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| RECOMMENDATIONS FOR INSTALLATION
The following are some of the salient factors which should be kept in view during installation of PVC Insulated Heavy Duty Cables:
- Before laying, the insulation of the cable should be checked with megger as preliminary check against any
probable damage.
- The drum should be always rolled in the "direction of arrow for rolling", marked on the drum. In the absence of any such mark, the drum should be rolled in the direction same as that of inside end of the cable and opposite to that of the outside end.
- Where the cable is to be joined with existing cable, the sequence of cores at the two ends to be jointed should be in the opposite direction, i.e. if at one end it is in clockwise direction, at the other end it should be in anticlockwise direction. This is necessary to avoid the crossing of cores while jointing. This will also decide the direction in which the cable is to be pulled.
- Wherever possible bending radius of 12 times the overall diameter of the cable should be maintained, but in any
case it should be less than 8 times.
- Where the cables are necessarily laid and jointed in very cold regions, both the cable and the ambient temperatures should be above O°C and have remained so far the previous 24 hours. During such conditions, the cable should also not bent to very small radius.
This is due to the reason that very low temperature PVC compounds become stiff and brittle, and are likely to crack and shatter when stuck hard or bent to small radius.
- A joint being the weakest point of the electric power transmission system, all necessary precautions should be taken. Jointing materials and accessories like conductor ferrules, solder, insulating and protective tapes, protective filling compound, joint boxes, etc. of right quality and sizes should be procured. Application of these materials should be made skilfully for the jointing work. In this connection, it is always advisable that the method and the working instructions of the supplier should be strictly followed.
- Armoured Cables: All bonding clamps at the joints and terminations and the armour wires should be thoroughly cleaned. The clamps should be adequately tightened. This is
necessary to ensure proper electrical contact, because armour is the only return path for earth fault current.
- Unarmoured Cables: In case of unarmoured cables, the external metallic earth bonding conductor of adequate size should be used.
- Earth: All joints, terminations, armour wires and external metallic bonding should be connected to earth. Wherever possible, armour at one end of the cable should be connected to main earth system at the supplying end by employing metallic connectors.
- Filling Compounds:
a. The design of the box and the composition of the filling compound should provide an effective sealing against entry of moisture to conductor ferrules and armour connectors.
b. If hot pouring protective compounds are used the temperature of the compound while pouring should not exceed 150°C.
- Test after installation: After the cable is installed, a D.C. voltage test may be carried out. Each core should be tested at 4 KV against others and the armour, the others connected to earth.
The voltage should be increased gradually to full value and maintained continuously for 15 minutes. No breakdown of insulation should occur during test.
Click Here For Cable Sizes For Motors with Star-Delta Starter
Click Here For Cable Sizes For Motors with Dol-Starters
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