1. OBJECTIVE 
This specification objective is to define the structural, dimensional and mechanical characteristic as well as the conditions of realization, supply and reception to be met by concentric copper and aluminum conductors. 
2. NORMS
the concentric conductors of copper and aluminum, is entirely consistent with the rules ASTM D 790, D 1248, D 2655, D 2656, UL 854, UL 44, numeral NEC 310.14.
3. CHARACTERISTICS OF THE COPPER AND ALUMINUM CONDUCTORS
3.1 CONSTRUCTIVE CHARACTERISTICS
Each material used in the conductor will be compatible with all other materials used in the manufacture of concentric conductor.
Concentric conductor consists of one or two conductors which in turn are coated with a bare conductor distributed helically around the conductors.
According to these configurations will have a phase and outer concentric neutral (bipolar), or two phases and these external neutral (tripolar)
Section of all conductors that form the concentric conductor of both phases as the concentric neutral is the same.
Conductor: 
The materials used in the manufacture of concentric copper conductors shall consist of soft copper wires class B and the composition of a pure copper will never lower than 99.85 and the concentric aluminum conductors formed by wires keychain aluminum alloy 8000 series (AA-8000).
Copper wires and aluminum shall comply with the provisions of ASTM B 3 standard and UL 854.
For bipolar concentric conductor, standard sections are # 8 and 10 AWG.
For tripolar concentric conductor, standard sections are # 8, 6, 4 y 2 AWG.
In the phase conductors with 7 wires, will be able to perform welding copper wires during wiring. Once this process is completed it will not be allowed two welds closer than 15m (50ft)
According to paragraph 6 of ASTM B 8, the wiring process will be as follows:
Over the central conductor will be braided the rest of the layers. Braiding step will be at a distance to vary between 8 and 16 times the outside diameter. The lay direction of the copper wires in the outer layer will be right.
Isolation:
Each phase conductor will contain an insulating layer of XLPE for a temperature of 90 C. in the bipolar cables, over the insulating layer will be the braided neutral conductor helically with a passage between 8 and 16 times the outer diameter. In the tripolar cables over the isolation of each phase will have a PVC insulation filling in the joint of both cables and over this will be placed the neutral conductor. 
Will be put over the concentric neutral conductor a tape and over this outer layer of XPLE. Must ensure the tightness of the set plus adequate resistance to ultraviolet rays (UV). 
This last layer besides adding firmness should be smooth in appearance and will not be observed depressions caused by unfilled spaces beneath this layer.
Should not produce bubbles, cuts, tears or the presence of foreign materials that are detectable to the naked eye. Besides the envelope will be well centered.
The disposition of the tape around the bare conductor shall be performed as follows:
A single layer of tape with a convenient width helically applied without wrinkles or folds and with an overlap of at least 6mm. The tape will consist of nylon, with a thickness of at least 0.09mm.
Covering the entire concentric conductor will be placed a XLPE coating according the ASTM D 790, D 1248, D2655, and D2656 Standards. 
The color should be:
-Black: 2x #8, 2x #10
Other possible configurations of the neutral will be allowed as long as admit they ensure the minimum coverage required. The area of the section of a conductor will be adjust as specified in Table 5 of ASTM B 8, not being less than 98% of the area of the section specified in the table above.

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