CA2413933A1 - Overhead powerline suspension system - Google Patents
Overhead powerline suspension system Download PDFInfo
- Publication number
- CA2413933A1 CA2413933A1 CA 2413933 CA2413933A CA2413933A1 CA 2413933 A1 CA2413933 A1 CA 2413933A1 CA 2413933 CA2413933 CA 2413933 CA 2413933 A CA2413933 A CA 2413933A CA 2413933 A1 CA2413933 A1 CA 2413933A1
- Authority
- CA
- Canada
- Prior art keywords
- tower
- cable
- power transmission
- suspension system
- section
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02G—INSTALLATION OF ELECTRIC CABLES OR LINES, OR OF COMBINED OPTICAL AND ELECTRIC CABLES OR LINES
- H02G7/00—Overhead installations of electric lines or cables
- H02G7/20—Spatial arrangements or dispositions of lines or cables on poles, posts or towers
Landscapes
- Suspension Of Electric Lines Or Cables (AREA)
Abstract
The invention is an overhead power line suspension system for use in the transmission of high-voltage electricity. It consists of a section of fully insulated cable with an electrically conductive core, connected at its longitudinal mid-section to a transmission line tower. The ends of the cable section extend out on opposite sides of the tower and are attached to one or more bare conductors of the power line. The cable section is long enough to assure that no electric charge flashover occurs from the bare conductors to the tower. The cable section thereby electrically connects the bare conductors on opposite sides of the tower and supports them in the air.
Description
OVERHEAD POWERLINE SUSPENSION SYSTEM:
FIELD OF INVENTION:
The present invention relates to suspension systems for high-voltage overhead power transmission lines.
BACKGROUND OF THE INVENTION:
Most electricity produced by power generation facilities is consumed many kilometers away. Large quantities of electricity must therefore be transported over significant distances via high voltage power transmission lines.
At present the most economically efficient transmission solution is to string high voltage power lines in the air along a corridor of specially constructed power transmission towers. The power lines can take one of two forms: bare conductors or electrically conductive cables with insulated sheaths.
The disadvantage of bare conductors is that they cannot touch or be near any uninsulated object which is electrically grounded. If the distance to electrical ground is too short, flashover will occur where electric charge jumps to the grounded object. Flashover is a safety hazard, cuts the power line's circuit and can damage equipment. Transmission towers are electrically grounded and therefore cannot be located too close to bare conductors which carry high voltage electricity.
To protect towers against flashover insulator string assemblies are used. These assemblies are hung from tower arms and suspend the bare conductors in the air. The assemblies, which do not conduct electricity, maintain a buffer between tower arms and conductors. The tower arms are also of sufficient length to protect the main tower body from z ' CA 02413933 2002-12-27 lateral flashover.
Transmitting high voltage electricity via bare conductors therefore demands complex tower structures with one or more arms. Given that most high voltage electricity is transmitted using three phase alternating current, with each phase requiring a separate conductor or set of conductors, most towers require at least three arms or three separately located hanging points for the insulator string assemblies. High voltage direct current, which is less commonly used, presently requires two conductors or conductor sets and demands two tower arms or hanging points.
These complex tower shapes are inferior to a simple pole or vertical structure for several reasons: they demand more structural materials, they face greater mechanical stresses and they require much wider right-of-ways. Each of these weaknesses significantly adds to the cost of bare conductor high voltage transmission systems.
Overhead transmission systems which use fully insulated cables avoid some of these weaknesses. Cables can be directly attached to towers eliminating the need for insulator string assemblies and large tower arms. Simple poles or vertical support structures may be used. Structural material requirements and mechanical stresses are greatly reduced and only narrow right-of-ways are required.
However, using insulated cables has several significant disadvantages. Cables are much heavier than bare conductors per unit of length for an equivalent maximum power throughput. Cables therefore create much larger physical loads on transmission towers and require either stronger towers or greater tower frequency. Both of these options significantly increase transmission system costs. Cables may also have difficulty in supporting their own weight over longer spans.
Cables are also much more difficult to work with than bare conductors. Cutting and attaching long sections is labour intensive and requires special machinery and skills.
Completing these tasks over the many kilometers of a transmission line can significantly add to project time and cost.
The final serious disadvantage of cables is that they are much more expensive per unit of length than bare conductor for the same maximum power througput. At certain high voltages cable can be up to twenty times more expensive than bare conductor. It is for these reasons that high voltage overhead cable transmission systems are very rarely used, and only for short distances where bare overhead conductors are not practical.
OBJECTS OF THE INVENTION
It is an object of this invention to provide a high voltage overhead transmission line suspension system which combines the cost, weight and construction simplicity advantages of bare insulator overhead transmission systems and the narrow right-of-way and tower simplicity advantages of fully insulated cable systems.
