- they easily rot below the ground level and are limited to line voltages of 20 kV
- of light in weight
- they can easily be fitted and erected
- of cheap in cost transmission lines
Answer: 1. they easily rot below the ground level and are limited to line voltages of 20 kV
Explanation:
Wooden poles are used for distribution purposes in rural areas as an economic proposition. They have comparatively smaller life and cannot be used for higher voltage levels.
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.
Wooden poles are not used because due to heat and moisture the wood gets damaged.
