Specifi cation for cables with extruded cross

BS 6622:1999 pdf free.Specifi cation for cables with extruded cross-linked polyethylene or ethy lene propylene ru b ber insul lation for rated Vo ltages from 3.8/6.6 kV up to 19/33 kV.
A conductor screen consisting of an extruded layer of cross-linkable semi-conducting compound shall be
applied over the conductor and cover the surface of the conductor completely.
NOTE A semi-conducting tape may be applied prior to the extruded layer at the discretion of the manufacturer.
The extruded conductor screen shall be applied in the same operation as the insulation and be fully bonded
to the insulation.
7 Insulation
The insulation shall be either Xl.PF. or EPR conforming to the requirements of 19.4.
The insulation shall be applied by extrusion and cross-linked to form a compact and homogeneous layer.
The colour of the insulation shall be such that it is easily distinguishable from the screening materials.
The minimum and minimum average thickness of insulation shall be as specified in Table 2 to Table 11.
8 Insulation screen
8.1 General
An insulation screen shall be applied to all cables and shall consist of a cross-linkable extruded
semi-conducting layer in combination with a metallic layer.
8.2 Extruded semi-conducting layer
The extruded semi-conducting layer shall consist of a bonded or strippable semi-conducting compound capable of removal for jointing and terminating (see C.5). It shall be applied in the same operation as the insulation, directly over the insulation, and shall cover the surface of the core completely.
NOTE At the discretion of the manufacturer, semi-conducting tape or a semi-conducting extruded layer may be applied over the semi-conducting insulation screen as a bedding for the metallic layer.
8.3 Metallic layer
8.3.1 General
The metallic layer shall be applied either around each core and)or as a collective screen. For rated voltages
above 8.7/15 (17.5) kV, a metallic screen shall be applied around each core.
8.3.2 Metallic screen on each core
A metallic screen applied directly over the core of single-core cables or each core in three-core cables, shall consist of either helically applied overlapped copper tape(s) or a concentric layer of copper wires applied helically or in a waveform.
The copper wires shall be spaced with an average gap not greater than 4 mm. No gap shall exceed 8 mm.
NOTE I At the discretion of the manufacturer, a copper equalizing tape may be applied.
NOTE 2 At the discretion of the manufacturer. a binder tape may be applied over the metallic screen of single-core cables.
8.3.3 Collective metallic screen
Three-core cables not having a metallic screen over each individual core shall have a collective screen applied after the cores have been laid up together and over the bedding layer (see 9.3).
NOTE I Three-core cablea having a metallic acreen over each individual core may alao have a collective wreen.
The collective screen shall consist of:
a) a concentric layer of copper wires applied helically or in a waveform. The average gap between adjacent wires shall not exceed 4 mm, and no gap shall exceed 8 mm: and/or
NOTE 2 At the diacretion of the manufacturer, a copper equalizing tape may be applied.
b) metallic sheath (see annex A): and/or
c) wire armour (see clause 10).
NOTE 3 At the discretion of the manufacturer, a binder tape may be applied over the metallic acreen.
9 Laying-up
9.1 General
For three-core cables, the cores shall be laid-up with a right hand direction of lay. Fillers shall be used to
form a substantially compact and circular cable. The fillers shall be compatible with adjacent materials.
9.2 Cables with a metallic screen on each core
The metallic screens of the three cores shall he in contact with each other.
NOTE At the diacretion of the manufacturer, a binder tape may be applied over the laid.up cores.
93 Cables with a collective metallic screen
An extruded or lapped bedding layer shall be applied around the laid-up cores.
NOTE If the bedding layer i extruded, the fillers may be applied integrally with the bedding layer.
For cables with a metallic screen on each core and a collective screen of dissimilar metal, the bedding layer shall be extruded, unless the collective screen is a lead sheath in which case the bedding layer may be extruded or lapped.
The thickness of a lapped bedding layer shall be approximately 0.6 mm. The thickness of an extruded bedding layer shall conform to the requirements for the separation layer specified in 10.1.
For cables not having a metallic screen on each core, the extruded or lapped bedding layer shall be semi-conducting. The shape of the fillers shall not prevent electrical contact between the insulation screen and the semi-conducting bedding layer.
The materials used for the bedding layer shall be suitable for the operating temperature of the cable and compatible with the other materials used in the cable construction.
10 Armour
10I Separation layer
When armour is to be applied to a cable having a screen of dissimilar metal, an extruded separation layer shall be applied between the two metallic layers. The material used shall conform to 11.1.
Nominal and minimum thicknesses of the separation layer shall be as specified in Table 2 to Table 11.
10.2 Metal layer
For the armouring of three-core cables, round galvanized steel wires shall be used.
NOTE 1 Where the purchaser requires a cable to operate at a higher system fault level, a number of galvanized steel wires may be replaced by tinned copper wires, subject to agreement between the purchaser and the manufaeturer.
NOTE2 When requested by the purchaser, galvanized steel tape armour may be used as an alternative to or in conjunction with the steel wire armour.
For the armouring of single-core cables either round aluminium wires or aluminium strips shall be used.
The nominal dimensions of the armour shall be as specified in Table 2 to Table 11.
Armour shall be applied helically in a single layer with a left-hand lay.
Joint.s in steel wire armour shall be brazed or welded and any surface irregularity removed. Joints in aluminium wire or strip shall be made by cold pressure or fusion welding and all surface irregularities shall be removed.
A joint in any wire or strip shall be not less than 1 m from the nearest joint in any other armour wire or strip in the completed cable.
11 Oversheath
11.1 General
The material for the extruded oversheath shall be PVC or MDPE in accordance with BS 7655.4.2: Type 9 or -10.1: Type TS 2. respectively.
NOTE I Oversheaths are normally black but colours other than black may he provided by agreement between the manufacturer and the purchaser, subject to their suitability for the particular conditions under which the cables are to he used.
NOTE 2 Cables with MDPE oversheaths are not designed to satisfy the requirements of BS EN 50265-1 and BS EN 50265-2-1.
11.2 Thickness for unarmoured cables
For unarmoured cables, the minimum and minimum average thickness of oversheath shall be as specified in Table 2 to Table 11.
11.3 Thickness for armoured cables
For armoured cables, the nominal and the minimum thickness of oversheath shall be as specified in
Table 2 to Table 11.
11.4 Semi-conducting layer
When the purchaser specifies that a d.c. voltage test is to be performed on the oversheath (see A.5). a semi-conducting layer shall be applied over its surface.
12 Marking
12.1 Marking of oversheath
The external surface of all cables shall be legibly marked with the following elements of marking, in any sequence that is deemed neither to confuse nor conflict.BS 6622 pdf free download.Specifi cation for cables with extruded cross