“Cables with stranded or solid conductors coated with polymeric insulation have been used for many years. These cables are used for power transmission or distribution, telecommunications, and video and data transmission. The conductors of these cables may be made of aluminum or copper, with aluminum being prevalent in most cases due to lighter weigh and lower cost.” Easter, US Patent 7,66,503 (2/23/2010) 

More on Cables ”The cable construction may also include jacketing, metal sheaths, or shields and metal armors over the polymeric insulation to seal out moisture and prevent damage to the insulation. Common 600 V electrical distribution cables may include a stronger, tougher outer insulation layer, but usually do not include a metal sheath or armor. All these cables may be subjected to damage during or after installation, especially when directly buried, installed in tunnels, or inside buried pipes, from cutting by sharp tools, accidental dig in with shovels and picks, backfill with sharp rocks, and the like. The damage can be partial or total rupture of the outer sheath and possibly also of the insulating layer, with consequent infiltration of moisture and generation of leakage current. Further, if the rupture of the coating layers reaches the conductor, the combined effect of leakage current and moisture lead to a gradual corrosion of the conductor until complete breakage of the conductor occurs.” ”Aluminum conductors are most susceptible to rapid corrosion due to leakage currents. As oxides build up on the conductor, the diameter increases and the damage in the insulation is widened or opened, causing more water ingress. Eventually, the wires in the conductor corrode until few are left to carry a current, resulting in a cable failure.” ”To obtain effective protection against mechanical abuses, the cable can be provided with an outer structure capable of withstanding both cutting and compression. This outer structure comprises a sheath made of a metal or of a plastic material combined with metal armoring. Besides being expensive, this solution leads to a considerable increase in cable dimension and rigidity, thus making this solution unsuitable for cable which require easiness of installation and low cost, such as low-voltage cables.” Easter, US Patent 7,66,503 (2/23/2010)

Recent US Patents

Comments