Spacer device
10181711 ยท 2019-01-15
Assignee
Inventors
Cpc classification
H02G7/12
ELECTRICITY
Y10T29/49227
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
International classification
Abstract
A spacer device includes an elongate spacing member extending a longitudinal axis for securing to electrical transmission lines, and has a minimum thickness d.sub.m. At least one thickened portion having a thickness T.sub.t and length d.sub.t is positioned intermediate along the spacing member to form at least two column lengths L.sub.c separated by the at least one thickened portion. Each column length L.sub.c has a portion with the minimum thickness d.sub.m. The thickness T.sub.t and length d.sub.t of the at least one thickened portion can be at least two times the minimum thickness d.sub.m to form at least one end support for the at least two column lengths L.sub.c, such the at least two column lengths L.sub.c behave as separate Euler type columns for producing increased Euler buckling strength with a minimal increase in weight.
Claims
1. A method of spacing two electrical transmission lines with a spacer device comprising: securing an elongate spacing member to the two electrical transmissions lines, the elongate spacing member extending along a longitudinal axis and having a minimum thickness d.sub.m, at least one thickened portion having a thickness T.sub.t and length d.sub.t being positioned intermediate along the spacing member to form at least two column lengths L.sub.c separated by the at least one thickened portion, each column length L.sub.c having a portion with the minimum thickness d.sub.m, the thickness T.sub.t and length d.sub.t of the at least one thickened portion being at least two times the minimum thickness d.sub.m to form at least one end support for the at least two column lengths L.sub.c, the spacing member having a column length to minimum thickness L.sub.c/d.sub.m ratio of about 5 to 18, a thickened portion thickness to spacing member minimum thickness T.sub.t/d.sub.m ratio of about 1.5 to 3, and a thickened portion length to spacing member minimum thickness d.sub.t/d.sub.m ratio of about 2 to 5, such that the at least two column lengths L.sub.c behave as separate Euler type columns for producing increased Euler buckling strength with a minimal increase in weight.
2. The method of claim 1 further comprising providing the thickened portion with a thickness T.sub.t that is at least two times the minimum thickness d.sub.m of the spacing member, and a length d.sub.t that is at least three times the minimum thickness d.sub.m.
3. The method of claim 1 further comprising providing a L.sub.c/d.sub.m ratio of about 6 to 7.
4. The method of claim 3 further comprising providing a T.sub.t/d.sub.m ratio of about 1.75 to 2.5.
5. The method of claim 4 further comprising providing a d.sub.t/d.sub.m ratio of about 2.5 to 3.5.
6. The method of claim 1 in which the spacing member is a rod, the method further comprising providing the rod with a length of about 1 to 3 feet long and a minimum thickness d.sub.m of about to inches.
7. The method of claim 6 further comprising providing the at least one thickened portion with a thickness T.sub.t of about 1 to 2 inches and a length d.sub.t of about 1 to 2 inches.
8. The method of claim 7 further comprising integrally forming the at least one thickened portion on the spacing member.
9. The method of claim 8 further comprising spacing at least two thickened portions apart about 5 to 11 inches.
10. The method of claim 1 further comprising providing the at least one thickened portion with a cylindrical shape and with a central axis orthogonal to the longitudinal axis of the spacing member.
11. The method of claim 10 further comprising providing the at least one thickened portion with a diameter of about 1 to 2 inches.
12. The method of claim 1 further comprising securing first and second clamps that are on opposite ends of the spacing member to respective electrical transmission lines.
13. The method of claim 12 further comprising allowing the clamps to rotate relative to the spacing member.
14. The method of claim 12 further comprising spacing the two electrical transmission lines about 30 to 32 inches apart.
15. The method of claim 12 in which the elongate spacing member is a first spacing member, the spacer device further comprising a second elongate spacing member secured to the first spacing member and having at least a third clamp secured to an end of the second spacing member for securing to at least another electrical transmission line.
16. A method of spacing two electrical transmission lines with a spacer device comprising: securing an elongate spacing member to the two electrical transmission lines, the elongate spacing member extending along a longitudinal axis and having a minimum thickness d.sub.m, at least one thickened portion being positioned intermediate along the spacing member to form at least two column lengths L.sub.c separated by the at least one thickened portion, the at least one thickened portion being shaped with a central axis orthogonal to the longitudinal axis of the spacing member, and having a length d.sub.t and thickness T.sub.t large enough to form at least one end support for the at least two column lengths L.sub.c, the spacing member having a column length to minimum thickness L.sub.c/d.sub.m ratio of about 18 or under, a thickened portion thickness to spacing member minimum thickness T.sub.t/d.sub.m ratio of about 1.5 to 3, and a thickened portion length to spacing member minimum thickness d.sub.t/d.sub.m ratio of about 2 to 5, such that the at least two column lengths L.sub.c behave as separate Euler type columns for producing increased Euler buckling strength with a minimal increase in weight.
