The insulation condition of XLPE cable is related with the security operation of power transmission and distribution system

thus it is of great significance to research the methods of condition monitoring and insulation diagnosis of cable. In this study

we summarized the condition monitoring and insulation diagnosis methods for different aging stages of XLPE cable during the service period according to the defect characteristics

fault causes

and testing methods features. Meanwhile we introduced that partial discharge testing that is fit for cable faults mainly coming from defects caused by manufacturing and installation in the early service stage

such as bubbles and scratches

including the principles and features of every kinds of sensors

and pointed out that the further research should mainly focus on the relationship between partial discharge pattern and defect type. Moreover

we summarized the research status of temperature and sheath current testing for the whole cable operation stage. For the overall aging of cable material in the middle and later service stage

it is considered that the testing methods based on trap parameters are suitable

such as Qt

space charge and polarization/depolarization current. And it is also pointed out that some testing standards about trap testing should be set

the universal relationship between trap parameters and insulation condition should be established

and the criterion for the above methods should be given in further studies.