Cables armoured

In armoured cables, armouring must be removed before passing the cable through the CBCT to avoid an induced e.m.f. through the armour and the corresponding magnetizing current which may affect the performance of the CT. 

Use of screened cables in the communication network and grounding the screen effectively. Metallic-sheath or armoured cables are not recommended. 

Test of clamping of non-armoured cables in cable entries... 

When an earth fault occurs at the far end of a cable it is possible that the armouring, cable gland and the frame of the consumer equipment can be raised to a dangerous potential with respect to electric shock exposure to human operators. This subject has been given considerable attention over the last 20 years, and is well documented in for example IEC60364. The international documentation concentrates on low voltage fixed and portable equipment protected by fuses and miniature circuit breakers. See also Chapter 13. 

Cubicle steelwork is invariably bolted to the floor, a floor frame or to a wall structure, and therefore bolted bonding straps are used in a similar manner as described above. Most cubicles are fitted with an internal copper busbar which is bonded internally to the steel. The busbar is used to receive the bonding connections from internal components, partitions, screening panels, cable glands, cable armouring, cable screens and gland plates. 

BS6724 Armoured cables for electricity supply having thermosetting insulation with low emissions of smoke and corrosive gases when affected by fire. 

BS7835 Specification for armoured cables with extruded cross-linked polyethylene or ethylene propylene rubber insulation for rated voltages from 3.8/6.6 kV up to 19/33 kV having low emission of smoke and corrosive gases when affected by fire. 

PVC insulated steel wire armour cables are used for wiring underground between buildings, for main supplies to dwellings, rising sub-mains and industrial installations. They are used where some mechanical protection of the cable conductors Is required. 

Fibre-optic cables look like steel wire armour cables (but of course they are lighter) and should be installed in the same way, and given the same level of protection, as SWA cables. Avoid tight-radius bends if possible and kinks at all costs. Cables are terminated in special joint boxes which ensure cable ends are cleanly cut and butted together to ensure the continuity of the light pulses. Fibre-optic cables are Band I circuits when used for data transmission and must therefore be segregated from other mains cables to satisfy the lET Regulations. 

PVC armoured cables terminated into accessories with approved flameproof glands or any other wiring system which is approved by the British Standard. All certified flameproof enclosures will be marked Ex, indicating that they are suitable for potentially explosive situations, or EEx, where equipment is certified to the harmonized European Standard. All the equipment used in a flameproof installation must camy the appropriate markings, as shown in Fig. 3.72, if the integrity of the wiring system is to be maintained. 

V three-phase for supplies to major items of plant having a rating above 3.75 kW such as cranes and lifts. These supplies must be wired in armoured cables. 

Non-armoured thermosetting, thermoplastic or lead Armoured cables sheathed cables... 

All fixed distribution cables carrying 400V or 230V must be protected with a metal sheath and/or armour which is continuous, effectively earthed and protected against corrosion. The HSE strongly recommend that any existing or new permanent fixed supply should not be used to supply contractors equipment during the construction work. Any movable plant such as lifts or hoists should be supplied by armoured cable. 

Use a metalclad wiring system. Armoured cables should not be served and MIMS cables should not be plastics-covered. 

In the past, there were fewer accidents because buried cables were better protected. Most of the supply authorities used paper-insulated, lead-sheathed, single-wire or steel-tape armoured and served cables and very often protected them with cable tiles. For economic reasons cable tiles are seldom used now and many of the mains laid in recent years are unarmoured CNE cables with plastic insulation and sheathing, such as PVC and cross-linked polyethylene (XLPE). The outer concentric conductor, which is the earthed neutral, is copper or aluminium tape and consequently more vulnerable to damage than a steel-wire-armoured cable. Every year more new mains cables of this type are laid so the resultant hazard to excavators is growing and more accidents can be expected to occur unless the construction industry becomes more effective at taking precautions against striking buried cables. 

Armoured cable with terminating clamps and glands... 

BS 6004, Electric Cables - PVC Insulated, Non-Armoured Cables for Voltages up to and Including 4501750 V, for Electric Power, Lighting and Internal Wiring, 2006. 

Paper insulated lead-covered steel wire armour cables are only used in systems above 11 kV. Very high-voltage cables are only buried underground in special circumstances when overhead cables would be unsuitable, for example, because they might spoil a view of natural beauty. 

Paper insulated lead covered steel wire armour cables... 

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