Low voltage branch aluminum power cable helps to save labor at construction sites

smart energy ecology

The trunk cable is an aluminum conducting cable,
while the branch cable is a copper conducting cable.
The branch mold was newly designed to be more compact,
allowing it to be run even through existing floor through-holes.

Low-voltage branch cables where branch cables are pre-connected to required spots in wire manufacturer plants are widely used in order to provide power from electrical rooms to each floor in buildings, condominium buildings, and other structures. Branches from the trunk cable are all processed in the plant, so there is no need to do so on-site. This provides a range of benefits such as simple cable laying and stable quality, so these cables are now used for most in-building distribution cables.

The Furukawa Electric Group has developed Ultralight Hybrid Building Harness Cable, a low voltage branch aluminum power cable that uses aluminum as the conductor in the trunk cable of the branch cable. The conductor used in the branch cable largely determines the mass of the product, so using aluminum for the conductor roughly halves the mass of the trunk cable (which accounts for much of the mass of the product), when compared with current Furukawa Electric building harness cables.

In order for an aluminum conducting cable to pass the same current as a copper conducting cable, the trunk cable must be increased to the next larger size. Even so, Furukawa Electric was able to reduce the mass of the resulting product around 30%.


Weight reduced 30%, with no changes to terminal connection work


Mass comparison

Aluminum is lighter than copper, making it easier to unload, transport, cross-cut, or hang cable when laying cable—and making it possible to save labor when laying cable. Copper conducting cable is used for the branch cable, so there are no changes necessary to how the product is connected to equipment compared with products using the conventional conductor. The cable combines the benefits of both aluminum and copper for 30% less weight and the same workability when connecting to equipment.


Flexibility comparison

Hard-drawn aluminum wire is used for the conductor in this new cable. The material is harder (has stronger repulsion) than the annealed copper wires used in existing copper conducting cable. This means that it would be harder to bend than current products if the same conductor configuration was used. However, Furukawa Electric carefully designed the conductor configuration of the new product to offer a flexibility 1.5 times that of existing products. This should make it possible to save labor when extending cable or treating terminals.


New product will also contribute toward solving the environment issue of copper resource depletion

With demand for wire expected to increase throughout the world, there are fears over copper resources becoming depleted. There is increasing hope that replacing these with aluminum wires could help to curb the amount of copper being used. This new product is expected to also contribute in this area.

Kei Kaizuka, Manager, EBC Team (note), had the following to say about future developments.

Ultralight Hybrid Building Harness Cable was developed together with Furukawa Electric Industrial Cable Co., Ltd., a Furukawa Electric Group company. The technology offers the same high reliability of Furukawa Electric building harness cables, but also incorporates the benefits of an aluminum conductor. The technology also uses connection material manufactured by Furukawa Electric Power Systems Co., Ltd., for a product that truly leverages the comprehensive strength of the Furukawa Electric Group.

The connections on the trunk cable and branch cable are made between aluminum and copper. Although joining dissimilar metals is known to result in issues such as corrosion at connection, Furukawa Electric was able to overcome these issues and bring the product to completion by utilizing the technical strengths it has built up in the overhead power transmission/distribution field to treat the surface and design the shape of terminals.

In contrast with the overhead power transmission/distribution field (in which aluminum wires are widely used), cables with aluminum conductors have only begun to be introduced for wires inside equipment in buildings and other structures. The lightweight nature of the aluminum conducting cable used in the trunk cables of Ultralight Hybrid Building Harness Cable makes it easier to install and remove the product. For this reason, Furukawa Electric is committed to promoting the use of the product as a possible means to help with labor shortages—even in facilities for the 2020 Tokyo Olympics, for which construction will begin in earnest.

(note) EBC Team: Energy Backcast Team, Industrial Cable & Power Cable Accessories Division, Energy Infrastructure Division, Furukawa Electric.


Feedback from construction sites

The product was supplied to a research lodging facility built inside an engineering laboratory by Hazama Ando Corporation.

Workers were overheard noting how light the product was when transporting or cross-cutting drums. When cross-cutting drums, it was especially light when rotating drums compared with other Cu-CVT drums.

Workers underground noted they did not need to call out to others because the product was so light. Although some workers noted that the product was hard, there was no problem drawing the cables and getting work done smoothly.