20 Chapter 2 • Cable joints and switchgear
2.2 Cable joints (Splices)
Cable jointing (splicing) requires a high degree of skill and knowledge of regulations which lay down certain rules with regard to aspects such as where joints may be made and what one may and may not do.
▲ 6.3.7.2 Joints and terminations shall not adversely affect the current-carrying capacity of the conductors, the earth continuity, or the insulation resistance of the cable,
Tere are five basic steps in making a joint in a cable:
1. Prepare the ends (make off the ends and prepare the surfaces). 2. Join the conductors. 3. Insulate. 4. Reshield (earth sock, armouring, screening, metal sheaths). 5. Rejacket.
2.2.1 Method
Jointing kits must be used as directed by the manufacturer regarding size, voltage rating, type of cable to be joined and the expiry date (if any) of the kit.
▲ 6.3.7.1 Joints and terminations of cables, cores and conductors shall be made in accordance with manufacturers’ instructions and any other necessary requirements. Flexible cables shall only be joined using cable couplers or manufacturers’ jointing kits. All joints shall be accessible and be protected against strain.
2.2.2 Sealing
Cable joints have to be sealed very carefully. It is of utmost importance to ensure that no moisture enters the joint while the joint is being made and that it is not possible for any to enter later on. Special attention must be paid to avoiding air bubbles and air pockets.
With paper insulated cables, pressure joints have the additional advantage of forcing the resin into the end of the cable for some distance, thus providing an oil seal as well.
Preparation of the joint is important. Tis includes, for example, the roughening of the surface and cleaning with a solvent where the resin is to seal the joint or where the hot or cold shrink sleeve is to seal the joint.
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