Cross-linked metal sheath connection is usually applied in long-distance high-capacity power cables to reduce or eliminate the induced voltages in the cable sheath. The cross-linked cable systems present an opportunity as well as a challenge for on-line measurement and diagnosis of cable conditions. Consequently

we put forward a methodology to identify cable faults through monitoring and analyzing the sheath system currents in a cross-linked cable system. Firstly

a numerical model is established to simulate the sheath currents in cross-bonded cable systems. Secondly

three typical kinds of faults

such as the theft of earthing conductors

water ingress to cable link boxes and breakdown of cable joint components

are analyzed

which happen frequently with serious consequences on the basis of current measurement at the link cable. Detailed simulations of normal operating condition and a selected fault conditions are given to determine the feasibility of proposed fault diagnosis method. A case study using field data from a cable tunnel considering the normal condition is adopted to verify the model. Results in normal condition from 2015-01 to 2016-01 show good consistency with field data with error less than 5%. From the analysis results

a set of criteria can be established with which typical cable fault type and localization diagnosis can be made in the future based on the monitoring of cable sheath currents.