Types of steel towers are:
1) Single circuit steel tower
2) Double circuit steel tower
These are used for transmission line support purposes. Their physical dimensions are much more compared to previous poles (used for distribution purposes). Steel towers have a lattice structure which increases mechanical strength. These are galvanized or painted to increase life. Due to higher mechanical strength, these can be used for larger spans (100 to 300 m). The bottom portion of the (footing) is properly earthed. Fig. 1. shows the steel towers. if the voltage level of line is increased, height also Increased. OR Increasing the voltage level the f transmission line, the height of the f tower has to be increased.
Advantages of Steel Towers
1) Strength is much more.
2) Span is greater, so less number of units required.
3) Life of tower is much more (years together),
4) They can withstand bad weather/storms.
5) Less maintenance is required.
6) It can be a nun in hilly areas.
7) Suitable for transmission lines 33 kV to even765 kV.
8) The overall weight is moderate.
9) Erection at the site.
10) The appearance of the lines is very good.
11) Iron and steel (galvanized) are used which is not costly.
12) Height is much more to keep sufficient ground clearance.
Disadvantages of Steel Towers
- One tower requires so many fittings.
- The erection cost is much more.
- The expert team is required.
- Fault attending consumes more time.
- Transport in hilly areas is difficult.
Applications of Steel Towers
1) For low voltage 33 kV, 66 kV simple structures as shown in Fig. 3.2.4 is used for transmission lines and also for feeder lines.
2) Medium voltage, high voltage and extra-high voltage up to 765 kV the transmission line Supporting towers are the only alternatives.
3)For generating station to receiving station, receiving station to a primary substation, line Supporting towers are needed.