SUMMARY OF THE INVENTION:
The present invention, which satisfies the foregoing objects, is a bare conductor power line suspension system consisting of a power transmission tower and a section of fully insulated cable. The tower is a single or multi-section post, a vertical lattice structure or any other tower structure common in the art. If necessary, guy wires may be used to help balance the tower.
FIELD OF INVENTION:
The present invention relates to suspension systems for high-voltage overhead power transmission lines.
BACKGROUND OF THE INVENTION:
Most electricity produced by power generation facilities is consumed many kilometers away. Large quantities of electricity must therefore be transported over significant distances via high voltage power transmission lines.
At present the most economically efficient transmission solution is to string high voltage power lines in the air along a corridor of specially constructed power transmission towers. The power lines can take one of two forms: bare conductors or electrically conductive cables with insulated sheaths.
The disadvantage of bare conductors is that they cannot touch or be near any uninsulated object which is electrically grounded. If the distance to electrical ground is too short, flashover will occur where electric charge jumps to the grounded object. Flashover is a safety hazard, cuts the power line's circuit and can damage equipment. Transmission towers are electrically grounded and therefore cannot be located too close to bare conductors which carry high voltage electricity.
To protect towers against flashover insulator string assemblies are used. These assemblies are hung from tower arms and suspend the bare conductors in the air. The assemblies, which do not conduct electricity, maintain a buffer between tower arms and conductors. The tower arms are also of sufficient length to protect the main tower body from z ' CA 02413933 2002-12-27 lateral flashover.
Transmitting high voltage electricity via bare conductors therefore demands complex tower structures with one or more arms. Given that most high voltage electricity is transmitted using three phase alternating current, with each phase requiring a separate conductor or set of conductors, most towers require at least three arms or three separately located hanging points for the insulator string assemblies. High voltage direct current, which is less commonly used, presently requires two conductors or conductor sets and demands two tower arms or hanging points.
These complex tower shapes are inferior to a simple pole or vertical structure for several reasons: they demand more structural materials, they face greater mechanical stresses and they require much wider right-of-ways. Each of these weaknesses significantly adds to the cost of bare conductor high voltage transmission systems.
Overhead transmission systems which use fully insulated cables avoid some of these weaknesses. Cables can be directly attached to towers eliminating the need for insulator string assemblies and large tower arms. Simple poles or vertical support structures may be used. Structural material requirements and mechanical stresses are greatly reduced and only narrow right-of-ways are required.
However, using insulated cables has several significant disadvantages. Cables are much heavier than bare conductors per unit of length for an equivalent maximum power throughput. Cables therefore create much larger physical loads on transmission towers and require either stronger towers or greater tower frequency. Both of these options significantly increase transmission system costs. Cables may also have difficulty in supporting their own weight over longer spans.
Cables are also much more difficult to work with than bare conductors. Cutting and attaching long sections is labour intensive and requires special machinery and skills.
Completing these tasks over the many kilometers of a transmission line can significantly add to project time and cost.
The final serious disadvantage of cables is that they are much more expensive per unit of length than bare conductor for the same maximum power througput. At certain high voltages cable can be up to twenty times more expensive than bare conductor. It is for these reasons that high voltage overhead cable transmission systems are very rarely used, and only for short distances where bare overhead conductors are not practical.
OBJECTS OF THE INVENTION
It is an object of this invention to provide a high voltage overhead transmission line suspension system which combines the cost, weight and construction simplicity advantages of bare insulator overhead transmission systems and the narrow right-of-way and tower simplicity advantages of fully insulated cable systems.
SUMMARY OF THE INVENTION:
The present invention, which satisfies the foregoing objects, is a bare conductor power line suspension system consisting of a power transmission tower and a section of fully insulated cable. The tower is a single or multi-section post, a vertical lattice structure or any other tower structure common in the art. If necessary, guy wires may be used to help balance the tower.
For each power line supported by the tower, a section of cable is fastened to the body of the tower. The cable has an electrically conductive core and outer insulation. The insulation fully insulates any object touching the outside of the cable from the high-voltage electricity on the inside.
This permits the longitudinal mid-section of the cable to be directly attached to the body of the tower without insulators.
Each end of the insulated cable section is, on opposite l0 sides of the tower, connected to a bare conductor of the power line. The cable thereby permits electricity to freely flow from one bare conductor to another. The insulated cable extends out far enough from both sides of the tower to assure that no flashover from a bare conductor to the tower occurs.
Should the bare conductor sections of the powerline consist of a bundle of conductors, the insulated cable is electrically connected to each conductor in the bundle.
Employing the invention over many power transmission towers results in a power line consisting of long sections of bare conductor interspersed with short sections of insulated cable.
