WO2001086772A1

WO2001086772A1 - Apparatus for elevated suspension of an overhead electrical conductor and overhead conductor suspension structure

Info

Publication number: WO2001086772A1
Application number: PCT/HU2001/000055
Authority: WO
Inventors: Péter TÁRCZY
Original assignee: Tarczy Peter
Priority date: 2000-05-12
Filing date: 2001-05-14
Publication date: 2001-11-15
Also published as: AU2001258664A1

Abstract

Apparatus for increasing electrical clearances of overhead electrical conductors to ground by means of insulator strings and jumpers. Electrical conductors (1) are attached to the support structure (13, 14, 15, 48) by a device ensuring their displacement along the direction of the line (4, 11) and insulator strings (2) arranged in a configuration resembling tension insulator strings and bridged by a jumper (7). Overhead conductor suspension structure with conductor suspension above described. The suspension is attached to the trunk (15) of the pole or inside the trunk (15), with a jumper (7) bypassing the suspension structure by means of the cross arm (13) of the pole or an auxiliary and/or insulator arm (50), or a jumper (7) passed through a suitably formed opening in the trunk. Suspension structure characterised in that supplementary arms (14) are mounted to the trunk (15) in the space freed up by the elevation of electrical conductors and supplementary electrical conductors (12) are suspended to the supplementary arms (14).

Description

Apparatus for elevated suspension of an overhead electrical conductor and overhead conductor suspension structure

The object of the invention is an apparatus for elevated suspension of overhead electrical conductors of power transmission lines and an overhead conductor suspension structure.

Overhead transmission lines usually consist of two types of pole: suspension and tension poles. Tension poles are equipped with tension insulator strings, while on suspension poles suspension insulator strings are applied. Both tension poles and suspension poles are dimensioned to support loads acting on them from a vertical direction (caused by e.g. ice) and loads from directions perpendicular to the track of the transmission line (caused by e.g. wind). The difference between tension and suspension poles lies in their ability to support loads collinear with the track of the transmission line.

Tension poles are classified to support different amounts of tensile load acting on them from the direction of the line depending on their type. Electrical conductors are attached to tension poles by means of so called tension insulator strings, which are situated in a substantially horizontal direction, collinear with the electrical conductors on both sides of the tension pole. Tension insulator strings convey tensile load to the electrical conductors and keep them in a stretched state. At tension poles the electrical conductors dead-ended to the insulator strings are connected by so called jumpers.

Though suspension poles are not dimensioned to bear tensile loads collinear with the transmission line, to a varying degree depending on their type they may be capable of supporting forces acting from the direction of the line. Suspension poles are equipped with suspension insulator strings that under operating conditions are situated in a substantially vertical position, and have the electrical conductors suspended on them by means of fittings attached to their lower ends. Upper ends of the suspension insulator strings are pivotally joined to the support structures in such a way that their lower ends can be displaced along the direction of the line, affected by forces collinear with the electrical conductors and caused for example by ice unevenly distributed along the span of the conductor. Displaced insulator strings can thereby reduce forces acting on the pole in the direction of the line below limit. At suspension poles electrical conductors are continuous.

Minimal clearances of overhead electrical conductors to underlying objects are prescribed by laws, standards and other regulations. Electrical conductors form chain curves between their suspension points, with their sag determined by the distance of suspension points, by attributes of material, by the temperature, and by the amount of strain force applied. A need for increasing electrical clearances of electrical conductors to ground can arise for either of the following two causes:

- because of the construction of new objects (e.g. a road) a clearance greater than the existing one is required,

- the capacity of the transmission line is to be increased (either using existing conductors, or applying new ones), and increased Joule loss caused by higher currents would result in rising conductor temperatures, which in turn would cause an increase in the sag of the conductor resulting in violated clearance requirements.

At present the known solutions to the problem of increasing electrical clearance to ground are the following:

- application of shorter insulator strings on suspension poles; has an elevating effect of a few dozen centimeters,

- increasing straining forces at tension poles and reinforcing poles if necessary; has an elevating effect of only a few dozen centimeters as well,

- reducing electric load; a rarely used option having an elevating effect of a few dozen centimeters only,

- replacing electrical conductors with a new type; has an elevating effect of only a few dozen centimeters,

- increasing the height of existing pylons, or replacing them with higher ones; a great disadvantage is serious cost, - adding new pylons either in the existing track of the transmission line or nearby; the main disadvantage is again its serious costs.

