**3.2 DC conductivity**

To clarify the influence of space charge accumulation to the conductivity behavior, space charge density and internal electric field are compared with DC conductivity. **Figures 9**–**11** show the maximum space charge density of negative charge, maximum positive internal electric field, and DC conductivity, respectively, under the applied field from 25 to 125 kV/mm for both polarities. To compare these figures, no remarkable influence on the conductivity by space charge accumulation inside polyimide at this level works. To establish a direct link between space charge dynamics and conduction phenomena, further evaluations are still necessary.
