An innovative approach for a very mature product

Electrical cables were developed immediately after the discovery of electrical current in the nineteenth century. They are therefore a product that has been on the market for many years and can be considered very “mature”. Scientific and technological innovations rarely occur in such products and their basic features remain unaltered for long periods of time.

There is nonetheless margin for innovation, which allows for improvement in cable and provides it with new or better features for electrical installations. As General Cable’s mission includes a commitment to ongoing improvement through innovation, it has therefore adopted an approach based on three main core areas:

- Safety of people and property.

- Ease of use for users.

- Sustainable development and environmental friendliness.

Safety first

Recent years have seen a process of change in the specifications required from low and medium voltage cables, that characteristics of which require them to provide a higher level of safety in the event of fire.

This process has been particularly focused on the specific risk of fire presented by electrical cables, which may be summed up in the following hazards:

- In electrical cable, power transported and varyingly combustible plastic materials are intrinsically combined.

- Cable is only active when transporting electrical power but is passive insofar as safety is concerned.

- Cable is distributed throughout buildings, parts of which feature accumulations of a very large number of cables. These are a potential cause of fire and could generate a secondary source of fire.

- Some plastic materials involve a special fire hazard because of the very swift generation of a large amount of opaque smoke and the emission of halogenated acids and corrosive gases, which cause serious damage to the health of people, to electrical and electronic equipment and even to building structures because they corrode concrete.

Anti-fire classification of cables

The electrical cable sector, aware of theses hazards, has developed a series of products that reduce the risks considerably:

- Non-flame propagating. Standard: UNE-EN 60332-1-2.

- Non-fire propagating. Standards: UNE-EN 50266 and IEC 60332-3.

- High Safety (AS). In addition to complying with the two above categories, during combustion the smoke generated allows the passage of light (UNE-EN 50268 and IEC 61034 standards) while the gases emitted are of low acidity and corrosiveness (UNE-EN 50267 and IEC 60754 standards).

-  Increased High Safety (AS+). These comply with all the characteristics of the High Safety (AS) cables and can also remain in operation during a fire, even if directly affected thereby. They are fire-resistant cables that comply with the UNE-EN 50200 standard.

Safety cables in the Low Voltage Electrotechnical Regulation (REBT)

Demand for cables with High Safety (AS) and Increased High Safety (AS+) specifications in the event of fire and of the effects of combustion has been included in the Low Voltage Electrotechnical Regulation for the following ITCs (Complementary Technical Instructions):

- ITC-BT-14 General mains line.

- ITC-BT-15 Individual branches.

- ITC-BT-16 Meter and electrical box cabling.

- ITC-BT-28 Premises for public use (general installations).

Both compulsory compliance, which has been a requisite of the REBT since 2003, and greater awareness of safety matters among all the agents involved (endorsers, users, distributors, manufacturers, etc.) have prompted fast growth in these cables, which have largely replaced traditional PVC-sheath cables.

Ease of use for users

Cable is a very mature product and therefore highly standardised. There are also quality control mechanisms on the market that guarantee compliance with minimum criteria established in standards. Differentiation of a product therefore requires focus to be placed mainly on qualities or features that are not compulsory in the standards yet are appreciated by end users, particularly installers.

This strategy of improving non-standardised aspects has been implemented since the nineteen-nineties and affects two very widely consumed products:

- The H07Z1-K type (AS) 450/750-V cable with copper conductor, insulated with halogen-free polyolefin for fixed protected installation, in accordance with UNE 211006 standard.

- The RZ1-K (AS) type 0.6/1-kV cable with copper conductor, insulated with reticulated polyethylene (XLPE) and covered with halogen-free polyolefin for fixed installations, in accordance with UNE 21123-4 standard.

The most outstanding innovations to affect either both or one of the cables are summarised below.

Flexible conductor

Rigid conductors (classes 1 or 2) have traditionally been used in cables for fixed installations while flexible conductors have been reserved for applications required in mobile services.

