CA1181501A - Low-audible noise aluminium conductors - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

The invention relates to a compound cable, such as an aluminum cable, an aluminum alloy cable, aluminum cable steel reinforced or an aluminum alloy cable steel reinforced with reduced audible noise for use in a high voltage trans-mission line.
The surface of each of the aluminum wires to constitute the outermost layer of the cable is treated in the water or aqueous vapor of more than 90°C so as to form a hydrophilic hydrated film on said surface, or more than 3 grooves are provided on the outer periphery of each of the aluminum wires in excess of 30% of such wires to constitute the outer-most layer of the cable, a hydrated film being caused to form on the surface including the grooves thereof, so that the raindrops adhering to the surface may readily disappear due to the improved hydrophilic property and draining property of the surface of the cable thereby enabling to prevent the development of the corona discharge.

Description

1 The invention relates to a compound cable comprising an aluminum cable, an aluminum alloy cable~ an aluminum cable steel reinforced or aluminum alloy cable steel re-inforced with reduced audible noise for use in a high voltage transmission line.
~ he aluminum cable~ alumi~um alloy cable t aluminum cable steel reinforced or aluminum alloy cable steel reinforced (hereinafter referred to as a compound cable) conventionally used in the overhead transmission line has played an important role in power transmission. In recent years -the transmission voltage has come to be elevated due to the necessity of large capacity transmission. However, when the voltage is as high a3, for example, lO00 EV9 the corona discharge, particularly the audible noise directly after rainfall9 poses a problem.
~ he audible noise directly after rainfall is caused by the corona discharge produced by the elevated surface potential gradient around the rainarop projecting beyond the surface of the compound cable. The invention ha~ succeeded in pre-venting the generation of the corona discharge by increasing the wetness (hydrophilic property) a well as the draining property of the surface of the compound cable thereby enabllng to cause the raindrops to disappear quickly from said surface, ~he hydrophilic property can be imparted to the aluminum ~urfaGe byv~rious methods. ~owe~er, the anodic oxidization treatment has a disad~antage in that lt is necessary to remo~e a rigid insulating film formed on ~he surfaceO

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s~ l 1 The invention has been made as a result of a series of tes-ts for the elimination of the said disadvantage~ ~he inventio.n is firstly characterized in that it can provide a compound cable with reduced audible noise by forming a specific surface treatment film on the surface of the aluminum wires or aluminum alloy wires (hereinafterrefe~red to as aluminum wires) to con~titute the outermost layer of the cable thereby enablïng ~o im~ro~e the hydrophilic property of the surface of said cable.
The invention is secondly characterized in that (1~
more than 30~ of the aluminum element wires to constitute at least the outermost layer of the cable are provided on the outer peripher~es thereof with more than 3 grooves formed continuou~ly and longitudinally of said wires respectively~ that (2) a specific surface treatmerlt film is provided on the surface including the grooves o~ each o~i the element wires, and that (3) said specific surface treatment ~ilm i~ provided af.ter subjecting the surface o~ theelement wire to rough surface treatment; thereby enabling to provide a compound cable with reduced audible noise.
In fine, the invention is characterized in that the surface of a compound cable comprising aluminurn wires ~tranded around the outer per~phery of a steel core is subjected to a treatment in the water or aqueous vapor at a temperature of 90C and upward or in aqueous vapor having a temperature abo~e 120~ and a pressure above 2 kg/cm2 ~o ~s to produce a hydrated film thereon thereby enabling the surface of the cable to have a hydrophilic-property~

