Function of Line supports:- The function of line supports is obviously to supports the conductors. Line supports must be capable of carrying the load due to insulators and conductors including the ice and wind loads on the conductors along with the wind load on the supports itself.The line supports are various type including;- 1. wood 2. steel 3. Reinforced concrete poles 4. steel tower.
The main requirements of the line supports are:-
1. High mechanical strength to withstand the weight of conductors and wind load.
2. Light in weight without the loss of mechanical strength.
3. Cheaper in cost.
4. Low maintenance cost.
5. Longer life.
6. Good looking.
1.Wooden poles:- These supports are cheapest , easily,available, provide insulating properties and are extensively used for the distribution purpose specially in rural electrification keeping the cost low.Their use is usually limited to pressures (22kv) and for short spans (upto 60 mtr) To prevent decay owing to snow and rain, the wooden poles are protected by an aluminium, Zinc,or cement cap at the top.
Normally the wooden pole lenths is 10 to 12 mtr .The main drawback of wooden supports are less mechanical strength, smaller life.
2. Steel Poles:- The steel pole are three type (a) tabular poles (b) rail poles (c) rolled steel joists. The tabular pole are of cross-section,the rail poles are of the shape of track used for railways and rolled steel joists are of I cross-section. such poles possess greater mechanical strength and permit to use longer spans (50-80 m) but cost is higher.
The advantages of tabular poles are that these poles are lighter in weight and easy ti install.
3. RCC Poles:- Poles made of reinforced cement concrete (RCC) usually called the concrete poles are used for low voltage distribution lines upto 33kv.These poles are two types in shape. one type is of square cross-section from bottom to top .The other type has rectangular bottom and square top with rectangular holes in it
4. Lattice steel Tower:- The Lattice steel tower are used for transmission at 1kv and 33kv and broad-base, lattice-steel taower are mechanically stronger and have got longer life due to their robust construction long spans (300m and above) can be used and are much usefull for crossing fields,valleys, railways lines,river.
