What factors influence the inspection frequency and maintenance requirements of underground distribution cables, and how are they assessed?

Several factors influence the inspection frequency and maintenance requirements of underground distribution cables. Cable age is a primary factor; older cables are more susceptible to degradation and require more frequent inspection. Cable type also matters; different insulation materials (e.g., XLPE, EPR, PILC) have different aging characteristics and require specific maintenance practices. Operating voltage influences inspection frequency, with higher voltage cables generally requiring more frequent monitoring. Soil conditions affect cable temperature and corrosion rates. Cables buried in corrosive soils or near sources of heat may require more frequent inspection. Load conditions also influence inspection and maintenance; cables subjected to frequent overloads or high fault currents may degrade faster. Environmental factors such as moisture, temperature variations, and the presence of chemicals in the soil also play a role. Inspection and maintenance are assessed through several methods. Visual inspection of cable terminations and splices for signs of damage or corrosion is performed. Insulation resistance testing (Megger test) measures the insulation's ability to withstand voltage stress. Partial discharge testing detects localized insulation defects that can lead to cable failure. Time domain reflectometry (TDR) is used to locate cable faults and identify areas of insulation degradation. Frequency domain spectroscopy (FDS) provides a more detailed assessment of the cable's insulation condition by measuring its response to varying frequencies. Oil analysis is performed on oil-filled cables to assess the condition of the insulating oil and detect the presence of contaminants. The results of these assessments are used to determine the appropriate maintenance actions, such as cable replacement, splicing repairs, or oil treatment.