L.T. CABLE : properties

L.T. CABLE :

Single/Multi-core low voltage cables shall be PVC/XLPE insulated, PVC sheathed armoured /non-armoured direct  burial type, termite proof, made and tested according to relevant IEC/VDE/BS/BDS for this type of installation rated voltage being 600/1000V. LT cable shall be used for domestic wiring, control and power wiring.

BYA Cable :

Description: Plain annealed Stranded Copper conductor of 99.99% purity, PVC insulated single core cable. 

Application: Suitable for use in surface mounted or cosseted PVC conduits or trunking. Also suitable for field protected installation in and appliances up to 1000 V a.c or up to 750 V to earth d.c.      

Reference Standards: IEC-60502-1, VDE-0250, BDS-900 and BS: 6004.

BYM Cable

Description: Plain annealed Stranded Copper conductor of 99.99% purity, PVC insulated, PVC outer sheathed single core cable.  

Application: Suitable for use in fixed installations in dry or damp premises clipped direct to a surface or on a cable tray unclosed and also for use in non-metallic conduit (PVC) to be used in appliances up to 1000 V a.c or up to 750 V to earth d.c.       

Reference Standards: IEC-60502-1, VDE-0250, BDS-900 and BS: 6004.

BYFYE Cable:

Description: Plain annealed Stranded Copper conductor of 99.99% purity, PVC  insulated, two core flat cable with earth continuity conductor and PVC sheathed.  

Application: Suitable for use in fixed installation in dry or damp premises and for installation in walls, on boards and in channels or embedded in plaster. Not to be used in three phase 400 V circuits.

Reference Standards: IEC-60502-1, VDE-0250, BDS-900 and BS: 6004.

NYY Cables

Description: Plain annealed Stranded Copper conductor of 99.99% purity, PVC insulated, PVC outer sheathed.

Application: Suitable for use in indoors, outdoors, underground and in water for continuous permissible service voltage of 720/1200 Volts.

Reference Standards: IEC-60502-1, VDE-0271, BDS-900 and BS: 600

NYFGbY Cable:

Description: Plain annealed Stranded Copper conductor of 99.99% purity, PVC insulated, 4 cores laid up, PVC inner sheathed, Galvanized steel strip armoured, PVC outer sheathed.

Application: Suitable for use in indoors, outdoors, underground and in water for continuous permissible service voltage of 720/1200 Volts.

Reference Standards: IEC-60502-1, VDE-0271, BDS-900 and BS: 6004.

INSTALLATION

Cable in conduits:

Generally, single core cable (non sheathed) are to be installed PVC conduits. The conduit sizes shall be as specified in the drawing. It must be ensured that cables are not scratched/damaged during pulling. For long lengths, Pull boxes must be used even if not indicated in the Drawings. Cable shall not be drawn round more than two 90° bends (or their equivalent) between drawing-in-boxes and any single bend must be less than 90°

Cable bending radii:

The internal radius of every bend in a cable shall be not less than the appropriate value stated below:

Insulation	Finish	Overall diameter	Factor to be applied to overall  diameter of cable to determine  minimum internal radius of bend.
Rubber of PVC Non (circular copper or  circular standard aluminium conductor	Non Armoured	Not exceeding 10mm Exceeding 10mm but not exceeding 25mm Exceeding 25mm	3 4 6
	Armoured	Any	6
PVC (solid) aluminium or shaped copper non-armoured conductor.	Armoured  or Any		8

Construction Joint Crossing :

At construction joint crossing, a brass expansion joint fitting as per drawing is to be installed and the cables are to be run through such fitting.

Cable Trench :

The size of the trench shall be of minimum 2’-9” depth and 1’-6” width for each cable to be laid. Where more than one cable is to be laid in the trench, the width of the trenches are to be increased by 6” for each extra cable for size below 70mm² (3&1/2 core or 4 core) and 12” for bigger size cables.

A cushion of sand of F.M. 1.5, 5” thick is to be placed over the bed of the trench over which the cables are to be laid.

After laying the cable first class brick on edge of flat are to be placed as separators in between the cables. After installation of the brick separators, sand filling is to be done upto 6” from the top of the bigger cable. After sand filling, two layers of first class brick flats are to be placed along  the length and breadth of the trench as a protection against injury and indication that a power cable is laid. The rest of the trench shall be filled with earth, watered and rammed at 6” layers. After cables are laid the original ground conditions shall be restored. But if brick pavement, drain, concrete road, or bituminous carpeting road are out across or damaged, they shall be remedied and restored to the original specification.

The cable route shall be as direct as possible and shall received the consultant’s approval before excavation.

All cable bends shall have a radius of not less than 2 times the diameter of the cable drum , or 20 times the diameter of the cable whichever is greater.

G.I. pipe shall be provided for all road and drain crossing. These pipes shall be laid direct in the ground without any sand bed, sand layer, brick or cable covers.

Cables shall always be laid out or laid into the ground through G.I. pipe of suitable size as decided by the Engineer-in-charge / Consultant/Consultant the length of the pipes over the ground shall not be less than 4’-0”. No extra cost shall be paid for such pipes. The exposed end of the pipes shall be sealed using PVC or wooden plugs.

The Contractor shall exercise great care in handling the cable and avoid forming ‘KINKS’. The cable drums shall preferably by conveyed on wheeled cable drum carried and unrolled and laid directly from the drum carrier. Carriage by trailer or truck can be allowed only if proper care is taken during unloading the drum, and unrolling is done after placing the drum or drum jacks and spindle. The cables shall be unrolled in the directions indicated on the drum by the manufacturer.

G.I. cable marker is to be supplied and installed at every turning point of the trench.

After the cable is laid, it shall be tested by the indicated placed by the Contractor at his own cost. No extra charge shall be allowed for this.

Any damage done to any other services by the Contractor for cable laying operations, shall be made good by the Contractor.

All chasing and passages necessary for laying of cable indoor shall be done by the Contractor and the same shall be made good to the satisfaction of the Consultant by the Contractor without any extra charge to the Owner.

Whenever trenches are left open at overnight , and where road is to be cut, the Contractor shall exhibit suitable danger signal such as banners, red flags and red lamps at his own cost. Temporary arrangement by placing wooden sleepers/sheet steel etc. across the road cutting for vehicular traffic are also be made by the Contractor at no extra cost. The Contractor shall be wholly responsible for any accident which may occur due to the negligence of the Contractor.

All road excavations shall be filled up in layers with power earth and suitably watered and rammed in such a manner that after completion of the work there is no land subsidence. The road top shall be reconstructed to match the existing road pavement.

No trench shall be dug until all cables meant for laying have been procured and brought at site store. Cost of any decent ring or shuttering and showing of trench required to be done shall be borne by the Contractor.

Single Core Cables :

Single core cables on ground/trench/non-metallic floor shall be laid in trefoil formation, wherever so required by the Engineer-in-charge / Consultant. Where more than one single core cable shall be used in parallel for the same system, these shall be separate, if necessary, from the relevant distribution board(s).

In these matter the instruction of the consultant shall be binding and final, no matter whether these are shown or not in the drawing or schedule. Rate for these shall be included into the cable laying rate. In cases where this type of system (i.e. more than one single core cable is parallel for the same system) are to be laid in the trefoil formation, they shall be found after regular suitable internal as per direction of the Consultant or  Engineer-in-charge / Consultant.

Insulation Test:

Insulation test of the whole installation shall be carried out using Megger, in presence of authorised representative of the Consultant, and result submitted to the Consultant for approval.

                The Contractor shall conduct the following tests with the help of the concerned department/authority and the costs of performing the tests should be included in the quoted rates: