Nonlinear phenomena in the constant electric field of insulation pressboard.

DC conductivity dependence of an oil-impregnated pressboard of the moisture content of 1.5% weight on the measuring temperature ranging from 40 °C to 80 °C and the electric field intensity ranging from 10 kV/m to 500 kV/m has been investigated. It has been found that within the temperature interval up to 50 °C, the conductivity is practically independent of the electric field intensity. For the temperature of 60 °C a weak dependence of the conductivity on the electric field intensity can be observed and it gets stronger along with the temperature growth up to 80 °C, when the electric field intensity increase from 10 kV/m to 500 kV/m brings about the increase of volumetric conductivity by about 1.57 times.