Low impedance surge protective device cables for power line usage

摘要

A coaxial cable (10) is for use in a power distribution network (N). The cable connects a surge protective device (SPD) in parallel with feeder lines (W1, W2) of the network. The SPD senses voltage surges on the feeder lines and clamps the voltages to a level at which loads (LD) connected downstream of the SPD are protected from excessive voltage levels. An inner conductor (12) and an outer conductor (14) have a dielectric material (16) separating them. The inner conductor is a round conductor, and the outer conductor forms a hollow cylinder in which the inner conductor and insulation material fit. A ratio of the inner diameter (D) of the outer conductor to the diameter (d) of the inner conductor is approximately 1.05. Thus, the diameter of the inner conductor is relatively large compared with the inner diameter of the outer conductor. A relatively large diameter of the inner conductor serves to minimize the dc resistance of the cable. Also, the dielectric material has a permittivity in the range of 2.0-4.0. Performance characteristics of the coaxial cable are compared with those of other conductors to illustrate the superiority of the coaxial cable in reducing "let through" voltage otherwise passed by a surge protector device to the loads.