Diagnostics is an important tool for the asset manager regarding questions suchas ”What to do now, what tomorrow and what can wait a bit longer?”. As an effective tool for the asset manager responsible for the maintenance of an underground power cable system, diagnostics assists him in:

• determining the present condition of the various system components. 
• providing guidance on identifying the actions required so that continued reliable performance is insured.
• developing a strategy that will focus resources on those actions that will have maximum impact on company profitability.  

Diagnostics methods should therefore be proactive and action oriented, not just provide information that is "nice to know".

• Condition-Based Maintenance (CBM) on underground power cable networks: an alternative to corrective and time-based maintenance that applies a systematic approach to develop a strategy that results in reduced maintenance costs and improved system reliability. 
• Medium voltage cable partial discharge diagnostics on paper and polymeric cable systems: This tool uses partial discharges as the most important indicator of weak spots in paper cables and in accessories of paper and polymeric cables. Correct analysis of the results is critical in determining the proper corrective actions. 
• Water tree diagnostics on polymeric cables by means of Dielectric Spectroscopy (DS): This technique is effective in determining the level of deterioration due to water trees in older polymeric cable, whether the cable can be repaired or should be replaced, and whether failure is imminent or corrective action can be delayed. Another benefit of DS testing is that it is possible to distinguish between the effects of water trees and faulty accessories. 
• Assessment of the condition of cable terminations: A method that measures partial discharges locally at live voltage.   When applied to polymeric cable systems, it is also possible to identify weak terminations. 
• Cable route and joint position tracing: Partial discharge diagnostics can identify the position of weak spots along the underground cable line, and this method is useful in identifying the corresponding locations on the surface for digging.
• Commissioning tests on polymeric cable circuits: It is important to apply the proper test methods during commissioning tests, since some testing methods may be harmful to the cable and produce results that are either incorrect or misleading. For example, DC testing of the main insulation is not effective and may even damage the cable, whereas AC testing is effective and not harmful! DC testing of the outer sheath, however, can provide useful information regarding damage during installation. In addition to understanding the proper method to apply, the limitations of each method should also be known.