ELECTROMECHANICAL DISCONNECTOR BETWEEN A HIGH-VOLTAGE OVERHEAD TRANSMISSION LINE AND A VOLTAGE TRANSFORMER

Abstract

An electro-mechanical disconnector mounted between an HV overhead power line conductor and a voltage transformer, mounted on a support of the support power line of HV overhead power line conductors. The electro-mechanical disconnector comprises an isolating element and a sacrificial element arranged in series with each other. The sacrificial element is made of a material capable of melting upon the passage of a fault current, and the sectioning element is capable of moving to an electrically insulating distance from the conductor following the melting of the element.

Claims

1. An electromechanical disconnector installed between an high-voltage overhead conductor of an high-voltage overhead transmission line and a voltage transformer mounted on a transmission tower for high-voltage overhead line conductors; said electromechanical disconnector comprising: a sectioning element and a sacrificial element arranged in series so as to electrically connect said conductor to said voltage transformer; said sacrificial element being made of a material suited to melt upon a passage of a fault current; and said sectioning element being suited to place itself at an air electrical insulation distance from said conductor following the melting of said sacrificial element.

2. The electromechanical disconnector according to claim 1, wherein said sectioning element comprises an operating arm having a first end connected to said sacrificial element.

3. The electromechanical disconnector according to claim 2, wherein said operating arm is a stiff rod or a flexible element.

4. The electromechanical disconnector according to claim 3, wherein said operating arm comprises a second end comprised in a hinge assembly suited to cause a rotation of the operating arm.

5. The electromechanical disconnector according to claim 1, further comprising a collecting cup arranged so as to surround said sacrificial element in order to gather the molten material.

6. The electromechanical disconnector according to claim 5, wherein said collecting cup is fixed to said operating arm close to the first end.

7. The electromechanical disconnector according to claim 1, wherein said sacrificial element is made of a material that melts due to the passage of a fault current and has a mechanical performance such as to resist wind action.

8. The electromechanical disconnector according to claim 7, wherein said sacrificial element is made of a material comprised in the group consisting of steel, copper, and conductive alloys.

9. The electromechanical disconnector according to claim 1, wherein said air electrical insulation is greater than 1.5 metres for an operating voltage of the high-voltage transmission line equal to 150 kV and greater than 3.5 metres for an operating voltage of the high-voltage transmission line equal to 380 kV.

10. A transmission tower for a high-voltage overhead transmission line, comprising a mechanical disconnector device according to claim 1 installed between a high-voltage overhead conductor of said high-voltage overhead transmission line and a voltage transformer associated with it.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] For a better understanding of the present invention, a particular embodiment is described below for illustrative and non-limiting purposes with the aid of the accompanying figures, in which:

[0016] FIG. 1 illustrates a support, for example of the trellis type, for the support of HV overhead electric line conductors on which an electro-mechanical disconnector according to the present invention is mounted;

[0017] FIGS. 2a and 2b illustrate the electro-mechanical disconnector of FIG. 1 in two operating phases and with parts represented in schematic form; and

[0018] FIG. 3 is an enlargement of a detail of the electro-mechanical disconnector of FIG. 1.

DETAILED DESCRIPTION

[0019] Number 1 in FIG. 1 indicates a support, for example of the trellis type, useful for supporting conductors 2 of an HV overhead electric line. In particular, the support of FIG. 1 is an anchor support, in which a plurality of brackets 3 support the conductors 2 through the insertion of suitable insulators 4. As known to a person skilled in the art, electrical continuity at the insulators 4 is ensured by an electrical connection 5, known in the jargon as a dead neck.

[0020] On the support 1 a voltage transformer 6 is mounted for the conversion of electrical energy from high voltage to low voltage. The voltage transformer 6 is supported by a special bracket 7 on which a discharger 8 is also positioned, necessary to protect the voltage transformer 6 from overvoltages.

