A New method of aging assessment for XLPE cable insulation based on dielectric response

In order to solve the problem of permanent damage caused by the traditional tensile strength test in insulation ageing assessment of XLPE (extrude low-density polyethylene) cables, this paper presents a new method of aging assessment for XLPE cables insulation based on ultra-low-frequency dielectric response measurements. On the basis of equivalent circuit, the measurement algorithm of dielectric response is analyzed, where after, the calculating formulas of dielectric parameters are obtained. In addition, XLPE cables samples were carried on accelerated thermal ageing under laboratory conditions. It is shown from the results that dielectric dissipation factor increases obviously at lower frequency range with the increasing aging time. The total FDS (frequency domain spectroscopy) curves shift towards the high frequency regions with the increase of test temperature. The minimum value of dielectric dissipation factor for XLPE cable samples is almost the same at different test temperatures and certain ageing time. Therefore, the minimum value of dielectric dissipation factor in frequency domain can be used as the reference criterion of insulation ageing status. The new dielectric response assessment method presented in this paper could be used as non-destructive ageing evaluation criterion of XLPE cables.