Reduction of stress voltages at control equipment terminals in a substation through inductive coupling between cable core and sheath

Considerable potential differences can develop between different parts, of an electric station's grounding grid during fault conditions, when circulating currents of great magnitude are involved. As a result, communications or control wires extending between these locations can subject the equipment they serve to damaging stress voltages. A limited reduction of the stress voltages can be achieved by increasing the density of grounding grid conductors. This paper examines a highly effective method of reducing stress voltages by enclosing these wires in low impedance metallic sheaths or conduit, and bonding the latter outer conductors to the grounding grid at the wire extremities.