US2118008A - Overhead electric transmission line - Google Patents

Description

F. M. CRAP@ OVERHEAD ELECTRIC TRANSMISSION LINE Filed May 23, 1955 May 17, 1938.

Patented May 17, 10:',a- 02,118,008,

UNITED STATES PATENT OFFICE.l

OVERHEAD ELECTRIC TRANSMISSION LINE Frederick M. Crapo, Muncie, Ind., assignor to Q Indiana Steel & Wire Company, Muncie, Ind.,

a corporation of Indiana Application May 23, 1935, Serial No. 23,009

10 Claims. (Cl. 173-13) My invention relates to overhead electric transrous conductor, the area in solid-line crossmission lines using ferrous conductors, with parhatching indicating the preferred area, and the ticular reference to a--c.- transmission lines alarea in broken-line cross-hatching indicating a -though my invention is not limited to a-c. lines. permissive area. v

My invention is applicable for instance, for pow- Heretofore the ferrous conductors in general er lines, telephone lines, telegraph lines, signal use for telephone, telegraph, and signal lines, and lines, etc., and is of especial value for telephone in some instances for power lines, have been of transmission lines; and the conductors involved three general commercial grades known as E. B.- may be not only the Wires of the transmission cir- B. (Extra Best Best), B. B. (Best Best), `and cuit proper, but also include various ancillary Steel, Approximate tensile strengths and d-c. 10

conductors, such as ground Wires, shield wires, resistivties of these grades are as follows:

messenger cables, catenary supports, etc., which 1 may be primarily for other than conducting pur- Approximate I Approximate poses and/or may actually serve to conduct cur- Grade @mrgsislliy gnsilungth l5 rent only occasionally. Therefore, by the term no pofd e sfaremcger 15 overhead electric transmission line, I mean an overhead line which may be required to carry electric current; and by the terms ferrous congj B ductor or "carbon-steel conductor I mean a St -0750 551000 conductor which may be required to serve as a 20 current-carrier for an electrical system and of f Three other commercial grades of ferrous conwhich the cross-section is mainly of ferrous maductors have also been used in some instances terial, specifically carbon steel in my invention, for power lines; especially for overhead ground and any coating (as of zinc or copper) is a relawires and/or shield wires, and for long spans such tivelysmall part of the cross-section. The term as wide river crossings. These other three grades 25 carbon steel is used in its accepted sense, (as` are commonly known as lSiemens-Martin, shown by The Making, Shaping, and Treating High strength", and Extra-high strength, and of Steel, by Camp and Francis, published by the ,are named in the order of increasing tensile Carnegie Steel Company, Fourth Edition, pages strengths and d-c. resistivity. Approximate 259 and 707, generally accepted as authorltative,) tensile strengths and d-c. resistivities of these 30 as meaning steels in which carbon is the element three grades are as follows: fundamentally Vemployed to control physical properties' and in which the manganese is 1es s in Approximate Approximate amount than about 1.0%, although 1n previous Grade Ad-- resistivity tensile Strength hypo-eutectoid carbon steels it has usually been m0 llfml e. msilrgxsic er 35 greater in amount than the carbon. It is the obJect of my .mventlon to produce a siemensMamn 7280 00' 000 transmission line of carbon-steel conductor (un- High strength 8320 140,000 coated or coated as with zinc or copper) which Exim-002111800118@ 9300 200,000

40 has its tensile strength and its electrical con- 40 ductivity both relatively high. Generally inthe In all the grades known as Siemens-Martin", prior art an increase in tensile strength in ferrous High strength",` and Extra-high strength", the conductors has been obtained at the cost of deadvantages of increased tensile strength have creased electrical conductivity, and an increase in been obtained at the sacrifice of electrical conelectrical conductivity at the cost of decreased ductivity; so that while the tensile strengths of 45 tensile strength; but by my invention I am able such grades are substantially greater than those to get both relatively high. of E. B. B., B. B., or Steel, above men- The accompanying drawing illustrates my irltioned, their electrical conductivities are subvention: InA such drawing, Fig. 1 is a diagram- 'stantiallyless Such increased tensile strengths matic view of an overhead electric'transmission .have been obtained fundamentally by making the 50 line, of ferrous conductor, in accordance with my wires of steels'which have high contents of Acarinvention,` the particular character" of ferrous bon, and/or to some extent and in some cases conductor being indicated by a legend on the by heat treatment and/or by cold-working the drawing; andFig. 2 is a diagram showing the material in the process of wire drawing.

