A study on three dimensional assessment of the aging condition of polymeric medium voltage cables applying very low frequency (VLF) tan δ diagnostic

Recently, diagnostic on Medium Voltage Cables using tan δ measurement that measures dissipation factor with 0.1Hz VLF (Very Low Frequency) high voltage source has emerged as an efficient way to assess water tree aging of MV (Medium Voltage) cables. This study verified the validity diagnostic evaluation criteria defined by IEEE400.2-2013 and it´s pervious drafts of DTD (Delta tan δ) and STDEV (Standard Deviation) - indicating voltage-stability and time-stability of tan δ respectively - by applying tan δ measurement to KEPCO (Korea Electric Power Corporation)´s power distribution system and suggested a new assessment factor being defined as Skirt, and its new formula in order to identify the precursor of insulation breakdown with patterns of tan δ. By visualizing complex correlations between various assessment factors and proposing a 3-dimensional assessment standard that can normalize the deterioration condition of a cable into a uniform value, this study has established a foundation to calculate the remaining life time of a cable through VLF tan δ diagnostic.