Optical Fiber
New range of special alloy conductors
– Advantages over ACSR & AAAC
conductors
Author
G L Prasad
Issued
May 2015
Abstract
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A new Aluminum alloy conductor having higher conductivity has
been developed. By using these special alloy conductors, electric
utility can achieve significant saving in both transmission and
distribution lines
Keywords
Alloy, Swedish conductors, AL-59, ACSR, AAAC
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INTRODUCTION
The categories of conventional type of Aluminium and Aluminium alloy overhead conductors
available globally are:
Homogeneous Conductors
AAC – All Aluminium Conductors
AAAC – All Aluminium Alloy Conductors
Non – Homogeneous Conductors
ACSR – Aluminium Conductor Steel Reinforced
AACSR-Aluminium Alloy Conductor Steel Reinforced
ACAR – Aluminium Conductor Alloy Reinforced
For several years, distribution and transmission lines have been designed using aluminum
conductors steel reinforced (ACSR) or in some countries all aluminum alloy conductors (AAAC).
Both types normally have a conductivity calculated on the total area of 53-54% copper (IACS).
Since the mid-1970s the cost of producing electric energy has grown rapidly, leading to an
increase in the cost of losses. An attempt to find new conductor material producing fewer
losses in the network was started in Sweden at the beginning of the 1970s and led in 1979 to
the release of a new conductor standard called Al-59, where “59” stands for its conductivity
(IACS).
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HISTORY
In 1920’s, within about 20 years of introducing ACSR, France introduced for the first time a
new type of electrical conductor made of an alloy of aluminium with magnesium and silicon
alloy. Other European countries also developed similar material as their conductor material US
also followed the same in 1960’s
The electrical conductor made of such alloy had higher strength than EC grade aluminium of
equal size with slight loss in conductivity. Due to the increased strength the conductors did not
require steel reinforced. AAAC thus made its advent as the most suitable current carrier in
transmission and distribution. IEC recommendation number 208 provides an internationally
acceptable standard for AAAC (Aluminium Alloy Conductors)
Figure 1 – Power Conductor Manufacturing Process: Rod Manufacture
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At the beginning of 70’s AB Electrokopper in Helinsburg developed an alloy with the trade name
DUCTALEX. It has a better conductivity than the alloys developed by the France but a slightly lower
mechanical strength.
Figure 2 – Power Conductor Manufacturing Process: Rolling Mill
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This new conductor alloy was laboratory tested at the Swedish State Power Board with respect to creep,
corrosion resistance, self damping and fatigue strength, all tests showed the same or better properties
than the ordinary alloy.
Figure 3 – Power Conductor Manufacturing Process: Wire Drawing
Figure 4 – Conductor Manufacturing Process: Wire Stranding
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Tests were made on actual distribution lines starting in 1975. As only
satisfactory results were obtained the new alloy was installed in 400 KV line.
The measurement of sag after five years showed a high degree of agreement
with what was predicted. Concurrent with all trials the Swedish
Standardization Committee worked out and issued the standards SS4240813
for AL-59 wires and SS4240814 for AL-59 conductors.
Figure 5 – AL-59 Alloy Conductor
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APPLICATION OF AL-59 ALLOY CONDUCTORS
Al-59 Alloy Conductors are used in power transmission and distribution lines for a wide voltage
range - low voltage to Ultra high Voltage.
COMPLIANCE WITH STANDARDS
AL-59 alloy conductor complies with the standard SS4240814 and AL-59 alloy wires complies
with standard SS4240813 that specifies the limits for conductivity, strength and creep
irrespective of the chemical composition which is not discussed in this standard. Other
properties are similar to conventional AAAC conductors.
REFERENCE OF USE OF AL-59 ALLOY CONDUCTORS
Al-59 Alloy Conductors have been used extensively by Swedish Electricity, Swedish Railways
and Norway Electricity.
MATERIAL PROPERTIES
Size of the Conductor
AL-59 conductors range from AL-59 31 sq-mm (7/2.38 mm) to AL-59 910 sq-mm (61/4.36
mm).