1 The invention i8 further characterized in that more than 3 groovas are formed on the outer peripheries of more than 3O% of the aluminum wires to constitute at least the outermost layer of the cable continuously and longitudinally of said aluminum wires9 respectivelyO
The outlIn~ of the accompanying drawings in the present invention i9 a~ follows:
Figs. 1 and 2 are cross-sectional views showing embodiments of the compound cable according to the inYention in which aluminum wires having hydrated films on the surfaces thereof respectiYely are used in the outermost layer of said cable.
Fig. 3 is a cross sectional view of ~n aluminum wire formed with grooves longitudinally thereof according to the invention~ -Fig. 4(A) to (D~ show cross-sectional views illustrat~
ing further embodiments of the grooves formed on the aluminum wires in different numbers and configurations, re~pectively.
A compound cable of the present invention will be described on an aluminum cable steel reinforced ~ACSR) as one of the most typiG~, compound cables as follows:
In Fig~ 1, around a steel reinforcement there are stranded an inner layer comprising aluminum wires 2 and then an outermost layer comprising aluminum wire~ 3 wnth surface treatment films formed on the surfaces thereof.
In Figo 2~ aluminum wire~ 2, 13 are stranded around a ~, /~ s steel reinforcement 1, surface treatment-fil~m 14 being formed on t~e outermost surfac~s of the aluminum wires 13 1 constituting the outermost layer~
According to the in~ention~ the surface treatment film is formed on the surface of each of the aluminum wires to cons~itute the outermost surface of the cable either by treating the surface of the compound cabls or by treating the surfaces in the ~tate of element wires prior to stranding of said element wires into a compound ~able. In both cases~
it is essential that the wP~e drawing lubricant is completely removed by an organic solvent before the film is formed on the surface.
In order to obtain a greater effect, it i5 preferable that the surface of the aluminum wire is subjected to a rough surface treatment~ such as blasting, liquid horning, etc.~ after the oil removing process by means of the organic solvent. According to the invention, the blast treatment comprises the ordinary sand blasting and shot blasting.
~he roughness of the surface treated by blasting or liquid horning i9 preferably about 10-50~since it has an advantage in that not only the hydrophilic property i~ satisfactory after the formation of the hydrated film but also mass production is feasible from the industrial viewpointO
When tha surface of the ACSR is simply subjected to the blast treatment or liquid horning treatment, the beads of raindrops adhering to the surface ha~e the same effect as the aforesaid projections thereofO It is impossible, there-~ore~ to reduce the audible noiseO ~nhen h~drated film is ormed on the sur~ace in the water or aqueous ~apor of 90C
and upward after it has been subjected to blast treatment or liquid horning treatment~ the surface has an improved 1 hydrophilic prope~tyO Thus the raindrops are uniformly dispersed over the surface without forming beads thereby enabling to greatly reduce the corona discharg0 and aceording-ly the audible noiseO Generally9 when a body is bro~ght into contact with water7 the relation between the contact angle ~ in case of a plane faced body and the contact angle ~' in case of a rough~faced body is as followsO
C08 ~ true sur~aee area _ _ = r cos 9 apparent surfaoe area In case o~ a rough face, the true surface are is larger than the apparent surface area. Since r~l, in case of OD< ~<~D~
~ . Thus the apparent contact angle becomes ~maller9 whereby the hydrophilic property of the rough face is improved~
However, a simple treatment of blasting or liquid horning is not sufficient to prevent the rain~rops from forming projections on the surfaceO Since the corona dis-charge is sub~t~ially.;same as in the case of the ordinary ~CSR, there is no improvement in the reduction of the audible noise. ~hus it has been found that the hydrophilic property is never impro~ed by simply roughening the surface~ When the hydrated film is caused to form ~h the water or aqueou~
vapor of 90 C and upward after the sur~ace has been sujected to blast treatment or liquid horning treatment~ the film is produced in grea~er amounts under the Sam8 conditions since the sur~ace area has been increased due to the roughen-ing process compared with that of the ordinary ACSR. In addition, -~he surface roughness of about 10-50~ after the blast treatment or liquid horning treatment is substantially doubled to about 20-lOOJ~ . Thus it has been ~ound that 1 the hydrophilic property of the surface of the cable is remarkably increased by the mul-tiplied effect of the improved hydrophilic property due to the hydratea film combined with the further roughening of the surface.
According to the invention, the hydrated film is cau~ed to form ~nthe water or aqueous ~apor of 90C and upward so that the surface may ha~e higher hydrophilic property and the surface roughness may substantially be -twice as large as that after the blast or liquid horn~ treatment thereby enabling to drastically improve the hydrophilic property of the surface of the cable~ When treated in aqueous vapor, the hydrophilic property is further increased compared with the ~ase of the water treatment in the same perlod of time.
If the temperature of the water or aqueous vapor is lower than 90C, the hydrophilic property of the surface is not improved satisfactorily~ In case of the aqueous vapor~ if the surface is treated in aqueous vapor of a high temperature above 120C having a pressure of 2 kg/cm2and I upward, the hydrated film can be formed in a shorter period of time co~pared with the case of the ordinary atmospheric pressure. ~he film has higher crystallizing property and stability compared with the film produced at a low temperature.
A surface treatment ~ilm of higher hydrophilic property is obtainable in the same period of time of treatment. To be nore precise~ -the invention has an industrial advantage in that a predetermined hydrophilic property is obtainable in a shorter period of processing time~
When the aqueous vapor has a pressure less than 2 kg/cm2 and a temperature below 120C~ it is impossible to - 6 =

