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In transmission lines, the cross-arms are made of
Steel
Wood
R.C.C
Either Steel or Wood
Either Steel or Wood
Cross-arms in transmission lines are structural horizontal members mounted on poles or towers to support insulators and maintain the required clearance for phase conductors. Both steel and wood are commonly used depending on the voltage level, mechanical load requirements, and geographical availability.
Cross-arms in transmission lines are structural horizontal members mounted on poles or towers to support insulators and maintain the required clearance for phase conductors. Both steel and wood are commonly used depending on the voltage level, mechanical load requirements, and geographical availability.
FmechтАЛ=T1тАЛ┬░2+T2тАЛ┬░2тИТ2T1тАЛT2тАЛcos╬╕тАЛ тАФ Resultant mechanical tension force on cross-arm
dminтАЛтИЭV тАФ Minimum clearance distance requirement proportional to voltage
The primary role of the cross-arm is to provide mechanical support to the string of insulators and to hold the transmission line conductors at a fixed distance from the pole/tower structure and each other. Steel is preferred for high-voltage transmission lines due to its superior mechanical strength and longevity, while wood is often utilized in distribution lines or rural environments for its natural insulating properties and ease of installation.
Cross-arms provide the necessary horizontal spacing between conductors to prevent flashovers.
Steel cross-arms require periodic painting or galvanization to prevent corrosion.
Wooden cross-arms may require treatment with chemicals like creosote to increase resistance to termites and rot.
The material selection is governed by the line voltage, span length, and expected mechanical loading.
Steel: High mechanical strength, durability, and resistance to environmental stress.
Wood: Naturally insulating, cost-effective for lower voltage distribution, and lightweight.
Steel: Prone to corrosion in coastal or industrial environments without protection.
Wood: Susceptible to decay, fire damage, and mechanical degradation over time.
Electrical distribution networks (Wood).
High-voltage and Extra-high-voltage transmission lines (Steel).
| Feature | Steel | Wood |
|---|---|---|
Strength | Very High | Moderate |
Insulation | Conductive (requires insulation) | Insulating (natural) |
Galvanized steel is the standard for long-term transmission infrastructure.
R.C.C (Reinforced Cement Concrete) is typically used for the main support pole rather than as the material for the cross-arm itself.
D is correct тАФ Cross-arms are manufactured from either steel or wood depending on the specific mechanical and electrical design requirements of the transmission system.
Always remember that while R.C.C is used for poles, it is too brittle and heavy to be a common material for horizontal cross-arms.