[0021] Mounted on the support 1 is an electro-mechanical disconnector 9 arranged between the voltage transformer 6 and a conductor 2. In particular, in its closed operating phase, the electro-mechanical disconnector 9 electrically connects the voltage transformer 6 to an electrical connection 5 of a related conductor 2.

[0022] As illustrated in FIGS. 2a and 2b, the electro-mechanical disconnector 9 comprises an operating arm 10, composed of a rod of conductive material, and a sacrificial element 11 (illustrated schematically) connected both to a first end 12 of the moving arm 10 and to the electrical connection 5 by means of, for example, a T-clamp.

[0023] According to a preferred embodiment, the operating arm 10 is a rigid rod. However, different from what has been described above, the operating arm 10 can consist of a cord or other flexible element, also of conductive material.

[0024] The sacrificial element 11 is composed of an electrically conductive element, which is made of a material apt to melt due to the passage of a fault electric current and which, at the same time, has a suitable mechanical performance such as to resist the action of the wind.

[0025] According to one aspect of the invention the sacrificial element 11 is made of steel or copper or other conductive alloy with suitable mechanical and electrical properties.

[0026] From the illustration in FIG. 2a, in the operating phase of closing the electro-mechanical disconnector 9, the assembly consisting of the operating arm 10 and the sacrificial element 11 constitutes an electrical connection line between the conductor 2 (with its related electrical connection 5) and the voltage transformer 6.

[0027] A second end 13 of the operating arm 10 is connected to a hinge assembly 14, illustrated schematically. As may be obvious to a person skilled in the art, the hinge assembly 14 also comprises a flexible conductor braid 16 useful for ensuring the connection also at the hinge gear.

[0028] The hinge group 14 is made in such a way that, once the sacrificial element 11 melts, the operating arm 10 performs a rotation moving into its opening phase as illustrated in FIG. 2b. In other words, when the sacrificial element 11 melts, the first end 12 of the operating arm 10 will no longer be constrained and the hinge assembly forces the operating arm 10 itself to rotate. The rotation of the operating arm 10 leads to obtaining a suitable electrical insulation distance d, which guarantees the electrical insulation between the electrical connection 5 and the voltage transformer 6.

[0029] In greater detail, the distance d is greater than 1.5 m if the operating voltage of the HV line is equal to 150 kV and greater than 3.5 m if the operating voltage of the HV line is equal to 380 kV.

[0030] Differently from what has been described above, the isolating element according to the invention can be different from an operating arm, provided it is capable of guaranteeing that the aforementioned electrical insulation distance in the air will be reached. In fact, the electrical insulation distance in the air is necessary for carrying out the opening operating phase of the electro-mechanical disconnector which must be able to guarantee the absolute absence of an electrical connection between the high voltage overhead power line and the voltage transformer involved in the fault.

[0031] In the event of a fault inside the voltage transformer 6, the line switches at the ends of the HV backbone open to isolate the section of line involved while, at the same time, the sacrificial element 11 melts as a fault current passes through it. The fusion of the sacrificial element 11 frees the first end 12 of the operating arm 10 which, consequently, opens, creating the necessary electrical insulation distance in the air. At this point, the faulty component is disconnected, and the line switches close automatically, restoring electrical operation of the HV backbone. All this is sorted out, therefore, with a voltage dip of a few milliseconds.

[0032] As illustrated in FIG. 3, the electro-mechanical disconnector 9 comprises a collection cup 15 fixed to the first end 12 of the operating arm 10 and arranged to surround the sacrificial element 11. In this way, when the sacrificial element 11 melts, the dissolved material is not dispersed in the environment but is deposited on the walls of the collection cup 15. This prevents problems both in terms of safety for third parties and in terms of potential environmental pollution.

[0033] Advantageously, the collection cup 15 also has the function of reducing the electric field around the sacrificial element which otherwise, due to its small section, would give rise to an intense electric gradient value on the surface, noise problems and radio interference due to the corona effect.