l obtain a surface treatment film of high hydrophilic property and stability. In practice9 however~ either the pressure or the temperature can be conformed to the said conditions7 since there is a correlation between the pressure and the temperature of the aqueous vapor~ The surface treatment film under the said conditions has a thickness below 10% of that of the anodized film. Thus the film according to the invention is readily broken when the wires are connected by means of a comprssion type sleeve thereby enabling an electric contact to be formed between the ACSR and the sleeve. The invention, therefore9 has an advantage in that there is no necessity for removing the filmO
The invention will now be described in detail in relation to the second characteristic thereof: more than 3 grooves formed on the outer periphery of each of the aluminum wires of the ou-termost layer continuously and longitudinally thereof.
When more than 3 grooves are formed on the outer periphery of an ~luminum element wire continuously and longitudinally of said wire, the number, size and configu-ration of the grooves ha~e a great influence not only on the formation of waterdrops but also on -the tensile strength and vibration fatigue resistance of the element wire and accordingly the ACSR.
According to the invention, on the outer periphery of each of the aluminum element wires to constitute at least the outermost layer of the ACSRg there are formed more than 3 grooves continuously and longitudinal~y of said element wire for the following reasons~ In order ~o reduce the t~

1 audible noise~ it is necessary that the hemispherical waterdrops formed on the outer surface of the AC~R are caused to disappear. If more than 3 grooves are formed on the surface of each of the element wires to constituts - the outermost layer of the ACSR for the said object, at least one groove appears on the surface of each of the element wires constituting the outermost layer of -the ~CSR exposed to the atmosphere~ raindrops being entrapped into the grooves due to the geometric onfiguration thereof. Thus the hemispherical raindrops on the surface are reduced in number7 while water flows along the grooves7 thereby enabling to greatly increase the draining proper-ty of the surface of the cable~
The grooves are provided on at least more than 30~O of the element wires constituting the outermost layer of the cable inasmuch as, if less than that, no satisfactory effect can be expected.
~ le opening of the groove should ha-ve a width of O l-

2 mm, since if wider than 2 mm~ the draining property is impaired and accordingly the effect of reducing -the audible noise is reduced9 the same being applicable to the case of less than 0.1 mm. The depth of the groove should be 2-25~o of the thickness of the element wire since if below 2 %7 the groove is imperfect in its configuration7 while if deeper than 25~ the vibration fatigue resistance is reduced thereby posing a problem in respect of practical use.
~igs9 3 and 4 show element wires S having grooves of U-shaped profiles and arcuate profiles~ respectivelyO
Though the groove may have a V-shaped profile~ U-shaped 1 profile is preferable because of its smaller stress concen-tration~
A hydrated film is formed on ~e outer surface of the aluminum wire including the grooves formed thereon in aqueous vapor having a temperature of 120C and upward; and preferably in the water or aqueous vapor above 90C after the outer surface has been subjected to rough surface treatment.