An apparatus similar to that provided by the present invention is disclosed in U.S. Patent No. 5,777,262. The apparatus according to the patent increases electrical clearances of overhead electrical conductors to ground by installing insulator strings resembling tension insulator strings on suspension poles. According to known solutions, however, the longitudinal displacement of electrical conductors along the direction of the line is only enabled if conventional vertical insulator strings, commonly used on suspension poles, are installed. That way the suspension height of the electrical conductor is decreased with respect to the attachment point on the support structure as the suspension point with the highest possible elevation by the amount of the length of the vertical insulator string. There are known solutions without vertical insulator strings but they do not provide the opportunity of displacement of the conductors along the direction of the line, so suspension poles have to support significant line direction loads without becoming damaged. Therefore, if the suspension pole cannot bear significant forces acting on it in the direction of the line, then the suspension height of electrical conductors decreases by the amount of the length of the vertical insulators, or, if vertical insulator strings are omitted, then the suspension poles have to support significant loads in the direction of the line.

The object of the present invention is the suspension of electrical conductors on support structures in such a way that clearances of electrical conductors to ground be increased by the amount of the length of conventional suspension insulator strings, or by a commensurate amount, without there arising a need for either reconstructing or reinforcing tension and suspension poles due to increased mechanical loads caused by the electrical conductors.

Elevated suspension of overhead electrical conductors in certain cases makes it possible to suspend supplementary conductors on support structures of a transmission line.

It is the object of the invention to provide an apparatus that would join advantageous traits of suspension and strain insulator strings relevant in achieving the objectives described above. The preferred solution has to meet requirements of electrical insulation, mechanical construction, and electrical continuity simultaneously. Requirements of insulation are met by means of insulator strings installed in a configuration resembling tension insulator strings. To meet mechanical requirements tension insulator strings are not rigidly attached to the pole, so the longitudinal displacement of insulator strings and electrical conductors attached to them along the direction of the line is enabled to such a degree that mechanical load to poles does not exceed specifications. In order to meet requirements of electrical continuity, tension insulator strings are bridged by a jumper.

In accordance with the present invention the apparatus for elevated suspension of the insulator strings and electrical conductors can be implemented in a number of ways. In the following, two advantageous implementations will be discussed: the suspension using rolling movement and the suspension using an inverted T chain.

The most important aspect of the suspension using rolling movement is that it employs a pulley or pulleys fit in bearings with axes substantially perpendicular to the longitudinal axis of the electrical conductor in order to provide for the longitudinal displacement of the electrical conductors along the direction of the line. To ensure the continuity of the pull force applied to electrical conductors, conductors are strained by insulator strings that are connected by means of tractive elements suitably selected with regard to corrosion, vibration and pull force. By tractive element here is meant any tensile loaded flexible machine. element (e.g. chain, stainless steel rope, plastic rope), regardless of structure or material. The tractive elements are supported by a pulley or pulleys with an axis or axes substantially perpendicular to the longitudinal axis of the electrical conductor, with the relative positions of the pulleys determined either by a steel structure attached to the trunk of the pole or to a cross arm, or by attachment points on the support structure. Electrical conductors are connected by means of a jumper. Depending on the position of the support structure and also on the terrain, pulleys may strain the electrical conductors downwards or in a lateral direction, which can especially be of advantage on hilly terrain. A distinctive feature of the suspension employing rolling movement is that the electrical conductor has no central position to which it would return automatically, so it is desirable that between the moving stop mounted to the tractive element that connects the insulator strings and the stationary stop mounted either to the steel structure bearing the pulleys or to the trunk or cross arm of the pole, a spring or springs be fitted. The solution herein described provides not only for a restoring force growing in proportion to displacement, as is the case with conventional suspension poles, but it also makes it possible to control that force. Consequently, the displacement of the electrical conductors along the line can also be controlled by installing springs of different strain force at individual poles, or even on the two sides of the same pole. The combined spring characteristic can be different in the two directions of the line and can also be not linear, progressive or more step characteristic in strain force versus displacement. This can be especially beneficial on hilly terrain.

