Surge Potentials on Underground Cable Sheath and Joint Insulation

Insulating sheath coatings and sheath-joint insulators have been punctured in service, apparently by transient voltages. It has been shown that the discontinuities caused by sheath cross-bonding result in 15% of an applied surge on a conductor, appearing on the sheath at a joint and 30% across the sheath insulator. Bonding transformers result in higher transients. Protective devices appear to be required at each joint. These may be lightning arresters or surge capacitors.