Overhead Suspension

a component of a contact system that provides stable contact between the overhead wires and the current collectors of rolling stock. A distinction is made among direct suspension, consisting only of overhead wires (one or two wires, arranged side-by-side); simple catenary suspension, consisting of one or two wires suspended by hangers from a longitudinal catenary cable attached to supports; and double suspension, consisting of one or two overhead wires suspended from a messenger wire attached to the catenary.

Direct suspension is used mainly in overhead systems for streetcars and trolleybuses, as well as for secondary networks in railroad stations (that is, for relatively low speeds). For main lines, direct suspension is used only with particularly strong wires of large cross section. For high speeds catenary suspensions provide a more stable contact between the contact wires and the current collector.

To improve current collection, the overhead wires or all the wires of a contact system are equipped with compensators that automatically maintain constant tension of the wires, which are exposed to temperature changes. Pull-offs or push-offs, which are attached to the supports by means of insulators, are used to prevent deflection of the wires by wind.