) is formed by a cable clip (12B) held on the support arm (3) via the strap (11A).

4. The support device according to claim 1, characterised in that the cradle (12) takes the form of a trough (12C) open at the top for receiving high-voltage power cables.

5. The support device according to claim 4, characterised in that said trough (12C) comprises, on its underside (13), means for interlocking (14) with the support arm (3).

6. The support device according to claim 4 or 5, characterised in that the trough (12C) comprises extensions (15A), (15B) on either side of the support device (1) to guide the high-voltage power cable(s) on each side of the jib (2).

7. The support device according to any one of the preceding claims, characterised in that the fastening means (11) are supplemented by one or more load-distributing cable clips (16).

8. The support device according to any one of the preceding claims, characterised in that the strap (11A) is made of aramid.