Practical experience using VLF Tan Delta and partial discharge measurement in medium voltage cable

Condition assessment of power cables is one of the most important tasks in maintenance and management of power networks. Significant investment has been made to ensure the reliability of cable systems. Very Low Frequency (VLF) test is an alternative method for 50 Hz AC voltage test. Using VLF voltage source, Tan Delta (TD) and Partial Discharge (PD) measurement can be carried out simultaneously. TD measurement is a nondestructive integral test to assess the overall cable condition, while PD measurement can be used to localize defects that generate electric discharge activities. This paper focuses on the practical experience using combined VLF testing with TD and PD to assess health condition and localize defects in medium voltage cables. Field experience with VLF TD and PD will be shared. Detailed testing and evaluation technique will be described.