Tape surface smoothness characterization and protrusion shape of semiconductive compounds for power cables

The author reports the development of a novel analytical instrument for measuring the surface smoothness of extruded tapes of semiconductor compounds used in power cables. This device can measure surface protrusions as small as 10 μm in height on semiconductive tapes by laser scanning. With computerized data processing, this instrument provides such information as the number, size, shape, and position of surface protrusions with excellent resolution. Since protrusion shape is very important to its electrical stress behavior, especially the sharpness at its tip, the shape of protrusions and its effect on electrical performance of semiconductive compounds are studied. Two parameters, the tip angle and the aspect ratio of a protrusion, are defined to portray the sharpness of a protrusion. The author discusses the implications of these parameters for electric stress enhancement