To explore the effect of Kraft pulp type on insulation performances of presspaper

four imported kinds of Kraft pulp

namely

Swedish pulp

American pulp

Canadian pulp and Russian pulp

were used to prepare presspaper samples. Mechanical property and electrical performances of the obtained presspaper samples were measured and analyzed. Microscopy results present a significant difference in cross-field pits of the softwood fibers with different fiber lengths and fiber diameters

which suggests the four kinds of imported Kraft pulp are made from various kinds of coniferous species. Tensile strengths of all the four presspaper samples are more than 100 MPa

obviously higher than 80 MPa recommended by industry standard. AC breakdown strengths in air and in oil are all above 10.7 k V/mm and 48.6 k V/mm

respectively

significantly higher than 9 k V/mm and 40 k V/mm given by industry standard. By comparing measurement error and difference between two kinds of presspaper

we draw the conclusion that the type of Kraft pulp will affect the relative permittivity and AC breakdown field in oil of presspaper

but hardly affect other properties including tensile strength

volume resistivity

dielectric loss factor

and AC breakdown field in air. Since presspaper made of Canadian Kraft pulp has the lowest relative permittivity and the highest AC breakdown strength in oil

it is suggested that Kraft pulp imported from Canada is slightly more suitable for manufacturing presspaper used under AC field.