contents of carbon and manganese in such fer- In the carbon-steel conductors -of the prior art 55 of overhead electric transmission, however, the carbon content and the manganese content and the relation between them have been such that when an increase in tensile strength has been obtained it has been at the cost of a decrease in electrical conductivity; Generally speaking, increases in tensile strength have been obtained 4by increasing both the carbon content and the manganese content, with the manganese content generally materially exceeding the carbon content until the carbon rises well. above 0.25%; for manganese is qualitatively like carbon in that an increase in it tends to; increase the tensile strength.

Both an increase in carbon and an increase in manganese, however, not only tend to increase tensile strength but also tend to increase d-c.

resistivity. But the effects of increases in carbon and manganese, respectively, diiier as between themselves in their eects dn tensile strength and on electrical conductivity; for the addition of carbon to carbon steel increases tensile strength in proportionately greater degree but increases d-c. resistivity in proportionately less degree than does the addition of an equal amount of manganese, and, conversely, the elimination of managnese decreases tensile strength in proportionately less degree but decreases d-c. resistivity in proportionately greater degree than does the elimination of an equal amount of carbon.l

Heretofore high manganese has in general been assumed to be necessary in any mediumcarbon and higher-carbon steels Iused in transmission lines, for various reasons and especially for cleansing the steel in the process of manufacture; and its effect in increasing the 'd-c. resistivity, if considered at all, either was deemed not seriously objectionableor was considered unavoidable. Y

I have done some previous work, partly in connection with Frank F. Fowle, in overcoming the diillculties of the general prior art referred to above; and either alone or jointlyv with him have illed certain patent applications relating thereto, as follows:

A. In the Crapo Patent No. 1,942,441, granted January 9, 1934, there is described -a carbonsteel conductor in which the carbon content is .not less than 0.25%.

B. In the co-pending Fowle & Crapo application, Serial No. 705,830, filed January 8, 1934, now Patent No. 2,019,447, granted October 29, 1935, there is described a carbon-steel conductor in which the carbon content is not less than 0.25%, and the manganese content is not in excess of 0.30%.

C. In the co-pending Crapo application, Serial No. 705,831, led January 8, 1934, now Patent No. 2,019,445, grantedoctober 29, 1935, there is described av carbon-steel conductor in which the carbon content is less than 0.50%, the manganese content is less than 0.30% when the carbon content exceeds 0.25%, and the carbon steel has the characteristics which are produced by quenching from above a critical temperature by a liquid medium having a temperature below the melting point of lead.

According to my present invention, the carshall be not in excess of the carbon content, and

e templates that there shall be at least some cold working either before or after the application of any protective metallic coating, and that effects of cold working shall persist in the iinal conductor.

The cold working may if desired be preceded by any desired annealing, either partial or complete, or by other desired heat treatment. Indeed, it is sometimes advantageous, especially when relatively'high tensile strength is desired, to subject' the conductor to patent-annealing prior to the final cold working; in which case the conductor will have properties characteristic of those produced by that combination of treatments.

It is not prohibitive to do some partial annealing after cold working; such as the partial annealing which incidentally occurs when a harddrawn ferrous conductor is passed through a bath ofl molten zinc in the hot-dip process of galvanizing. It is sometimes desirable to avoid even that partial annealing; in which case any metallic protective coating which is applied after the nal cold working may be applied by electrodeposition.

