Rating an enhanced strength conductor

Abstract

A conductor may be rated. first, a conductor core comprising a first material and having a core elongation may be provided. Next, a plurality of conductor strands may be provided. The plurality of conductor strands may comprise a second material. The elongation of the plurality of conductor strands may be one of greater than the core elongation or equal to the core elongation. Then a rating for a conductor comprising the conductor core and the plurality of conductor strands may be provided. The rating may include a composite rated breaking strength of the conductor being a function of the core elongation and not being limited by the elongation of the plurality of conductor strands.

Description

RELATED APPLICATIONS

This application is

wherein n_con is the number of conductor strands in the plurality of conductor strands; n_core is the number of conductor strands in the conductor core; STR_con is the average breaking strength of the conductor strands in the plurality of conductor strands at the core elongation; STR_core is the average breaking strength of the conductor strands in the conductor core at the core elongation; RF_con is a rating factor of the plurality of conductor strands; and RF_core is a rating factor of the conductor core, respectively.

Calculating the rated strength for an ACSR conductor may comprise the sum of the strengths of two different materials multiplied by the appropriate stranding factors specified in ASTM. ACSR conductor, with galvanized core strands, may be manufactured in accordance with ASTM Standard B232. The 1350-H19 aluminum strands meet the requirements of ASTM Standard B230 and the galvanized steel core strands meet the requirements of ASTM Standard B498. ASTM Standard B232 defines the rated strength of ACSR conductors as being the aggregate sum of the strengths of the individual aluminum and steel component strands of the overall ACSR conductor. The tensile strength of the individual aluminum strands is the minimum average tensile strengths for the specified strand diameter. Because the 1350-H19 strands elongate to no more than 1% at their “ultimate tensile strength”, the accompanied steel strands must be limited to their strength at 1% elongation, when calculating ACSR's composite rated breaking strength. 1350-H19 strands may be limited to a 1% elongation because 1350-H19 strands may break or become otherwise unusable as electrical conductors if stretched beyond a 1% elongation. Consequently, the steel strands in conventional ACSR can stretch (to a higher percentage elongation at the steel strands' ultimate tensile strength) more than the aluminum strands can (at the aluminum strands' ultimate tensile strength.)

For example, a “Drake” conductor's steel strand size has a 0.1360 inch diameter and has a strength at 1% elongation is 180 ksi. This is from ASTM 498 Table 4. From the same table, the same steel strand has an ultimate tensile strength of 200 ksi where it has an elongation of 4%. This higher strength figure for the steel strands is never reached with conventional ACSR because the aluminum strands, which are elongating along with the steel strands, may all have broken before the 4% elongation is reached. In other words, the higher strength value of the steel strands is not utilized because of limitations of the aluminum strands in conventional ACSR. Consistent with embodiments of the invention, a material (e.g. an alloy of aluminum) may be used for the conductor strands that can maintain the conductor strand's strength up to, for example, 4% elongation and not break or otherwise become unusable as conductor strands. Accordingly, with embodiments of the invention, the higher strength of the steel core strands may be available to increase the composite rated breaking strength of conductor 100.

The following is an example that first shows conventional ACSR using 1350-H19 aluminum conductor strands (e.g. wires) with class A steel core strands and then embodiments of the invention using Aluminum Zirconium for the conductor strands. The tensile strength of conventional 795 kcmil-26/7 ACSR “Drake” conductor (26×0.1749-inch 1350-H19 strands and 7×0.1360 inch steel strands) is calculated below. The minimum average tensile strength for a 0.1749-inch diameter 1350-H19 strand is 24.0 ksi. A single strand breaking strength is:

$\mathrm{Al}.\mathrm{Wire}\mathrm{Strength}=\frac{\pi }{4}{\left(0.1749\right)}^2\left(\mathrm{24,000}\right)=576.6\mathrm{lbs}$
The minimum average tensile stress at 1% elongation for a 0.1360-inch diameter Class A galvanized steel strand (e.g. wire) is 180 ksi. The breaking strength of a single steel strand is:

$\mathrm{St}.\mathrm{Wire}\mathrm{Strength}=\frac{\pi }{4}{\left(0.136\right)}^2\left(180\text{,000}\right)=2.615\mathrm{lbs}$
Accordingly, Drake's rated breaking strength is:
Rated Strength=(26)(576.6 lbs.)(0.93)+(7)(2,615 lbs.)(0.96)=31,515 lbs.
Rounding the rated breaking strength to three significant places, Rated Strength=31,500 lbs. for conventional 795 kcmil-26/7 ACSR “Drake”.

As stated above, 1350-H19 strands may be limited to a 1% elongation because 1350-H19 aluminum strands may break or become otherwise unusable as a conventional ACSR conductor if stretched beyond a 1% elongation. Because 1350-H19 strands' elongation is limited to approximately 1%, the steel core strands' tensile strength must also be limited to the steel's tensile strength at 1% elongation when calculating conventional ACSR's composite rated breaking strength. In other words, because 1350-H19 strands may be limited to 1% elongation, the steel core's strands should have the same limitation because conventional ACSR is a composite of the two materials, high strength (HS) steel and 1350-H19 Aluminum. Consequently, even though the HS steel used for the core may be elongated beyond 1% and have a higher tensile strength at the higher elongations, conventional ACSR core's tensile strength may be limited by the conductor strands when the conductor strands comprise 1350-H19 Aluminum.

