Since single-parameter monitoring of power cable sheath fault cannot be evaluated fault accurately andmulti-parameter fault monitoring is not enough for data fusion analysis

an on-line cable faults method based on differ-ential current analysis is proposed to precautions for early failures of high-voltage cable lines. This method measuresgrounding current at the direct grounding box and the cross-connected grounding box and calculate the fault and nor-mal conditions of the grounding wire three-phase current for ratio analysis and unbalance to identify the fault. Thefault criteria and fault database are established by fuzzy control based on the change of character parameter such as ec-centricity

and inclination angle of the locus. The faults such as grounding box water inlet

coaxial cable broken

jointopen circuit

joint short circuit in different locations are simulated. A set of cable insulation on-line monitoring systemis designed and simulated at laboratory which includes the front-end signal acquisition unit

micro-controller masterunit

as well as background data analysis and processing unit. The actual monitoring results show that the cable onlinemonitoring system based on this method can truly reflect the insulation characteristics of the cable.