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Maximum permissible span for wooden poles is
10 meter
20 meters
60 meters
200 meters
60 meters
Wooden poles used in overhead electrical distribution lines are generally limited to a maximum span of 60 meters. Due to the mechanical strength limitations and the tendency of wood to decay or bend under heavy conductor loads, spans exceeding this length are typically serviced by steel or concrete poles.
Wooden poles used in overhead electrical distribution lines are generally limited to a maximum span of 60 meters. Due to the mechanical strength limitations and the tendency of wood to decay or bend under heavy conductor loads, spans exceeding this length are typically serviced by steel or concrete poles.
S=8TwL2тАЛ тАФ Sag formula where S is sag, w is conductor load, L is span, and T is tension.
TmaxтАЛ=╧Г├ЧA тАФ Maximum allowable tension before material failure, where ╧Г is stress and A is cross-sectional area.
The span length is determined by the mechanical sag tension and the pole's cantilever strength. According to the sag formula S=8TwL2тАЛ, where w is weight per unit length, L is the span, and T is the tension, an increase in span length significantly increases the sag and the tension forces exerted on the cross-arms and the pole base. Wooden poles possess lower elastic modulus and fracture strength compared to reinforced concrete or steel, necessitating shorter spans to maintain ground clearance and structural integrity.
Wooden poles are mostly used for low-voltage (LV) or distribution lines up to 11 kV.
The maximum span is governed by the pole's cantilever strength and conductor sag requirements.
Decay and weather conditions (moisture, wind) effectively reduce the service life and permissible span of wooden poles over time.
Standard spans for distribution lines are usually kept between 40 to 60 meters for safety.
Economical for rural electrification
Easy to install and transport in difficult terrains
Naturally insulating properties
Susceptible to decay and termite attack
Lower mechanical strength compared to steel/RCC
Limited lifespan (typically 15-25 years)
Rural electrical distribution
Temporary construction sites
Low-voltage secondary distribution lines
Wooden poles are treated with creosote or other preservatives to resist moisture and insect damage.
Options like 200 meters are typically reserved for high-voltage transmission lines using steel lattice towers.
C is correct тАФ The maximum permissible span for wooden poles is limited to 60 meters due to mechanical strength constraints.
Always remember that span length is directly proportional to the square of the distance, so doubling the span increases sag by four times, which is why material strength is the primary constraint.