Jointing A Multi-Core Cable

Jointing A Multi-Core Cable Points : Jointing A Multi-Core Cable For multi-core cables also the tapered lead sleeve joints are the best, since approximates to expensive and takes more time, so such joint are not justified for low voltage and medium voltage cables. For such cables, the conductor joints so made (without lead sleeve) can well be insulated compound. The method of making a straight joint for 3,500 V. 3-core paper cable is as explained blow:

1) Mark the cutting points, giving an allowance of 2.5cm for overlap.
2) Bind the armouring of the cable with a 16 S.W.Q. binding wire giving about 6 or 7 turns as a distance of about 20cm. from either end of the cable and remove the armouring of the cable up to this point with a triangular file.
3) Remove the lead sheath up to a length of 18cm.
4) Remove paper insulation and bare the conductor for a length of about 2.5 cm.
5) Protect the exposed paper insulation from moisture and solder etc. with the help of an impregnated cotton tape.
6) Twist the conductor ends and insert the two conductors in a tinned brass connector so that both the conductors meet each other.
7) Solder perforated tinned copper bonding strips before soldering brighten the lead sheath under the bonding strip.
8) Over the lead sheath at the point shown, bind the compounded canvas tape until the overall diameter is slightly more than the internal diameter of the inner gland. For proper adhesion each turn is warmed up with blow lamp.
9) At the points where both the cables are to be gripped, clean the armouring of each cable and bind with lead strip 1.5mm thick until the overall diameter is slightly more than the internal diameter is slightly more than the internal diameter of the armour clamp.
10) The three cores joined together should he separated with the help of porcelain spreader which must be quite dry. For this purpose before use, it is immersed in a hot compound.
(11) Place the bottom half of the box under the joint so made and provide the armour clamp as shown and bolt it to the cable. The inside of the clamp must be well cleaned in order to ensure better electrical contact.
(12) With the stud, connect the lead bonding strip to the box.
(13) Warm the bottom half of the box with filling compound and while the compound is hot, place the upper half of the box over it and provide a bolt.
(14) Remove the manhole and heat up the box from outside and fill it up with the compound.
(15) Remove the filling plugs of the glands and provide sealing compound over the glands.
(16) Allow the joint to cool down, and after the contraction of the insulating compound, provide more quantity of it.
(17) After the contraction is complete, fill the groove shown with the sealing compound and replace the manhole. Before replacing the manhole, sealing compound should be provided there.
(18) All the openings should be sealed with the sealing compound.
19) When the job is complete it should be painted black with bitumen paint, in addition several metres of cable on both ends of the joint are coated with bitumen paint.