Consistent with embodiments of the invention, a material may be used for first conductor layer 105 and second conductor layer 110 that may have an elongation greater than 1% to take better advantage of core 115's tensile strength when core 115 is made, for example, of HS steel. In this way, with embodiments of the invention, conductor 100's composite rated breaking strength may be increased when using a material for first conductor layer 105 and second conductor layer 110 that may have an elongation greater than 1%. For example, a material may be used for first conductor layer 105 and second conductor layer 110 that may have an elongation of between 1% and 7%. In this way, conductor 100 made with first conductor layer 105 and second conductor layer 110 made from a material having an elongation of between 1% and 7%, core 115's elongation limit could be increased to first conductor layer 105's and second conductor layer 110's higher elongation. In this case, core 115 would not have to be limited to the steel's tensile strength at 1%, but could be increased to the steel's tensile strength at the higher elongation (e.g. between 1% and 7%.) Thus an ACSR's composite rated breaking strength may be enhanced consistent with embodiments of the invention.

First conductor layer 105 and second conductor layer 110 may be made of an Aluminum Zirconium alloy. Aluminum Zirconium alloy is an example, and other materials may be used. Because the elongation of Aluminum Zirconium alloy strands (e.g. wires) is approximately 5%, the tensile strength of the steel wire at 4% or 3% elongation (e.g. per Table 4 in ASTM 498) may be used in calculating the composite rated breaking strength of ACSR using Aluminum Zirconium alloy consistent with embodiments of the invention.

The following is an example using Aluminum Zirconium alloy strand (e.g. wire). The tensile strength of 795 kcmil-26/7 ACSR “Drake” conductor (26×0.1749-inch Aluminum Zirconium alloy strands and 7×0.1360 inch steel strands) will be calculated. The minimum average tensile strength for a 0.1749-inch diameter Aluminum Zirconium alloy strand (e.g. any of first conductor layer strands 130 and second conductor layer strands 135) is 23.500 ksi. A single strand breaking strength is:

$\mathrm{Al}.\mathrm{Wire}\mathrm{Strength}=\frac{\pi }{4}{\left(0.1749\right)}^2\left(23.5\right)=564.6\mathrm{lbs}$
The minimum average tensile stress at 4% elongation for a 0.1360-inch diameter class A galvanized steel strand (e.g. wire) is 195 ksi (according to ASTM 498 T6 Table 4.) The breaking strength of a single steel strand (i.e. any of outer core strands 125 and center strand 120 comprising core 115) is:

$\mathrm{St}.\mathrm{Wire}\mathrm{Strength}=\frac{\pi }{4}{\left(0.136\right)}^2\left(195\text{,000}\right)=2832.7\mathrm{lbs}.$
Consequently, consistent with embodiments of the invention, the conductor's rated breaking strength is:
Rated Strength=(26)(564.6 lbs.)(0.93)+(7)(2832.7 lbs.)(0.96)=32,687.9 lbs.
Rounding the rated breaking strength to three significant places, Rated Strength=32,700 lbs. for 795 kcmil-26/7 ACSR “Drake” consistent with embodiments of the invention. As shown above, the Rated Strength for conventional 795 kcmil-26/7 ACSR “Drake” is 31,500 lbs. Accordingly, the Drake ACSR made consistent with embodiments of the invention has a higher rated breaking strength.

Consistent with embodiments of the invention, using a material (e.g. Aluminum Zirconium alloy) for first conductor layer 105 and second conductor layer 110 that may have elongation properties better than 1350-H19 (e.g. an elongation greater than 1%) may take better advantage of core 115's tensile strength when core 115 is made of HS steel. Accordingly, consistent with embodiments of the invention, an ACSR conductor made with the material having the aforementioned better elongation properties may have an enhanced rated breaking strength as compared to conventional ACSR made using, for example, 1350-H19 Aluminum. Consistent with embodiments of the invention, outer core strands 125 and center strand 120 may comprising core 115 may comprise HS 285 steel strands.

As illustrated above, elongation may mean how much core strands or conductor strands can be stretched and still allow the core strands or conductor strands to be used in an electrical conductor, for example, an ACSR conductor. With conventional ACSR conductors, the composite rated breaking strength of conventional ACSR conductors is limited by the elongation of the conventional conductor strands and not by the elongation of the conventional core strands. Consistent with embodiments of the invention, a material may be used for the conductor strands that has an elongation that is greater than the elongation of conventional conductor strands. In this way, the composite rated breaking strength of an electrical conductor, consistent with embodiments of the invention, may not be limited by the elongation of the conductor strands and may now be more of a function of the elongation of the core strands.

