NILED

The french Aerial Bundled Conductors consists of three insulated hard pure aluminium phases twisted around one neutral insulated «» messenger. This «» is an alloy made of aluminium, magnesium, silicone and iron.

As compared with overhead bare conductors, this technology offer lot of advantages :

improve operating conditions by eliminating accidental contact with foreign bodies,
Easier construction (accessories easy to install, possibility to build networks supporting other aerial lines (as telecom conductors, or Medium voltage cables)
Very competitive solution (reduced cost of the accessories, quick installation of the bundle...)
Improve operating conditions in case of broken pole
Eliminate some electrical risks ( forest fire can start when bare lines fall down)
Increase the electrical fiability (waterproofness of the connexions, mechanical performance of the anchoring devices...)
Reduce trees clearance in wooden area
Improve safety in icy areas, allows the action on live networks
Esthetic possibility in case of architectural interest (the bundle can be hidden under eves or along cornices existing)

The neutral messenger is fixed in the dead-end clamp by means of a plastic conical wedging system. No tools are required for the installation. The plastic wedges insure a double insulation of the neutral wire, and avoid any damage of the cable insulation.

Dielectric performance test :
the clamp must resist to 6kv with bare conductor placed inside the plastic wedges.

Mechanical test : neutral messenger’s slipping or breaking must not appear before the specified value (1500 or 2000 daN tensile strength).

The suspension clamp consists in a body and tightening lever made of plastic material. The suspension clamp is fixed to the bracket by means of movable link wich allows transversal & longitudinal motions.

Either vertical breaking between 650 & 900 daN for the fuse-suspension assembly ESF54-70
(this system, complying with the technical standard NF C3 33-044, means that the suspension clamp acts as a mechanical fuse in case of over-loading on the bundle.So, when breaking, suspension assembly relieves the network of loading, and preserves dead-ending.

The bundle is composed with four similar insulated conductors. Each of them is made of similar aluminium alloy.
The conductors are twisted togeither.

In this system, the fixing accessories hold up the four cables.

For main networks (cross section >35 mm2), the fitting has to be realized using specific tightening tools (Especially for the anchoring clamp).

Because of the need to use tooling, and compared with the french technology, the handling of the fixing devices is not so easy.

Providing an higher mechanical resistance, the four conductors are very rigid and quite difficult to install in the clamps.

The advantage of this self-supporting system is the mechanical performance. As an example, a bundle of 4x 70mm2 conductors can satisfy 4500DaN tensile strength. Of course, this solution has to be used with poles (pylons) able to resist to similar stress values.

The economic aspect is the bad side of this method because of installation and fittings costs.

This technology is quite similar to the french system, except that the messenger is uninsulated.The bundle consists of three insulated phase conductors made of aluminium alloy, twisted around a bare steel or alu alloy messenger. This messenger is also the neutral conductor.

Electrical risk : In case of networks falls (under unexpected loads like falling trees),the uninsulated “neutral” may touch voltage, and present big electrical risk. Proper earthing is essential. Fixing devices (suspension/anchoring) have to be installed using tightening tools.

Mechanical performance : neutral messenger’s slipping or breaking must not appear before the specified value (1500 or 2000 daN tensile strength). Advantage of this method : like French ABC, the accessories hold the only messenger. This make easier the installation. The disadvantage is of course the screw-system, and the need to use tool.