BRIEF DESCRIPTION OF THE DRAWINGS:
A more complete understanding of the invention can be obtained by reference to the accompanying drawings in which:
Figure 1 is a side view of the power line support system;
Figure 2 is a cross section of the cable;
Figure 3 is a side view of a section of a power line where multiple power transmission towers utilize the power line support system;
Figures 4 - 6 are prior art transmission tower constructions;
Figures 7 and 8 are simpler transmission tower constructions made possible by the invention's power line suspension system.
DETAILED DESCRIPTION OF THE DRAWINGS:
Figure 1 is a side view of the invention suspending a single bare conductor power line 5. The system is elevated from the ground using a tower structure 1. In this embodiment the tower consists of a pole structure. The pole may be wood, cement, metal, aluminum, or any other pole commonly used to elevate overhead power lines.
Alternatively, the tower may be any other power line support structure known in the art, such as a steel lattice structure.
Attached to the pole is a section of fully insulated cable 2. As the cable is fully insulated it may be directly attached to the tower structure, even though the cable is a conduit of high-voltage electricity. The cable may be attached to the tower by any cable clamping or support mechanism known in the art 3.
The section of cable supports the two bare conductors on opposite sides of the tower by being clamped to the conductors using any clamping mechanism known in the art 4.
In this way the bare conductors are supported in the air and are electrically connected by the section of cable. As the electricity in the bare conductors will flashover to the tower, the cable is of a length to assure that the bare conductors are never within flashover distance.
Figure 2 is a cross-section of an electric cable which could be used in the power line suspension system. The cable has a conductive core 6 of aluminum alloy, aluminum, copper or any other conductor. Heavier conductive materials such as copper may be used as the cable section is relatively short and weight is not a factor. The outer surface of the cable 8 is fully insulated from the electricity in the conductive core by insulation 7. Many cable insulation methods are know in the art, including combining an inner conductor screen, insulation, insulation screen and liquid barrier screen with a polymeric outer surface.
Figure 3 is a side view of a three phase high voltage alternating current circuit suspended by the invention over a distance of several towers. As the spans between the towers are large relative the length of cable necessary to avoid flashover, the ratio of bare conductor to cable over the length of the power line is large. This is important as bare conductor is much cheaper, lighter and easier to work with than cable.
Power lines consisting of bare conductor alone cannot be directly attached to transmission towers. More complex towers as shown in figures 4, 5 and 6 must be used. In these towers the bare conductors are supported and separated from the towers by insulator string assemblies 9. Ground wires 10 which protect power circuits from voltage imbalances and lightening strikes normally do not carry electricity and may be connected directly to tower structures.
The present invention allows the use of the simpler tower structures shown in figures 7 and 8. Figure 7 is a steel lattice tower structure supported by guys, wherein the three power lines of a high-voltage alternating current circuit are drawn through the structure. This structure could replace the prior art towers in figures 4 and 5.
Figure 8 is a solid pole tower structure with the 6 power lines of a high voltage alternating current double circuit attached directly to the sides of the tower. This tower could replace the prior art tower in figure 6. These new tower arrangements made possible by the invention have narrower aerial right-of-ways, are simpler and can result in significantly smaller footprint areas.
This permits the longitudinal mid-section of the cable to be directly attached to the body of the tower without insulators.
Each end of the insulated cable section is, on opposite l0 sides of the tower, connected to a bare conductor of the power line. The cable thereby permits electricity to freely flow from one bare conductor to another. The insulated cable extends out far enough from both sides of the tower to assure that no flashover from a bare conductor to the tower occurs.
Should the bare conductor sections of the powerline consist of a bundle of conductors, the insulated cable is electrically connected to each conductor in the bundle.
Employing the invention over many power transmission towers results in a power line consisting of long sections of bare conductor interspersed with short sections of insulated cable.
BRIEF DESCRIPTION OF THE DRAWINGS:
A more complete understanding of the invention can be obtained by reference to the accompanying drawings in which:
Figure 1 is a side view of the power line support system;
Figure 2 is a cross section of the cable;
Figure 3 is a side view of a section of a power line where multiple power transmission towers utilize the power line support system;
Figures 4 - 6 are prior art transmission tower constructions;
Figures 7 and 8 are simpler transmission tower constructions made possible by the invention's power line suspension system.
DETAILED DESCRIPTION OF THE DRAWINGS:
Figure 1 is a side view of the invention suspending a single bare conductor power line 5. The system is elevated from the ground using a tower structure 1. In this embodiment the tower consists of a pole structure. The pole may be wood, cement, metal, aluminum, or any other pole commonly used to elevate overhead power lines.
Alternatively, the tower may be any other power line support structure known in the art, such as a steel lattice structure.
Attached to the pole is a section of fully insulated cable 2. As the cable is fully insulated it may be directly attached to the tower structure, even though the cable is a conduit of high-voltage electricity. The cable may be attached to the tower by any cable clamping or support mechanism known in the art 3.
