Dielectric Phenomena Related to the Use of Carbon Black Paper Screening in High-Voltage Fully Impregnated Paper Cables

Carbon black (CB) paper screening is today commonly used in oil-filled cables since, besides the well-known advantages already experienced with solid-type cables, it provides a considerable increase of the a-c dielectric strength. CB paper, however, causes an increase of the ``ionization factor.´´ These phenomena are studied and the conclusion is drawn that they are closely interrelated. This fact is shown to be related to movements of charged particles in oil gaps adjacent to CB paper. Measurements and theoretical calculations are in good agreement.