CZ272795A3 - HIGH-VOLTAGE CONDUCTOR FOR OVERHEAD LINE AND FOR VOLTAGE 60 kV AND HIGHER - Google Patents

Abstract

The invention relates to a high-voltage conductor for overhead lines for voltages of approximately 60 kV and higher and to the use of an insulation-coated conductor (3) shielded against spark-over generated by contact with another conductor in alternating-current and direct-current overhead lines for voltages of approximately 60 kV and higher. In accordance with the invention, the conductor (3) is covered with an insulation and shielded against spark-over generated by contact with another conductor, the insulator coating on the conductor (3) comprising a semi-conductive layer (4) enveloping the conductor, an outermost weatherproof surface insulation layer (2), and an actual insulation layer (1) therebetween.

Description

High voltage conductor for overhead lines and for voltage kV— and above

Technical field

The invention relates to a high voltage conductor for overhead lines and for a voltage of about 60 kV and above.

BACKGROUND OF THE INVENTION

The high-voltage line used up to now and in which the phase conductor voltage exceeds 20 kV has bare unprotected conductors. It must therefore be placed on poles so as to ensure a fairly large space between the conductors, thus avoiding contact between them.

On the other hand, there is a PAS line using overhead conductors provided with a simple plastic sheath using a voltage in the range of about 20kV and replacing the bare conductor line. In these conductors the insulation is made of XLPE cross-linked polyethylene (PEX). The insulation is designed to withstand the voltage surges that may occur when the wires touch each other, but cannot completely insulate the wires in the cable. The PAS conductor is an alternative to a much more expensive underground cable.

Neither insulation nor sheathing is used for conductors designed for voltages in excess of 60 kV, and especially not for 110 kV and above, since the previously known insulation layers used for overhead conductors would have to be considerably thick to ensure sufficient insulation. For this reason, mast constructions, insulators, insulation and conductor clamps are designed especially for bare conductors.

Over the past decade, attention has been paid to the electric and magnetic fields generated by power lines that may affect the health of those who live near that line. Electric and magnetic field limits have already been set in some US states and Italy.

The electric and magnetic fields can be influenced by the mutual placement of the conductors in the transverse plane. Placing the conductors as close together as possible, for example at the top of an equilateral triangle, provides a minimal field. Similarly, wires placed close together require narrower transmission paths of wires, which should bring savings in the built-up area. The minimum required distances for bare high-voltage wires, which should avoid short-circuit circuits, lightning flashes, and drift effect, make it virtually impossible to reduce the magnetic and electric fields in the wire path and in the vicinity.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a high voltage overhead line conductor that is suitable for a narrow transmission path and that generates a smaller electric and magnetic field. To achieve this, the high voltage selector is coated with insulation, and is protected from sparks which may be caused by contact with another conductor, the insulating conductor sheath comprising a semiconducting layer surrounding it, an outer insulating layer and a true insulating layer therebetween.

By appropriately selecting the conductor insulation layer of the present invention and investing a considerable amount of testing work to determine the safety and resistance of the conductors, a thin, high-voltage conductor can be obtained which can also be produced economically. Such a selector solves most of the problems associated with the wiring of conventional construction. Using the conductor of the present invention, the transmission path can be reduced from the current width of 15 m to about half (vertical exposure), at a voltage of about 110 kV, where the magnetic field is much less than the conductor used so far.

Other preferred embodiments of the invention are set forth in the following claims.

The present invention will be described in more detail with reference to the accompanying drawing of a conductor.

Overview of the drawings

Figure 1 shows a 110 kV conductor sample.

DETAILED DESCRIPTION OF THE INVENTION

The 110 kV conductor in Fig. 1 comprises an aluminum alloy round conductor with strands of wires 3 having a diameter of about 20mm. The entry of water between the layers is prevented, for example, by grease or hydroexpansive powder. The protective layer of the conductor 4 is made of a semiconductor plastic or rubber material. Semiconductivity can normally be achieved by impregnating a crosslinked insulating material with a carbon black concentration of 30-40% (if insulating carbon black is used, semiconductivity is achieved by adding only about 10% of the carbon black). For a 110 kV conductor with a protective layer, this layer is about 1-2 mm thick. The purpose of this layer is to neutralize the voltage spikes on the uneven surface of the metal wire stranded wire, thereby preventing the formation of discharge sites.

The actual insulating layer 1 surrounding the semiconductive layer 4 is made of high purity XLPE plastic material about 5mm thick for 110V. High purity is necessary to minimize the risk of sparks jumping over the insulating material at high voltage. Most cross-linked polyethylene is used due to its high purity value, high heat resistance, strength and good insulating properties. The outer layer is an insulating layer with a thickness of about 1.5mm saturated with carbon black to achieve water resistance. The carbon black content is approximately 2-3%, which provides sufficient protective properties, for example against UV radiation, which does not contribute to the high conductivity of the conductor surface layer.

Ethylene propylene rubber, EP rubber (EDPM or EPR) can also be used as raw material instead of cross-linked polyethylene (XLPE, PEX). Further information on the 110 kV sample conductor: external diameter of about 39mm, weight 1730 kg / km, limit load 108 kN, current load 660 A. In addition to the line for i

The AC current can also be used for direct current where the three phase conductors are replaced by two conductors (current + ground).

