According to voltage level
Low voltage (L.T.) cable: It consist of one circular core of tinned stranded copper (or aluminum) insulated by layers of impregnated paper. These cables are used up to 1 kV.
High voltage (H.T.) cable: It consist of either circular shaped or oval or sector shaped 3 core stranded copper or aluminum. These cables are used up to 11 kV.
Super tension (S.T.) cable: The insulation on each core is covered with aluminum foil or own lead sheath or metallized paper. These cables are used up to 33 kV.
Extra high tension (E.H.T.) cable: Oil filled cable and gas pressure cable are types of E.H.T. cable. Oil filled cable is consist of oil channel at the center of core by stranding the conductors wire around the hollow cylindrical steel spiral tape. Gas pressure cable is laid in a gas tight steel pipe which is filled with dry nitrogen at 12 to 15 atmosphere pressure produces radial compression and closes the voids. These cables are used up to 66 kV.
Extra super voltage cable: These cables are used up to 132 kV and above.
According to insulating material
Insulation is provided on conducting material to block the path of leakage current from the conductor, thus minimizing the risk shock and fire.
Normally cables are classified according to the insulation used over the conductor. The various classification of cable commonly used for domestic wiring are as follow:
Vulcanized rubber sheathed (V.I.R.) insulated cables: These consists of a copper conductor covered with a insulation layer of Vulcanized Indian Rubber (VIR). A cotton tape covering is provided over this insulation layer to protect the wire from moisture and to provide mechanical strength to the wire. The thickness of the Vulcanized Indian Rubber depends on the voltage.
Cab Tyre sheathed (T.R.S.) cables: These C.T.S or T.R.S wires consists of vulcanized rubber insulated conductor. This insulation layer is covered by a layer made of tough rubber (or) tough rubber sheathed covering is provided over this insulation layer. This covering will be very hard and protects the wire from moisture and provides mechanical strength to the wire. These wires are available in single core, twin core, triple core etc. As these wires have tough rubber covering no additional protection or strength is required.
Weather – proof cables: These wires consists of conductor provided with an insulation layer made up of hard rubber. Over this cotton sheathed and cotton tape covering is provided especially to protect the wire from moisture. These wires are used where the moisture is present.
Polyvinyl chloride (P.V.C.) insulated cables: These wires consist of a conductor over which an insulation layer made up of Polyvinyl Chloride is provided. These wires cannot resist much heat and they have relatively low melting points, so they aren’t used in hot places and also these wires are not used with heating appliances. PVC wires are available in almost all colors.
Lead sheathed cables: These wires consist of vulcanized Indian rubber insulated conductor over which a Lead sheath is provided which gives mechanical strength to the wire and it also protects the wire from moisture. These wires are generally used where there is chances of moisture like in snowy places. As Lead is a good conductor of electricity the Lead covering may give electric shock to us so to prevent this the Lead covering is provided with earth wire. These wires are available in single core, twin core, triple core etc. size.
