Power distribution - A question of cost


Traditionally copper has been the material of choice when it comes to electrical conductors, but in February 2011 its price per tonne broke through the $10,000(US) barrier for the first ever time. And, AS with fuel prices here in the UK, it looks set to continue rising. So what does the spiralling cost of copper mean to the electrical industry? Electrical Review spoke to Steve Marr, the marketing manager of Legrand’s power distribution division, to find out more

For as long as any of us care to remember copper has been the chosen material when it comes to conducting electricity, but in recent years this position has begun to be undermined by the growing acceptance of aluminium as a suitable alternative.

And now, with the soaring cost of copper putting it in real danger of becoming prohibitively expensive, aluminium looks like it could have the opportunity to make its move and become the electrical conductor of choice here in the UK.

But how do the two rate against one another? In the past aluminium tended to be seen as the poor relation to copper, but today it’s very much a high performance product that compares favourably with copper in terms of mechanical strength, heat stability and thermal conductivity.

Nowhere can this transformation be better seen than its performance in two key power distribution product groups – namely busbars and cast resin transformers.

Over the last 50-years, busbar power distribution systems have increased in versatility and sophistication and are now widely regarded as the first-choice solution for power distribution projects in most industrial and commercial applications.

An interesting element of the busbar’s development has been the significant shift away from copper to aluminium solutions – both in terms of manufacture and specification.

The reasons for its surge in popularity are plentiful, but interestingly one of the key ones is cost. On the world’s commodity market aluminium’s value is far more stable than copper, and is not so sensitive to the ‘ebb and flow’ of consumer demand, political uncertainties and other economic and climatic factors. For example, the flooding and cyclone in Australia earlier in the year had a significant impact on the price of copper due to the fact copper mines, such as Mount Isa in Townsville, Queensland, were forced to temporarily shut down. As a result, aluminium can consistently provide significant cost savings.

The benefits of aluminium do though stretch far beyond the simple question of cost. Take for example, conductivity. Although aluminium’s conductivity is only 62% that of coppers, it is 70% lighter - for example our Zucchini 4000A busbar is 62.7kg per metre in aluminium, compared to 101kg per metre in copper. This not only saves money on transportation, but helps to reduce time, effort and, of course, cost during installation. In return for this substantial weight saving the aluminium bar is slightly deeper, but only by an extra 40mm with a total depth of 480mm. What this means is when you compare an aluminium system against a copper-based system of equal size and weight, aluminium is scored twice as conductive as copper

Historically, the key concern specifiers had with aluminium was its susceptibility to oxidisation, which caused significant problems with contact conductivity at the joint. This issue is no longer a concern with any Zucchini busbar system as all our aluminium conductors are electro-tin plated specifically to eliminate this problem.

Moving on, the plus points in aluminium’s favour come thick and fast. For example, unlike ferrous metals, aluminium doesn’t generate sparks when used in combination with other metals, making it ideal for use in potentially flammable or explosive environments.

Also, as aluminium is nonmagnetic it’s ideal for use in applications that need minimum magnetic interference. These include high-voltage applications as well as electronics.
And if that wasn’t enough, aluminium alloys have a mechanical resistance of 60 to 530 Newton/mm², which is more than sufficient, and compares favourably with copper.

When taken as a whole, we feel these benefits mean the advantages of specifying aluminium busbar systems easily outweigh those of copper systems in terms of performance, safety and cost.

Despite all of these advantages, the debate over the best busbar solutions still rages on. So much so that the majority of manufacturers still offer bother copper and aluminium solutions, simply on the basis that there are still consultants and specifiers who will always opt for copper and that there are certain installations where copper is seen by many – often mistakenly – as the best option.

Cast resin transformers
In contrast, the debate when it comes to cast resin transformers is very much done and dusted, with aluminium standing triumphant over its copper foe. In fact, a growing number of manufacturers now only offer aluminium solutions.

The reason for this is simple – the benefits of aluminium far outweigh copper in these systems.

Perhaps most importantly, the coefficient of thermal expansion of aluminium is more similar to the coefficient of the resin than copper. What this means is that when the transformer is loaded the compatibility between the expansion coefficient of aluminium and the resin used for the casting ensures against the potential for possible cracks in the cast resin coils – a guarantee that copper simply can’t deliver.

In addition, because aluminium windings work at a lower current density than copper windings this enables them to have a better short term overload capacity.

The vast difference in the weight of the two materials again comes into play, with aluminium wound cast resin transformers being far lighter than copper wound ones. And finally, the efficiency of aluminium wound products is guaranteed to be the same as the equivalent copper wound version.

What happens next?
As with any industry, the path to significant change in the electrical industry is a slow and arduous one. People with long-held beliefs need to be educated as to the benefits of the newer solution and why it should usurp the traditional one.

In the majority of cases this process alone is unlikely to convince everybody, which is why you see the kind of situation arising that we currently have in the busbar market. This being that despite the fact the overwhelming evidence points towards the advantages of aluminium solutions far outweighing those of copper, there are still enough decision makers within the market who prefer copper to warrant manufacturers producing both solutions.

Of course, there is one factor that can always be relied upon to change people’s mind – money. Yes, aluminium has a host of attributes, in terms of mechanical strength, heat stability and thermal conductivity that put it on a par, if not ahead of copper, but it is the financial aspect that will almost certainly tip the scales in its favour as the conductor of choice here in the UK.

To recap, copper prices are at an all time high. And when you consider the global economy is unlikely to deliver the kind of stability needed to rein these prices in at any stage soon, and add to that the fact the climate is also weighing in with its own natural problems, it seems certain the only way is up for the price of copper. All of which means one thing, the future surely has to be aluminium.

Legrand offers a wide selection of aluminium busbars and cast resin transformers. Its Zucchini MR aluminium busbar range is available in all sizes from 160 to 1,000A, while its SCP busbar range is offered in all sizes up to 5,000A. Both systems feature a large selection of tap-off boxes that allow the supply and protection of a wide range of loads using different devices such as fuses, MCBs and MCCBs. The company also manufactures both products with copper conductors.

In contrast, Legrand’s range of cast resin transformers is manufactured solely with aluminium conductors. The Zucchini EdM range satisfies high power, medium voltage market needs, with bespoke solutions available upto 17,000kVA.