Implements or apparatus for applying pushing or pulling force – Method or apparatus for placement of conductive wire – Utility pole guide
Patent
1990-07-31
1993-01-12
Watson, Robert C.
Implements or apparatus for applying pushing or pulling force
Method or apparatus for placement of conductive wire
Utility pole guide
B65H 5900
Patent
active
051783681
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
As it is well known to all experts in the art of power line construction, stringing single and/or bundles of conductors, on suspension and/or strain or dead-end towers, requires: 1) the use of large quantities of pilot and/or service cords and/or draw cables in the initial stage of the stringing procedure and 2) the use of a brake (or tensioner) and a winch (or puller). The winch being mostly used to recover said pilot and/or service and/or draw cables and substitute them with conductors, and the brake being mostly used to tension said conductors and keep them always raised from the ground.
The brake and the winch are usually positioned 4 to 6 miles from each other with several towers between them. All stringing operations usually start from the brake and move toward the winch.
Pilot cords are light cables, usually of synthetic material such as nylon, normally used in conjunction with helicopter stringing, whereas service cords and draw cables are relatively heavy steel cables capable of withstanding considerable tension and torques, and normally used to pull conductors or bundles of conductors.
If the stringing is carried out with the most traditional manual method, said service cords have to be first laid out on the ground, then raised and conveyed over the pulleys suspended from the towers, tensioned by means of a brake and a winch, and finally replaced with larger draw cable (particularly when dealing with more than one conductor per phase) before the conductors can be pulled. In other words the traditional method of stringing power lines usually comprises the following operations: and one per each earth-peak: each tower between the brake and the winch: coupled with a larger draw cable; with conductors;
The just described stringing method encounters considerable difficulties which may readily be understood and are well known to those skilled in the art. The problems relate to the initial laying out of said service cords on the ground, the consequent need for cutting all the plants along the entire power line and the handling of large quantities of service cords and draw cables.
These difficulties are correspondently greater when the conductors have to cross mountainous regions, crops, rivers, swamps, highways, other power lines, and build-up areas.
In an attempt to alleviate these difficulties and the associated long periods of work, it has been proposed to use helicopters to position pilot cords directly on the towers. A helicopter moves along the route of the line above the towers and gradually unwinds one pilot cord at a time. These pilot cords are then either conveyed over the suspended pulleys by operators or automatically run on specially-shaped pulleys.
After the pilot cords have been positioned, they have to be replaced with larger service cords and/or draw cables before the conductors can be pulled.
The method of stringing power lines with the help of helicopters has the great advantage of reducing damage to the vegetation, and shortening work time, but is not free from disadvantages.
In fact, the helicopter pilots have to be particularly skillful: first of all, because the helicopter motion is opposed by the pilot cord, which is at least partly under tension; secondly, because the pilot cord must be positioned on the towers with high accuracy; thirdly, due to the need for accuracy, the helicopter has to fly at very low altitudes over the towers; and last but not least, since the most important power lines normally have six phases and at least one earth-peak, the difficulties and risks have to be multiplied by a factor of seven. In fact, the helicopter in order to accompany the pilot cords nearly as far as the lowest crossarms, has to descend to an altitude at which the rotor blades may be dangerously near the tip of the tower or actually below it. Moreover, the pilot cords, which are only partly under tension, may get caught in the trees, brake, and therefore cause a loss of both time and material, or even worse tend to pull the helicopter down.
For these reasons the aforemention
REFERENCES:
patent: 2155053 (1939-04-01), Kuenzi
patent: 4018422 (1977-04-01), Bozeman
patent: 4596379 (1986-06-01), Saracini
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