The section of cable supports the two bare conductors on opposite sides of the tower by being clamped to the conductors using any clamping mechanism known in the art 4.
In this way the bare conductors are supported in the air and are electrically connected by the section of cable. As the electricity in the bare conductors will flashover to the tower, the cable is of a length to assure that the bare conductors are never within flashover distance.
Figure 2 is a cross-section of an electric cable which could be used in the power line suspension system. The cable has a conductive core 6 of aluminum alloy, aluminum, copper or any other conductor. Heavier conductive materials such as copper may be used as the cable section is relatively short and weight is not a factor. The outer surface of the cable 8 is fully insulated from the electricity in the conductive core by insulation 7. Many cable insulation methods are know in the art, including combining an inner conductor screen, insulation, insulation screen and liquid barrier screen with a polymeric outer surface.
Figure 3 is a side view of a three phase high voltage alternating current circuit suspended by the invention over a distance of several towers. As the spans between the towers are large relative the length of cable necessary to avoid flashover, the ratio of bare conductor to cable over the length of the power line is large. This is important as bare conductor is much cheaper, lighter and easier to work with than cable.
Power lines consisting of bare conductor alone cannot be directly attached to transmission towers. More complex towers as shown in figures 4, 5 and 6 must be used. In these towers the bare conductors are supported and separated from the towers by insulator string assemblies 9. Ground wires 10 which protect power circuits from voltage imbalances and lightening strikes normally do not carry electricity and may be connected directly to tower structures.
The present invention allows the use of the simpler tower structures shown in figures 7 and 8. Figure 7 is a steel lattice tower structure supported by guys, wherein the three power lines of a high-voltage alternating current circuit are drawn through the structure. This structure could replace the prior art towers in figures 4 and 5.
Figure 8 is a solid pole tower structure with the 6 power lines of a high voltage alternating current double circuit attached directly to the sides of the tower. This tower could replace the prior art tower in figure 6. These new tower arrangements made possible by the invention have narrower aerial right-of-ways, are simpler and can result in significantly smaller footprint areas.
Claims (6)
1) An overhead power transmission line suspension system wherein a section of cable with an electrically conductive core and a fully electrically insulating sheath is fastened at its longitudinal mid-section to a power transmission tower, with each end of the flexible cable connected, on opposite sides of the power transmission tower, to the ends of the bare conductors of a power transmission line so the flexible cable electrically interconnects the bare conductors, with the flexible cable being of a length which prevents electrical flashover from the bare conductors to the power transmission tower.
2) An overhead power transmission line suspension system according to Claim 1 wherein the cable passes through the body of the power transmission tower.
3) An overhead power transmission line suspension system according to Claims 1 or 2 wherein the conductive core of the cable is aluminum.
4) An overhead power transmission line suspension system according to Claims 1 or 2 wherein the conductive core of the cable is copper.
5) An overhead power transmission line suspension system according to any of the Claims 1 to 4 wherein the power transmission tower is a lattice structure.
6) An overhead power transmission line suspension system according to any of the Claims 1 to 4 wherein the power transmission tower is a post structure.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2413933 CA2413933A1 (en) | 2002-12-27 | 2002-12-27 | Overhead powerline suspension system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2413933 CA2413933A1 (en) | 2002-12-27 | 2002-12-27 | Overhead powerline suspension system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2413933A1 true CA2413933A1 (en) | 2004-06-27 |
Family
ID=32514047
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2413933 Abandoned CA2413933A1 (en) | 2002-12-27 | 2002-12-27 | Overhead powerline suspension system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2413933A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109458034A (en) * | 2018-12-21 | 2019-03-12 | 江苏神马电力股份有限公司 | A kind of power transmission tower |
| WO2019110204A1 (en) * | 2017-12-04 | 2019-06-13 | Axpo Power AG | Overhead line conductor bridging device and use thereof in a retrofitting or production method for electricity pylons |
-
2002
- 2002-12-27 CA CA 2413933 patent/CA2413933A1/en not_active Abandoned
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2019110204A1 (en) * | 2017-12-04 | 2019-06-13 | Axpo Power AG | Overhead line conductor bridging device and use thereof in a retrofitting or production method for electricity pylons |
| CH714403A1 (en) * | 2017-12-04 | 2019-06-14 | Axpo Power AG | Conductor bridging device and use in a retrofit or manufacturing method for overhead power pylons. |
| CN109458034A (en) * | 2018-12-21 | 2019-03-12 | 江苏神马电力股份有限公司 | A kind of power transmission tower |
| CN109458034B (en) * | 2018-12-21 | 2024-12-17 | 上海神马电力工程有限公司 | Power transmission tower |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |