Electrical characterization of aramid, organic and inorganic papers and polyester films submitted to AC electrical fields

This work is devoted to electrical characterization (internal space charge, breakdown voltage, capacitance, Thermally Stimulated Discharge Current) of different papers (thickness from 80 to 125 μm) used in electrical engineering (insulation for electric motors, transformers...): aramid paper, hybrid organic and inorganic paper and polyester film with mineral resin. We have tested these papers in real conditions by poling with AC voltage (field from 7.5 to 15.5 kV/mm RMS) at 25 and 100°C. Residual electric field distribution and space charge density are measured by Thermal Step Method (TSM) and comparisons are made with breakdown value. Aramid paper presents the best electrical behavior with the highest breakdown strength and the lowest space charge density. On the contrary, polyester paper and inorganic paper contain more space charges and their breakdown field is smaller