The use of flexible conductors nonetheless provides users with some very clear benefits, which are clearly shown in the following diagram:

The higher initial cost involved in the purchase of cable with flexible conductors is more than compensated by cost reductions in installation, and by the reduction in manufacturing costs achieved by the cable industry as a result of productivity improvements in the industrial processes involved.

The introduction of flexible conductors has brought some extraordinary advances in these cable types with respect to their rigid counterparts, as is shown in the following graphs:

The graph shows the virtual disappearance on the RZ1-K (AS) cable market of the RV cable with rigid conductor, which has been replaced completely. There has also been notable growth in RZ1-K (AS) type cable at the expense of RV-K type cable after the implementation of the REBT.

On the H07Z1-K (AS) cable market, the decline of the rigid conductor has also been very pronounced and reflects the same trends as those of 0.6/1-kV cable.

This situation has arisen mainly because of the extraordinarily warm welcome from installers, who have appreciated the benefits of working with flexible conductor.

The 0.6/1-kV also features a magnificent innovation that is designed to improve handling and ease the installation of cables with flexible conductors even further: the flexible sectoral conductor SECTORFLEX^®.

The Sectorflex conductor

Sectorflex is a sector-shaped flexible conductor with which a multi-polar cable can be formed, thus optimising the space occupied by conductors and yielding considerable improvements in different aspects with regard to conventional circular conductors.

Smaller diameter because of the huge reduction in the space between conductors 

Lighter because of the decreased diameter and reduction in the layers that cover the conductors
 

Easier to install and lay 
 

Longer sections 
 

Easier handling 
 

Use of conventional terminals and accessories

In addition to all these benefits, which significantly influence the energy cost involved in acquiring materials, manufacture, storage, transport and laying and installing cable, the cable energy efficiency of Sectorflex is also greater during operation.

Sectorflex provides proof that innovation ensures ongoing economic benefits (in this case energy efficiency), and maintains sustainability and environmental friendliness criteria without compromising economic and social progress.

Further innovations geared for users

To facilitate installation work, General Cable has developed other innovations in its products:

450/750-V H07Z1-K (AS) cable

- Optimum slip because of the SPEEDY-SKIN system that provides for effortless installation or removal of cables even in the most sinuous and complex circuits. This feature is inherent in the material used and efficiency is not lost throughout the cable’s useful life.

- Easily-stripped insulation, even with the simplest of tools. This streamlines connection tasks, which are particularly important in small sections with a large number of connections.

- Reinforced box resistant to impact and falls, with an anti-tangle cable uncoiling system that reduces material losses to a minimum. General Cable works with the best packaging to optimise distributor and installer costs.

- Box transportation trolley, which allows for convenient, safe transport of boxes and meanwhile facilitates cable installation.

0.6/1-kV RZ1-K (AS) cable

- Easily-stripped insulation, even with the simplest of tools. This facilitates jacket removal work, especially of small-section cables.

- Flexible jacket that makes performance of these cable types similar to the corresponding RV-K cable with PVC jacket. The special fireproof jacket provides for excellent cable handling and laying, and makes installers’ work easier.

Environmental factors

European-wide legislation is evolving gradually and making increasingly demanding environmental requirements on electrical products. A very clear example was the prohibition of lead (Pb) and other hazardous substances from all electrical products. The updating of RoHS directive proposals on health and safety at work are likewise designed to extend the list of prohibited substances and in some cases even proposes the prohibition of vinyl polychloride (PVC).

Although these proposals may not be approved, they provide an obvious sign of underlying current in Brussels to exert clear pressure for the use of “environmentally compatible products and components”. This pressure is not only from environmental groups, but also comes from powerful groups of users such as electronic equipment manufacturers, who are now also making such demands.

In this context, “halogen-free materials”, whether in their current fire-safety version or in other versions yet to be developed, provide an alternative to traditional materials such as PVC.

A possible threat could therefore also be perceived as an opportunity for introducing new materials and components, which add value to products and bring improvements to the market. Perhaps the urban legend that the word crisis comes from a Greek term meaning opportunity can be made effective reality.

Xavier Gol

General Cable Commercial Technician