17. A method of spacing two electrical transmission lines with a spacer device comprising: securing an elongate spacing member to the two electrical transmissions lines, the elongate spacing member extending along a longitudinal axis and having a minimum thickness d.sub.m, at least one thickened portion having a thickness T.sub.t and length d.sub.t being positioned intermediate along the spacing member to form at least two column lengths L.sub.c separated by the at least one thickened portion, each column length L.sub.c having a portion with the minimum thickness d.sub.m, the thickness T.sub.t and length d.sub.t of the at least one thickened portion being at least two times the minimum thickness d.sub.m to form at least one end support for the at least two column lengths L.sub.c, wherein the spacing member is a rod having a length of about 1 to 3 feet long and a minimum thickness d.sub.m of about to inches, the at least one thickened portion having a thickness T.sub.t of about 1 to 2 inches and a length d.sub.t of about 1 to 2 inches, such that the at least two column lengths L.sub.c behave as separate Euler type columns for producing increased Euler buckling strength with a minimal increase in weight.
18. A method of spacing two electrical transmission lines with a spacer device comprising: securing an elongate spacing member to the two electrical transmissions lines, the elongate spacing member extending along a longitudinal axis and having a minimum thickness d.sub.m, at least one thickened portion having a thickness T.sub.t and length d.sub.t being positioned intermediate along the spacing member to form at least two column lengths L.sub.c separated by the at least one thickened portion, each column length L.sub.c having a portion with the minimum thickness d.sub.m, the thickness T.sub.t and length d.sub.t of the at least one thickened portion being at least two times the minimum thickness d.sub.m to form at least one end support for the at least two column lengths L.sub.c, the at least one thickened portion having a cylindrical shape with a central axis orthogonal to the longitudinal axis of the spacing member, such that the at least two column lengths L.sub.c behave as separate Euler type columns for producing increased Euler buckling strength with a minimal increase in weight.
19. A method of spacing two electrical transmission lines with a spacer device comprising: securing an elongate spacing member to the two electrical transmissions lines, the elongate spacing member extending along a longitudinal axis and having a minimum thickness d.sub.m, at least one thickened portion having a thickness T.sub.t and length d.sub.t being positioned intermediate along the spacing member to form at least two column lengths L.sub.c separated by the at least one thickened portion, each column length L.sub.c having a portion with the minimum thickness d.sub.m, the thickness T.sub.t and length d.sub.t of the at least one thickened portion being at least two times the minimum thickness d.sub.m to form at least one end support for the at least two column lengths L.sub.c, such that the at least two column lengths L.sub.c behave as separate Euler type columns for producing increased Euler buckling strength with a minimal increase in weight, and; securing first and second clamps that are on opposite ends of the spacing member to respective electrical transmission lines, the elongate spacing member being a first spacing member, the spacer device further comprising a second elongate spacing member secured to the first spacing member and having at least a third clamp secured to an end of the second spacing member for securing to at least another electrical transmission line.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The foregoing will be apparent from the following more particular description of example embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments of the present invention.
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DETAILED DESCRIPTION
(22) A description of example embodiments of the invention follows.
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(24) The thickened portions 16 can be relatively short, squat or flattened round, or curved bulges that can be cylindrical, puck, or disc shaped, with their central axes 21 transverse, orthogonal or at a right angle to the spacer rod 12 and axis 17. The thickened portions 16 can have a round or curved outer diameter or perimeter surface 27, and flat end surfaces 25 on opposite axial ends (
(25) By positioning the thickened portions 16 at intermediate locations along the spacer rod 12, the intermediate thickened portions 16 can form two or more short spaced apart Euler column lengths 12a along axis 17, having the nominal or minimum thickness or diameter of the spacer rod 12, which are separated from each other by the thickened portions 16. The thickened portions 16 can be made long and large enough not to bend themselves, and to act as fixed end supports for the Euler column lengths 12a of the spacer rod 12. Consequently, each shortened column length 12a can resist higher compressive Euler buckling forces than the spacer rod 12 could resist if the thickened portions 16 were not present. Euler buckling forces are typically compressive forces acting on a column at the ends of the column in the direction of or along the longitudinal axis, which if large enough, can cause buckling of the column. A column subjected to such forces can be described or designated as a Euler column. The strength of a given Euler column is related to the square of the column length. For example, if a given Euler column is shortened by a factor of two by a thickened portion 16, the column can be increased in strength by a factor of four. The column lengths 12a typically have a round cross section which can provide uniform strength in all radial directions, but alternatively can have other cross sectional shapes, such as square, rectangular, hexagonal, octagonal, polygonal, oval, complex curves, etc.