As stated above, consistent with embodiments of the invention, first conductor layer 105 may comprise first conductor layer strands 130. Second conductor layer 110 may comprise second conductor layer strands 135. First conductor layer strands 130 and second conductor layer strands 135 may be considered conductor strands. Center strand 120 and outer core strands 125 may be considered core strands. The core strands, for example, may comprise, but are not limited to, high strength steel, high strength steel meeting ASTM Standard B232, high strength steel 285 steel, or Class A galvanized steel. Consistent with embodiments of the invention, the conductor strands may have an elongation greater than or equal to an elongation of the core strands. For example, the conductor strands may comprise, but are not limited to, Aluminum Zirconium alloy. Notwithstanding, the conductor strands may comprise a material with an elongation that is greater than an elongation of 1350-H19 aluminum strands meeting ASTM Standard B230.

While certain embodiments of the invention have been described, other embodiments may exist. Further, the disclosed methods' stages may be modified in any manner, including by reordering stages and/or inserting or deleting stages, without departing from the invention. While the specification includes examples, the invention's scope is indicated by the following claims. Furthermore, while the specification has been described in language specific to structural features and/or methodological acts, the claims are not limited to the features or acts described above. Rather, the specific features and acts described above are disclosed as example for embodiments of the invention.

Claims

1. A method comprising:

manufacturing a conductor comprising a conductor core and a plurality of conductor strands, the conductor core comprising a plurality of core strands and a core elongation at an ultimate tensile strength of the conductor core, wherein manufacturing the conductor comprises;:

providing the conductor core comprising a first material, and

stranding the plurality of conductor strands around the conductor core, the plurality of conductor strands comprising a second material, wherein an elongation of the plurality of conductor strands is one of the following: greater than the core elongation and equal to the core elongation, the second material configured to cause the plurality of conductor strands not to break at the elongation of the plurality of conductor strands; and

rating the manufactured conductor with a composite rated breaking strength equal to as calculated by an equation:

the composite rated breaking strength=(n_con*STR_con*RF_con)+(n_core*STR_core*RF_core);

2. The method of claim 1, wherein providing the conductor core comprises providing the conductor core wherein the core elongation is between 1% and 4% inclusively.

3. The method of claim 1, wherein providing the conductor core comprising the first material comprises providing the conductor core comprising the first material comprising high strength steel.

4. The method of claim 1, wherein providing the conductor core comprising the first material comprises providing the conductor core comprising the first material comprising high strength (HS) 285 steel.

5. The method of claim 1, wherein providing the conductor core comprising the first material comprises providing the conductor core comprising the first material comprising Class A galvanized steel.

6. The method of claim 1, wherein stranding the plurality of conductor strands around the conductor core comprises stranding the plurality of conductor strands around the conductor core wherein the elongation of the plurality of conductor strands is less than 7%.

7. The method of claim 1, wherein stranding the plurality of conductor strands around the conductor core comprises stranding the plurality of conductor strands around the conductor core wherein the elongation of the plurality of conductor strands is less than 4%.

8. The method of claim 1, wherein stranding the plurality of conductor strands around the conductor core, the plurality of conductor strands comprising the second material comprises stranding the plurality of conductor strands around the conductor core, the plurality of conductor strands comprising the second material wherein the second material comprises Aluminum Zirconium alloy.

9. The method of claim 1, wherein stranding the plurality of conductor strands around the conductor core comprises stranding the plurality of conductor strands around the conductor core wherein each of the plurality of conductor strands has a trapezoidal cross-sectional shape.

10. The method of claim 1, wherein stranding the plurality of conductor strands around the conductor core comprises stranding the plurality of conductor strands around the conductor core wherein each of the plurality of conductor strands are compacted.

11. The method of claim 1, wherein providing the conductor core comprises providing the conductor core having the plurality of core strands wherein the plurality of core strands comprise a center strand with a plurality of outer core strands helical wrapped around the center strand.

12. The method of claim 1, wherein stranding the plurality of conductor strands around the conductor core comprises stranding the plurality of conductor strands around the conductor core wherein the plurality of conductor strands comprise a second conductor layer helical wrapped around a first conductor layer.

13. The method of claim 12, wherein stranding the plurality of conductor strands around the conductor core comprises stranding the plurality of conductor strands around the conductor core wherein the first conductor layer and second conductor layer are wrapped in respective alternating hand lay.

14. The method of claim 1, wherein rating the manufactured conductor comprises rating the manufactured conductor wherein the manufactured conductor comprises aluminum conductor steel reinforced (ACSR).

15. A method comprising:

manufacturing a conductor comprising a conductor core and a plurality of conductor strands, the conductor core comprising a plurality of core strands and a core elongation at an ultimate tensile strength of the conductor core, the conductor having a composite rated breaking strength equal to as calculated by an equation:

the composite rated breaking strength=(n_con*STR_con*RF_con)+(n_core*STR_core*RF_core);

16. The method of claim 1, wherein:

STR_con is an average breaking strength equal to the average of a conductor strand breaking strength of each of the plurality of conductor strands; and

STR_core is an average breaking strength equal to an average of a core strand breaking strength of each of the plurality of core strands;

wherein each of the conductor strand breaking strength and the core strand breaking strength is a minimum breaking strength calculated as the product of a minimum average tensile strength and a cross-sectional area for each of the plurality of conductor strands and each of the plurality of core strands, respectively.