`My present invention is thus concerned fundamentally with th carbon content and the manganese content, and the production of characteristics due to cold working, in the general class of carbon steels. Various other elements which may exist in carbon steels, such as silicon and phosphorous and sulphur, may also be present in varying small amounts; and the carbon steels may be copper-bearing steels. The phosl phorous desirably does not exceed 0.04% if the conductor is to be coated by electro-deposition, and 0.08% if it is to be coated by hot-dipping as with zinc; .the sulphur desirably does notv exceed 0.05%; and the silicon desirably does not exceed 0.025% unless a zinc coating is to be applied by hot-dipping, and even then desirably should not exceed 0.12%. Even with hot-dipping. it is desirable that only phosphorous, or only silicon, but not both, exceed the lower limit given. Copper, if present, as to improve corrosion resistance, may be Yof the usual amount employed, commonly not over 0.30%.v

Thus my transmission line comprises a carbon-steel conductor (coated or not) which has carbon and manganese contents and cold-worked characteristics as defined above.

Such a transmission line has the advantage of relatively hifh electrical conductivity, for both direct currents and alternating currents, as compared with previous ferrous transmission lines of corresponding carbon contents. It is especially advantageous for alternating or pulsating currents, because of the decreased magnetic permeability andthe consequent `decreased skin effect due to the carbon and to the coldworking, and to the patenteannealing ifv used. AAt the same time, by having the carbon and manganese contents in the range noted, and by the lcold working, and by the patent-annealing if used, I get high tensile strength. Thus Iy combine high tensile strength with high electrical conductivity.

The followingtwo examples are illustrative of my invention: Y

a. An example of carbon-steel conductor used in my' invention is a No. 12 B. W. G. galvanized steel wire in which the steel contained approximately 0.21% of carbon, and approximately 0.17% of manganese; and in which the silicon was 0.014%, the phosphorous 0.014%, the sulphur 0.030%, and the copper 0.24%. This wire has been cold-drawn in the -customary manner, and was then so galvanized By the hot-dip process that its temperature was not raised sufficiently high to eliminate the effects produced by the cold-drawing.

b. Another sample of this wire was processed in the same way, except that it was patent-annealed before cold-drawing.

The following table shows the properties of the two samples just discussed, in contrast to those of an example of commercial B. B. telephone wire of the same No. 12 B. W. G. size:

I claim as my invention:

1. An overhead electric transmission line, comprising a conductor which is to carry current, and which is of carbon steel which has been cold-worked andI in which substantial effects characteristic of those produced by such coldworking persist; and of which the carbon content is less than 0.25% but not less than 0.12%, and the manganese content is not in excess of 11A; times the carbon content and in any case is not in excess of 0.30%.

2. An overhead electric transmission line, comprising a conductor which is to carry current, and which is of carbon steel which has been cold-worked and in which substantial eiects characteristic of those produced by such coldworking persist; and of which the carbon content is less than 0.25% but not less than 0.12%, and the manganese content is not in excess of 11A, times the carbon content and in any case is not in excess of 0.30%, and the sum of the carbon content and manganese content is not over 0.40%.

3. An overhead electric transmission line, com- Tensile D-c. re- Etective Skim Ratio of tenstrength: sistance: a-c. resisteffect silc strength in pounds in olli lnce: in resistance to eilectlivte per square per o ms per a-c. res s inch met 100e feet m0 am Example oi commercial B. B. telephone wire. v57, 500 6. 35 9. 97 1. 670 5, 767

Exemples l telephone wires oi this application:

non-patented before cold drawing 101, 200 6. 8. 94 l. 394 ll, 320 (b) Patented before cold drawing 114,000 6. 8.93 1.386 12,770

The three wires compared are all galvanized wires. The a-c. currents used had a frequency of 1000 cycles per second, and a strength of 5 milliamperes. I took a frequency `-of 1000 cycles per second as a fair single-equivalent voice frequency; and I took a current of 5 milliamperes as being within the ordinary range of telephonie transmission currents.