The aqueous vapor treatment should be effected at a temperatw e above 120C inasmuch as the film can be formed in a shorter period of time~ Moreover, the film thus obtained has higher crystallizing property and stability compared with the film obtained at a lower temperature, thereby enabling to improve the hydrophilic property and draining property and accordingly to reduce the audible noise9 The hydrated film is provided on the surface including the grooves of each of the element wires to constitute the outermost layer of the cable. Alternatively~ said film may be provided on the outer surfaces of the grooved element wires constituting the outermost layer of -the cable after it has been strandedO The effect is identlcal in both cases a According to the invention, more than 3 grooves are formed on the periphery of each of the element wires corresponding to 30~ and upward of the element wires constituting the outermost layer of thecable thereby enabling to reduce the audible noise in conformity with the object of the inventionO It is also within the scop~ of the i.nvention -to provide more than 3 grooves not only on the _ 9, 1 elemenk wires of the outermost layer but also on all the aluminum wires with e~ception of the core wires thereby enabling to reduce the weight of the compound cable, for example, ACSR~
According to the invention, the reinforce~ent in the center of the cable comprises all kinds of steel wires, aluminum wires and the like used singly or in plurality~
A compound cable the outermost surface of which is composed of a surface treatment film as described herein-before, or a compound cable in which more than 3 grooves are formed on each outer periphery of more than 30% of the element wires to constitute the outermost layer continuously and longitudinally of said wires, or a compound cable on which a hydrated film is formed or a hydrated film is formed after rough surface treatment has an advantage in that not only its hydrophilic property but also its draining property is improved thereby enabling to reduce the audible noise in a short period of time directly after rainfall.
Although the aluminum cable steel reinforced as one of the compound cables has been described in detail, it is to be understood that the present invention is not limited to ACSR only, but that a core wire composed of steel wire or aluminum wire and a cable in combination with a steel wire or aluminum wire may be used. In the present invention~ it is necessary that at least the outermost layer of the cable is composed of a compound cable consisting of an aluminum wire, aluminum alloy wire, aluminum-clad steel wire or aluminum-alloy-clad steel wire~

1 ~he invention will hereinunder be described in detail in reference to the following examples~
Example 1 Heat resisting aluminum alloy wires were stranded into ACSR (60T ACSR) having a sectional ar~a of810 mm2 and a conductivity of 60~o~ the surface thereof being subjec-ted to continuous sand blast treatment until the surface rough-ness of the aluminum alloy wires of the surface of the ACSR
was on the order of 15~.
~he cable thus obtained was su~jected to oil removing treatment by an organlc solvent, hydrated films being caused to form under different conditions as shown in Table 1, to produce ACSR samples according to the invention.
By way of comparison7 thera were prod~ced an ordinary new 60~ ACSR (No. 13)7 60T ACSR subjected to sand blast treatment only (Nol 12), and 60T ACSR treated under ~he conditions of No.14 and No~15 of Table 1 after sand blast treatment~
An audible noise test was made on said ACSR samples, the results being as shown in ~able 1. The audible noise test was mada by comparing the audible noises at a maximum surface potential gradient of 15~5 KV/cm after flooding for 1 minute at an intensity of 1~6 mm/hr on the hypothesis of directly after rainfall. The noise levels (dB, A character-istic~ in Table 1 show the values of measurement in the lapse of 5 minutes after flooding~

1 Table . _ '~reatment Treatment Noise Level No. Temperature Time ~dB, A characteristic) (C) (m~n) 2 ~ 95 10 47

3 ~ 95 20 46 ~ 4 .~ 95 3o 46 H 5 _ 95 50 46 ~ 6 ~ 100 15 ~7 ~ 7 g 100 3o 46 9 o 120 20 46 1~ ~ 140 10 43 .~ 140 20 ~4 12 h 54 13 ~ . . 57 ~ ~ 14 ~ 1 70 3o 53 o ~ 15 1 70 5 52 As is clear from Table 1, the ACSR samples according to the invention show lower noise levels by as much as 8-14 dB compared with the ordinary ACSR sample (No.13).
With the comparative sample subjected to sand blast treat-ment only (No.12) and those treated in the water of a low temperature (NoO14 and No.15), the reduction of the noise levels is very small.
Example 2 An ACSR (6GT ACSR) having a sectional area of 810 mm2 and a conductivity of 60% was produced by use of heat resisting aluminum alloy wires. The ACSR was de-greased by use of an organic sol~ent~ surface treatment film being ~ 5 ~ ~ I