(26) The use of the thickened portions 16 can allow the nominal or minimum thickness or diameter of the spacer rod 12 to be made smaller than if the spacer rod had a constant diameter large enough to withstand the desired buckling force F, thereby minimizing the weight. In addition, by using thickened portions 16 that are round or cylindrical in shape, with the central axis 21 transverse, orthogonal or at a right angle to the spacer rod 12 and axis 17, the thickened portions 16 can have a configuration that is large enough, and long enough in the direction of axis 17 to act as fixed end supports to form a series of Euler type columns extending along axis 17 that are separated from each other, while also minimizing weight and material. The cylindrical shape with flat opposed surfaces 25 minimizes weight on the opposite axial ends along axis 21, and the curved outer perimeter surface 27 maximizes the length of the thickened portion 16 between the column lengths 12a in the direction of axis 17 while also minimizing weight. The curved outer perimeter surface 27 extends the length of the cylindrical thickened portion 16 along the junction with the column lengths 12a, while minimizing material and weight at radially outward locations away from the spacer rod 12. The length of the thickened portion 16 if too short, might not sufficiently act as an end support and might not provide sufficient strength. In addition, the thickened portions 16 can also have a central hole 16a (
(27) The clamps 14 can include two opposed jaws 13 having hub portions 23, that can be rotatably connected to each other about axis 14a on opposite sides of end portions 16b of spacer rod 12, by bolts 20, washers 24 and nuts 22 (
(28) In some embodiments, the spacer rod 12 can be about 1 or 2 to 3 feet long, and about % to inches in nominal or minimum thickness or diameter d.sub.m (
(29) The column lengths 12a can have a column length L.sub.c to nominal or minimum diameter or thickness d.sub.m ratio L.sub.c/d.sub.m of about 5 to 18, often about 5 to 12, or 5 to 8. The thickened portion 16 thickness T.sub.t and the column length 12a thickness or diameter d.sub.m can have a ratio T.sub.t/d.sub.m of about 1.5 to 3, and often about 1.75 to 2.5. The thickened portion 16 length or diameter d.sub.t and the column length 12a thickness or diameter d.sub.m, can have a ratio d.sub.t/d.sub.m of about 2 to 5 and often about 2.5 to 3.5. This can help provide a spacer rod 12 having maximum strength against Euler type buckling with a minimum weight.
(30) In one embodiment, spacer device 10 can have a spacer rod 12 which is about 24 inches long between the axes 21 of the two end portions 16b, which when clamps 14 are attached that have a distance of about 3 to 4 inches between axis 14a and jaw portions 13a, can space conductors 18 apart from each other about 30 to 32 inches. The spacer rod 12 can have three intermediate thickened portions 16 spaced apart from each other and the end portions 16b by a distance or span S of about 6 inches between center axes 21 to form four Euler column lengths 12a in series separated from each other along axis 17. The column lengths 12a can have a nominal or minimum diameter d.sub.m of about inches and a length L.sub.c of about 4 inches. The thickened portions 16 can have a length or diameter d.sub.t of about 2 inches and a thickness T.sub.t of about 1 inches. The end portions 16b can have a diameter of about 2 inches and a thickness of about 0.68 or 11/16 inches. The holes 16a can be about inches in diameter. This can provide a L.sub.c/d.sub.m ratio of about 6 to 7, such as about 6.4, a t.sub.t/d.sub.m ratio of about 2, and a d.sub.t/d.sub.m ratio of about 3.2. Although column lengths 12a are shown to have a diameter with a smooth outer surface, it is understood that the outer surface can have corrugations or irregularities.
