Arching protection device for coated overhead cables

Abstract

 The invention relates to an arching protection device for coated overhead cables, comprising a first electrode (4, 5) which is fastened to a wire (2) with a clamp (3) penetrating through the wire insulation and a second electrode (6) which is fastened to a pole crossarm or some other insulator support at such a distance from the first electrode that an electric arc can be controllably ignited and sustained between the electrodes. Said electrodes (4, 5 and 6) extend crosswise to each other, whereby movements of the cables (2) do not have a substantial effect on the distance between the electrodes.

Description

[0001] The present invention relates to an arching protection device for coated overhead cables, comprising a first electrode which is fastened to a wire with a clamp penetrating through the wire insulation and a second electrode which is fastened to a pole crossarm or some other insulator support at such a distance from the first electrode that an electric arc can be controllably ignited and sustained between the electrodes.

[0002] The Applicant's patent publication EP-0387865 discloses an arching protection device for coated overhead cables, wherein an electrode is fastened to a wire with a wire-insulation penetrating clamp. This solution has proved to be highly useful and in most cases very functional. The only discovered defect is that one electrode alone does not always function at low short-circuit currents. The inclusion of a second electrode, which is mounted on the crossarm of a pole or some other insulator support at a suitable distance from the wire electrode, enables the controlled ignition of an electric arc even at low short-circuit currents. However, a problem found in such a two-electrode system is that, as the wires are moving in vertical and lateral directions as a result of e.g. trees and ice loads, the distance between electrodes changes and, thus, the functionality of the arching protection device changes as well e.g. in such a manner that a fault may be caused by circuit overloads.

[0003] An object of the invention is to eliminate this problem and to provide an arching protection device of the above type, wherein the distance between electrodes does not substantially change as a result of movements undertaken by the wires.

[0004] This object is achieved by means of a solution as set forth in claim 1. The non-independent claims disclose preferred embodiments for the invention.

[0005] One exemplary embodiment of the invention will now be described in more detail with reference made to the accompanying drawing, in which

fig. 1

shows an arching protection device of the invention in a side view and

fig. 2

shows the same in the direction of a line.

[0006] An insulator 1 mounted on the crossarm of a pole or some other insulator support carries a coated overhead cable 2, to which is fastened a first arching protection horn 4 by means of a clamp 3. The protection horn 4 is a rod-like electrode, which is dimensioned to withstand an electric arc. For improved endurance, the protection horn 4 may have its end provided with a thickening 5. The barrier horn 4 extends crosswise relative to the wire 2, in the present case downwards. The clamp 3 is provided with teeth 3a which pierce through the insulation of the wire 2 as clamping screws 3b are tightened. This establishes a galvanic contact from the wire 2 by way of the clamp 3 to the protection horn 4, 5.

[0007] In the depicted case, a second electrode 6 takes the form of a horizontal rod, which is attached to a pole crossarm or some other insulator support or an insulator by means of a multi-section arm whose arm sections 7, 9, 11 can be secured in various relative positions by means of adjusting elements 8 and 10. Adjustment of the arms 9 and 11 can be used for adjusting the relative distance or gap between the electrodes 6 and 4, 5. Adjustment of the arms 7 and 9 an be used for adjusting the vertical position of the electrode 6, which in the operative condition is located slightly above the level of the bottom end 5 of the first electrode 5, 4. One or both electrodes 6, 4 can be protected by means of bird guards 12 in order to eliminate faults possibly caused by birds and small animals. The bird guard 12 comprises a plastic insulation coating, which leaves an electric-arc discharge area uncovered.

[0008] An essential feature in the invention is that the electrodes 6 and 4, 5 are located crosswise to each other and at the same time transversely to the wire 2, whereby movements of the wires 2 do not have a substantial effect on the distance between the electrodes. Indeed, the distance between the electrodes can be maintained quite constant by giving the electrodes just modest curvatures. Since, as the wire 2 executes a movement, the electrode 4 moves in vertical or lateral direction, its distance from the electrode 6 does not substantially change, which also enables the controlled ignition of an electric arc.

[0009] The invention is not limited to the above-described exemplary embodiment. For example, the electrodes may have an orientation which is different from what is described above, such that the electrode 4 has its end provided with a horizontal section which extends crosswise to a vertical electrode replacing the electrode 6. By using suspended insulator chains, the electrode rod 4 can also be directed upwards. The electrodes may also have a cross-section which varies from a round rod to a more or less flat plate. The connection between the electrode 4 and the clamp 3 can also be implemented in a variety of ways, e.g. with a separate screw attachment.

Claims

1. An arching protection device for coated overhead cables, comprising a first electrode (4, 5) which is fastened to a wire (2) with a clamp (3) penetrating through the wire insulation and a second electrode (6) which is fastened to a pole crossarm or some other insulator support at such a distance from the first electrode that an electric arc can be controllably ignited and sustained between the electrodes, characterized in that said electrodes (4, 5 and 6) extend crosswise to each other, whereby movements of the cables (2) do not have a substantial effect on the distance between the electrodes.

2. An arching protection device as set forth in claim 1, characterized in that the first electrode (4, 5) extends down- or upwards and the second electrode (6) is elongated in horizontal direction and that both electrodes (4, 5; 6) lie transversely relative to the wire (2).

3. An arching protection device as set forth in claim 2, characterized in that the second electrode (6) is located slightly above the level of the bottom end (5) or below the top end of the first electrode (5, 4).

4. An arching protection device as set forth in any of claims 1-3, characterized in that the electrodes (4, 5 and 6) are substantially rod-shaped.

5. An arching protection device as set forth in any of claims 1-4, characterized in that the vertical position and distance of the second electrode (6) from the first electrode (4, 5) are adjustable by means of adjusting elements (8-10).

6. An arching protection device as set forth in any of claims 1-5, characterized in that the supporting arm of the second electrode (6) consists of several arm sections (7, 9, 11), which are attachable to each other in various relative positions for adjusting the distance between the electrodes and preferably also for the vertical adjustment of the second electrode (6).

7. An arching protection device as set forth in any of claims 1-6, characterized in that at least one of the electrodes (6, 4) is protected by means of a bird guard (12).

Drawing