GB1098478A - An arrangement for the protection of telecommunication lines from the proximity effect of electrical power equipment - Google Patents

Abstract

1,098,478. Preventing inductive disturbances. KABELWERK DUISBERG. Sept. 2, 1965 [Sept. 3, 1964], No. 37574/65. Heading H4R. To reduce the effect of currents induced in a telecommunication cable by neighbouring electric power lines or a sudden rise in earth potential due to the short-circuit by some electrical equipment, the cable is coiled in one or more turns around magnetic cores spaced along the length of the cable, in order to increase the inductance, and the cable conductors are connected in parallel by connecting both ends of each conductors to earth through impedances, so reducing the cable resistance and draining away to earth any induced currents. The conductor ends may be earthed through over-voltage diverters (Fig. 1, not shown) which only connect to the ends to earth when they respond at a given voltage level, or pairs of conductors forming a two-wire transmission path may be connected to a winding of a repeater coil having an earthed centre-tap (Fig. 2, not shown). The cable may or may not have a metal sheath. For a cable with few conductors the cable resistance may be reduced still further by paralleling an additional conductor, either in the form of a central core or outer strip.