CABLE INSTALLATION

(a) General Requirement

This section of the specification covers the general requirements for the supply, installation, testing and commissioning of all cables that are required for the complete installation of the electrical system.

 

All the power cables and busducts involved in this Sub-contract shall be of copper conductor which are shown on the drawings and This Sub-contractor shall provide all the necessary cable trays, conduits, supports, glands, shrouds, end boxes, clamps, compounds, specialist tools, etc., necessary to install, terminate and connect the cables in accordance with good engineering practice.

 

All cables shall be provided with identification labels at each end.

 

Where multi-core cables are for indication, protection and control applications, each core shall have an identification number and This Sub-contractor shall in addition to the cable identification labels provide engraved ferrules over the cable tails. The ferrules shall be numbered according to a wiring diagram approved by the Engineer. All wires shall be terminated with an approved type of clamp connector.

 

Cables running horizontally at high level shall be supported by perforated cable trays unless otherwise specified.

 

The tray design and strength and/or the tray supports shall be spaced at such intervals, to ensure that tray sag is not noticeable when installed with all cables.

 

Where cables are clipped to wall or ceiling, they shall be secured by means of space saddles at centres. The space saddles shall be of the galvanised steel deep spacer type fixed to the surface by means of "rawlplugs" or other equal method. Each cable shall be fixed by a saddles fixed to bases by two cadmium plated fixing screws.

 

This Sub-contractor shall be responsible for the off loading and handling of the cables on site and shall ensure that cables are new and delivered to site on new drum and properly protected against mechanical damage and loss with manufacturer's seals still intact.

 

(b) M.I.C.C. & S. Cables

Mineral insulated copper conductor, copper sheathed and PVC sheathed cable (M.I.C.C. & S.) shall be provided for the installation in accordance with the drawings.

 

M.I.C.C. & S. cables shall be installed in accordance with the requirements of the latest edition of the I.E.E. Regulations. Proper tools shall be employed as recommended by the manufacturer during the installation work.

 

M.I.C.C. and cable accessories shall comply with BS EN 60702 and shall be light duty type 600V grade for lighting and small power outlets and heavy duty type 1000V grade for power supplied to equipment.

 

Cable terminations, etc., shall be made by means of cold compound screw-on pot-type seals and in conjunction with compression ring type universal glands. Brass locknuts with serrated washers shall be used. For termination of single core cables, a piece of nonferrous plate must be used. Screw on cable lugs shall be provided for the cable connections. All cable glands shall be covered with PVC shroud.

 

Jointing of M.I.C.C. & S. cables shall not be allowed unless authorised by the Engineer in writing. Proper jointing material shall be used as recommended by the manufacturer when jointing is allowed.

 

All joints and termination joints shall be of approved manufacture and carried out strictly in accordance with the manufacturer's recommendations.

 

Where M.I.C.C. & S. cables are fixed directly to the structure, This Sub-contractor shall provide PVC covered metal space saddles. Multiple runs shall be limited to a maximum of four cables. Brass round head screws with minimum length of 25mm and of suitable size shall be used. PVC served space saddles securing single cables shall be of one fixing screw pattern. Two screw patterns shall be used for multiple cable runs. Spacing of cable saddle fixings shall be of manufacturer's recommendation.

 

Multiple cable runs (exceeding four cables) shall be supported with PVC strips secured to perforated cable tray.

 

This Sub-contractor shall keep all cables entirely separate from pipework associated with other services. No direct contact shall be permitted between the cables and such pipes.

 

This Sub-contractor shall satisfy the Engineer that all labour employed in the installation of M.I.C.C. & S. cables shall be competent and have been properly trained in the methods of installation as recommended by the cable manufacturers.

 

Final cable termination to the motor or equipment shall be coiled in order to avoid excessive vibration being transmitted to the cable termination.

 

All cables shall be properly run and arranged to reduce the eddy currents to a minimum in the circuits.

 

(c) PVC/PVC Cable

PVC insulated PVC sheathed copper cables (PVC/PVC) shall be of single core or multicore with full neutral and shall be 600V/1000V grade complying with B.S. 6346. The cores of these cables shall be high annealed copper conductors complying with B.S. 6360.

 

The PVC insulated cores shall be colour coded and shall be sheathed with PVC.

 

The minimum bending radius shall be not less than eight times the overall cable diameter.

 

Where cables run horizontally, they shall be properly supported on perforated cable trays and cleated at intervals of not exceeding 2m directly on the tray. Where cables are installed vertically, they shall be cleated at distances not exceeding 1m.

 

(d) XLPE/SWA/PVC Copper Cable

600/1000V cross-linked polyethylene (XLPE) insulated, PVC sheathed copper cables with armour, single-core, two-core, three-core or four-core, suitable for conductor operating temperature not exceeding 90°C – IEC 60502-1.

 

Conductors of power cables shall be of high-conductivity copper and all meet the requirements of IEC 60228 and IEC 60228A. Copper conductors shall be circular stranded. The neutral conductor shall not be less than that of the phase conductors, unless otherwise specified.

 

The armour shall be of galvanised steel single with for multi-core cables. Single core cables shall be provided with non-ferrous sheathing and shall be without steel armour. The armour of the cable shall be covered with extruded PVC oversheath.

 

Cables shall be terminated in a gland fitted with an armour clamp. The gland body shall be provided with an internal conical seating to receive the armour clamping cone and a clamping nut which shall secure the armour clamping cone firmly to the armour wires, ensuring that the armour wires shall be tightly clamped between the armour cone and conical armour seating. The spigot on the gland body shall be threaded to suit standard conduit accessories. A PVC shroud shall be fitted to cover the entire gland body.

