Type of Electrical Poles : Overhead Line Supports
Overhead transmission lines requires some support to carry the conductors.The supporting structures for overhead transmission line conductors are various types of poles and towers called line supports or electrical poles.
Properties of Line Supports :-
(i) Line Supports should have high mechanical strength to withstand the weight of conductors and wind loads etc.
(ii) Light in weight without the loss of mechanical strength.
(iii) Poles should be cheaper in cost and eco-friendly .
(iv)High life time because frequent replacement of poles may economical .
(v) Easy accessibility of conductors for maintenance.
Various types of poles:-
We have different types of electrical poles to carry various types of conductors,we can't use any one of the below line support for all types of conductors.
1.Wooden poles2.Steel poles
3.R.C.C. poles
4.Lattice steel towers.
1. Wooden poles:-
Wooden poles are made of wood (sal or chir) and are suitable for lines short distance (up to 50m) and less area lines.wooden pole supports are cheap in cost,easily available, provide natural insulating properties and moreover economical.The wooden poles generally tend to rot below the ground level, causing foundation failure. In order to prevent this, the portion of the pole below the ground level is impregnated with preservative compounds like creosote oil.but now a days these poles are out of use,they are replaced by R.C.C poles because of their long life.
Disadvantages of wooden supports are :
(i) tendency to rot below the ground level
(ii) comparatively smaller life (20-25 years)
(iii) cannot be used for voltages higher than 20 kV
(iv) less mechanical strength and
(v) require periodical inspection.
2. Steel poles:
The steel poles are used as a replacement for wooden poles.Because steel poles possess greater mechanical strength, longer life than wooden poles and able to withstand longer spans.These poles are generally used for distribution purposes in the cities. This type of supports need to be galvanised or painted in
order to prolong its life.
The steel poles are of three types viz.,
(i) rail poles
(ii) tubular poles and
(iii) rolled steel joints.
3.RCC poles:
RCC stands for reinforced concrete.These poles have become very popular as line supports in recent years.They have greater mechanical strength, longer life and permit longer spans than steel poles. Moreover, they give good outlook, require little maintenance and have good insulating properties.Expect high weight and manufacturing cost they are very good alternative for all types of line supports.
4.Steel towers:
In practice, wooden, steel and reinforced concrete poles are used for distribution
purposes at low voltages, say upto 11 kV.To transmit higher voltages than 11kv we use steel tower.Steel towers have greater mechanical strength, longer life, can withstand most severe climatic conditions and permit the use of longer spans and we can increase or decrease length of the pole by assembling some more cross arms.these are more efficient but requires more space to establish.
These are the different types of electric poles which we can see in daily observations.
