For domestic wiring,the most extensively used conductor matirial is aluminium and copper which are properly insulated. wires used for ordinary purpose are of single strand. but for the power circuit such as mixer point,refrigerator point,iorn point,etc.where current may be more than 5Amp in such cases multistrand wires are used. following are the different types of wires used in electrical installation work: 1.V.I.R. wires 4.lead alloy sheathed wires 2.C.T.S or T.R.S. wires 5. weather proof wires 3.P.V.S. wires 6. flexible wires
Tinning of conductor prevents the sticking of rubber to yhe conductor. thickn A V.I.R wire mainly consist of a tinned conductor having rubber coating. ess of rubber mainly depends on the opreting voltage to whichwire is designed. a cotton bradding is done over the rubber insulation to protect the conductor against the moisture.
now a days these wires are not used since a better quality wires are available at a cheaper rate. finally the wire is finished with wax for cleanliness.
This type of wire is modification of V.I.R wire. It consist of the ordinary rubber coated conductors with an additional seath of tough rubber. this layer provides better protection againts moisture and wear and tear.also it provides an extra insulation. these wires are genrally available in singal conductor, two conductors or three conductors.
this is the most commonly used wire for wiring purpose. conductor is insulated by P.V.S. P.V.S. has following properties. 1.Moisture proof 2. tough 3.Durable 4. chemically inert
the ordinary wires can be used only at dry places but for damp places these wires are coverd with continuous lead sheaths. the layer of lead covring is very thin like 0.12 cm thick. these wires provides little mechanical protection to the wires.
these types of wires are used outdoor providing a service connection from overhead line to building etc. in this type of wire the conductor is not tinned and the conductor is coverd with three braids of fibrous yarn and saturated with water proof compound.
these wires consist of number of strands instead of a single conductor. the conductor is insulated with P.V.C.matirial. these wires are very useful for household portable appliances where flexibility of wire is more important.
Underground cables are genrally classified into two ways: 1. according to the voltage level 2. according to the insulating matirial used. Generally first method of classification is prefferred and it is further classiffied as: 1.Low tention cables = upto 1000v 2. high tention cables = upto 11000v 3. super tention cables = from 22kv to 33 kv 4. extra high tention cables = from 33 to 66 kv 5. extra super voltage cables = beyound 132 kv.
these cables are genrally used for voltages up to 1000 v. these cables can be used for 6600 v. also as the electrostatic stress developed in the cables are very small. fig shows the cross section of a single core low tention cable. it consist of one circular core of tinned strand copper conductors insulated by layers of impregnated paper.
fig shows the cross sectional view of 3 cope belted type high tention cable. these cables are used upto 11000 v it consist of three cores of strands copper. these three cores are insulated from each other by layers of impregnated paper.
three insulated cores are bunched together and wrapped with impregnated paper. to have a circular cross sectional area the gaps between the insulated core are filled with fibrous insulating material. lead sheath is wrapped around the paper belt which provids the protection against moisture. cable is provided with armouring to protect the cable against the mechanical injury. finally serving is provided over the armouring.
For voltage above 11000 v special construction of cable is required. screened cables are used upto 33000 v in which leakage currents are diverted to earth through metalic sheath.