The conductor of the present invention is thus protected by an insulating layer which is much thinner than that of a conventional conductor. The insulation layer is sized to prevent breakdowns between the phase conductors within the span. Since no attempt has been made to completely insulate the conductor with an insulating layer, except for the leakage current existing on the outer layer, in milliamperes, it is very dangerous to touch the 110 kV conductor with your bare hand.

During the test, at which there was a voltage of 120 kV between the conductors, the conductors were pulled together 540,000 times without sparking. In addition, a test was conducted for 17 days in which the conductors were leaning against each other without sparking. The conductors of the present invention may collide with each other as a result of short-circuit forces or strong winds. The necessary distance between conductors must be calculated on a different basis, which can be applied to a given situation than the case of a short circuit. It has been shown that it is possible to reduce the distance between the phase conductors at 110 kV from two meters (as has been the case so far) to half.

Protected conductors have been shown to make it possible to substantially reduce the spacing of conductors and shorten the transmission path. The result is a reduction in the electric and magnetic field generated by the protected conductor line when compared to conventional lines.

WIRE TABLE 1 (B) max 0.1 λΤ 0.2 Bare horizontal 1 33 23 Bare vertical 0.68 33 21 Bare triangle. 0.45 25 16 Protected Triangle. 0.39 21 13 Protected by the horizontal. 0.33 16 10 Protected vertical 0.32 18 11

and

Protected delta 0.21 13 6

B _{mai £} = mutual maximum flux density of magnetic field 0.1 Ta 0.2 T - reduction of flux density to this level, found at a distance from the center of the line.

and

Table 1 shows the magnetic flux density curves for high voltage overhead lines for different types of conductors. The values are compared between the conductors, including conventional uninsulated horizontal, triangular and vertical conductors with a standard 2 m phase layout, and between the protected PAS lines of this invention with a horizontal, vertical, triangular and delta configuration with a 1.15 m phase distribution.

The basic data for the measured results shown in Table 1 are as follows:

- U = 123 kv

- current load 100A, P = 18 MW protected conductor: SAX 355, = 40 N / mm ² bare conductor: Duck, = 40 N / mm ²

- lightning conductor: Sustrong, = 60 N / mm ² conductor temperature + 15 ° C

- lightning conductor temperature + 5 ° C

- distance (ground clearance) of the lowest conductor from the ground 5.9 m at 70 ° C (permissible minimum height)

- span a = a = 200 m

With respect to the magnetic field, the following observations can be made based on Table 1:

- if the exposure of the conductors is horizontal, the maximum flow density »value in the PAS lines decreases to one third compared to the corresponding non-insulated line. Flow density decreases to ´ background radiation level (Ο, Ι ^ Τ) at 33 m and 9 m respectively. 16 m, measured from the center of the line.

- if the exposure of the conductors is vertical, the maximum flow density value in the PAS line decreases by about one-half compared to a conventional line. The density of the stream decreases to the level of background radiation at a clearness of 33 m resp. 18 m, measured from the center of the line.

- when triangularly exposed to conductors, the maximum line density value does not differ significantly from that of a typical line. For PAS conductors, the flow density decreases to the background emission level at a clearance of 21 m, measured from the center of the line, while a corresponding 25 m clearance is required for the corresponding uninsulated line. This rather small difference is attributable to factors other than the spatial layout , determines the location of wires. This means that the construction of both conductors is roughly the same. In the PAS line, half the peak value of the electric field strength was measured.

- Exposure of delta (equilateral triangle) PAS lines is the best solution for field generation. Compared to a non-insulated horizontal tower, the maximum flow density is about one fifth, while the flow density decreases to the level of ambient radiation at a distance of 13 m from the line.

The conductor according to the invention can be manufactured by known methods without any significant changes, for example in insulated cables for underground cables. By means of the triple extrusion technique, all sheath layers can be produced in one step.

It will be apparent to those skilled in the art that various embodiments of the present invention are not limited to the samples that have been mentioned but may vary within the scope of the claims.

Claims (5)

PATENT CLAIMS High-voltage conductor for overhead lines and for a voltage of 60 kV and above, characterized in that the conductor (3) is covered with insulation and protected against sparks which may arise from contact with another conductor, where the insulating sheath of conductor (3) consists a semiconducting layer (4) which surrounds the conductor, a surface of the weatherproof outer insulating layer (2), and an actual insulating layer (1) therebetween. Conductor according to claim 1, characterized in that the cross-linked polyethylene (XLPE) is used as an insulating material. Conductor according to claim 1, characterized in that the rubber material EP (EPDM or EPR) is used as an insulating material. Conductor according to claim 1, characterized in that the weather-resistant surface insulation layer (2) is produced by admixing 2-3% black carbon black into the insulating material. Use of a spark-proof insulated conductor (3) in contact with another conductor, said insulating sheath comprising a semiconducting layer (4), a weather-resistant outer outer layer (2) and a true insulating layer (1) located between them, in an AC and DC overhead line for a voltage of approximately 60 kV and above.