1. RCC and PCC poles
2. steel towers
3. steel poles
4. wooden poles, steel poles, RCC and PCC poles and steel towers
Answer: 4. wooden poles, steel poles, RCC and PCC poles, and steel towers
Explanation:
Wooden poles, steel poles, RCC, and PCC poles are used for distribution purposes and steel towers are used for transmission purposes.
Wooden poles:
- Wooden poles are used for temporary electrical line. The length of wooden pole is kept 6-9 meters out of which 1-2 meter length buried in the ground.
- The diameter of the pole is kept 15-25 cm so as to have safety factor of 3.5. Maximum permissible span for wooden poles is 75 meter.
Steel poles:
- Steel poles possess greater mechanical strength and thus permit the use of longer spans (60 to 80 metres).
- These poles have the longer life (more than 40 years) which can further be increased by regular painting.
- These poles need protection against corrosion. Hence at the bottom (the portion which is buried underground), these poles are set in concrete muffs in order to protect them from chemical reactions.
- RCC and PCC poles:
In a service line of a residential colony normally RCC poles are preferred. RCC means reinforced cement concrete.