1 caused to form by the batch system under different conditions as shown in ~able 2, to obtain ACSR samples according to the invention~ Since there is a correlation between the pressure and temperature of the aqueous vapor~
the condi-tions hereinafter will be designated by the pressure onlyO By way of comparison, there were p~oduced a sample of ordinary new 60T ACSR in the state in which oil had been removed (NoO8) and 60T ACSR samples with the surfaces thereof being treated under the conditions of No.9 and NoO10 of Table 20 The results of an audible noise test made on said ACSR samples were ~s shown in Table 2.
The audible noi~e test was made by comparing the audible noises after flooding at an intensity of 1~6 mm/hr for 1 minute and a maximum surface potential gradient of 15~5 KV/cm on the hypothesis of directly after rainfall.
The noise levels (dB~ A characteristic) in Table 2 shows -the values of measurement in the lapse of 5 minutes after the suspension of flooding.
As is apparent from Table 2, all the ACSR samples according to the invention have lower noise levels by as much as 4-9 dB compared with the noise level of the comparative sample No.8, while the comparative samples, No.9 and No.107 show poor results, the noise level being still high even in the case of No~10 treated for 60 minutes~

1 ~able 2 _ .
Aqueous Treatment Noise ~evel NoO Vapor 2 Time (min~ (dB 9 A haracter Pressure (Kg/cm ) istic) =~ __ ~_~ .
1 2~5 5 50 2 2~5 15 47 3 2.5 30 47

4 2.5 50 46 ~0 10 46 ~ 6 3O0 30 46 ~ 7 3~0 50 45 8 . - _ ~ 54 .
~.~ 9 1.0 30 52 E ~10 1 . O 6 ~ . `

Example 3 Hard-drawn aluminum wires of 4.8 mm~ were subjected to continuous oil removing treatment and then to aqueous vapor treatment under different conditions as shown in Table 3.
The wire thus treated were stranded as element wires GO constitute the outermost layer of ACSR having a sectional area of 810 mm20 Since the wires had no oil on their surfaces, a lubricant was applied thereto prior to strand-ing so as to pre~ent the parts brought into contact with guide rolls and the like from receiving damage7 said lubricant being removed after stranding~
The samples thus obtained were subjected to the same audible noise test as in Example 1. The results were as shown in ~able 3O

1 ~able 3 , .
Aqueous Treatment ¦ Noise ~evel No G Vapor Time ~min) ¦ (dB, A Characteristio) Pressu~e (Kg/cm ) __, . . _ _ 4Oo 1 47 ~.0 5 46 6 4~0 10 45 lo 7 4O5 0~5 47 ~ , . _ _ _~___ .
As is apparen-t from Table 3, all the ACSR samples according to the invention show highly satisfactory results9 the noise levels being reduced by as much as 7-9 dB
compared with the case of the comparative sample No~ 8 of Table 2.
Example 4 U-shaped grooves of different depth3 as shown in Fig. 3 were provided on the peripheries of heat resisting aluminum alloy element wires 4.8 mm~in outside diameter~
The vibration fatigue resistance of said element wires was examined to obtain the results as shown in Table 4O
The op~ning of the groove had a width of 1-1.5 mm.

1 ~able 4 ~ ~.
Depth of Groove Vibration Fatigue (% relative tc diameter of Resistance (kg~mm2) element wire) at 10' Times 0 5q5

5~
5~5 5~5 4~0 It ha~ been found from Table 4 that, when the depth of the groove is as mucha~ 30% of the diameter of the element wire, the vibration fatigue resistance of the wire is decreased thereby reducing the utility of said wire for use in a cable.
Example 5 Samples of ACSR of the same construction as that of 810 mm2 ACSR were produced by use of aluminum element wires 408 mm~ in outside diameter for the outer layer of the cable with 4 grooves formed continuously and longitudinally of said wires respectively, each of said grooves having a U~shaped profile as shown in Fig. 3 with its opsning having a width of 1 mm and its depth extending to 20~o of the diameter of ~aid wire.
~he ~CSR samples thus produced were subjected to different surface treatments as sho~ in Table 5 and then to an audible noise test.
The audible noise test was made under the conditions of maximum surface potential gradient 14.0 KV/cm after ~looding for 1 minute at an intensity of lo 6mm/hr on the hypo thesis o f dire c tly after rain f all 4 By way of comparison, the same test was made on an ordinary 810 mm2 ACSR (No.10). Table 5 shows the results of the test.
- The rough surface treatment was effected by sand blast treatment.