In order to limit the longitudinal displacement of the conductor collinear with the line or introduce a restoring force increasing in proportion to longitudinal displacement along the direction of the line it is possible to exploit the torque transfer relationship between the tractive element and the pulley. In that case, displacement of the electrical conductor along the direction of the line results unconditionally in the angular displacement of the pulley. By limiting the angular displacement of the pulley or by introducing a restoring force proportional to said angular displacement a restoring force increasing as a function of the longitudinal displacement of the electrical conductor and/or the limitation of the longitudinal displacement thereof can be achieved.

The most important aspect of the suspension using an inverted T chain is that the electrical , conductor is strained by insulator strings. Second ends of the insulator strings are connected to each other, and at the connection point a support device is pivotally attached. The second end of the support device is pivotally attached to a point of attachment on the pole. Rotation of the support structure enables displacement of the electrical conductors along the direction of the line, thereby reducing forces acting on the pole in said direction. Electrical conductors are connected by means of a jumper. A distinctive feature of the suspension using an inverted T chain is that the range of displacement of the electrical conductor in the direction of the line can be modified by means of modifying the length of the support device. That way, either by replacing the support device itself or by replacing the spacer element in the support device, the load applied to the overhead electrical conductor in the direction of the line can be adjusted and adapted to requirements of winter and summer operation. Both the suspension using pulleys and the suspension using an inverted T chain makes it possible to elevate individual electrical conductors by different amounts. This may be useful in certain cases. Both suspensions have the advantage of decreasing swinging length on support structures by the length of the insulator strings. Consequently, the suspension point of the electrical conductor can get closer to the trunk of the support structure. In some cases it is even possible to suspend the electrical conductor on the trunk or inside the trunk by means of the suspension using pulleys, at the same enabling the jumper that connects ends of the conductors to bypass the pole by means of a conventional auxiliary arm. As the suspension point gets closer to the trunk of the pole, width of the right-of-way can be smaller. Also, mechanical load to support structures is decreased as the suspension point is situated closer to the trunk because the arm of torsion becomes shorter, which reduces torsional load applied to the pole. A further advantage is that in some cases phase clearances between electrical conductors can also be lowered.

Elevated suspension of overhead electrical conductors increases free space under the conductors. The space freed up that way can be used not only for adding new engineering or other objects near the transmission line but for adding new electrical conductors to the support structures. This is possible by installing additional cross arms on the poles and suspending new electrical conductors on them. That way new transmission lines can be constructed without there being a need for a new right-of -way. To fulfil the objective of reducing the intensity of the electric field near the transmission line it is possible to suspend grounded cables or lower voltage conductors below original energised conductors. Adding new cross arms, however, is not the only means for suspending additional electrical conductors on existing poles: it is also possible to make use of the other type of suspension described above and suspend electrical conductors on the trunk of the pole by means of the suspension comprising pulleys, with jumpers either bypassing the pole by means of auxiliary arms, spacer insulators or the original cross arms or passing through an opening of sufficient size in the trunk of the pole.

The present invention relates to increasing electrical clearances of overhead electrical conductors to ground by means of an insulator string bridged by a jumper. Electrical conductors are attached to the support structure by a device enabling their displacement along the direction of the line, with insulator strings arranged in a configuration resembling tension insulator strings and bridged by a jumper, ensuring that forces acting on the support structure in the direction of the line are reduced.

In one embodiment the apparatus comprises a pulley or pulleys with axes substantially perpendicular to the longitudinal axis of the conductor, attached to a steel structure or to the support structure by a bearing in such a way that they strain a tractive element.

In another embodiment the inventive apparatus comprises a spring or springs installed between the insulator string or strings and a stationary stop or stops connected to the attachment point in such a way that they are compressed or strained by the displacement of the electrical conductor along the direction of the line.

In yet another embodiment the apparatus comprises a support device attached pivotally at both ends thereof between the insulator strings and the attachment point on the support structure and can be rotated by the displacement of the conductor along the direction of the line.

The overhead electrical conductor support structure provided by the present invention is equipped with a conductor suspension device herein described. The electrical conductors attached to the support structure are elevated by different amounts.

