High-voltage direct current (HVDC) power transmission is an efficient solution for energy transmission over long distances and asynchronous coupling between two AC networks. One major concern of HVDC transmission is the design of an optimal insulation system. The insulation materials in HVDC insulation system are exposed to composite AC, DC and mixed stresses. Therefore, the determination of electric field distributions within multi-layered insulation systems requires understanding of electrical conductivity and permittivity of insulation materials. This thesis investigates the electrical conductivity of insulating oil and oilimpregnated pressboard.weiterlesen