Comparison of AAAC with ACSR

COMPARISON OF AAAC WITH ACSR
Aluminium alloy conductor is revolutionary break-through in conductor technology. Users all over the world are switching over to AAAC due to its technical superiority.	Aluminium conductor steel reinforced is outdated in technology. Its use is obsolete in developed countries due to technical and economical shortcomings.
Heat-treated AI-Mg-Si alloy makes AAAC totally free from bimetallic corrosion and exceptionally resistant to environmental corrosion.	In ACSR, corrosion (bi-metallic and environmental) because of steel core sets in within 2 years, lowering efficiency.
Service life is around 60 years-twice as durable as ACSR.	Service life ranges between 15-30 years. Particularly less in industrial and sea line atmospheres.
Hard to cut and impossible to recycle into utensils. Excellent inhibitor of theft, eliminating unwanted power breakdowns.	Easily cut and recycled overnight for making utensils. Stolen ACSR till date adds up to Rs. 100 crores even by conservative estimates.
AAAC has higher strength to weight ratio ranging between 10.6: 11.6 on an equal diameter basis. Offers savings due to reduction in number of towers, foundations and accessories.	ACSR has lower strength to weight ratio ranging between 88.4:9.4; hence requires lesser spans than AAAC. Lower cost of ACSR is offset due to higher cost of towers etc.
Suffers no reduction in strength on temperature rise upto 90 C since it is specially heat treated at 160 C temps. Can be loaded to higher level of capacity.	Strength of ACSR reduces with rise in temperature above 65 C. Not suitable for overloading.
No steel core means, no magnetic losses. Thus zero additional line losses due to electromagnetic effect.	Steel core induces eddy current and hysteresis losses.
Repair and replacing, dead ending is easier because AAAC is monometallic. Ordinary fitting and accessories without steel inserts can be used. Works out to be economical in the long run.	Repairs are time consuming and frequent, requiring special procedures. Maintenance costs and inherent defects make it costlier in the long run.

Many other Advantages are also claimed for AAAC as listed below:

Lesser stretch	AAAC stretches much less than AAC (All Aluminium Conductor) and less than ACSR under normal operating tension.
Higher Ampacity	AAC when compared to ACSR size, possess about 10% higher conductivity. In other words, for equal temperature rise, AAAC can carry 10% extra current on the line.
Higher creep resistance	AAAC stranded overhead conductors when subjected to static tensile stresses for a long period of time, have relatively smaller increase in sag

Characteristics of All Aluminium Alloy Conductor

AAAC alloy 6201 is claimed to have better corrosion resistance and better strength to weight ratio and improved electrical conductivity than ACSR on an equal diameter basis. This makes the AAAC better suited in corrosive areas like sea coast and industrial areas where high metallic corrosion sets in. The higher strength to weight ratio facilitates lesser sags on larger spans.

Advantages of AAAC

1. Compatible thermal stability: AAAC can perform at 90 C continuously for a period of one year literally with no loss of strength and it can operate safely at 150 C for 3 hours. Under short circuit conditions, temperatures upto 200 C for 0.5 Seconds can beeasily withstood.
2. Ease of repair: AAAC being monometallic in construction lends itself to easy repairs, splicing and dead-ending. It is claimed that there is a saving of about 50% time. Reduction of cost of work at site is about 20 to 25%
3. Corrosion Resistance: Almelec AAAC exhibits excellent corrosion resistance in corrosive atmospheres like industrial areas.

However, laboratory tests at CPRI indicate that all Aluminium alloy materials are prone to marine corrosion in chloride atmospheres (pitting corrosion). Resistance to this 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 effect other properties of materials.

Of course there is no possibility of galvanic corrosion since the material is not bimetallic.

Power Saving Capability of AAAC:

1.       The power saving by use of AAAC was quantified by CPRI. The details are enumerated in the ensuing paragraphs.

2.       The saving in power results from lower resistance of AAAC compared to that of ACSR conductor for equal conductor diameter. The resistances pertaining to AAAC conductors are those furnished by the manufacturers. For ACSR conductors the resistances have been computed using the standard hand book (Wasting Hose Fourth U.S. Edition Oxford and IBH Publishing Corporation) and suitably extrapolating to match the size to conductor used in our country. Table 2 shows the resistance value of a few commonly used ACSR conductors and their AAAC equivalents.

3.       Further, the percentage reduction in losses by use of AAAC as substitute for ACSR conductor has been computed in two ways.

a)      Considering a hypothetical 100km line loaded to its full capacity i.e. 92A, 122A. & 180A for Weasel, Rabbit and Dog ACSR conductors and their AAAC equivalent respectively.

b)      Taking a practical system with typical loading and applying ACSR and its equivalents AAAC conductors, for calculating energy loss, loss load factor was used (LLF+) 0.2 * LF +0.8 * LF² ). A diversity factor of 1.5 was assumed for the loads. The practical feeder, considered is enclosed at Annexure-II, system details are at Annexure-III.

4.       The findings pertaining to the hypothetical system is given in Table 3. Calculations are given in Appendix I.

5.       Similar results for practical system are show in Table 4, The load factor was varied from 0.4 to 1.0 to study the dependence of economy on load factors. The details of calculations are appended in Appendix- IV.

6.       Observations: it can be seen from Table 3 that the savings in peak load power loss by use of AAAC equivalent conductors varies between 12% and 14.5% depending on the type of conductor considered. In a practical system percentage saving in peak load power loss was found to be about 16.3 % (See Table 4 ) Under these conditions, the savings in annual capitalised cost due to lower energy loss with AAAC is found to vary from 2.5% at a load factor of 0.4 to 11.2% at a load factor 1. The other advantages claimed for AAAC can be verified only after obtaining the feedback from the field after long time use.

Conclusion

1.       AAAC is superior to ACSR conductors when used in overhead distribution system,

2.       The increased cost of AAAC (claimed to be 15% to 20% costlier than corresponding ACSR conductors ) is offset by the saving in power loss.

3.       Other advantages of AAAC are better thermal stability, ease of repair, corrosion resistance, longer service life, less prone to pilferage as known through literature.