The suspension device is attached to the trunk of the support structure or inside the trunk thereof, with a jumper bypassing the trunk of the support structure by means of the original cross arm of the pole or using an auxiliary arm or a spacer insulator, or the jumper is passed through an opening of sufficient size in the trunk.

To make use of the space freed up by the elevation of the electrical conductors there is a supplementary arm or there are supplementary arms attached to the trunk of the pole, with supplementary electrical conductors suspended on them.

The attached drawings exemplify embodiments of the conductor suspension device comprised by the inventive apparatus, particularly an embodiment using pulleys and another containing an inverted T chain. Support structures with said suspension devices are also depicted in Figures 1 -6, where Fig. 1 shows the suspension device comprising pulleys,

Fig. 2 shows the embodiment with an inverted T chain, whereas in Figs. 3 and 4 the modification of an existing support structure, and in Figs. 5 and 6 the suspension of the electrical conductor inside the trunk of the pole is shown.

The conductor suspension device comprising pulleys, shown in Fig. 1, is used for suspending an electrical conductor 1 on the trunk of the support structure 15 or on a cross arm 13 or supplementary arm 14. The electrical conductor 1 is connected to insulator strings 2 from both directions of the line. The insulator strings 2 are connected by a flexible tractive element 3. The tractive element 3 is guided onto a pulley or pulleys. The pulley 4 or pulleys are pivotally attached to the attachment point 6 either through a steel structure 5 or directly. The conductors are connected by a jumper 7. Taking into account that the conductor has no preferred central position in this suspension configuration, it is desirable that a strain machine element, preferably a spring 10 strained by the displacing tractive element 3 be installed between the moving stop 8 mounted on the tractive element 3 and the stationary stop 9 mounted on the steel structure 5 that is attached to the pulleys 4. The position of the pulley 4 is affected by the terrain dependent direction of the force transferred by the electrical conductor 1 to the support structure 48. It may so happen that the pulley 4 stretches the electrical conductor downwards or in a lateral direction.

In case the pulley 4 is not able to slide over the tractive element 3, that is there is a torque transfer relationship between the tractive element 3 and the pulley 4, it is possible to limit the longitudinal displacement of the electrical conductor 1 or exert a restoring force increasing in proportion to displacement on it by a configuration that limits the angular displacement of the pulley 4 and/or applies a restoring force increasing in proportion to the angular displacement thereof.

If suspension devices comprising pulleys are used along the overhead transmission line, the restoring forces can be different at individual poles and thereby the movement of the electrical conductor along the direction of the line can be controlled. That can especially be profitable in settings where loads on electrical conductors (caused by wind, ice, or level differences) are highly dependent on location. The suspension described above ensures the longitudinal displacement of the electrical conductors so, within certain limits, harmful forces acting on the pole can be avoided.

Similarly to the suspension described above, the suspension device using an inverted T chain, shown in Fig. 2, is employed for suspending an electrical conductor 1 on the trunk 15 of the support structure or on a cross arm 13 or supplementary arm 14. The electrical conductor 1 is connected to insulator strings 2 from both directions of the line. Second ends of the insulator strings are pivotally attached to each other, either directly or by means of tensile loaded, not necessarily flexible machine elements. To their point of attachment a support device 11 is pivotally joined. The second end of the support device 11 is pivotally attached to the attachment point 6. Electrical conductors 1 are connected by a jumper 7. The length of the support device 11 is chosen in such a way that in the event of uneven load distribution or of one of the conductors breaking the support device 11 is rotated by an amount that provides for the longitudinal displacement of the electrical conductor which sufficiently limits forces acting in the direction of the line.

As a specific feature the proposed solution permits the necessary seasonal adjustment of conductor suspension length even during the operation of the transmission line by way of modifying the length of the support device 11 or adjusting the length of the component between the support device 1 1 and the insulator string 2. This way the need for different conductor suspension heights and requirements for different longitudinal displacement ranges for electrical conductors during winter and summer operation can be met.

