Investigation of the dependence of DC insulation resistivity of ultra-clean polyethylene on temperature and electric field

The present work aims at determining the dependence of the de insulation re sistivity on temperature and electric field for a super-clean low density p olyethylene (LDPE) used in manufacturing modern high voltage ac cables. Res istivity measurements were made using relatively thick (similar to 2 mm) sa mples at different temperatures and de electric fields. Based on the presen t experimental data, a mathematical model for the relationship between the insulation resistivity of the polymer, temperature and electric field was d etermined using: i) computer curve fitting techniques, ii) Artificial Neura l Networks (ANN) method. Comparison between the present results and previou s measurements, using less clean grades of LDPE, indicates that the inheren t dependence of the de insulation resistivity of LDPE on temperature and el ectric field has not been appreciably improved by using an ultraclean polym er. It is concluded that the successful utilization of LDPE for HVDC cables will require the modification of such dependence.