On-line monitoring is now getting more focus on detecting defects in HV insulated cable system in order to prevent failures. Cross Bonding (CB) configurations are widely used in long power transmission land lines in order to reduce the circulating currents through cable metal sheath. This paper presents a general criterion for detecting defects in cable sheaths in CB configuration. Three types of defects are studied in this paper; open circuit fault in sheath loop, two phase short circuit in linkboxes (breakdown between sectionalized sheaths) and flooding in linkboxes. ATP software is used for the simulation of these defects on the modelled system. The criterion developed is studied on a real double circuit cable system in order to show the influence of varying the load of each one of the parallel lines. Real measurements have been performed on this cable system under normal condition; there is a good agreement between the measured and simulated results.