The effects of temperature, mechanical pressure and air pressure on the dielectric properties of multilayers of dry kraft paper

Kraft paper is used extensively in the electrical engineering industry for the insulation of high-voltage cables, capacitors and transformers. Methods used to assess the quality of the paper include: measurement of the capacitance, the dispersion of capacitance with change of frequency, the dielectric loss tangent, the DC insulation resistance and the moisture content. The paper presents experimental results of the variation of the loss tangent of a 40 layer stack of 10 μm thick capacitor tissues under vacuum in the frequency range 50 Hz-20 kHz, the temperature range 20-130°C and the compression range 3-336 kPa. The variations of the DC insulation resistance and the dielectric dispersion are also given. The long-term variation of the loss tangent after a step change in either the temperature or the air pressure is shown