(31) In some embodiments, the maximum allowed stress on an aluminum column length 12a is about 10,000 lb/in.sup.2. For a column length 12a having a minimum diameter d.sub.m of about inch, maximum loads for various column lengths L.sub.c, can be as follows: for L.sub.c of 6 inches about 1848 lbs, for L.sub.c of seven inches about 1807 lbs, for L.sub.c of 8 inches about 1759 lbs, and for L.sub.c of 9 inches about 1705 lbs. For a column length 12a having about a 0.7 inch diameter, the following maximum loads for various column lengths L.sub.c can be as follows: for L.sub.c of 6 inches, about 3733 lbs, for L.sub.c of 7 inches about 3692 lbs, for L.sub.c of 8 inches about 3644 lbs, and for L.sub.c of 9 inches about 3590 lbs. These spacer rods 12 can be heat treated. In compressive testing where the spacer rod 12 is subjected to a compressive force exerted at the end portions 16b via bolts through holes 16a (for example diameter bolts), from a compressive test machine, embodiments of the spacer rod 12 when heat treated can buckle at about 2200 lbs, and at about 2440 lbs if the bolts through the end portions 16b are tightened to about 100 ft/lbs to prevent rotation. Embodiments of the spacer rod 12 that are not heat treated can buckle at about 3130 lbs, and at about 3780 lbs if the bolts through the end portions are tightened to about 100 ft/lbs.
(32) In some embodiments, when the spacer device 10 is cast from aluminum, the spacer rod 12 can weigh about 21 lbs and the clamps 14 about 3 lbs each. The bolts 20 and nuts 22 can be about 2 lbs for each set. This can provide spacer device 10 with a light weight to allow faster and easier installation on an electrical transmission line from a helicopter.
(33) In some embodiments, for a 600 foot span, 3 spacer devices 10 can be secured to and spaced along the span about 200 feet from each other. Referring to
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(37) In addition to wind loads on electrical transmission lines, cables or conductors 18, another possible loading condition can be short circuit loading. This can occur when there is a line fault and the current may change from a normal value of about 1,000 amps to a short circuit value of 25,000 amps or more. Circuit breakers at the sub-station will react quickly, in about ten cycles or a time span of 0.10 seconds. In a bundled circuit, the phase conductors 18 will be electromagnetically attracted to each other. In a twin bundle, two conductors 18 will start to move toward the middle of the bundle. In a triple bundle, three conductors 18 will start to move. In a quad bundle, four conductors 18 will start to move. If the spacer devices 10 are oversized, for example, 30 to 32 inches instead of the pre-existing standard of 18 inches, the force of the attraction between the conductors 18 is much less in the 30 to 32 inch spaced bundle than for the 18 inch bundle due to the increased spacing or distance apart. Since each bundle is a dynamic system having mass and stiffness, the motion is governed by Newton's laws of motion, and is not instantaneous, and will be determined by the natural modes of vibration. So, while the short-circuit current is instantaneous, and the relay operation occurs within a 0.1 second time frame, the force F moving the conductors 18 towards each other is an impulse in time over a time period of 0.1 second.
(38) The use of oversized spacer devices 10 of 30 to 32 inches has many desired benefits which include, (i) increase the power delivery capacity of the transmission line over long distances, (ii) strengthen the ability of the bundle to resist forces F caused by short circuits, (iii) increase the wind speed at which galloping may occur, and (iv) prevent sub-conductor oscillation in large diameter sub-conductors.
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(40) One use of the spreading tool 35 can be for installing spacer devices 10 that space conductors 18 about 30 to 32 inches apart from each other in a bundle having conductors 18 that are currently spaced only 18 inches apart. Referring to
(41) In some embodiments, the mechanical stops 50a and 50b, and arms 36a and 36b, can be configured to provide other angles .sub.1 and distances D.sub.1 and D.sub.2, as desired. The mechanical stops 50a and 50b can have other suitable configurations, and can be located outside the hubs 39a and 39b. The clamps 14 can be set to rotate relative to arms 36a about axes 14a, if desired. Although clamps 14, and arms 36a and 36b having a similar design to spacer device 10 are shown, it is understood that in some embodiments, the arms 36a and 36b can have other suitable configurations. For example, the arms 36a and 36b can be formed of round, oval, square, rectangular, polygonal or complex curved tubing or solid members, or can have an I beam cross section. In addition, a version of the clamps 14 can be integrally formed with the arms 36a and 36b, or the clamps 14 can be omitted, with the arms 36a and 36b having slots or openings for engaging the conductors 18. Although the spreading tool 35 is typically formed of aluminum, alternatively, other suitable materials can be employed such as steel, wood, composites, fiberglass, etc.
(42) While this invention has been particularly shown and described with references to example embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.
(43) For example, the devices described above and shown in the drawings are not limited for use with electrical transmission lines, but can also be used for support or suspension cables, for example, towers, bridges, etc. In addition, the sizes or dimensions of the devices and their features can vary depending upon the application at hand. Although the components are typically integrally cast from aluminum for weight and manufacturing purposes, it is understood that other suitable metals and materials can be used, and that other configurations of the components and manufacturing methods can be employed.