Figs. 3 and 4 show a modification of a conventional support structure that allows the suspension of supplementary electrical conductors 1 by means of new supplementary arms 14 attached to the trunk 15 of the pole under the original cross arms 13, in the space freed up by the antecedent elevation of the electrical conductors 1 using one of the solutions previously described. This means that using the existing track and support structures the capacity of the transmission line can be increased or, alternatively, new transmission line or lines can be constructed. If grounded cables or lower voltage conductors are added instead of supplementary electrical conductors, the intensity of the electric field below the conductors can be decreased significantly. Figs. 5-6 exemplify the suspension of the electrical conductor inside the trunk of the pole. If the electrical conductor 1 is suspended on the support structure 48 of the transmission line by the suspension device comprising pulleys or the suspension device with an inverted T chain described above, the suspension point of the electrical conductor 1 is elevated by an amount of the length of the insulator string 2 placed vertically on conventional support structures. Apart from increasing the electrical clearance of the conductor to ground that has the beneficial effect that the insulator string 2 ceases to be a swinging element and therefore the suspension point of the conductor can get closer to the trunk 15 of the support structure 48. If the electrical conductors are connected by means of a jumper7 and a conventional insulator arm 50, the suspension point of the electrical conductor 1 can be situated on the trunk 15 of the support structure 48 or inside it. This implies that electrical conductors 1 can be redistributed over existing support structures 48 in a more favourable way, and also that new suspension structures 48 can be constructed, characterised in that they do not have cross arms 13, only auxiliary and/or insulator arms 50 used for spacing the jumper 7 from the trunk 15 of the pole. The jumper 7 can be passed through a conventional, suitably formed opening in the trunk 15 of the support structure 48. As electrical conductors 1 are suspended closer to the vertical axis of the support structure 48, torsional load acting on the trunk of the support structure 48 is diminished and required clearance to surrounding objects can be reduced.

A further advantage of the solution is that the swinging length of the electrical conductors 1 is reduced by the length of the insulator string 2 so chances for conductor swinging are diminished and thus phase clearances can be lowered.

In addition to the technical and economic advantages of the solutions, both the elevated suspension of electrical conductors and overhead conductor suspension structures employing the suspension herein described provide a significant aesthetic and environmental surplus.

Claims

1. Apparatus for increasing electrical clearances of overhead electrical conductors to ground by means of insulator strings and jumpers, characterised in that the electrical conductors (1) are attached to the support structure (48) by a device enabling displacement along the direction of the line (4, 11), with insulator strings (2) arranged in a configuration resembling tension insulator strings and bridged by a jumper (7), ensuring that forces acting on the support structure in the direction of the line are reduced.

2. The apparatus according to Claim 1, characterised in that between the insulator strings (2) connected to the electrical conductor (1) and the suspension point (6) or points on the suspension structure it comprises a pulley (4) or pulleys with axes substantially perpendicular to the longitudinal axis of the conductor (1) attached to a steel structure (5) or to the support structure (13, 14, 15, 48) by a bearing in such a way that they strain a tractive element (3).

3. The apparatus according to Claim 2, characterised by that between the insulator string (2) or strings and the stationary stop (9) or stops joined to the attachment point (6) it comprises a spring (10) or springs that are stretched or compressed by the displacement of the electrical conductor (1) along the direction of the line.

4. The apparatus according to Claim 1 , characterised by that between the insulator strings (2) connected to the electrical conductor (1) and the suspension point (6) on the support structure (13, 14, 15, 48) it comprises a support device (11) attached pivotally at both ends thereof, rotated by the longitudinal displacement of the conductor along the direction of the line.

5. The apparatus according to Claim 4, characterised by that it comprises a variable-length support device (11) that modifies the suspension height of the electrical conductor (1).

6. Overhead conductor support structure wherein the suspension according to any of Claims 1-5 is applied, characterised in that individual electrical conductors are elevated by different amounts.

7. Overhead conductor suspension structure wherein the suspension according to any of Claims 1-5 is applied, characterised in that the suspension device is attached to the trunk of the suspension pole (15) or inside the trunk (15) thereof, and the jumper (7) bypasses the trunk of the pole (15) by means of the cross arm (13) of the pole or using an auxiliary and/or insulator arm (50), and/or spacer insulator or the jumper is passed through a suitably formed opening in the trunk.

8. Overhead conductor support structure wherein the suspension according to any of Claims 1-5 is applied, characterised in that it comprises a supplementary arm (14) attached to the trunk of the pole (15) using the space freed up by the elevation of the electrical conductor, and supplementary electrical conductors (12) suspended on the supplementary arm (14).