Frequency-Dependent Line Parameters of an XLPE Power Cable Relating to outer Deformations

Abstract:
Deformations to the outer cable geometry are possibly the result of pressure on the cable or installation issues. This may lead to an elliptical profile of the cable or crushed outer components. Due to the symmetrical to elliptical or crushed change in the cable cross section, the line parameters and their related value rates can vary. To predict the changes of the line parameters, a 2D finite element simulation was performed, which calculated the line parameters over a frequency range from 1 mHz up to 100 MHz by different variation steps and types. The line parameters are of interest for further diagnostic investigations examining such geometrical deformations. Possible diagnostic methods are Line Resonance Analysis or frequency domain reflectometry, both of which work in the frequency domain. Due to the frequency domain of the diagnostic methods, the line parameters are calculated by variation over a broad frequency range. The latter chosen line parameters in the diagnostic simulations are based on realistic values because of the calculated results in this investigation. The calculated results of the investigation are also grounded in the electrical and physical background. The results of the investigation show small changes in the line parameters as a result of an elliptical or outer crushed geometry variation. As a consequence, a later investigation with diagnostic simulations led to a challenge concerning the detection of the impedance changes or their related position. The work represents the line parameters of a medium-voltage power cable over a broad frequency range involving an elliptical and crushed geometry variation.