 

The minimum bending radius shall be not less than eight times the overall cable diameter.

 

Where cables run horizontally, they shall be properly supported on perforated cable trays and cleated at intervals of not exceeding 2m directly to the tray. Where cables are installed vertically, they shall be cleated at distance not exceeding 1m.

 

(e) PVC Copper Cables

The cables shall consist of copper conductors insulated with PVC complying to B.S. 6004. Cables for three phase and single phase circuits shall be 450V/750V grade.

 

The cables shall be enclosed in PVC conduits. Joints or connectors shall not be allowed in any such cable length, except that connectors may be used in accessible positions within fittings.

 

Only cables of the same circuit shall be accommodated in a single conduit in accordance with the DSSOPT regulations.

 

For copper cables terminations, compression type cable connectors/lugs shall be used for all switchgears over and equal to 160A, all MCCB units, main gas/water bondings and all equipotential bondings. If for any practical reason different termination method is used, prior endorsement must be obtained from the Engineer.

 

Connections to fixed electrical equipment shall be by means of PVC cables in conduits, with the final connection being made by PVC pliable conduit, and suitable adapter. In fire-protective area, club house or the area requested by F.S.D., metallic flexible conduit shall be used instead of PVC pliable conduit. A separate PVC copper cable earth continuity conductor in accordance with I.E.E. Regulations and B.S. 6004 of not less than 2.5mm2 shall be provided outside the flexible tube and solidly connected at each tube termination.

 

(f) XLPE/PVC Copper Cable

XLPE insulated PVC sheathed copper cables (XLPE/PVC) shall be of single core or multi-core with full neutral and shall be 600/1000V grade complying with BS 5467. The cores of these cables shall be high annealed copper conductors complying with BS EN 60228BS 6360.

 

The XLPE insulation shall be able to operate continuously at a conductor temperature of 90oC.

 

The minimum bending radius shall be not less than eight times the overall cable diameter.

 

Where cables run horizontally, they shall be properly supported on perforated cable trays and cleated at intervals of not exceeding 2m directly on the tray. Where cables are installed vertically, they shall be cleated at distances not exceeding 1m.

 

(g) XLPE/PVC cable with Branchmatic XLPE/PVC Copper Cable

The specification or this type of cable shall be the same as the XLPE/PVC copper cable plus the following particular requirement.

 

The cable T-off/joint shall be factory prefabricated. Injection mould shall be adopted for insulating the branch off portion. Factory test shall be carried out regarding the connection between the main feeder and branch off portion, and the water tightness of the PVC moulding. Type test certificates to verify the short time rating and short-circuit withstanding capacity of the cable joint to be not less than that of the main cable riser shall be submitted for Project Manager’s approval.

 

(h) Flexible Cords

Flexible cords shall be PVC sheathed with copper conductors of 300V/500V grade to B.S. 6500. Minimum size of cord shall be 1.5mm2.

 

(i) Fire Resistant Power Cables

The fire resistance cables shall be low smoke and zero halogen compound outer sheathed overall and rated at 600/1000V complying with BS 6387 and shall be able to carry the rated current at rated voltage under fire condition.

 

The cable shall be of F.S.D./F.O.C. approved type and relevant certificate shall be submitted by This Sub-contractor to the Project Manager for approval.

 

The cable shall be flame-retardant to BS 4066 Part 1 and reduced flame propagation to BS EN 50266.

 

(j) 11kV Cable (Not applicable)

11kV cross-linked polyethylene (XLPE) insulated, PVC sheathed copper cables with armour, three-core, suitable for conductor operating temperature not exceeding 90°C, manufactured to IEC 502.

 

Copper conductors shall be circular stranded.

 

The armour shall be of galvanised steel single with for multi-core cables. The armour of the cable shall be covered with extruded PVC oversheath.

 

The minimum bending radius shall be not less than twelve times the overall cable diameter.

 

Where cables run horizontally, they shall be properly supported on perforated cable trays and cleated at intervals of not exceeding 2m directly to the tray. Where cables are installed vertically, they shall be cleated at distance not exceeding 1m.

 

D4. CABLE TRAY

(a) Cable trays shall be of a perforated pattern formed from minimum 1.2mm thick minimum plain steel sheet and galvanized overall. Cable trays shall be galvanized after perforation.

 

(b) Cable tray shall be provided with returned edges.

 

(c) Trays shall be supported from the soffit of structural slabs and beams by mild steel rods not less than 6mm dia. and/or mild steel underslung angle brackets fixed on side wall. A sample of the supporting bracket shall be submitted for approval.

 

(d) Tray supports shall be spaced according to the number and size of cables being carried on the tray, but nowhere shall they be at greater than 1.2m intervals.

 

(e) Cables mounted on the trays shall be laid after installation of the tray and spaced in accordance with the I.E.E. Regulations to avoid derating of the cables. Cables shall be grouped in circuits and individually clipped, cleated or tied at intervals of not less than 2m lengths on horizontal runs and 1m lengths on vertical runs, using PVC strip or equal and approved fixing. Single core cables shall however be fixed non-ferrous materials.

 

(f) Notwithstanding the minimum gauge of metalwork specified, gauges shall be of sufficient strength to prevent sagging between supports.

 

(g) Cables leaving cable trays shall be installed properly without damage to cables by cutting edges of trays and rubber pads shall be inserted to underside of cables.

 

(h) Site fabricated fittings and manufacturer’s standard fittings are both accepted. The sample of site fabricated fittings shall be submitted for approval. Cable trays shall be supported at either sides of junction.

 

(i) Where trays are exposed to the weather, they shall be coated with epoxy resin before painting. PVC coating is not acceptable.