ALUMINIUM vs COPPER_Cost & Characteristics Comparison_20100315

8/3/2019 ALUMINIUM vs COPPER_Cost & Characteristics Comparison_20100315

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© ABB GroupApril 5, 2010 | Slide 1

Aluminum vs. CopperVacuum Cast Coil Transformers forLonza 2.5

March 2010, PPTR, Chang-Hyeon Lee




Introduction (1)

During the 2nd World War, Copper became scarce andmanufacturers started using Al as an alternative conductor forelectrical transmission and distribution.

For transformers, up to the last 30 years, there were notmany suppliers of Al strips, thin foils or wires as conductors

Only LV windings were made in Aluminum

There were not many manufacturers of special HV foilwinding machineries

So everybody was using Copper on HV windings

Because they had no other options…




Introduction (2)

… the option appeared

There were several reasons that led the changes

Aluminum is the second most plentiful metallic element on the Earth,so no problems with supply

Second lowest density

High corrosion resistance thanks to its Alumina protection

High electrical and thermal conductivity

Higher conductivity than copper, weight for weight

And it is cheap & light with stable price, which is also interesting!




Comparing Aluminum & Copper (1)Common reasons for winding material choice :

FalseTrueCommon reasons for choice of winding material

XAluminum-wound transformer terminations are incompatible with

copper line and load cables.

XProperly terminating line and load connections is more difficult for

aluminum-wound transformers.

XLine and load connections to copper-wound transformers are more

reliable than those of aluminum-wound transformers

XCopper-wound transformers can be made with smaller size than

aluminum-wound equivalents.

XAluminum-wound transformers have higher hot-spot temperaturesbecause copper is a better thermal conductor than aluminum.

XAluminum-wound transformers have higher losses because copper

is a better conductor.

XAluminum-wound transformers are lighter in weight than theircopper-wound equivalents as well as cheaper price




Comparing Aluminum & Copper (2)Physical properties of two conductors in general




Comparing Aluminum & Copper (3)Coefficient of thermal expansion

Coefficient of expansion of Aluminum : 23.1

Coefficient of expansion of Copper : 16.5

Aluminum expands one third more than copper

Some says it creates problems with bolted connections

But, using proper hardware aluminum joints are equalto copper joints




Comparing Aluminum & Copper (4)Electrical conductivity

Aluminum (σAl) : 37.8 x 106 Ω-1m-1

Copper (σCu) : 59.6 x 106 Ω-1m-1

Aluminum has only 61% of conductivity against copper, sohigher losses?

For two identical transformers (same winding

resistance and length , amps/turns), the conductorcross-section will be inversed to the electricalconductivity. The cross-section on Al conductor will be1.6 times against copper,

Sal

/Scu

= σCu

/ σAl

=59.6/37.8 = 1.6 Sal

= 1.6Scu

With the increase of cross-section, the result in energylosses are the same

Comparing the cost of both materials, lower losses will

be cheaper on Aluminum




Comparison of Transformer (Al vs Cu)General specification to be compared

General specification of transformer (same on both Cu & Al TRs)




Comparison of Transformer (Al vs. Cu)Electrical characteristics and dimension

Characteristics & Price comparison on 1600kVA transformers

All electrical and dielectric characteristics are the nearly same on bothCu and Al transformers

Price comparison except accessories 100% 75~77%

Price comparison is based on material costs dated on Mar. 15, 2010. It may be changed according tocommodity price variation.




Thermal ability to withstand to short-circuitRequirements according to IEC 60076-5 (2006)




Thermal ability to withstand to short-circuitWinding temperature calculation while short-circuit

200200350350Max. permissible Avg. winding temp

162183161191Highest Avg. winding temperature

LVHVLVHV

AluminumAluminumCopperCopper




Ability to withstand the dynamic effects of short circuit

High reliability on the coil structures

Robust mechanical coil structure thanks to encapsulation ofconductor material in solid insulation

Ability to withstand the dynamic effects of short circuit shall bedemonstrated either

by tests, or

by calculation and design and manufacture considerations

The reference list for type tests including dynamic short-circuittest is enclosed on next slide




Ability to withstand the dynamic effects of short circuitType & Special Test List (conducted by authorized third parties)




Comparison of VCC Transformer (Al vs. Cu)General comparison

Cost (Initial investment)Cost (Initial investment)

Dimension & WeightDimension & Weight

Overload CapacityOverload Capacity

Dielectric StrengthDielectric Strength

Short Circuit CapabilityShort Circuit CapabilityElectrical CharacteristicsElectrical Characteristics

AluminumAluminumCopperCopper




Comparison of Transformer (Al vs. Cu)Advantages on Al transformers

Less initial investment costs even if the operational running costsare the same (approx. 25% less expensive)

Same life cycle expectation because transformers are run at

equivalent operating temperatures, the insulation systems age atthe same rate for each design, it means that longer life cycle on ALtransformer on the same price

Lower operational running costs due to higher efficiency based on

the same price Thermal expansion of Al and epoxy resin is more similar, so

thermal stresses are kept to the minimum

Major VCC transformer manufacturers apply Aluminum VCC as

their standard products

ABB, Siemens, Areva, ….

Aluminum VCC is a standard product in Americas, Europe, Asiaand so on




Comparing Aluminum & Copperin terms of transformer characteristics

Copper Aluminium

Efficiency & Losses according to customer's request according to customer's request

Weight (%) Heavy (100)Lighter (85)

Easy for handling and transportion

Small (100) a little bigger (105)

%Impedance

Regulation

Ratio

Dielectric characteristics

Temperature rise

Thermal ability to withstand

short-circuit

Ability to withstand the

dynamic effects of short-

circuit

Mechnical Strength

Al and Cu conductor transformers have different criteria for maximum permissible

values of the average temperature of winding after short-circuit, so both different types of

transformers can comply with international standards.

It depends on properties of the maximum permissible temperatures on the soild

insulation system,so both kinds of transformers can comply with the requirement.

No relation with conductor material (depending on %IZ and Loss )

It depends on properties of expoxy system with mechanical reinforcement, so both kinds

of transformers can comply with the requirement.

No relation with conductor material

The dynamic effects can be demonstrated either by tests or calculations & design

considerations, so both different types of transformers can comply with international

standards. The transformers have much stronger ability to withstand while short-

circuiting because the windings are encapsulated in the soild insulation system.

No relation with conductor material

No relation with conductor material (depending on turns and geometric )

In case of the same kVA, it needs more AL(sqmm) than CU to reduce the current density

due to different conductivity. So the size of AL transforemr is a little bit bigger(1.05~1.1)

than CU transformer depending on the kVA, primary voltage and impedance.

Size of Tr (%)




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ALUMINIUM vs COPPER_Cost & Characteristics Comparison_20100315