PPLP and kraft paper under high voltage in liquid nitrogen

Liquid nitrogen impregnated PPLP and Kraft lapped papers are compared in terms of space charge distribution measurements for high voltage insulation in high power HVDC superconducting cables. Measurements with the pressure-wave-propagation method have shown that PPLP and Kraft paper samples behave similarly up to 30 kV/mm. No space charge has been observed in the insulation. Partial discharges at the interfaces of the carbon loaded paper electrodes are observed and produce an injection like phenomenon.