'J~~ $~ `

1 ~able 5 ~,. ,, __ ~
Rough ~ydrated Film Audible Noise No~ Surface ~reatment I ~est Treat- Treatment Treatment ~Audible noise ment ~emperature(C) Time (min) level in lapse of 3 minutes after suspension -of flooding3 Character-i~tic) _ . . _ _ ___ 1 _ _ _ 49 2without in aqueous 20 46 3pOoOrc .i 140C 30 42 ~ 5 with 100C 10 44 H 6 ll ., : ~ 7 ll 120C 10 40 8 ll in wa~er 9 . ~1 95C 60 ~5 . _ __ , _ _ ~ 10 _ _ _ 53 ~ ~ _ _ , _ - . ~_ -.
It ha~ been found from ~able 5 that the ACSR s~mples according to the invention have a high effect in reducing the audible noise lsvels by as much as 4-14 dB compared with the ca~e of the conventional ACSR.

Claims (8)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A low audible noise compound cable comprising aluminum wire, aluminum alloy wire, aluminum-clad steel wire or aluminum alloy-clad steel wire stranded at least on the outer periphery of cable characterized in that after the surface of each of said aluminum wire, aluminum alloy wire, aluminum-clad steel wire or aluminum alloy-clad steel wire has been subjected to rough surface treatment it is treated in water or aqueous vapor of at least 90°C
so as to cause a hydrated film to form thereon thereby enabling the surface of the cable to have a hydrophilic property.

2. A low audible noise compound cable as defined in claim 1 characterized in that the hydrated film is caused to form after the surface of the aluminum wire, aluminum alloy wire, aluminum-clad steel wire or aluminum alloy-clad steel wire has been sub-jected to blast treatment or liquid horning treatment.

3. A low audible noise compound cable as defined in claim 1 characterized in that the hydrated film is caused to form by treating the surface in aqueous vapor having a pressure above 2 Kg/cm2 and a temperature above 120 C.

4. A low audible noise compound cable as defined in claim 1 characterized in that the formation of the hydrated film on the surfaces of the aluminum wire, aluminum alloy wire, aluminum-clad steel wire or aluminum alloy-clad steel wire constituting the outermost layer of the compound cable is applicable to surfaces including more than 3 grooves formed on the outer peripheries of more than 30% of said aluminum wire, aluminum alloy wire, aluminum-clad steel wire or aluminum alloy-clad steel wire continuously and longitudinally thereof.

5. A low audible noise compound cable as defined in claim 4, characterized in that more than 3 grooves are formed on the outer peripheries of more than 30% of the aluminum wire, aluminum alloy wire, aluminum-clad steel wire or aluminum alloy-clad steel wire continuously and longitudinally thereof, the hydrated film being caused to form on the surfaces including said grooves after rough surface treatment.

6. A low audible noise compound cable as defined in claim 5 characterized in that more than 3 grooves are formed on the outer peripheries of more than 30% of the aluminum wire, aluminum alloy wire, aluminum-clad steel wire or aluminum alloy-clad steel wire continuously and longitudinally thereof, the hydrated film being caused to form on the surfaces including said grooves after blast treatment.

7. A low audible noise compound cable as defined in claim 4 characterized in that the opening of the groove has a width of 0.1-2 mm.

8. A low audible noise compound cable as defined in claim 4 characterized in that the groove has a width coinciding to 2-25% of the thickness of the aluminum wire, aluminum alloy wirer aluminum-clad steel wire or aluminum alloy-clad steel wire.