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INTRODUCTION TO AAA CONDUCTORS

The per capita consumption of electricity is an index of industrialization of the country .The economy of a country in a sense, hinges on this factor. Developing countries like India are striving hard to increase their generation capacity to meet the challenges of extensive industrialization. A substantial share in the country’s plan expenditure is being allotted to the power sector. However, the gap in the per capita electricity consumption between India and the advanced countries is quite large at present and all around effort is needed to reduce this gap. A major portion of the allocation in power sector goes for generation of electricity. One of the major impediments in utilising the generated electric power optimally is the system loss. At present, the national average on T&D losses is about 23% compared to around 8% losses in advanced countries.

It is the task of power planners to seek all avenues to bring down the losses. System planning on scientific lines is essential for bringing the losses to an optimum level. Planning and design of distribution system on scientific lines coupled with the practice of using right type of materials to achieve this is to be taken up on a priority basis.

One of the areas where the Indian power systems could possibly benefit is in the usage of a conductor, which is superior to the familiar composite conductor. The ACSR, for overhead transmission and distribution applications, A ready solution is use AAAC (All Aluminium Alloy Conductor) This conductor has been manufactured and used in advanced countries since 1930. The advocates of these conductors claim that by use of AAAC, a substantial reduction in losses in the system can be effected. The material is unattractive to the habitual thieves and therefore pilferage reduces. A small saving of supports cost also can be achieved due to the higher current carrying capacity of the conductor. The effective power saving in spite of the higher cost of these Conductors is about 15 to 20% higher than the conventional ACSR conductor.

CPRI undertook a study to verify and quantify these claims in Indian conditions. Equivalent AAAC conductors were used in place of ACSR Conductors in a typical distribution system feeder and the economics of the two materials, ViZ., ACSR and AAAC conductors, were compared. The result of this study is presented in this paper.

Of late a few electricity boards are also enthusiastically using the AAAC conductors in place of ACSR conductors specially in coastal areas and industrial areas. This has now been under use for more than 7-8 years and the experience gained in usage of AAAC has been published.

CHARACTERISTICS OF ALL ALUMINIUM ALLOY CONDUCTOR (AAAC)

AAAC is a conductor made from aluminium magnesium silicon alloy of high electrical conductivity containing enough magnesium silicide to give it better mechanical properties after the treatment. AAAC has been used in many places with great success and has become a popular substitution for ACSR (Aluminium conductor steel Reinforced). This family of alloys is marketed worldwide under different trade names and under various manufacturing standards as shown in Table 1.

AAAC is claimed to have better corrosion resistance and better strength to weight ratio and improved electrical conductivity than ACSR on equal diameter basis. This makes the AAAC better suited in corrosive areas like seacoast and industrial areas where high metallic corrosion sets in. The higher strength to weight ratio facilitate lesser sage on larger spans.

ADVANTAGES OF AAAC

• One of the main advantages of AAAC is the lower power loss compared to that of an ACSR Conductor.
• Many other advantages are also claimed for AAAC, which is listed below.
• AAAC stretches much less than AAC (All Aluminium Conductor) and less than the ACSR conductor under normal operating tension.
• AAAC when compared to ACSR, size to size, possesses about 10% higher conductivity. In other words, for equal temperature, AAAC can carry 10% extra current in the line.
• AAAC stranded overhead conductor when subjected to static tensile stresses for a longer period of time have relatively smaller increase in sag.
• AAAC can perform at 900C continuously for a period of one year literally with no loss of strength and it can operate safely at 1500C for there hours, under short circuit conditions, temperatures up to 2000C for 0.5 seconds can be easily withstood.
• AAAC being monometallic in construction lends itself easy for repair, splicing and dead-ending. It is claimed that there is a saving of about 50% time on repairs. Reduction of cost of work at site works out to about to 20-25%
• Corrosion Resistance-AAAC exhibits excellent corrosion resistance in corrosive atmospheres like industrial areas. However, laboratory tests at CPRI indicate that All Aluminium and Aluminium Alloy materials are prone to marine corrosion in chloride atmosphere (pitting corrosion). The resistance to this type of marine corrosion has been investigated at CPRI and it has been found that a coating of zinc on the individual strands of the conductor will improve the life of the conductor as a whole. The zinc coating does not affect the other properties of the materials .Of course, there is no possibility of galvanic corrosion since the material is not bimetallic.
• It has been observed in the field that AAAC has longer life compared to ACSR and AAC. The experience of TNEB is that because of the corrosion resistance and other properties of AAAC, thee conductors give better maintenance of power supply without frequent interruption where as the damages caused to ACSR conductor in coastal and industrial areas by galvanic corrosion require replacement with in a period of two years forcing financial burden and frequent outage of lines.
• Steel content in conventional ACSR varies form 30 to 40% by weight. All Aluminiun alloy conductors are free from steel core and are therefore lighter by around 20 to 25%. Because of this, there is reduction in tension and hence lighter lower would be satisfactory.

BNSR ACSR Conductors


Code Name Area Code
Sqmm
Calculate
of Area MM2

Aluminiu
m No./Dia
Steel
No./Dia a
Aluminui
m Kg/Km

Wt
Steel
Kg./Km

Wt
Total
Wt.Kg/Km
BRAKING LOAD
ALU STEEL
(Before / After)
Mole  6.5  12.4  6/1.50  1/1.50  29.250  13.750  43.000  0.32/0.30  2.46/2.34 
Squirrel  13  24.43 6/2.11 1/2.11 57.700 27.300 85.000 0.63/0.60 4.60/4.37
Gopher 16 30.6 6/2.36 1/2.36 71.900 34.100 106.000    
Weasel 20 37 6/2.59 1/2.59 86.800 41.200 128.000 0.89/0.85 6.92/6.57
Ferret 25 49.6 6/3.00 1/3.00 116.200 54800 171.000 1.17/1.11 9.29/8.83
Rabbit 30 61.9 6/3.35 1/3.35 145.000 69.000 214.000 1.43/1.36 11.38/11.0
Mnk 40 73.9 6/3.66 1/3.66 172.900 82.00 255.000    
Horse 42 116.1 12/2.79 7/2.79 210.000 332.000 542.000    
Beaver 45 87.7 6/3.99 1/3.99 205.500 57.500 263.000    
Racoon 48 99.1 6/4.09 1/4.09 215.500 102.500 318.000 2.08/1.98 17.27/16.4
Otter 50 98 6/4.22 1/4.22 229.900 109.100 339.000    
Cat 55 113 6/4.50 1/4.50 261.000 124.000 385.000    
Dog 65 118345 6/4.72 7/1.57 287.600 106.400 394.000 2.78/2.64 2.70/2.57
Leopard 80 150.1 6/5.28 7/1.76 359.500 133.500 493.000