IEC 60708-2005 pdf – Low-frequency cables with polyolefin insulation and moisture barrier polyolefin sheath

IEC 60708-2005 pdf – Low-frequency cables with polyolefin insulation and moisture barrier polyolefin sheath.
1 Scope This standard is intended to define polyolefin-insulated cables for insertion into local outdoor networks. This standard is applicable to polyolefin insulated and moisture barrier polyolefin sheathed telephone cables, filled or unfilled with copper conductors, and used as: a) Cables suitable for installation in ducts. b) Cables suitable for direct burial in the ground. c) Cables with integral suspension strand for aerial installations. This standard is in accordance with ITU-T Recommendations. This standard includes general design details and requirements for dimensions and other constructional details as well as mechanical, electrical and environmental characteristics for all types of low-frequency cables with polyolefin insulation (solid or cellular), filled or unfilled, and moisture barrier polyolefin sheath (with integral suspension strand). 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60028, International Standard of Resistance for Copper IEC 60189-1, Low-frequency cables and wires with PVC Insulation and PVC sheath – Part 1: General test and measuring methods IEC 60304, Standard colours for insulation for low-frequency cables and wires IEC 60794-1-2, Optical fibre cables – Part 1-2: Generic specification – Basic optical cable test procedures IEC 60811-1-1, Common test methods for insulating and sheathing materials of electric cables – Part 1: Methods for general application – Section 1: Measurement of thickness and overall dimensions – Tests for determining the mechanical properties IEC 60811-1-2, Common test methods for insulating and sheathing materials of electric cables – Part 1: Methods for general application – Section Two: Thermal ageing methods
4.2 Insulation 4.2.1 Insulation material The conductor shall be covered with solid or cellular polyolefin insulation or any combination thereof. For cellular insulation, the cells produced by the expanding process shall be uniformly distributed circumferentially and should be substantially non-intercommunicating. The material for the insulation shall be a virgin thermoplastic compound suitably stabilized. Examples of suitable materials are: – Polyethylene. – Polypropylene. 4.2.2 Insulation thickness The insulation shall be continuous and shall have a thickness such that the completed cable will meet the electrical requirements specified. 4.2.3 Colour of insulated conductor The insulated conductors shall be coloured. Colours shall be readily identifiable and shall correspond reasonably with the standard colours shown in IEC 60304. 4.3 Cabling element A cabling element (Figure 1) shall be: – a pair of two insulated conductors twisted together and designated wire a and b respectively, or – a quad of four insulated conductors twisted together and designated wire a, wire c , wire b, and wire d respectively. The maximum length of lay in the finished cable shall not exceed 150 mm. NOTE Forming the element with a variable lay can lead to the infrequent but acceptable occurrence of the maximum lay being longer than specified. 4.4 Stranding The cable elements shall be formed into a number of sub-units or units which can be stranded into a regular make up to produce the required number of pairs. 4.5 Colour code 4.5.1 General Three different colour schemes for identifying pair or quad counts are defined. One with 10 pair or 5 quad sub-units, one for 25 pair colour groups and a third for 25 quad colour groups.
4.5.2 Sub-units, units and cables up to and including 100 pairs or 100 quads 4.5.2.1 10 pair or 5 quad count The pairs or quads shall be identified by each insulated conductor having a single colour in accordance with the colour scheme given in Annex A. Sub-units of 10 pairs or 5 quads shall be identified by coloured bindings of tape or threads according to the colour scheme given in Annex B for assembly into units of 50 pairs (25 quads) or 100 pairs (50 quads). 4.5.2.2 25 pair count The pairs shall be identified by each insulated conductor having a single colour in accordance with the colour scheme given in Annex C. Sub-units shall be identified by coloured bindings of tape or threads. Each group of sub-units making up a 25 pair count shall be identified by a common colour of bindings. For 50 and 100 pair cables the colours of the bindings are given in Annex D. 4.5.2.3 25 quad count The quads shall be identified by each insulated conductor having a single colour in accord- ance with the colour scheme given in Annex E. Sub-units shall be identified by coloured bindings of tape or threads. Each group of sub-units making up a 25 quad count shall be identified by a common colour of bindings. For 50 quad (100 pair) and 100 quad (200 pair) cables the colours of the bindings are given in Annex D.