wp0007 - new range of special alloy conductors _al59

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New range of special alloy conductors New range of special alloy conductors New range of special alloy conductors New range of special alloy conductors –––– Advantages over ACSR & AAAC Advantages over ACSR & AAAC Advantages over ACSR & AAAC Advantages over ACSR & AAAC conductorsconductorsconductorsconductors

AuthorAuthorAuthorAuthor

G L Prasad

AbstractAbstractAbstractAbstract

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

KeywordsKeywordsKeywordsKeywords Alloy, Swedish conductors, AL-59, ACSR, AAAC

Document: WP0007


INTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTION

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).

HISTORYHISTORYHISTORYHISTORY

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


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

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


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.

APPLICATION OF ALAPPLICATION OF ALAPPLICATION OF ALAPPLICATION OF AL----59 ALLOY CONDUCTORS59 ALLOY CONDUCTORS59 ALLOY CONDUCTORS59 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 STANDARDSCOMPLIANCE WITH STANDARDSCOMPLIANCE WITH STANDARDSCOMPLIANCE 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 ALREFERENCE OF USE OF ALREFERENCE OF USE OF ALREFERENCE OF USE OF AL----59 ALLOY CONDUCTORS59 ALLOY CONDUCTORS59 ALLOY CONDUCTORS59 ALLOY CONDUCTORS

Al-59 Alloy Conductors have been used extensively by Swedish Electricity, Swedish Railways and Norway Electricity.

MATERIAL PROPERTIESMATERIAL PROPERTIESMATERIAL PROPERTIESMATERIAL PROPERTIES

Size of the ConductorSize of the ConductorSize of the ConductorSize 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 wireStrength of the wireStrength of the wireStrength 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 wireResistivity of the wireResistivity of the wireResistivity of the wire

- Individual resistivity: 29.30 nΩm

- Average resistivity: 29.08 nΩm

Creep of the conductorCreep of the conductorCreep of the conductorCreep of the conductor

Maximum conductor Creep at 23 oC at 40 % of rated tensile strength and 1500 hours are as follows

- 7 strands: 350 mm/Km

Figure 5 – AL-59 Alloy Conductor


- 19 and 37 strands: 400 mm/Km

- 61 strands: 450 mm/Km

Figure 6 – Specialized Laboratory for Quality Testing

COMPARISION WITH CONVENTIONAL ACSR AND AAAC COMPARISION WITH CONVENTIONAL ACSR AND AAAC COMPARISION WITH CONVENTIONAL ACSR AND AAAC COMPARISION WITH CONVENTIONAL ACSR AND AAAC

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 Table 1 Table 1 Table 1 ---- Comparison of various Transmission conductors Comparison of various Transmission conductors Comparison of various Transmission conductors Comparison of various Transmission conductors

ACSR MOOSE AAAC MOOSE AL-59 Alloy

Typical Factors 54/7/3.53 61/3.55 61/3.52

Reference Specification IS 398 PART II IS 398 PART IV SS 4240814

Conductor Diameter (mm) 31.77 31.95 31.68

Cross Sectional Area (sq-mm)

596.69 603.47 593.31

Ambient Temperature (oC) 40 40 40

Current Carrying Capacity (Amperes) at 80oC

1092 1089 1313


*** 1343 1620

Sag (meter)

At 350 meter span, 80oC 10.917 9.472 10.515

At 350 meter span, 100oC *** 10.402 11.387

Mass per unit length


kg/km 1998 1666 1640

Tensile Strength

Kgf 16269 17124 14577

DC Resistance

Ohm/km 0.05595 0.0568 0.0501

Note: Current Carrying Capacity calculation based on wind velocity of 1 m/sec and solar absorption coefficient is 0.6

Table 2 Table 2 Table 2 Table 2 ---- Comparison of 7 strand Distribution conductors Comparison of 7 strand Distribution conductors Comparison of 7 strand Distribution conductors Comparison of 7 strand Distribution conductors

ACSR WEASEL AAAC WEASEL 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 (sq-mm)

36.86 34.34 34.34

Ambient Temperature (oC) 40 40 40


183 176 187


*** 212 225

Sag (meter)

At 350 meter span, 80oC 90.03 72.85 86.74

At 350 meter span, 100oC *** 72.99 86.86

Mass per unit length

kg/km 128 94 94

Tensile Strength

Kgf 109.09 99.18 84.10

DC Resistance

Ohm/km 0.9289 0.9900 0.8777


0

50

100

150

200

250

300

50 60 70 80 90 100 110

TEMPERATURE (Degrees C)

CU

RR

EN

T(A

mps)

AAAC Weasel 7/2.50

ACSR Weasel 7/2.59

AL 59 7/2.50

Figure 7 - Comparison of AAAC Weasel, ACSR Weasel and AL-59 conductors.

0

500

1000

1500

2000

2500

50 60 70 80 90 100 110


CU

RR

EN

T(A

mp

s)

AL-59 61/4.36

AAAC 61/4.26

ACSR BERSIMIS /42/4.57 +7/2.54

Figure 8 - Comparison of AAAC 61/4.26, ACSR Bersimis and AL-59 910 sq.mm conductors.

0

250

500

750

1000

1250

1500

1750

2000

50 60 70 80 90 100 110


CU

RR

EN

T(A

mp

s)

AL-59 61/3.52

ACSR 54/3.53+7/3.53

AAAC 61/3.65

Figure 9 - Comparison of AAAC Moose, ACSR Moose and AL-59 conductors.


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.

ADVANTAADVANTAADVANTAADVANTAGES OVER ACSR AND AAACGES OVER ACSR AND AAACGES OVER ACSR AND AAACGES 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 AWARAPPROVALS AND AWARAPPROVALS AND AWARAPPROVALS AND AWARDSDSDSDS

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.

Figure 10 – IEEMA Best Product Award

CONCLUSIONCONCLUSIONCONCLUSIONCONCLUSION

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 STANDARDSREFERENCE STANDARDSREFERENCE STANDARDSREFERENCE 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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wp0007 - new range of special alloy conductors _al59

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