Polarization in cables with current load

In this paper theoretical and experimental results are presented relating to the polarization which appears as a consequence of non-uniform temperature spacing in cable insulation. A simple model of the polarization is outlined and analyzed regarding to the influence on the measurable parameters of a cable. The analysis of the dielectric data showed, that the polarization can be identified in the range of very low frequency. The methods of acquiring data in the mentioned range of frequency are also discussed. Additionally the question of separating the data from the polarization and conduction processes is solved. The final results were acquired on a line cord with PVC insulation, where the polarization was generated by heating of two cores. The results proved possibilities of the polarization identification. The only obstacle by these measurements is that they require very long time for reaching a steady state. Reliable results can be expected at frequencies of a few mHz.