When fault occurred in power cable like short circuit,ground and phase break in any reason required to repair by the process of jointing. In faulty power cable outer sheath and core insulation get damage.For jointing these power cable it is essential to adopt special technique and good quality insulating materials.Jointing also done when tap from main cable for service purpose and termination from transformers and other electrical equipments.The use of proper insulating materials depends on voltage rating of the power cable.For repairing of PVC insulated cable fabric and PVC tape used rated up to 6600 volts and impregnated paper tape suitable for 11kv and above.For repairing lead sheth lead tape and lead sleeve is suitable and armour is repair by using of copper flexible wire. Epoxy resin and bitumen used as a sealing compound protect from moisture.Bitumen compound is suitable up to 11kv and Oil resin compound suitable for 22 and 33Kv.The power cable mainly made up of aluminium and copper conductor, special technique used to jointing these cable. Aluminium conductor quite difficult to joint compared to copper conductor because presence of highly tenacious film of aluminium oxide is insulating in character and impairs the conductivity at joint. This film reforms in presence of air as soon as it is removed.We can joint the aluminium conductor by welding,soldering,compression and crimping of solderless lugs and in line connector. Welding is the best method of jointing the aluminium to aluminium conductor because electrically and mechanically stronger then the solder joints.In this method strip the insulation carefully without the scratches and cut in the conductor provide similar heat resistant such as asbestos,loose the conductor strand and clean the properly.Place the carbon mould around the conductor and heat until it became red than weld the conductor strand together by puddling with an iron wire add more aluminium.Such type of method used to aluminium to aluminium conductor joint,straight joint and tee joints.Soldering method special types of solders fluxes used like tin,lead Zinc and Cadmium.Due to presence of highly tenacious film of aluminium oxide which prevents flow of solder between conductor strands by capillary action, while jointing the aluminium conductor by soldering method conductor should be proper cleaned for proper operation of fluxes.Temperature should be maintained around 300-350℃ at the time of jointing by using thermometer.All the accessories and conductor kept the same temperature and removed the dross formed on the surface of the solder should be removed.Straight through joints and tee joint should be done from this method.Compression and crimping of solderless lugs is the simplest method of jointing aluminium conductor.In this method suitable size lugs and In line connector used and crimp with manual crimping tools,hydraulic compressor tool with suitable die depend on the size of the cable.Uniform joint and no any special technique required in this method to prevents the chances of Bi-metallic corrosion special metal alloy like zinc,tin,and silver coated sleeve is used. The advantage of jointing the conductor through this method having high electrical and mechanical strength. If aluminum conductor joint with other materials like copper due to presence of moisture corrosive chemical action takes place, So only tinned copper/brass connector should be used for bimetallic connections or joints and oxide inhibiting compounds should be used.Aluminium has also lower bending strength than copper therefore ,the conductor should be taken straight in to the connector or connected directly to the terminal lugs in the switchgear.The small aluminium conductors up to 4 sq mm in size may be formed in to an eye and connected to the post. The jointing of copper conductor is much easier than aluminum discussed previously.Soldering technique same as aluminum conductor for jointing copper conductor ordinary tin and lead solders are used and soldering flux removes oxide and prevents its formation during soldering ,so that the solder may flow readily and result in proper jointing. The composition of tin and lead varies for the different application and temperature required accordingly.Example 60%(tin) and 40%(lead) is used for electronics applications at temperature 182-184℃.45%(tin) and 55%(lead) is used for sheet metal work at temperature 182-225℃ and 40%(tin) and 60%(lead) is used for plant applications at temperature 182-235℃. The outer insulation or protective sheathing of a cables to be repaired by insulating tape and vulcanizing process especially trailing cable used for give supply for portable and transportable electrical equipments.It is must to use same insulating materials tape same as the core insulation.Such as paper insulated cable a impregnated paper tape is suitable to repair, similarly PVC tape for PVC insulated cable and rubber tape for rubber insulated tape.While performing repairing work the surface should be properly clean on which the tape is to be applied tightly to exclude any air or moisture.First applied insulation tape then few layers of waterproof empire tape finally friction adhesive tape as the finishing tape is called temporary repairing. In vulcanizing process we can repaired the rubber insulated cable joints are completely waterproof ,neat and good looking is called permanent repairing. Hot and cold vulcanizing process used the repairing of outer sheathing of cable.In hot vulcanizing process vulcanizing machine used it is must to maintained the correct water level and 2 bar steam pressure otherwise machine will burn out for completing a joint it will take half or one hour depends on weather conditions. Jacket rubber and insulating rubber is suitable for repairing of outer sheath and core respectively.In cold vulcanizing process self vulcanizing tape used to repair outer insulation of the cable. Outer sheathing repair by using with patches.Patches should be six times larger than damaged rubber covering bevel rubber cover towards center of damage and brush of rubber scrapings after that apply vulcanizing fluid with clean brush and let it dry.Patches and stitch on the outer sheathing firmly from center towards edges with rollers.Other method of repairing outer rubber insulation by bandaging for rubber covering up to 2 mm used 35mm cable wrapping strip if rubber covering more thicker than 2 mm used 50 mm cable wrapping strip.In cold process bevel both ends of cut out approximate 30 mm inward with knife and brush of rubber scrapings thoroughly.Apply vulcanizing fluid with clean brush roughened area bandage inner rubber covering 25mm insulating rubber tape allowing no gapes.
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