crossarm

A crossarm is a horizontal structural member used on utility poles and lattice transmission towers to support electrical conductors. It provides a mounting surface for insulators and hardware, keeps wires separated to prevent arcing, and distributes the mechanical load from wind, ice, and the weight of the conductors.

In traditional wooden distribution systems, the crossarm is a wooden beam attached perpendicularly to the pole. Insulators are mounted at the ends or along the arm to suspend conductors. Crossarms are treated to resist decay, with older installations often using creosote. Modern crossarms may be wooden, steel, or composite materials such as fiberglass-reinforced polymers, chosen for durability and weather resistance. On higher-voltage transmission lines, crossarms are frequently metal and form part of the lattice framework of the tower, sometimes accommodating multiple circuits.

Configuration options include single, double, or triple crossarms, and arrangements that allow two or more circuits to be mounted on the same structure. The spacing of insulators and conductors is designed to maintain adequate clearance, reduce the risk of arcing, and accommodate local voltage regulations and weather conditions.

Maintenance and safety considerations: crossarms are inspected for cracks, rot, splits, or corrosion and for loosening hardware. Damaged crossarms are replaced to preserve pole integrity and line reliability. Insulators and clamps are cleaned or replaced as needed to prevent contamination, tracking, and electrical faults.