Sheath Overvoltages in High-Voltage Cables Resulting from Special Sheath-Bonding Connections

Systems of sheath bonding which eliminate sheath losses in single-core cables cause sheath overvoltages as a result of transients and faults. Equations for transient sheath voltages are derived for the first incident wave, through the use of equivalent circuits to represent bonding points. The method is extended to subsequent reflections with a digital computer; calculated results are given for several values of the relevant parameters, and the effect of these parameters is discussed. Transient sheath voltages can be limited by the surge diverter described in this paper; and the necessary sheath insulation levels, with and without surge diverters, are discussed. Equations for sheath overvoltages caused by external steady-state faults are given. Calculated and measured sheath voltages when compared, show reasonable agreement for both transient and steady-state cases.