Although the d-c. resistances of the wires embodying the present invention are very closely similar tothe dc. resistance of the "B. B. telephone wire, yet the effective a-c. resistances of lthe wires of the present invention are materially lower than the a-c. resistance of the B. B. telephone wire, and the tensile strengths of the wires of the present invention are almost double the tensile strength of the B. B. telephone wire; so that the ratio of tensile strength to effective ar-o. resistance is about twice as great as thatrratio for the B. B." telephone wire.

By building an overhead transmission line of a carbon-steel conductor (coated or uncoated) conforming to the above requirements, it is possible to have both high tensile strength and high electrical conductivity. Such a transmission line is of value for both alternating and direct currents, and for the transmission of electric power as well as of telephone, signal, and telegraph currents.

It is also advantageous for ground wires, shield wires, messenger cables, catenary supports, etc.; and either as a single wire or in a stranded cable. But it is of special advantage for the transmission of relatively high-frequency currents, such as those used in telephonie transmission; where the frequency is voice frequency, of the order of 100 to 3000 cycles per second, and the currents are usually small, n otexceeding about 50 milliamperes.

prising a conductor which is to carry current, and which is of carbon steel which has been coldworked and in which substantial eifects characteristic of those produced by such cold-working persist; and of which the carbon content is less than 0.25% but not less than 0.12%, and the manganese content is not in excess of the4 carbon content.

4. An overhead electric transmission line, comprising a conductor which is to carry current. and which is of carbon steel which has been cold-worked and in which substantial effects characteristic of those produced by such coldworking persist; and of which the carbon content is less than 0.25% but not less than 0.12%. andthe manganese content is not in excess of the carbon content, and the sum of the carbon content and manganese content is not over 0.40%.

5. An overhead electric transmission line, com-V prising a conductor which is to carry current, and which is of carbon steel which has been cold-worked and in which substantial effects characteristic of those produced by such coldworking persist; and of which the carbon content is less than 0.25% but-not less than 0.15%, and the manganese content is not in excess of 11/3 times the carbon content andin any case is not in excess of 0.30%.

6. An overhead electric transmission line, comprising a conductor which is to carry current, and which is of carbon steel which has been cold-worked and in which substantial effects characteristic of those produced by such coldworking persist; and of which the carbon content is less than 0.25% but not less than 0.15%, and the manganese content is not in excess of 1% times the carbon content andin any case is not in excess of 0.30%, and the sum of the carbon content and manganese content is not over 0.40%.

7. An overhead electric transmission line, com prising a conductor which is to carry current, and which is of carbon steel which has been cold-worked and Ain which substantial eiccts characteristic of those produced by such coldworking persist; and of which the carbon content is lessthan 0.25% but not less than 0.15%, and the manganese content is not in excess of the -carbon content.

8. An overhead electric transmission line, comprising a conductor which is to carry current, and. which is of carbon steel which has been cold-worked and in which substantial effects characteristic of those produced by such cold- 15 working persist; and oi which the carbon con- -tent is less than 0.25% but not less than 0.15%, and the manganese content is not in excess of the carbon content, and thesum of the carbon content and manganese content is not over 9. An overhead electric transmission line, comprising a conductor which is to carry current, and which is of carbon steel which been cold-worked and uin which substantial. effects characteristic of'those produced by such coldworking persist; and of which the carbon content is less than 0.25% but not less thanv 0.12%, and the manganese content-is not in excess of 1% times thevcarb'on content and in anycase is notin excessof 0.30%; .and which has been patent-annealed prior' to the cold-working.

10. An overhead electric transmission line. comprising a conductor which is to carry current, :and which is of carbon steel which has .been cold-worked andin' which substantial efi'ects characteristic of those produced bysuch cold-'working persist; and of which the carbon content is less than 0.25% but not less than 0.15%, and the manganese content is not in excess ci' 1%, times the carbon content and in any case is not in excess of 0.30%; and which has been patent-snnealed'prior to the cold-working. 20

FREDERICK u.

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