Strength of the wire
- For diameter less than 3.5 mm: 250 MPA
- For diameter less than 4 mm: 240 MPA
- For diameter less than 4.5 mm: 230 MPA
Resistivity of the wire
- Individual resistivity: 29.30 n m
- Average resistivity: 29.08 n m
Creep of the conductor
Maximum conductor Creep at 23 oC at 40 % of rated tensile strength and 1500 hours are as
follows
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- 7 strands: 350 mm/Km
- 19 and 37 strands: 400 mm/Km
- 61 strands: 450 mm/Km
Figure 6 – Specialized Laboratory for Quality Testing
The comparison is based on the current carrying capacity, strength of the conductor and sag.The
comparison for transmission as well as for the distribution is as detailed below:
Table 1 - Comparison of various Transmission conductors
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Tensile Strength
Kgf
Typical Factors
Reference Specification
ACSR MOOSE
AAAC MOOSE
AL-59 Alloy
54/7/3.53
61/3.55
61/3.52
IS 398 PART II
IS 398 PART IV
SS 4240814
Conductor Diameter (mm)
31.77
31.95
31.68
Cross Sectional Area (sqmm)
596.69
603.47
593.31
Ambient Temperature (oC)
40
40
40
1092
1089
1313
***
1343
1620
At 350 meter span, 80oC
10.917
9.472
10.515
At 350 meter span, 100oC
***
10.402
11.387
Current Carrying Capacity
(Amperes) at 80oC
Current Carrying Capacity
(Amperes) at 100oC
Sag (meter)
Mass per unit length
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kg/km
1998
1666
1640
16269
17124
14577
0.05595
0.0568
0.0501
Tensile Strength
Kgf
DC Resistance
Ohm/km
Note: Current Carrying Capacity calculation based on wind velocity of 1 m/sec and solar
absorption coefficient is 0.6
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Table 2 - Comparison of 7 strand Distribution conductors
ACSR WEASEL
AAACWEASEL
AL-59 Alloy
Typical Factors
6/ 1/ 2.59
7/ 2.50
7/ 2.50
Reference Specification
IS 398 PART II
IS 398 PART IV
SS 4240814
Conductor Diameter (mm)
7.77
7.50
7.50
Cross Sectional Area (sqmm)
36.86
34.34
34.34
Ambient Temperature (oC)
40
40
40
Current Carrying Capacity
(Amperes) at 80 oC
183
176
187
Current Carrying Capacity
(Amperes) at 100 oC
***
212
225
At 350 meter span, 80 oC
90.03
72.85
86.74
At 350 meter span, 100 oC
***
72.99
86.86
128
94
94
109.09
99.18
84.10
0.9289
0.9900
0.8777
Sag (meter)
Mass per unit length
kg/ km
Tensile Strength
Kgf
DCResistance
Ohm/ km
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AAAC Weas el 7/2.50
ACSR Weas el 7/2.59
250
CURRENT(Amps)
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300
AL 59 7/2.50
200
150
100
50
0
50
60
70
80
90
100
TEM P ERA TURE (Degrees C)
110
Figure 7 - Comparison of AAAC Weasel, ACSR Weasel and AL-59 conductors.
2500
AL-59 61/4.36
AAAC 61/4.26
CURRENT(Amps)
2000
ACSR BERSIMIS /42/4.57 +7/2.54
1500
1000
0
50
60
70
80
90
100
TEMPERATURE (Degrees C)
110
Figure 8 - Comparison of AAAC 61/ 4.26, ACSR Bersimis and AL-59 910 sq.mm conductors.
CURRENT(Amps)
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500
2000
AL-59 61/3.52
1750
ACSR 54/3.53+7/3.53
1500
AAAC 61/3.65
1250
1000
750
500
250
0
50
60
70
80
90
100
TEMPERATURE (Degrees C)
110
Figure 9 - Comparison of AAAC Moose, ACSR Moose and AL-59 conductors.
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Even though strength of the AL-59 conductor is less compared to conventional AAAC, AL-59 is
strung at the same tension as like conventional AAAC. The Important factor for choosing
tension from the vibrating point of view is tension divided by the conductor mass. This value is
independent of Ultimate tensile strength.
ADVANTAGES OVER ACSR AND AAAC
- Higher current carrying capacity with lesser cross sectional area.
- Higher power transfer capacity with lesser cross sectional area.
- Commercial benefits due to lower power loss and higher power transfer capacity.
APPROVALS AND AWARDS
Sterlite’s 774 sq-mm AL-59 sample was type tested (for creep and ultimate
tensile strength) and approved by J-Power Systems Corporation, Japan. The
result of creep achieved was 436 mm/Km which superior to the specified
requirement of 450 mm/Km. Sterlite has supplied these conductors globally.
Sterlite received the ‘Best Product Award’ from by IEEMA for AL- 59 Alloy
Conductors
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Figure 10 – IEEMA Best Product Award
CONCLUSION
Power for all by the year 2012 is the vision of the Ministry of Power, Government of India. The Government of
India’s Transmission Perspective Plan focuses on the creation of a ‘National Grid’ in a phased manner by adding over
60,000 km of Transmission Network by 2012. Such an integrated grid is envisaged to evacuate additional 1,
00,000 MW by the year 2012 and carry 60% of the power generated in the country. The existing inter-regional
power transfer capacity is 9,000 MW, which is to be further enhanced to 30,000 MW by 2012 through creation of
“Transmission Super Highways”. On a global level, ABS Research, UK reports that the global market for power
transmission conductors was valued at about US$12.3 Billion in 2006 and has a CAGR of 7% from 2004 through
2006. ABS Research also anticipates a stable demand growth in the global market from 2007 through 2010 at a
CAGR of about 7%. In view of development of new power transmission and distribution grids by global power
incumbents, Al-59 Alloy Conductors would have a special significance while designing
transmission line networks, as the properties of these conductors enable superior power
evacuation while optimizing the cost of the entire grid.
REFERENCE STANDARDS
Swedish Standards:
SS4240814: Aluminium alloy stranded conductors for overhead lines – Al 59 Conductors.
Ss4240813: Aluminium alloy wire for stranded conductors for overhead lines – Al 59 Wires.
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